Climate review and Experimental Long Range Forecast for SW England. April 2024.

Published 23 April 2024

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A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of April. Areas around the south of the UK, Europe, Mediterranean show 1 or 2 Celsius positive anomalies. Pacific ocean anomalies along the equator show a weakening El Nino state and the tropical Atlantic looks to have similar anomalies to those in March.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through Summer and into Autumn 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) show a quickly weakening El Nino state and forecast to become neutral during by the start of May becoming La Nina during the Summer. Indication are for the formation of a strong La Nina in the second half of 2024.

The North Atlantic Oscillation index (500hPa index shown below)is in a neutral state. A positive NAO reflects a more mobile westerly type but neutral conditions are inconclusive.

2. Tropical storms etc: (Data from Wikipedia)

Southern Indian Ocean 2023-2024. Tropical cyclones 4, intense cyclones 2. Fatalities 46.

South Pacific Ocean 2023-2024. Tropical cyclones 4, severe cyclones 2. Fatalities 2

Australia region 2023-2024. Tropical cyclones 8, severe cyclones 6. Fatalities 1. Damage 675million USD.

Named storms UK and Eire:

Storm Kathleen, named by the Irish Met Service 4 to 7th April. Details on the WIKI page: https://en.wikipedia.org/wiki/2023%E2%80%9324_European_windstorm_season

Preliminary reports suggest the strongest wind from Kathleen are in Northern Ireland was recorded at 69mph (111 km/h) at Orlock Head in County Down. However, in Scotland, an unofficial windspeed of 101mph (162km/h) was recorded at Cairn Gorm. This is awaiting verification from the Met Office.

See also Storm Nelson was named on 26 March 2024 by Spain‘s AEMET, Storm Pierrick named by Meteo France on 8 April 2024 and Storm Renata named by Meteo France on 14 April 2024. All had some impact on parts of the UK.

3. Recent Climatology

SW England: The mean temperature has been about one degree above the thirty year average up to 22nd April. Rainfall has almost reached the April average in many places and possible exceeded this over the hills.

Reservoir levels, according to SW Water, are above the long term average across SW England as of 14th April 2024.

Met Office provisional Temperature and Rainfall anomalies for January, February and March 2024 are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period (right hand mini pictures) when comparing the images for the earlier 30 year averaging period. Temperatures in most areas were above average for the three month period thanks to a much milder December when compared to the recent 30 year average. Rainfall was notably above average in the S and central England UK whereas W Scotland and parts of N Ireland had near or below average precipitation.

March 2024 – 10th consecutive record warm month globally

According to climate.copernicus.eu March 2024 is the tenth month in a row to be the hottest for the respective month in the ERA5 data record, going back to 1940.

Europe Climate:

Copernicus, European sourced temperature and rainfall anomalies for March 2024 and year to date, compared with the 30 year periods 1991-2020 (top) and 1981-2010 (lower) shown below:

River flows and ground water levels in March 2024 can be found in the Hy d rological Summary

The Global Flood Awareness System – GloFAS – forecast from April 1st 2024 to end of July 2024. The map shows enhanced flood risk across the UK and Eire. Flash flooding, from for example thunderstorms, is not covered by this system.

B: Forecast data:

1. Stratosphere:

The North Polar Stratospheric Vortex completely warmed out early in March and has transitioned to its “summer” state earlier than average. Plot above shows 10hPa temperature anomaly and contour for 23rd April 0600UTC.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2024 May June July. Charts suggest that Atlantic mobility is reduced with possible ridging across northern Europe.

3. Lower Troposphere:

A selection of model solutions for May June July 2024 using April data are shown below. The full set can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

May to July 2024

NMME data (above) CAUTION SCALE/COLOURS for rain reversed blue above normal

Data from WMO:

Three month average anomaly followed by May June July 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown is multi model probabilistic mean anomaly.

Individual members of the WMO super ensemble are shown below. (Pune India missing Pretoria looks cold).

Summer model graphics can be seen at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output for UK area:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for January to March 2024, using December 2023 data.

Observed data

Temperature. Above normal, note January was near normal.

Rainfall. Above normal for most of England and Wales but the N and Scotland normal and probably below in NW Scotland.

Sunshine. Due to sunnier than normal January the three months may work out above average but both February and March had below average sunshine.

Pressure. Below normal overall

Original Summary – 19DEC2023 –

Temperature: For the three month period overall the temperature is expected to be above average. There are a number of models suggesting nearer or normal or even below normal for parts of the UK for February and this may well start later January and not last all of February. Even near normal would be colder than recent winters and models struggle to pick out cold spells.
Precipiation: For the three month period overall rainfall above normal, initially in the west but possible in the East during March. Chance of dier periods across N or NW Scotland later in the period. Chance of drier spells in February more widely. Snow above average for northern mountainsm below average elsewhere except in late January or February when there could be an increased snow risk for many areas compared to average.

Note 1: Large scale blocking with easterly types seem to only be reliably forecastable about two weeks ahead.

Comment: Good indication for above average temperatures but any hints at nearer normal or cooler values were misleading. Signal for wetter than average rainfall was good for the southern half of UK as was the hint at drier for NW Scotland later.

Scoring will attempt to state good, fair, poor or no signal for the 3 month period (not individual months).
Revised order
1. Russia (WMO): Temp fair. PPN good.
2. USA – CFS2 : Temp good. PPN poor.
3. UKMO Contingency: Temp fair. PPN fair.
4. UKMO : Temp good. PPN good.
5. USA – IRI : Temp fair. PPN poor.
6. KMA APCC : missing .
7. JMA : Temp good. PPN good. PMSL fair
8. NMME : Temp good. PPN poor .
9. WMO multi : Temp good. PPN good.
10. BCC : Temp good. PPN fair.
11. NASA : Temp v good. PPN mostly good .
12. CanSips : Temp fair. PPN fair.
13. Copernicus Temp good. PPN fair. PMSL fair
14. CMCC Temp good. PPN poor. PMSL poor
15: DWD Temp good. PPN fair. PMSL fair
16. EC Temp good. PPN poor. PMSL fair
17 JMA Temp good. PPN fair. PMSL poor
18 UKMO Temp good. PPN poor. PMSL poor
19. MF Temp good. PPN good. PMSL good
20 NCEP Temp good. PPN good. PMSL fair
21 ECCC Temp: fair. PPN fair. PMSL fair

WMO low res data:
BoM Temp good. PPN poor.
Can Temp fair. PPN good.
DWD Temp poor. PPN good.
KMA Temp good. PPN good.
MOSC Temp fair. PPN poor.
WASH Temp good. PPN good.
CMA Temp good. PPN fair.
ECMWF Temp good. PPN fair.
UK Temp good. PPN poor.
JMA Temp good. PPN good.
MF Temp good. PPN good.
CMCC Temp good. PPN poor.
CPTEC Temp fair. PPN good.

D: Text Forecast for SW England

Remainder of Spring 2024 (May).

Temperature is likely to be above average by around 1 degree Celsius .

Rainfall for SW England is most likely to be near normal but with a 30% chance of above normal. A drier than average May (suggested by Russia, Indian, NMME and NASA output) is roughly a 20% chance.

May climate: 1981-2010 average mean temperature 11 or 12°C. Average May rainfall roughly 70mm but 150mm over moors and 40mm in drier East of region.

Summer 2024 (June July August) limited data.

Temperature expected to mean about 1 or 2 degrees Celsius above climatology. Rainfall totals likely to be near average, although there are again hints at longer drier spells in July and/or August. Very localised thunderstorms can increase the rain totals so perhaps a below average number of rain days might be a better indication than the rainfall total.

Summer climate: 1981 to 2010 average daily mean temperature 14 or 15°C in many areas to 16 or 17°C in main urban areas also locally east of the moors and more widely in Somerset. Maximum temperatures average 19 to over 21°C in similar areas. July often warmer than August. Average 1981 to 2010 rain 300mm over the moors, typically 200 to 250mm in many coastal and eastern areas. June often drier than July and July drier than August.

Autumn 2024 (September October November) limited data

Milder/warmer than average. The start of Autumn could be wetter than average but the second half drier..

Autumn climate: 1981 to 2010 average mean temperature 11 or 12°C but nearer 10°C in rural areas. Maximum temperatures average 14 to 16°C. November normally colder than October which is colder than September. Average 1981 to 2010 rain 300 to 400mm, 600 to 800mm over the moors but east of the moors and in lowland Somerset more like 200 to 300mm. September often drier than October or November.

Winter (December 2024 January and February 2025) minimal data

Milder than normal winter overall although January and February may be nearer average. Precipitation above average for the season but with a chance of nearer normal values in January and February. Snow probably near average so perhaps some days with snow accumulation at low levels.

Winter Climate: 1981-2010 average temperature values for lowland areas 7°C in the West and 5°C in the East. Rainfall; Dec and Jan typically wetter than February. 1981-2010 Autumn average 300-400 mm lowlands but 200-300 mm areas to E of Dartmoor. Snow climatology less than 5 days lying snow over lowland areas, 5 to 10 days over hills around or above 200 metre elevation – one in three years have no lying snow on low ground.

E: Caution.

Experimental Long Range Forecasts do not have a good success rate, especially with regards to precipitation. The models are good at predicting above average values but not for picking out a one off colder month. The data used for the above forecast summary can be seen at here.

The attempt at a Regional Forecast for SW England aims to test whether such a forecast of temperature and rainfall variation from average can be made using numerical model data available on the internet. The forecast should not be used for any other purpose. A brief verification summary for the UK and Eire is routinely published at http://www.weather-info.co.uk/wxsvc/Verification.html or Click here for the Teignmouth and Dawlish summary

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

GLOFAS Acknowledgement: Data were provided by the Global Flood Awareness System – GloFAS (http://www.globalfloods.eu/) of the European Commission Joint Research Centre and the European Centre for Medium-Range Weather Forecasts.
Reference: Alfieri, L., Burek, P., Dutra, E., Krzeminski, B., Muraro, D., Thielen, J., and Pappenberger, F.: GloFAS – global ensemble streamflow forecasting and flood early warning, Hydrol. Earth Syst. Sci., 17, 1161-1175, doi:10.5194/hess-17-1161-2013, 2013.

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. March 2024.

Published 21 March 2024

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of March. Areas around the south of the UK, Europe, Mediterranean show 1 or 2 Celsius positive anomalies. Pacific ocean anomalies along the equator show a weakening El Nino state and the tropical Atlantic looks to have similar anomalies to those in February.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies into Summer 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in a weakening El Nino state and forecast to become neutral during Spring and La Nina during the Summer. Indication are for the formation of a strong La Nina in the second half of this year.

The North Atlantic Oscillation index (500hPa index shown below)is in a neutral state as of March 18th. A positive NAO reflects a more mobile westerly type but neutral conditions are inconclusive.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Tropical storms etc: (Data from Wikipedia)

Southern Indian 2023-2024. Tropical cyclones 3, intense cyclones 2. Fatalities 27.

South Pacific Ocean 2023-2024. Tropical cyclones 4, severe cyclones 2. Fatalities 2

Australia region 2023-2024. Tropical cyclones 5, severe cyclones 4. Fatalities 1. Damage 675million USD.

UK Named storms:

None recently. Details of the storms can be found on the Met Office Storm web page: https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/index

3. Recent Climatology

SW England: The mean temperatures has been about 1 degree above the thirty year average up to 19th March. Rainfall has reached or exceeded the March normal and sunshine has been well below average.

Reservoir levels, according to SW Water, are above the long term average across SW England as of 17th March 2024.

UK winter December 2023, January and February 2024

Met Office provisional Temperature and Rainfall anomalies for 2023 December, 2024 January and February and for the winter period are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period (right hand mini pictures) when comparing the images for the different 30 year averaging period. Temperatures in most areas were above average for the three month period thanks to a much milder December when compared to the recent 30 year average. Rainfall was notably above average in the S and E of the UK whereas W Scotland and N Ireland had near or below average precipitation.

Scatter plot for February 2024 showing temperature and rainfall combined.

River flows and ground water levels in February 2024 can be found in the Hy d rological Summary

The Global Flood Awareness System – GloFAS – forecast from March 1st 2024 to end of June 2024. The map shows enhanced flood risk across Southern England. Flash flooding, from for example thunderstorms, is not covered by this system.

Global Climate:

February 2024 was the warmest February in the ERA5 data record, going back to 1940. Every month since last June was the warmest compared to the same month in the series, according to the latest Climate Bulletin of the Copernicus Climate Change Service (C3S).

Europe Climate:

Copernicus, European sourced temperature and rainfall anomalies for February 2024 compared with the 30 year periods 1991-2020 (left) and 1981-2010 (right) shown below:

B: Forecast data:

1. Stratosphere:

According to the “Tokyo Climate Center”, a second (minor) stratospheric sudden warming (SSW) event started at 30 hPa level in the Northern Hemisphere around 14 February 2024 becoming a major event on the 17th. Plot below shows N pole stratospheric temperature at 30hPa and 10hPa.

The North Polar Stratospheric Vortex completely warmed out early in March and has transitioned to its “summer” state earlier than average. Plot above shows 10hPa temperature anomaly and contour.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2024 April May June. Charts may suggest Atlantic mobility is further south in April.

3. Lower Troposphere:

A selection of model solutions for April May June 2024 using January data are shown below. The full set can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

April to June 2024

Data from WMO:

Three month average anomaly followed by April May June 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown is multi model deterministic mean anomaly.

Individual members of the WMO super ensemble are shown below. (Pune India missing Pretoria looks cold).

BOM Australia (Lower row rainfall multi model prob charts)

Summer model graphics can be seen at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output for UK area:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for December 2023 to February 2024, using November 2023 data.

Observed data

Temperature. Above normal locally normal in N Scotland

Rainfall. Above normal

Sunshine. Below normal

Pressure. Below normal overall (WSW). January the exception being above normal.

Original Summary – 181123 –
Temperature strong signal for above normal values for the winter season as a whole. A few hints at near normal values in December and February chiefly across the S and W (of UK and Eire). Low chance of below average values in S or SE in February. Main theme is for above average precipitation although northern areas, mainly Scotland, could be near average with the strongest signal for the lowest above normal being in January but this is not consistent across models. Snowfall probably below average except over high ground, small increase in snow risk across the south in February but very uncertain.

Note 1: Large scale blocking with easterly types seem to only be reliably forecastable about two weeks ahead.

Comment: Good indication for above average temperatures but any hints at nearer normal values was misleading. Signal for wetter than average rainfall was good as was the hint at a less wet January.

Scoring will attempt to state good, fair, poor or no signal.
Revised order
1. Russia (WMO): Temp fair . PPN poor .
2. USA – CFS2 : Temp good . PPN good . monthly graphical data poor for Jan rain.
3. UKMO Contingency: Temp fair . PPN fair .
4. UKMO : Temp good . PPN fair . PMSL fair
5. USA – IRI : Temp fair . PPN poor .
6. KMA APCC : Temp good. PPN fair .
7. JMA : Temp fair . PPN fair . PMSL fair
8. NMME : Temp good . PPN fair . (Monthly ppn detail mostly ok)
9. WMO multi : Temp good . PPN good .
10. BCC : Temp good . PPN fair but good signal for Jan .
11. NASA : not available.
12. CanSips : Temp fair . PPN poor .
13. Copernicus Temp good . PPN good . PMSL good
14. CMCC Temp good . PPN fair . PMSL poor
15: DWD Temp good . PPN good . PMSL good
16. EC Temp good. PPN good . PMSL good
17 JMA Temp good. PPN fair . PMSL poor
18 UKMO Temp good . PPN poor . PMSL poor
19. MF Temp poor . PPN poor . PMSL fair
20 NCEP Temp good. PPN poor . PMSL fair
21 ECCC Temp: fair. PPN fair. PMSL fair

WMO low res data:
BoM Temp good . PPN good .
Can Temp good . PPN fair .
DWD Temp fair . PPN good .
KMA Temp good . PPN fair .
MOSC Temp good . PPN good .
WASH Temp good . PPN good .
CMA Temp good . PPN fair .
ECMWF Temp good . PPN good .
UK Temp good . PPN good .
JMA Temp good . PPN good
MF Temp good . PPN good .
CMCC Temp good . PPN fair .
CPTEC Temp good . PPN good .

D: Text Forecast for SW England

Remainder of Spring 2024 (April May).

Temperature for the remainder of Spring is likely to be above average.

Rainfall for SW England is likely to be above average for the remainder of the Spring period although there are some hints at a drier, or at least near normal, rainfall in May although this is not consistent between models with some suggesting a wet month..

Spring climate: 1981-2010 average mean temperature 9 or 10°C but a few degrees cooler over the moors. Roughly Apr 8 or 9°C May 11 or 12°C. Average 1981 to 2010 rain similar totals in April and May roughly 70mm but 150mm over moors and 40mm in drier east each month.

Summer 2024 (June July August) limited data.

Temperature expected to mean about 1 or 2 degrees Celsius above climatology. Rainfall totals likely to be near average, although hints at longer drier spells in July and/or August are not reliable. Very localised thunderstorms can increase the rain totals so perhaps a below average number of rain days might be a better indication.

Autumn 2024 (September October November) minimal data

Milder/warmer and wetter than average although September could be drier/near normal rainfall.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. February 2024.

Published 20 February 2024

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of February. Areas around the UK, Europe, Mediterranean show 1 or 2 Celsius positive anomalies. Pacific ocean anomalies along the equator show an established El Nino state and the Atlantic looks to have similar anomalies to those in December.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies into Summer 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to become neutral during Spring. Indication are for the formation of a strong La Nina in the second half of this year.

The North Atlantic Oscillation index (500hPa index shown below) became negative in early January 2024 then turned positive except for a short dip in early February. The forecast trend is towards a neutral state by early March. A positive NAO reflects a more mobile westerly type but neutral conditions are inconclusive.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Tropical storms etc: (Data from Wikipedia)

Southern Indian 2023-2024. Tropical cyclones 3, intense cyclones 2. Fatalities 25.

South Pacific Ocean 2023-2024. Tropical cyclones 4, severe cyclones 2. Fatalities 2.

Australia region 2023-2024. Tropical cyclones 4, severe cyclones 3. Fatalities 1. Damage 675million USD.

UK Named storms:

January 19th, Storm Isha centre moved across the fat N of Scotland but brought gale or severe gale winds to many areas, including SW England where Amber and Yellow warnings were in force. January 22nd storm Jocelyn followed quickly but this depression passed further to the north of Scotland with strong to gale winds for SW England.

Details of the storms can be found on the Met Office Storm web page: https://www.metoffice.gov.uk/weather/warnings-and-advice/uk-storm-centre/index

3. Recent Climatology

SW England: The mean temperatures has been two or three degrees about the February long term average and rainfall has also been well above average. This is illustrated by the temperature anomaly for the period 4th to 10th February and rainfall total for the same period as shown below.

Reservoir levels, according to SW Water, are above the long term average across SW England as of 11th February 2024.

UK October November December 2023, January 2024

Met Office provisional Temperature and Rainfall anomalies for 2023 November and December and January 2024 are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period (right hand mini pictures) when comparing the images for the different 30 year averaging period. Temperatures in most areas were above average for the three month period thanks to a much milder December when compared to the recent 30 year average. Rainfall was notably above average in the S and E of the UK whereas W Scotland had below average precipitation.

River flows and ground water levels in January 2024 can be found in the Hydrological Summary

The Global Flood Awareness System – GloFAS – forecast from February 1st 2024 to end of May 2024. Although the map does not shown any enhanced flood risk across Southern England a look at individual rivers suggest higher than average flows are more likely than below average flow over the months ahead. Flash flooding, from for example thunderstorms, is not covered by this system.

Europe Climate:

Copernicus, European sourced temperature and rainfall anomalies for January 2024 and the 12 months to the end of January compared with the 30 year periods 1991-2020 (left) and 1981-2010 (right) shown below:

B: Forecast data:

1. Stratosphere:

According to the “Tokyo Climate Center”, a second (minor) stratospheric sudden warming (SSW) event started at 30 hPa level in the Northern Hemisphere around 14 February 2024.

The North Polar Stratospheric Vortex weakened or a period due to a significant warming and then redeveloped. The current warming has displaced the vortex and a series of ongoing warming events may lead to the early demise of the winter vortex as shown in the forecast sequence below.

The median date for “summer vortex” when winter stratospheric polar vortex breaks down and switches semi-permanently from westerly to easterly winds is April 12th. The latest final warming (FW) on record occurred 11 May 1981.

Current guidance indicates that a FINAL WARMING might occur around 7th March, which is about 4 weeks earlier than average. The earliest date on record occurred in 2016 on March 5th which was also a strong El Niño winter. The demise of the westerly stratospheric flow over the Atlantic/Europe could mean that a cold spell may develop in March due to reduced Atlantic mobility OR it could mean an early Spring is possible – something that has already started in SW England.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2024 March April May. Charts may suggest reduced Atlantic mobility.

3. Lower Troposphere:

A selection of model solutions for February March April 2024 using January data are shown below. The full set can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

March to May 2024

Data from WMO:

Three month average anomaly followed by March April May 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown is multi model anomaly probability charts except for Pune, India Met Department which shows deterministic mean anomaly.

Individual members of the WMO super ensemble are shown below. (Beijing missing).

C: Comparing previous output for UK area:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for November 2023 to January 2024r, using October 2023 data.

Observed data

Temperature. Overall above average for the three month period mostly due to December. November and January near the 1991-2020 average but each month above the 1961-1990 average.

Rainfall. NW/W Scotland below average for the three month period elsewhere above averahelargely due to wet December.

Sunshine. Wales below average elsewhere mostly above average

Pressure. Below average despite January being slightly above average

Original Summary -171023.

Temperature for the three month period all models suggest the mean is likely to be above average although a few models suggest reduced anomalies and hint at near normal in the south of UK in December and / or January. Rainfall, main theme is for above normal rainfall, especially in western and southwesterly parts. The N or NW of the UK may have normal or below normal winter rainfall. Some indication of longer drier spells but detail inconsistent. Snowfall probably below normal in south but normal in the north. Dominant theme is for unsettled westlery types and below average pressure but does not preclude a colder anticyclonic period some time in December and or January.

Note 1: Large scale blocking with easterly types seem to only be forecastable about two weeks ahead.

Comment: 030324, overall indication of above average temperature anbd rainfall was good and hint a drier colder spell for December and or January turned out ok for January but not December which had the higher positive anomalies. Good signal for below averaghe rain in NW of UK but less good for W of UK alough SW and S England was above average except in January.

Scoring will attempt to state good, fair, poor or no signal for the 3 month period average not individual months.
Revised order
1. Russia (WMO): Temp Missing .
2. USA – CFS2 : Temp good . PPN fair .
3. UKMO Contingency: Temp fair . PPN good .
4. UKMO : Temp good . PPN good . PMSL good
5. USA – IRI : Temp good . PPN good .
6. KMA APCC : Temp missing
7. JMA : Temp good. PPN good . PMSL good
8. NMME : Temp good . PPN good.
9. WMO multi : Temp good . PPN good .
10. BCC : Temp good . PPN good .
11. NASA : Temp good . PPN poor .
12. CanSips : Temp good . PPN good.
13. Copernicus Temp good . PPN good . PMSL good
14. CMCC Temp good . PPN good . PMSL fair
15: DWD Temp good . PPN good . PMSL fair
16. ECMWF Temp good . PPN good . PMSL fair
17 JMA Temp good . PPN good . PMSL good
18 UKMO Temp good . PPN good . PMSL fair
19. MF Temp good . PPN fair . PMSL poor
20 NCEP Temp good. PPN good . PMSL fair
21 ECCC Temp: good . PPN good . PMSL good

WMO low res data: 3 month period. Temperature UKMO hinted at higher anomalies in December but overall models were a little warm. Rainfall CMCC CPTEC and BoM had the wetter anomalies in December and lower ones otherwise.
BoM Temp good. PPN good .
Can Temp good. PPN good .
DWD Temp good. PPN good .
KMA Temp good. PPN good .
MOSC Temp good. PPN good/fair .
WASH Temp good. PPN good .
CMA Temp good. PPN good .
ECMWF Temp good. PPN good .
UK Temp good. PPN good .
JMA Temp good. PPN good
MF Temp good. PPN good .
CMCC Temp good. PPN good .
CPTEC Temp good. PPN fair.

D: Text Forecast for SW England

Spring 2024 (March April May).

Temperature for the season likely to be above average although there is a chance that March, after a mild start, could turn colder and be nearer normal or even a little colder than average. This colder theme might also extend into early April but cold spells are unlikely to be prolonged.

Rainfall for SW England is likely to be above average for the the Spring period although this may be largely due to a wet May. March could well see near average rainfall totals and above average incidence of snow (and frost) for short period during the month, probably after mid March. Rainfall in April probably near average across with May wetter than average.

Spring climate: 1981-2010 average mean temperature 9 or 10°C but a few degrees cooler over the moors. Roughly Mar 7 or 8°C Apr 8 or 9°C May 11 or 12°C. Average 1981 to 2010 rain 200 to 300mm lowest values in E Devon and over parts of Somerset.

Summer 2024 (June July August) limited data.

Temperature expected to mean about 1 or 2 degrees Celsius above climatology. Rainfall totals likely to be near average, perhaps drier early and wetter later in the summer. Very localised thunderstorms can increase the rain totals so perhaps a below average number of rain days might be a better indication.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. January 2024.

Published 20 January 2024

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of January. Areas around the UK, Europe, Mediterranean show 1 or 2 Celsius positive anomalies although the N Sea and Baltic are colder due to the recent wintry weather across the N and NE of Europe. Pacific ocean anomalies along the equator show an established El Nino state and the Atlantic looks to have similar anomalies to those in December.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through to Summer 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so until late Spring 2024. This may help push average global temperature to the 2023 record levels again in and 2024.

The North Atlantic Oscillation index (500hPa index shown below) became negative in early January 2024. When westerlies are suppressed, as in the case of a negative NAO, the temperature across Europe can be more extreme suggesting colder temperature and more blocked patterns. The NAO has recently turned positive reflecting the change to a more mobile westerly type which is forecast to persist at least to early February.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Tropical storms etc:

Following the end of the season in the northern hemisphere the tropical storm focus changes to the Southern Indian and South Pacific Oceans.

New storms are expected over the next week but to date there has been two storms in the South Indian Ocean producing 29 fatalities to date. Storm Balel moved across La Réunion causing significant flooding as well as affecting Mauritius. Damage estimates are not yet available.

In the Australia region there has been one severe tropical cyclone cause in Fatality and $675 million USD. For the South Pacific there has been two severe tropical cyclones resulting in two fatalities but unknown damage costs.

Named storms:

Storm Gerrit, brought damaging winds and heavy rain to the UK from 27 to 28 December
with Wales, north-west England and Scotland worst affected. In the most exposed
locations, winds gusted at over 70Kt (81mph) while heavy rain led to increased flooding
concerns. There was heavy snow across parts of Highland Scotland and a mini-tornado in
Greater Manchester. This storm contributed to the generally prolonged, very wet and
unsettled spell of weather lasting through much of December. The 27th was the wettest day of the month for parts of Devon.

Full details Met Office link storm Gerrit

Storm Henk, the 8th storm of the 2023-2024 storm season, brought damaging winds and
heavy rain to southern and central parts of England and Wales on 2 January 2024. Winds
gusted widely at over 50Kt (58mph), even in inland locations, while Exeter Airport recorded
a gust of 70Kt (81mph).

Full details Met Office link storm Henk

The next storm, Isha is due to arrive over the UK on 21st / 22nd.

3. Recent Climatology

Global temperatures: 2023 warmest year on record, close to 1.5°C above pre-industrial level.

2023 is confirmed as the warmest calendar year in global temperature data records going back to 1850
2023 had a global-average temperature of 14.98°C, 0.17°C higher than the previous highest annual value in 2016
2023 was 0.60°C warmer than the 1991-2020 average and 1.48°C warmer than the 1850-1900 pre-industrial level
It is likely that a 12-month period ending in January or February 2024 will exceed 1.5°C above the pre-industrial level

According to Copernicus Climate Change Service/ECMWF December 2023 was the warmest December on record globally, with an average surface air temperature of 13.51°C

Copernicus, European sourced temperature and rainfall anomalies for December 2023 and the 12 months to the end of December compared with the 30 year periods 1981-2010 (lower row) and 1991-2020 (upper row), are shown below:

UK October November and December 2023 and Year 2023

Met Office provisional Temperature and Rainfall anomalies for 2023 October November and December also for 2023 (boxed) are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period (right hand mini pictures) when comparing the images for the different 30 year averaging periods. Temperatures in most areas were above average for the three month period except in November when compared to the recent 30 year average. Rainfall was notable above average in the S and E of the UK whereas W Scotland had lower anomalies.

River flows and ground water levels in December 2023 can be found in the Hydrological Summary

Reservoir levels, according to SW Water, are above the long term average across SW England as of 17th January 2024.

The Global Flood Awareness System – GloFAS – forecast from January 1st 2024 to end of April 2024 shows no enhanced flood risk across Southern England reflecting the recent dry weather. Flash flooding from for example thunderstorms is not covered by this system.

SW England

January to the 19th: After a wet and at times windy start to the month High pressure and winds between N and W brough a spell of drier and colder weather across the region.

Temperature dropped significant from about the 5th with the average value around 5 Celsius almost 2 degrees below the 30 year average. Milder wetter and windy weather set to start from 21st may lift the month average closer to normal. Due to the wet start rainfall to the 19th is about half of the month average at around 50mm. Sunshine so far is a little above the January average.

B: Forecast data:

1. Stratosphere:

According to the “Tokyo Climate Center”, a minor stratospheric sudden warming (SSW) event started at 30 hPa level in the Northern Hemisphere around 31 December 2023. This can be seen in the 30hPa and 10hPa plots below.

The North Polar Vortex has been weakened by significant warm which has produced a reversal of the stratospheric winds across N America. Although relocation from its normal location the vortex may well strengthen as shown in the forecast sequence below. However should the weakening of the stratospheric flow across the Atlantic in the early February forecast (lower right frame) extend further then this may have a knock on effect in delaying the onset of Spring across the UK in March 2024.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2024 February March April.

3. Lower Troposphere:

A selection of model solutions for February March April 2024 using January data are shown below. The full set can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

February to April 2024

Data from WMO:

Three month average anomaly followed by February March April 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown is multi model anomaly probability charts except for CMCC which shows deterministic mean anomaly.

Individual members of the WMO super ensemble are shown below.

Spring 2024 WMO multi model chart can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output for UK area:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for October to December, using September 2023 data.

Observed data

Temperature. Mostly above normal although N Scotland normal.

Rainfall mostly above normal. W Scotland and NW England nearer normal overall and below in November.

Sunshine. Scotland near normal elsewhere below normal.

Pressure. Below normal (W).

Forecast data

Original summary – 180923 –
Temperatures likely to be above normal for the three month average and possibly for each month. December forecast data hints at nearer normal in some models though the majority indicate above average values.
Precipitation, the main theme is for above normal rainfall in the S and W of UK and Ireland but nearer normal elsewhere with a chance of below normal across the N, mainly N Scotland. In the North the main chance for below average seems to be in November and to a lesser extent December associated with near normal values and possibly average snowfall for N Scotland.

Note 1: Large scale blocking with easterly types seem to only be forecastable about two weeks ahead.

Comment: Temperature forecast for above average was good although Scotland especially the north was nearer normal.

Scoring will attempt to state good, fair, poor or no signal based on three month average.
Score V good used when November rainfall was good.
1. Russia (WMO): Temp missed .
2. USA – CFS2 : Temp good. PPN good .
3. UKMO Contingency: Temp good. PPN good .
4. UKMO : Temp good . PPN good . PMSL fair
5. USA – IRI : Temp good . PPN good .
6. KMA APCC : Temp missed .
7. JMA : Temp good . PPN good . PMSL good
8. NMME : Temp good . PPN V good.
9. WMO multi : Temp good . PPN poor .
10. BCC : Temp good. PPN V good .
11. NASA : Temp good . PPN good.
12. CanSips : Temp good. PPN good .
13. Copernicus Temp good . PPN good . PMSL good
14. CMCC Temp good . PPN good . PMSL good
15: DWD Temp good . PPN fair. PMSL poor
16. EC Temp good . PPN good . PMSL good
17 JMA Temp good . PPN good . PMSL fair
18 UKMO Temp good . PPN good . PMSL fair
19. MF Temp good. PPN good . PMSL good
20 NCEP Temp good . PPN poor . PMSL
21 ECCC Temp: good . PPN good. PMSL good

WMO low res data:
CMA Temp good. PPN poor .
CMCC Temp good. PPN fair .
BoM Temp good . PPN fair .
Can Temp good. PPN poor .
DWD Temp good. PPN good .
KMA Temp good. PPN fair .
MOSC Temp good . PPN poor .
WASH Temp good . PPN good .
ECMWF Temp good . PPN good .
UK Temp good . PPN poor .
JMA Temp good . PPN fair .
MF Temp good . PPN good.
CPTEC Temp good . PPN poor .

D: Text Forecast for SW England

Remainder of Winter (February 2024)

After a mild wet and windy start a return to colder and drier weather is probable by about mid month with increased frost and snowfall risk but also longer dry spells. It is not clear if this will persist or other milder and wetter interludes occur.

Caution:
1: Due to large scale stratospheric warming of the polar vortex there is increased uncertainty for the second half of February and for early March.
2: Large scale blocking with cold easterly types seem to only be forecastable about two weeks ahead.

Winter Climate: 1981-2010 February average temperature values for lowland areas 6 or7°C in the West and 5 or 6°C in the East. Rainfall; February, lowland areas 80-100mm but 60-80mm in east. Around 200mm over moors. Snow climatology February possibly around 2 days on average with lying snow for low ground less than 5 days lying snow over lowland areas 5 to 10 hills, say hills around 200 metre elevation – one in three years have no lying snow.

Spring 2024 (March April May).

Temperature for the season likely to be above average although the risk that March could start colder has increased and seems more likely than not. Rainfall for SW England above average for the period largely due to a wet April. March could well see below average rainfall totals and above average incidence of snow (and frost) in the first half of the month. Rainfall in May near or perhaps above average across SW England.

Summer 2024 (June July August) limited data.

Temperature expected to mean about 1 degree C or so above climatology. Rainfall totals likely to be near or below average although very localised thunderstorms can increase the rain total so perhaps a below average number of rain days might be a better indication.

E: Caution.

Experimental Long Range Forecasts do not have a good success rate. especially with regards to precipitation. The models are good at predicting above average values but not for picking out a one off colder month. The data used for the above forecast summary can be seen at here.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. December 2023.

Published 19 December 2023

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of December. Areas around the UK, Europe, Mediterranean and the Baltic show 1 or 2 Celsius positive anomalies. Ocean anomalies along the equator show an established El Nino state in the Pacific and warmer than average values across the Atlantic.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through Spring 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so until late Spring 2024. This may help push average global temperature to new records for both 2023 and 2024.

The North Atlantic Oscillation index (500hPa index shown below) became positive on the 7th of December but is forecast to become neutral and perhaps negative in early January 2024. If westerlies are suppressed, as in the case of a negative NAO, the temperature across Europe can be more extreme suggesting colder temperature in mid-winter across Europe. Blocked patterns are typical but depending where the high pressure block forms a location can be in the “high” or in the associated slow moving “low” pressure zone. Neutral states are inconclusive.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Arctic November sea ice extent remained below the average and well below the 1981-2010 average as shown in the lower of the two images below.

2. Tropical storms etc:

Final data for the Atlantic Hurricane season of 2023. There have been twenty tropical storm strength systems and seven hurricanes three of which were CAT 3 or stronger. Fatalities to date at least 16* (*updated since November) with total damage estimate more than 4.19* billion USD. (Wikipedia). Atlantic tracks and timeline shown below.

Updated figures for the East Pacific has had 10 hurricanes and over 64* known fatalities with estimated damage of 16.8* Billion USD. The West Pacific has had 10 typhoons (4 super typhoons) 191* known fatalities and damage estimated at 18.5* Billion USD.

Northern Indian Ocean to date 6* cyclonic storms, 5* severe storms and 4 extremely severe storms equalling the record set in 1999 and 2019. There were 523* attributed fatalities and damage estimated at 2.47* billion USD. The increase here probably due to Severe Cyclonic Storm Michaung which approached the east coast of India on 4th December. India’s meteorological department issued a red alert for the region. Heavy rain and strong winds battered the coastal areas. Persistent rains caused widespread flooding and inundation in Chennai, the capital of Tamil Nadu. Rivers including Cooum and major lakes overflowed in Chennai causing further water logging in the low-lying areas along the banks. At least 17 people were killed, and more than 41,000 people were evacuated and temporarily relocated, including 32,158 in Tamil Nadu and 9,500 in Andhra Pradesh. Power supply was cut off by the government in flooded areas in Chennai as a preventive measure to avert electrocution.

2023/24 South Pacific cyclone season starts officially 1st November. First storm 19th October 2023. Two severe tropical cyclones to date with 2 fatalities but no damage estimate.

2023/24 Australian cyclone season starts officially 1st November. First storm 4th December – Jasper ongoing event major flooding in NE Australia / Cairns area. Known fatalities 1 no damage estimate yet. Record rainfall reported.

SW England storms and floods:

Wikipedia stated “conditions in early December resulted in 50 flood warnings across the UK. In Dorset, the River Frome flooded in the village of Stratton near Dorchester. The warnings spanned along the Jurassic Coast from Bridport to Chideock and Charmouth and also Dorchester, Maiden Newton and Beaminster. In Somerset, roads were flooded. The A358 road near Ilminster became unpassable in both directions.….”

BBC source: December 4th Somerset 67mm in 24 hours caused flooding of road network as well as some property flooding. 7th December Cornwall and Devon also affected by flooding and road closures and rail lone flooding near Exeter.

Named storms:

Storm Elin and Fergus occurred on the 9th and 10 December 2023 and detail can be found on the UK Storm page click here for pdf from UK Met Office

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

3. Recent Climatology

According to Copernicus Climate Change Service/ECMWF November 2023 was the warmest November on record globally, with an average surface air temperature of 14.22°C, which follows on from a record October.

Copernicus, European sourced temperature and rainfall anomalies for November 2023 and the 12 months to the end of November compared with the 30 year periods 1981-2010 (lower row) and 1991-2020 (upper row), are shown below:

UK: Autumn 2023.

Met Office provisional Temperature and Rainfall anomalies for 2023 September October and November are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period (right hand mini pictures) when comparing the images for example in September where anomalies are shown as a darker red when using the earlier 1961-1990, 30 year period as the base. Temperatures in most areas were above average for the three month period. October was unusually wet in Eastern areas of England and Scotland as well as parts of N Ireland making the season wet overall except for parts of W Scotland.

River flows and ground water levels in November 2023 can be found in the Hydrological Summary

Reservoir levels, according to SW Water, are above the long term average across SW England as of 17th December 2023.

The Global Flood Awareness System – GloFAS – forecast from December 1st 2023 to end of March 2024 shows a slightly enhanced flood risk across Southern England – does not cover flash flooding from for example thunderstorms.

SW England

December through to 18th had an average temperature ranging from around 9 C in the west and 7 C in the East. For many areas that was 1 to 2 Celsius above average. Rainfall was above average with many places already recording totals reaching the average for the whole month. Sunshine was probably near or a bit below average.

Example of changes to 30 year average. Teignmouth December (UKMO data) :

1981-2010: 9.8C 4.4C 3.6 60.4 102.9 12.7

1991-2020: 10.4C 4.6C 3.0 59.2 101.3 13.4

B: Forecast data:

1. Stratosphere:

The North polar vortex has established in the winter mode. GFS 19/06UTC December analysis at 10hPa is shown below along with forecast charts for the 23rd and 26th of December and 4th January 2024. The forecast chart show stratospheric warming moving over Canada and extending across the Atlantic. A few seasonal forecast models are hinting at a temperature change to colder types in late January or in February but this is by no means certain as not all stratospheric warming events lead to colder easterly types at the surface across Europe.

In the southern hemisphere the Ozone column minimum has been at record lows for the time of year as shown by the graphic below:

The stratospheric Southern Hemisphere Ozone “hole” is now filling.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2024 January, February and March. Hints at upper level ridging in February.

3. Lower Troposphere:

A selection of model solutions for January February and March 2024 using December data are shown below. The full set, including available graphics for Spring 2024 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

January to March 2024

Data from WMO:

Three month average anomaly followed by January February and March 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown is multi model anomaly probability charts except for CMCC which shows deterministic mean anomaly.

Individual members of the WMO super ensemble are shown below.

Spring 2024 WMO multi model chart can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output for UK area:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for Autumn, August 2023 data.

Observed data

Temperature. Above normal although Scotland near normal October and November (below normal compared to most recent 30 year average)

Rainfall. W Scotland normal or below normal elsewhere above normal. Wettest month October especially in E of UK.

Sunshine. Wales below normal elsewhere a little above normal

Pressure. below normal (SW)

Forecast data

Original Summary -180823 –

Temperature: Available models, apart from Russia (which tends to a little colder than other models), suggests above normal for the season and for each month although a few models suggest nearer normal in the south in September and more widely in November.
Rainfall: THREE Month summary: Uncertain mixture of solutions for the season based on some above and some below normal ending up near normal. Month to month data also lacks consistency but the strongest indication for above normal looks to be for western and southern areas of UK and Ireland. Normal or below normal perhaps more likely in the north. Month to month data hint at September having the highest change of being drier than average and October the higher chance of wetter than average. November Eire and western half of UK more likely to be wetter than average.

Comment: Temperature forecast for above normal good, September hint at nearer normal poor but OK for November. Rainfall good steer for the less wet areas and for the wetter months and good for above average overall away from the W Scotland.

Scoring attempts to state good, fair, poor or no signal.
Revised order
1. Russia (WMO): Temp poor. PPN poor.
2. USA – CFS2 : Temp good. PPN poor.
3. UKMO Contingency: Temp good. PPN poor.
4. UKMO : Temp good . PPN fair . PMSL good
5. USA – IRI : Temp good. PPN poor .
6. KMA APCC : Temp good. PPN good .
7. JMA : Temp good . PPN fair . PMSL
8. NMME : Temp good . PPN fair .
9. WMO multi : Temp good . PPN poor .
10. BCC : Temp good . PPN fair .
11. NASA : Temp good . PPN fair
12. CanSips : Temp good. PPN fair .
13. Copernicus Temp good. PPN fair PMSL poor
14. CMCC Temp good. PPN fair PMSL poor
15: DWD Temp good. PPN poor PMSL poor
16. EC Temp good. PPN poor PMSL poor
17 JMA Temp good. PPN poor PMSL poor
18 UKMO Temp good. PPN good. . PMSL good.
19. MF Temp good. PPN poor PMSL poor
20 NCEP Temp good. PPN poor PMSL fair
21 ECCC Temp: good. PPN fair PMSL fair

WMO low res data:
BoM Temp good. PPN fair. (Wetter OCT)
Can Temp good. PPN fair.
DWD Temp good. PPN poor.
KMA Temp good. PPN poor.
MOSC Temp poor. PPN poor.
WASH Temp good. PPN poor.
CMA Temp missing .
ECMWF Temp good. PPN poor.
UK Temp good. PPN good.
JMA Temp good. PPN poor.
MF Temp fair. PPN poor.
CMCC Temp good. PPN fair.
CPTEC Temp good. PPN poor.

D: Text Forecast for SW England

Remainder of Winter (January and February 2024)

January probably above average but bay turn near or below average late in the month and / or in February for a time before milder types return later in February (uncertain cold spell in an otherwise milder than average winter period. Rainfall average or above for the season but with a chance that February could see longer drier spells and Eastern parts of the region may have nearer normal values. Snow probably again below average in January but increasing risk of snow and ice for a time late January and/or in February which could lead to above average snowfall across the district, not just for the moors (uncertain and low confidence) .

January and February Climate: 1981-2010 average temperature values for lowland areas 7°C in the West and 5°C in the East similar for both months. Rainfall; January typically wetter than February. 1981-2010 January average 100-150 mm lowlands but over 200-300 mm over the Moors. February average 80-100mm for lowland areas, less in the east and a little more in the west. Moors over 150mm. Winter snow climatology less than 5 days lying snow over lowland areas 5 to 10 hills, say hills around 200 metre elevation – one in three years have no lying snow for lower ground

Spring 2024 (March April May) limited data.

Temperatures likely to be above average although small risk that March could start colder. Rainfall for SW England above average for the period but perhaps near average later on.

Summer 2024 (June July August) minimal data.

Temperature expected to mean about 1 degree C or so above climatology. Rainfall totals likely to be above average especially in August. Chance of drier July and near average June. Despite above average rain totals the number of “rain days” may not be above average.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. November 2023.

Published 18 November 2023

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of November. Areas around the UK, Europe, Mediterranean and the Baltic show 1 to 3 Celsius positive anomalies. Ocean anomalies along the equator show an established El Nino state in the Pacific . The extent of the cold anomaly to the west of North America is similar to values in October. Sea surface temperature for the extrapolar oceans (over 60°S–60°N) was the highest on record for October at 20.79°C.

October marked the sixth consecutive month that Antarctic sea ice extent remained at record low levels for the time of year, with a monthly value 11% below average. Sea ice concentrations were most below average in the northern Ross Sea and the South Atlantic sector, while above-average concentrations prevailed in the Bellingshausen Sea and the western Pacific sector.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through Winter 23/24 and into Spring 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so until Summer 2024. This may result in a record global average temperature for both 2023 and 2024.

Daily sea surface temperature (°C) averaged over the extra-polar global ocean (60°S–60°N) for 2015 (blue), 2016 (orange), 2022 (yellow), and 2023 (black line). All other years between 1979 and 2021 are shown with grey lines. The average conditions for 1991-2020 are shown by the dashed grey line. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

Global-mean and European-mean surface air temperature anomalies relative to 1991-2020 for all months from January 1979 to October 2023 with the darker coloured bars denoting the October values. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

Global-mean and European-mean surface air temperature anomalies relative to 1991-2020 for each October from 1979 to 2023. Data source: ERA5. Credit: Copernicus Climate Change Service/ECMWF.

Note: comparison using earlier 30 year reference show even larger anomalies

Atlantic Hurricane season 2023 has seen twenty tropical storm strength systems and seven hurricanes three of which were CAT 3 or stronger. Fatalities to date at least 15 with total damage estimate more than 3.09 billion USD. (Wikipedia). Atlantic tracks and timeline shown below. As of 18th November a depression designated 22L is producing heavy rain and flooding across parts of the Caribbean.

Timeline.

The East Pacific has had 10 hurricanes and over 60 known fatalities with estimated damage of 12.14 Billion USD. This is a big increase in deaths and damage largely due to Hurricane Otis which in around 24 hours changed from a weak tropical storm to an intense CAT 5 storm hitting Acapulco with very little warning on the 25th of October (UTC date). The storm was markedly under forecast with only a few hours warning given of such a severe event. The West Pacific has had 10 typhoons (4 super typhoons) 187 known fatalities and damage estimated at 17.3 Billion USD. Northern Indian Ocean to date 4 cyclonic storms, 4 severe storms and 3 extremely severe storms equalling the record set in 1999 and 2019. There were 493 attributed fatalities and damage estimated at 1.6 billion USD.

For the UK Storm Ciarán on the 1st and 2nd of November was an exceptionally severe storm for the time of year, bringing damaging winds across northern France and the Channel Islands which bore the brunt on the southern flank of the storm.

In the UK, the storm caused major transport disruption with the port of Dover temporarily closed
and ferry services cancelled more widely. The Met Office states that “Flights and rail services were also cancelled, with the Great Western Line closed both west of St Austell, Cornwall, and between Exeter and Taunton (Somerset). Many commuters were advised to work from home. Hundreds of schools were shut
and almost 150,000 homes were left without power.

Large waves battered the South Coast with several vehicles swept into the sea and a major incident declared in Hampshire and the Isle of Wight. Storm Ciarán exacerbated existing flooding problems with many rivers bursting their banks. At West Bay in Dorset, a section of cliff collapsed into the sea. In Surrey, storm Ciarán caused a power outage at three water treatment plants leaving thousands without a water supply”

Torro, the Tornado Research Organisation, confirmed that a Tornado of T7 strength (T0-T10 scale) made landfall at St Clement causing severe damage along its 8km track.

The North Atlantic Oscillation index (500hPa index shown below) became negative in mid September and is forecast remain neutral for the next few weeks. If westerlies are suppressed, as in the case of a negative NAO the temperature across Europe is more extreme suggesting colder temperature in winter across Europe. Blocked patterns are typical but depending where the high pressure block forms one can be in the high or in the associated slow moving low pressure zone. Neutral states are inconclusive

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Recent Climatology

According to Copernicus Climate Change Service/ECMWF. “October 2023 was the warmest October on record globally, with an average surface air temperature of 15.30°C, 0.85°C above the 1991-2020 average for October and 0.40°C above the temperature of the previous warmest October, in 2019. The global temperature anomaly for October 2023 was the second highest across all months in the ERA5 dataset, behind September 2023. The month as a whole was 1.7°C warmer than an estimate of the October average for 1850-1900, the designated pre-industrial reference period.

For the calendar year to date, January to October, the global mean temperature for 2023 is the highest on record, 1.43°C above the 1850-1900 pre-industrial average, and 0.10°C higher than the ten-month average for 2016, currently the warmest calendar year on record. For Europe, October 2023 was the fourth warmest October on record, 1.30°C higher than the 1991-2020 average. The average sea surface temperature for October over 60°S–60°N was 20.79°C, the highest on record for October. El Niño conditions continued to develop in the equatorial Pacific, although anomalies remain lower than those reached at this time of year during the development of the historically strong 1997 and 2015 events.”

SW England

November through to mid-month had average temperature around 10 Celsius which is 1 to 1.6 degrees Celsius above normal. Sunshine was slightly below average and rainfall well above average.

UK: last three months.

Met Office provisional Temperature and Rainfall anomalies for 2023 August September October are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period when comparing the image for September where anomalies are shown as a darker red when using the earlier 30 year period as the base. Temperatures in most areas were above average for the three month period. October was unusually wet in Eastern areas of England and Scotland as well as parts of N Ireland.

Copernicus, European sourced temperature and rainfall anomalies for October 2023 and the 12 months to the end of October compared with the 30 year periods 1981-2010 (left) and 1991-2020 (right), are shown below:

River flows and ground water levels in October 2023 can be found in the Hydrological Summary

Reservoir levels, according to SW Water are above the long term average across SW England as of 12th November 2023.

The Global Flood Awareness System – GloFAS – forecast from November 1st 2023 to end of February 2024 shows a “enhanced” flood risk across SW England – does not cover flash flooding from for example thunderstorms.

B: Forecast data:

1. Stratosphere:

The polar vortex has established in the winter mode. GFS 18/06UTC November analysis at 10hPa is shown below. Forecast chart for the 18th shows stratospheric warming moving towards Canada but it is too early to say what effect this might have on the vortex.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2023 December, January and February 2024. Hints at strong jet flow hence more mobility especially in January but more ridging in December and February at least in the CFS2 model.

. Lower Troposphere:

A selection of model solutions for 2023 December, January and February 2024 using November data are shown below. The full set, including available graphics for Winter 2023/24 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

December 2023 to Feruary 2024

NASA not available / delayed on normal website

Data from WMO:

Three month average anomaly followed by 2023 December, January and February 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution.

Data shown in multi model anomaly probability charts.

Individual members of the WMO super ensemble are shown below.

NCEP USA

Spring 2024 WMO multi model chart can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast for August to October, July 2023 data.

Observed data

Temperature. Above average for three month period although August neaer averag on recent 30 year data above for 1961-1990 data period.

Rainfall. near or above average

Sunshine. near or below average

Pressure. below average (SW)

Forecast data

Original Summary – 180723
Strong indication for above average temperatures for the three months and for each month (typical 1 C anomaly). Rainfall forecast very messy, normal or above normal more likely in Ireland and western UK and perhaps also some northern areas. (Below average forecast being offset by above average forecast leading to normal but looks like there are more above average solutions.)

Comment: Temperature anomalies above average but perhaps slightly lower than actually occured. Rainfall above average for most areas although parts of W Scotland could be near average

NMME had some idea of wetter October as did KMA and CMA

Scoring will attempt to state good, fair, poor or no signal.
Revised order
1. Russia : Temp good. PPN poor .
2. USA – CFS2 : Temp good. PPN poor .
3. UKMO Contingency: Temp good. PPN fair .
4. UKMO : Temp good. PPN fair . PMSL fair
5. USA – IRI : Temp good. PPN poor .
6. KMA APCC : Temp good. PPN poor .
7. JMA : Temp good. PPN fair . PMSL good
8. NMME : Temp good. PPN good .
9. WMO multi : Temp good. PPN poor .
10. BCC : MISSING
11. NASA : MISSING .
12. CanSips : Temp good. PPN fair .
13. Copernicus Temp good. PPN poor . PMSL poor
14. CMCC Temp good . PPN poor . PMSL poor
15: DWD Temp good . PPN poor . PMSL poor
16. EC Temp good . PPN fair . PMSL poor
17 JMA Temp good . PPN poor . PMSL poor
18 UKMO Temp good . PPN poor . PMSL poor
19. MF Temp good . PPN poor . PMSL poor
20 NCEP Temp good . PPN poor. PMSL poor
21 ECCC Temp: good . PPN poor . PMSL fair

WMO low res data:
BoM Temp good. PPN poor.
Can Temp good. PPN fair.
DWD Temp good. PPN poor.
KMA Temp good. PPN fair .
MOSC Temp good. PPN poor .
WASH Temp good. PPN poor.
CMA Temp MISSING
ECMWF Temp good. PPN poor .
UK Temp good. PPN poor .
JMA Temp good. PPN poor
MF Temp good. PPN poor .
CMCC Temp good. PPN poor .
CPTEC Temp good. PPN poor.

D: Text Forecast for SW England

Winter (December 2023 January and February 2024)

Milder than normal winter overall although a few models suggest a colder spell in December and February values may be nearer average. Rainfall average or above for the season but with a chance that February could see longer drier spells and Eastern parts of the region may have nearer normal values. Snow probably again below average so any accumulations more likely to be across the moors although slightly increased risk compared to average for snow in February, which is similar to last months forecast.

Spring 2024 (March April May) limited data.

Temperatures likely to be above average although some hints at a less mild May. Rainfall for SW England above average especially in first half of period, perhaps near average later on.

Autumn 2023 (September October November) minimal data

Above average temperature. Below average rainfall early in Autumn then wetter except perhaps in the north.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. October 2023.

Published 17 October 2023

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies across the North Atlantic remain warmer than climatology for the middle of October. Areas around the UK, western Europe, western Mediterranean and the Baltic show 1 to 4 Celsius anomalies. Ocean anomalies along the equator show an established El Nino state. The extent of the cold anomaly to the west of North America is similar to values in September.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through Winter 23/24 and into Spring 2024. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so until Summer 2024. This may result in a higher global average temperature for 2023 and 2024 and there are suggestions that over the next few years the global temperature average will set further new records.

The effects of the El-Nino may be difficult to predict due to the excessive heat in water around coastal western Europe. A statistical link between El-Nino and rainfall suggests near normal rainfall for the winter 2023/2024, the higher probs being in eastern areas but warmer air holds more moisture so this link may be unreliable.

According to Samantha Burgess, Deputy Director of the European Copernicus C3S stated: “The unprecedented temperatures for the time of year observed in September – following a record summer – have broken records by an extraordinary amount. This extreme month has pushed 2023 into the dubious honour of first place – on track to be the warmest year and around 1.4°C above preindustrial average temperatures…..”

In Europe, September 2023 was the warmest September on record by an even larger anomaly – 2.51°C above the 1991-2020 average and 1.1°C higher than 2020, the previous warmest September in the region.
The global average sea surface temperature over the extra-polar oceans was also the warmest on record for September, at 20.92°C, and the second warmest for any month, only behind August 2023, while El Niño conditions continued to develop over the equatorial Pacific.

Note using earlier 30 year reference periods would show even larger anomalies.

Atlantic Hurricane season 2023 has seen nineteen tropical storm strength systems and six hurricanes three of which were CAT 3 or stronger. Fatalities to date at least 15 with total damage estimate 2.59 billion USD. (Wikipedia). Atlantic tracks and timeline shown below.

The East Pacific has had 8 hurricanes but only 6 known fatalities with estimated damage of 614.7 million USD. The West Pacific has had 10 typhoons (4 super typhoons) 187 known fatalities and damage estimated at 17.3 Billion USD. Northern Indian Ocean to date 3 cyclonic storms, 2 severe to extremely severe storms, with 480 attributed fatalities and damage estimated at 1.6 billion USD.

On the 17th Met Office named storm Babet to the SW of the UK is expected to bring heavy rain and strong winds to many areas as the storm moves north over the UK. Met office yellow and amber rain warnings have been issued for the N and E of the UK. Image below 17/0300UTC with rain total estimate to 17/06UTC, 17/0001UTC GFS track and ECMWF ensemble track of the low centre.

The North Atlantic Oscillation index (500hPa index shown below) became negative in mid September and is forecast remain neutral or negative through to the end of October. If westerlies are suppressed, as in the case of a negative NAO the temperature across Europe is more extreme in summer leading to heat waves and colder temperature in winter across Europe. Blocked patterns are typical but depending where the high pressure block forms one can be in the high or in the associated slow moving low pressure zone.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Recent Climatology

Following the global hottest ever June, Nasa announced that July 2023 had the highest global temperature recorded for that month since 1880. It was also the warmest month on record. In the UK however July was wet with nearer normal temperatures. August 2023 ranks as the second warmest month ever recorded in the European C3S ERA5 reanalysis dataset by a large margin, after July 2023. In Europe, September 2023 was the warmest September on record across Europe and in the UK it was the joint warmest September on record in a series which goes back to 1884 according to provisional Met Office statistics. England and Wales had their respective warmest September on record according to mean temperature values.

October started very warm and across southern Europe it was dry too..

NOAA temperature anomaly 1st to 7th October 2023 and total rainfall

SW England

October through to mid-month had average temperature 14 to 15 Celsius about 2 degrees above normal. Sunshine was above average and rainfall below average. However from the 15th cold east to southeast winds brought the temperature below average.

UK: last three months.

Met Office provisional Temperature and Rainfall anomalies for 2023 July August September are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period when comparing the image for July where anomalies are shown as negative when compared to the newer thirty year period. Temperatures in most areas were above average for the three month period. Due to the wet July rainfall ended up near or above average in many places but below average for the three month period in SE England. Changes in rainfall are less clear cut but suggest slightly higher rainfall in the most recent 30 year average.

Copernicus, European sourced temperature and rainfall anomalies for September 2023 and the 12 months to the end of September compared with the 30 year periods 1981-2010 (left) and 1991-2020 (right), are shown below:

River flows and ground water levels in September 2023 can be found in the Hydrological Summary

River flows across SW England were average or above average in September 2023. River flow data for the 13th October from the UK Water Resources Portal shows mostly normal or above normal flows.

Reservoir levels, according to SW Water are above the long term average across SW England as of 8th October 2023.

The Global Flood Awareness System – GloFAS – forecast from October 1st 2023 to end of January 2024 shows a “normal” flood risk across SW England – does not cover flash flooding from for example thunderstorms.

B: Forecast data:

1. Stratosphere:

The polar vortex is establishing as it moves towards winter mode. GFS 17/0001UTC October analysis at 10hPa is shown below.

In the Southern Hemisphere observations from the European Space Agency’s (ESA) Copernicus Sentinel-5P satellite indicate the ozone hole reached approximately 10 million square miles (26 million square kilometers) in area on Sept. 16, 2023 — making it one of the largest seasonal holes ever observed. The true largest ozone hole maximum occurred in 2000.

Image below is 16 October 2023

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for 2023 November December and January 2024. Hints at strong jet flow hence more mobility especially in CFSv2 for December and January

3. Lower Troposphere:

A selection of model solutions for 2023 November December and January 2024 using October data are shown below. The full set, including available graphics for Winter 2023/24 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

November 2023 to January 2024

Data from WMO:

Three month average anomaly followed by 2023 November December and January 2024. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution. Note rainfall anomalies show cancellation between wetter and drier solutions in some of the multi model ensembles.

Data shown in multi model deterministic anomaly (probability charts not available)

Individual members of the WMO super ensemble are shown below.

CPTEC Brazil

Winter 2023/24 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.
Review of details looked for in seasonal forecast for July to September

Observed data

Temperature. Above average for three month period due to very warm September. Looking for trend from near average to above average in forecast

Rainfall. Above average for three month period due to very wet July and locally wet other months. Note parts of the East Midlands, far NE Scotland and E/SE England may be below normal or normal.

Sunshine. Below average for three month period despite a sunnier (in places) September.

Pressure. Below normal overall for three month period

Forecast data

Original Summary – 19June23.

Temperature: A few models suggest eastern areas of the UK could be nearer normal in September, otherwise all models suggest above or well above average values for the three month period and each month.
Rainfall: Mixed signals with wetter/drier solutions cancelling each other in the multi model ensembles. Overall suggestion of normal or above rainfall totals, more especially in western areas. Fairly strong indication of some longer drier spells with S and E most likely to be drier. Totals could easily be higher due to higher temperature and increased thundery activity but still with same or even lower number of dry days compared to average.
Comment: Temperature overall signal for above average correct for the 1961-1990 climate period but less of a different for more recent 30year period due to being closer to the period. Rainfall distorted due to wet July hence above average then a rather messy picture for August and September. Overall signal for normal or above normal was ok and the hint of drier in some S and E parts.

Scoring will attempt to state good, fair, poor or no signal.
Temperature will be marked good if signal for a much warmer sept and fair if above average overall. Rainfall good if wet July and hint of normal or below in N Scotland and E England, otherwise fair for above average overall.
1. Russia (WMO): Temp fair. PPN fair.
2. USA – CFS2 : Temp fair. PPN fair.
3. UKMO Contingency: Temp fair. PPN poor. Monthly data not sampled.
4. UKMO : Temp fair. PPN fair. PMSL fair
5. USA – IRI : Temp fair. PPN poor. Monthly data not sampled.
6. KMA APCC : Temp fair. PPN fair.
7. JMA : Temp fair. PPN poor. PMSL poor
8. NMME : Temp fair. PPN fair.
9. WMO multi : Temp fair. PPN poor.
10. BCC : Temp fair. PPN poor.
11. NASA : Temp good. PPN good.
12. CanSips : Temp fair. PPN poor.
13. Copernicus Temp good. PPN poor. Monthly data not sampled for remainder good = above normal.
14. CMCC Temp good. PPN good.
15: DWD Temp good. PPN poor.
16. EC Temp good. PPN fair.
17 JMA Temp good. PPN fair.
18 UKMO Temp good. PPN poor.
19. MF Temp good. PPN poor.
20 NCEP Temp good. PPN fair.
21 ECCC Temp: good. PPN fair.

WMO low res data: Three month period only
BoM Temp good. PPN fair.
Can Temp good. PPN poor.
DWD Temp good. PPN poor.
KMA Temp good. PPN good.
MOSC Temp good. PPN poor .
WASH Temp good. PPN fair.
CMA Temp good. PPN poor.
ECMWF Temp good. PPN poor.
UK Temp good. PPN poor.
JMA Temp good. PPN fair.
MF Temp good. PPN poor.
CMCC Temp good. PPN fair.
CPTEC Temp good. PPN fair.

D: Text Forecast for SW England

Remainder of Autumn 2023 (November)

Temperature: A milder than average November is most likely, consistent across models with anomalies of around 0.5 to 1 C.

Rainfall: November likely to be wetter than average although a few models suggest near normal values.

Autumn climate: 1981 to 2010 average mean temperature 11 or 12°C but nearer 10°C in rural areas. Maximum temperatures average 14 to 16°C. November normally colder than October. Average 1981 to 2010 rain 300 to 400mm, 600 to 800mm over the moors but east of the moors and in lowland Somerset more like 200 to 300mmAutumn climate: 1981 to 2010 average mean temperature 11 or 12°C but nearer 10°C in rural areas. Maximum temperatures average 14 to 16°C. November average around 9 or 10 Celsius. Average 1981 to 2010 rain 300 to 400mm, 600 to 800mm over the moors but east of the moors and in lowland Somerset more like 200 to 300mm. November totals range from around 80mm east of the moors to over 200mm over the moors..

Winter (December 2023 January and February 2024)

Milder than normal winter overall although February may be nearer average. Rainfall average or above for the season but with a chance that February could see longer drier spells and Eastern parts of the region may have nearer normal values. Snow probably again below average so any accumulations more likely to be across the moors although slightly increased risk compared to average for snow in February.

Spring 2024 (March April May) limited data.

Temperatures likely to be above average although some hints at a less mild May. Rainfall for SW England above average though perhaps near or below average in May.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. September 2023.

Published 19 September 2023

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies in most of the North Atlantic remain warmer than climatology for the middle of August. Areas around the UK, western Europe, western Mediterranean and the Baltic show 1 to 3 Celsius anomalies. Cold paths in the Atlantic due to recent hurricane activity, the larger area due to Hurricane Lee. Colder area in the Med off Libya due to storm Daniel.

Ocean anomalies along the equator show an established El Nino state. The extent of the cold anomaly to the west of North America is similar to values in August.

Atlantic Hurricane season 2023 has seen fifteen tropical storm strength systems and six hurricanes three of which were CAT 3 or stronger. Fatalities to date at least 14 with total damage estimate 2.29 billion USD. (Wikipedia). Atlantic tracks and timeline shown below.

The East Pacific has had seven hurricanes but only thee known fatalities. The West Pacific has had 8 typhoons (3 super typhoons) 167 known fatalities and damage estimated at 15.8 Billion USD.

Indian Ocean to date 3 cyclonic storms, 2 severe to extremely severe storms, with 480 attributed fatalities and damage estimated at 1.6 billion USD.

The recent storm in the Med (Daniel) which affected Greece, parts of Türkiye and later contributed to the disaster in Libya has resulted in 2023 being the costliest European windstorm season on record. Greece, Bulgaria, Turkey, 15 deaths. Libya, at least 11,300 people have died and another 10,100 are missing from the coastal city of Derna. An estimated 170 people have been killed as a result of the flooding elsewhere in the country.

Below: 10/0300UTC sat image, 24 hour rainfall estimate map to 10th 0600UTC and multi model forecast rain accumulation to 11th 1200UTC.

Below: Sat image 11/0300UTC and 24 hour rainfall map to 11th 0600UTC showing estimates of over 200mm accumulation.

The Tropical Atlantic sea temperature anomalies are warmer than average and are forecast to maintain positive anomalies through Winter 23/24. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so until Spring 2024. This may result in a higher global average temperature for 2023 and 2024 and there are suggestions that over the next few years the global temperature average will set further new records.

The North Atlantic Oscillation index (500hPa index shown below) became negative in mid September and is forecast remain neutral or negative for the next few weeks. If westerlies are suppressed, as in the case of a negative NAO the temperature across Europe is more extreme in summer leading to heat waves and colder temperature in winter across Europe.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Recent Climatology

SW England

Up until mid month September 2023 was sunnier, very much warmer and drier than average. Although there were thunderstorms on the night of the 9/10th the storms of the early hours of the 17th and those later in the day were of a different order. Rainfall became extremely heavy with 35mm to 90mm falling in a short space of time leading to significant flooding in parts of the SW, especially South Devon.

RADAR image 17/0200UTC and 1230UTC

The river gauge in Dawlish shows how quickly river levels rose. It should be noted that this was not a record level. The record level back in 2012 was associated with days of heavy rain rather than short period violent rainfall.

UK:

Met Office provisional Temperature and Rainfall anomalies for 2023 June July August and then combined summer period, are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period when comparing the image for July where anomalies are shown as negative when compared to the newer thirty year period. Temperatures in most areas were above average. Due to the wet July rainfall ended up near or above average in many places but below average for the three months in SE England, parts of Wales and Scotland. Changes in rainfall are less clear cut but suggest slightly higher rainfall in the most recent 30 year average.

Copernicus, European sourced temperature and rainfall anomalies for August 2023 and the 12 months to the end of August compared with the 30 year period 1991-2020, are shown below:

River flows and ground water levels in August 2023 can be found in the Hydrological Summary

River flows across SW England were average or above in August 2023. River flow data for the 18th September from the UK Water Resources Portal shows mostly normal flows but the blue dots east of Exeter are due to the recent heavy rain.

Reservoir levels, according to SW Water are above the long term average across SW England as of 10th September 2023. The long standing hosepipe bans remain in force across Cornwall and much of Devon until the 25th September when all restrictions are due to be lifted according the SW Water.

The Global Flood Awareness System – GloFAS – forecast from September 1st to end of December 2023 shows a “normal” flood risk across SW England – does not cover flash flooding from for example thunderstorms.

B: Forecast data:

1. Stratosphere:

The polar vortex remains in summer mode as shown by the GFS 18/0001UTC analysis at 10hPa

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for October November December 2023. Hints at strong jet flow hence more mobility especially in CFSv2 for December

3. Lower Troposphere:

A selection of model solutions for October November December 2023 using September data are shown below. The full set, including available graphics for Winter 2023/24 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

October to December 2023

Data from WMO:

Three month average anomaly followed by October November December 2023. Top row temperature anomaly and lower row precipitation anomaly.

Data shown in multi model deterministic anomaly (probability charts not available)

Individual members of the WMO super ensemble are shown below.

WMO super ensemble for Winter 2023/24

C: Comparing previous output:

Observed data

Temperature.
Summer overall above average thanks mainly to June with July and August mostly near average or slightly above.

Rainfall. Most areas wetter than average summer except for NE Scotland and parts of E of England. Main thing to look for is drier June and wetter July with nearer normal August.

Sunshine. Summer near average, local indications for Teignbridge suggest below average.

Pressure. Below average (WSW)

Forecast data

Original Summary – Summary – 190523
Overwhelming indication for above average temperatures for the season and each month although some models suggest Scotland could be nearer normal and some models hint at nearer normal values in June which looks unlikely. Rainfall very little consistency month to month except for Scotland where normal or below normal rainfall seems most likely. Elsewhere for the season hints at above normal in places but uncertain as to whether this is more wet days or just shorter spells of heavier rain with fewer wet days compared to average. Suggestion of E/SE being more likely to be below normal but unreliable.
Pressure more likely to be above average in the north with risk of below average in the south. 200hPa anomalies suggest drier start to season and possibly wetter end (thundery showers).

Comment: Overall signal for above average summer temperature was good but month to month detail unreliable. Hints at less wet in parts of E/SE England and parts of Scotland were OK as was the overall indication for above average rainfall. Teignbridge indications show there were more dry days than average despite above average rainfall but elsewhere in SW England there looks to have been fewer dry than average.

Scoring will attempt to state good, fair, poor or no signal for the three month period as a whole.
Revised order
1. Russia (WMO): Temp good. PPN poor.
2. USA – CFS2 : Temp good. PPN fair but reasonable sequence.
3. UKMO Contingency: Temp good. PPN fair.
4. UKMO : Temp good. PPN poor. PMSL poor
5. USA – IRI : Temp fair. PPN no signal .
6. KMA APCC : Temp missing
7. JMA : Temp good. PPN fair. PMSL fair
8. NMME : Temp good. PPN fair.
9. WMO multi : Temp good. PPN poor.
10. BCC : Temp good. PPN poor.
11. NASA : Temp good. PPN poor.
12. CanSips : Temp good. PPN poor.
13. Copernicus Temp good. PPN poor. PMSL poor
14. CMCC Temp good. PPN poor. PMSL poor
15: DWD Temp good. PPN poor. PMSL poor
16. EC Temp good. PPN poor. PMSL
17 JMA Temp good. PPN good. PMSL good
18 UKMO Temp good. PPN poor. PMSL poor
19. MF Temp good. PPN poor. PMSL poor
20 NCEP Temp good. PPN poor. PMSL poor
21 ECCC Temp fair. PPN good. PMSL good

WMO low res data:
BoM Temp good. PPN poor.
Can Temp good. PPN poor..
DWD Temp good. PPN poor.
KMA Temp good. PPN poor.
MOSC Temp good. PPN poor.
WASH Temp good. PPN fair.
CMA Temp good. PPN poor.
ECMWF Temp good. PPN poor.
UK Temp Missing.
JMA Temp good. PPN fair.
MF Temp good. PPN poor.
CMCC Temp good. PPN poor.
CPTEC Temp good. PPN poor.

D: Text Forecast for SW England

Remainder of Autumn 2023 (October November)

Temperature: A milder than average period is most likely, consistent across models. Each month likely to be above average with anomalies of around 1 C.

Rainfall: October and November likely to be wetter than average although some models suggest near normal values for October.

Winter (December 2023 January and February 2024)

Spring 2024 (March April May) limited data.

Temperatures likely to be above average although some hints at a colder May but mainly in the north of UK. Rainfall for SW England above average though perhaps near average in May.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. August 2023.

Published 18 August 2023 delayed due technical issues until 24 August 2023

A: Overview

1. Influences.

Changes in sea temperature

Ocean anomalies along the equator show an established El Nino state. The extent of the cold anomaly to the west of North America has markedly decreased in size.

Atlantic Hurricane season 2023 has seen nine tropical storm strength systems but only one hurricane and only one known fatality. The East Pacific has had six hurricanes and five known fatalities. The west Pacific has had 6 typhoons (2 super typhoons) 163 known fatalities and damage estimated at 15.6 Billion USD.

Time line to late August shown below (Wikipedia).

Potential new developments as stated by NOAA on the 18th August.

The Tropical Atlantic sea temperature anomalies are warmer than average having exceeded the forecast issued in June. Sea temperature in the tropical region are forecast to maintain positive anomalies through Winter 23/24. (see Met Office graphic below).

Tropical Pacific Sea Surface Temperatures (Nino3.4) are in an El Nino state and forecast to remain so into 2024. This may result in a higher global average temperature for 2023 and 2024 and there are suggestions that over the next few years the global temperature average will set further new records.

The effects of the El-Nino may be difficult to predict due to the excessive heat in water around coastal western Europe. A statistical link between El-Nino and rainfall suggests a slightly increased probability for a wetter than average autumn.

The North Atlantic Oscillation index (500hPa index shown below) became negative in early July through to mid August and is forecast to remain neutral or negative for the next few weeks. If westerlies are suppressed, as in the case of a negative NAO the temperature across Europe is more extreme in summer leading to heat waves which in 2023 has led to record high temperatures across many parts of Europe.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Recent Climatology

There have been two named storms in August so far.

SW England

August to the 18th has been rather mixed with near average temperature (17 C) slightly above average rainfall and near or a little below average sunshine.

UK:

Met Office provisional Temperature and Rainfall anomalies for 2023 May June July are shown below. You can see the effect of an increase in average temperatures in the 1991 to 2020 period when comparing the image for July where anomalies are shown as negative when compared to the newer thirty year period. Temperatures in most areas were above average. Due to the wet July rainfall ended up near or above average in many places but below average for the three months in SE England, parts of Wales and Scotland. Changes in rainfall are less clear cut but suggest slightly higher rainfall in the most recent 30 year average.

Copernicus, European sourced temperature and rainfall anomalies for July 2023 and the 12 months to the end of July compared with the 30 year period 1991-2020, are shown below:

K River flows and ground water levels in July 2023 can be found in the Hydrological Summary

River flows across SW England were average or above in July 2023. River flow data for the 13th August from the UK Water Resources Portal shows mostly above normal flows.

Reservoir levels, according to SW Water are above the long term average across SW England as of 13th August 2023. Despite this hosepipe bans remain in force across Cornwall and much of Devon.

The Global Flood Awareness System – GloFAS – forecast from August 1st to end of November 2023 shows a “normal” flood risk across SW England – does not cover flash flooding from for example thunderstorms.

B: Forecast data:

1. Stratosphere:

The polar vortex remains in summer mode as shown by the GFS 17/1200UTC analysis at 10hPa

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle row) and NMME anomaly (lower row) for September October November 2023.

3. Lower Troposphere:

A selection of model solutions for Autumn 2023 using August data are shown below. The full set, including available graphics for Winter 2023 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

September to November 2023

Data from WMO:

Three month average anomaly followed by September October November 2023. Top row temperature anomaly and lower row precipitation anomaly.

Individual members of the WMO super ensemble are shown below (Beijing China missing)

WMO super ensemble for Winter 2023/24

C: Comparing previous output:

May to July 2023 – based on April 2023 data.

NOTE: 30 year period 1981-2010 no longer available from UKMO web site now using newer 30 year period 1991 to 2020 which has higher temperature averages. 1961-1990 shown for comparison.

Review of details looked for in seasonal forecast.

Observed data

Temperature. Despite a cooler/near average July values were above average for season.

Rainfall. Difficult to fully quantify but looks like the wet July more than offset the previous drier months in some places. More clear cut in the 1961-1990 averages. Scotland and Wales below average but England and N Ireland above. Did models suggest wet July?

Sunshine. Above average sunshine for the three months despite cloudier July.

Pressure. Three month average above normal but July was well below normal

Forecast data

Original Summary – 18April2023
Consistent forecast for above normal temperature but hints at nearer normal in May and strong signal for above normal in June and / or July. Rainfall forecast rather messy with wetter models cancelling drier output. Hint at wetter than average or normal but with slightly stronger signal for drier than average in the south in June.
Notes: 1: Large scale blocking with easterly types seem to only be forecastable about two weeks ahead.

Comment on summary: Signal for warmer June good not so clear for July, overall above average good signal. Rainfall overall above average good as was drier June in south.

Scoring will attempt to state good, fair, poor or no signal.
SCORE based on THREE MONTH AVERAGE
1. Russia (WMO): Temp fair . PPN fair .
2. USA – CFS2 : Temp good . PPN fair .
3. UKMO Contingency: Temp fair . PPN fair .
4. UKMO : Temp good . PPN good . PMSL fair
5. USA – IRI : Temp fair . PPN poor .
6. KMA APCC : Temp good . PPN poor .
7. JMA : Temp good . PPN poor . PMSL poor
8. NMME : Temp good . PPN poor .
9. WMO multi : Temp good . PPN fair .
10. BCC : Temp good . PPN poor.
11. NASA : Temp good . PPN fair.
12. CanSips : Temp good . PPN poor.
13. Copernicus Temp good . PPN fair. PMSL fair
14. CMCC Temp good . PPN poor . PMSL good
15: DWD Temp good . PPN poor . PMSL good
16. EC Temp good . PPN poor . PMSL good
17 JMA Temp good . PPN poor . PMSL good
18 UKMO Temp good . PPN good . PMSL fair
19. MF Temp good . PPN poor . PMSL fair
20 NCEP Temp good . PPN poor . PMSL good
21 ECCC Temp: fair . PPN fair. PMSL fair

Only Canada got the monthly sequence best for temperature but perhaps a little cool.
WMO low res data:
BoM Temp GOOD . PPN poor.
Can Temp GOOD . PPN fair.
DWD Temp GOOD . PPN poor.
KMA Temp GOOD . PPN fair.
MOSC Temp poor . PPN fair .
WASH Temp GOOD . PPN fair .
CMA Temp GOOD . PPN good .
ECMWF Temp GOOD . PPN poor .
UK Temp GOOD . PPN good .
JMA Temp GOOD . PPN poor
MF Temp GOOD . PPN fair .
CMCC Temp GOOD . PPN poor .
CPTEC Temp poor . PPN fair.

D: Text Forecast for SW England

Autumn 2023 (September October November)

Temperature: A milder than average Autumn is most likely, consistent across models.

Rainfall: Probably wetter than average for the season. Month to month detail unreliable but hints at a drier start and wetter end to the season can still be found.

Winter (December 2023 January and February 2024)

Milder than normal winter overall although February may be colder than average. Rainfall average or above for the season but with a chance that December and / or February could see longer drier spells which is consistent with July data. Snow probably again below average so any accumulations more likely to be across the moors.

Winter Climate: 1981-2010 average temperature values for lowland areas 7°C in the West and 5°C in the East. Rainfall; Dec and Jan typically wetter than February. 1981-2010 Autumn average 300-400 mm lowlands but 200-300 mm areas to E of Dartmoor. Snow climatology less than 5 days lying snow over lowland areas 5 to 10 hills, say hills around 200 metre elevation – one in three years have no lying snow.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

Climate review and Experimental Long Range Forecast for SW England. July 2023.

Published 19 July 2023.

A: Overview

1. Influences.

Changes in sea temperature

Sea temperature anomalies in most of the North Atlantic remain warmer than climatology for the middle of July. Areas around the UK, western Europe, western Mediterranean and the Baltic show 1 to 3 Celsius anomalies with the Mediterranean area 3 to 5 Celsius above average.

Ocean anomalies along the equator show an established El Nino state. The extent of the cold anomaly to the west of North America has again increased in size a little.

(Error in June edition spell checker changed to Adriatic should read read Arabian Sea)

Atlantic Hurricane season 2023 has seen some tropical storm strength systems but not a full hurricane. (Wikipedia)

Western Pacific and Indian Ocean tracks are shown below along with the time line.

According to Wikipedia Northern Indian Ocean storms have contributed to 480 fatalities and a cost of 1.5 Billion US dollars. Western Pacific storms have led to 11 fatalities and a cost of $137million although it is too early to assess the effects of the recent storm Talim which produced some damage and flooding in southern China.

The effects of the El-Nino may be difficult to predict due to the excessive heat in water around coastal western Europe.

The North Atlantic Oscillation index (500hPa index shown below) became negative in early July and are forecast to turn to neutral state over the next few weeks. Affects on the UK area are inconclusive for a neutral state.

See https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

2. Recent Climatology

See wiki pages with regards to heat waves:

https://en.wikipedia.org/wiki/2023_European_heat_waves

https://en.wikipedia.org/wiki/2023_heat_waves

In addition to a record breaking June there have been a lot of new all time temperatures records broken in July across parts of southern USA and Southern Europe as well as in Asia.

SW England

July to 17th 2023, has been cool than of late although temperatures have still been marginally above average. Rainfall has largely reached or exceeded the full month total and sunshine looks to be slightly below average to mid month.

UK:

Met Office provisional Temperature and Rainfall anomalies for 2023 April May June are shown below. Temperatures in most areas were above average. Rainfall was above average. in most places hence it is shocker that hosepipe bans are require although there has been climate data showing increased run off rather than retention of water in the soils.

Due to the ongoing rise in temperatures over the last 60 years, 30 year averages used for comparisons have increased hence what appears to be average as in April 2023 when using to 1991 to 2020 values would have been above average using the 1961 to 1990 values. Changes in rainfall are less clear cut but suggest slightly higher rainfall in the most recent 30 year average.

Copernicus, European sourced temperature and rainfall anomalies for June 2023 and the 12 months to the end of June compared with the 30 year period 1991-2020, are shown below:

UK River flows and ground water levels in June 2023 can be found in the Hydrological Summary

River flows across SW England were below average in June 2023. River flow data for the 14th July from the UK Water Resources Portal shows mostly above normal flows following the recent wet weather although North Devon and North Cornwall seem to have nearer normal flows

Reservoir levels, according to SW Water are approaching the long term average across SW England as of 16th July 2023. Despite this hosepipe bans remain in force across Cornwall and much of Devon.

The Global Flood Awareness System – GloFAS – forecast from July 1st to end of October 2023 shows a “normal” flood risk across SW England – does not cover flash flooding from for example thunderstorms.

B: Forecast data:

1. Stratosphere:

The polar vortex remains in summer mode as shown by the GFS 19/1200UTC analysis at 10hPa

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (lower row) for August September October 2023.

3. Lower Troposphere:

A selection of model solutions for August to October 2023 using July data are shown below. The full set, including available graphics for Autumn 2023 can be found at https://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly. Lower row precipitation anomaly

August to October 2023

CFSv2 E3 data (below)

NMME data (below)

ECMWF (below)

NASA (below)

Data from WMO:

Three month average anomaly followed by August September October 2023. Top row temperature anomaly and lower row precipitation anomaly.

WMO super ensemble (below) is a mean of data supplied by National Meteorological organisations across the globe. Because of the amount of data the output is a low resolution. Note rainfall anomalies show marked cancellation between wetter and drier solutions in some of the multi model ensembles. Due to problems with the host web site WMO means are shown rather than the probability charts.

Individual members of the WMO super ensemble are shown below (Beijing China missing)

C: Comparing previous output:

April to June 2023 – based on March 2023 data.

Observed data.

Temperature: above average for season.

Rainfall: mostly below average for season although April was wetter in places and a few places may have been near average overall.

Sunshine: above average all of UK due to sunny June

Pressure: above average for season and each month

Original Summary – 190323 Temperature: for the three month period above average most likely. Most models suggest slighly larger anomalies for the second half of the period with a chance of near normal values early in the forecast period, perhaps more especially in the south. Rainfall: Overall near normal for the period. Some hints at above average early in period and below average later. Lots of uncertainty but slightly more models have drier rather than wetter June. Pressure: near normal with hint at above normal. Caution: 1: Large scale blocking with easterly types seem to only be forecastable about two weeks ahead.

Comment on summary: Good temperature forecast and trend through season, only fair for location of near average early in season.
Rainfall signal for drier June was good as was wetter start to season. Overall forecast of near normal less good. Indication for above average pressure was good.
Scoring will attempt to state good, fair, poor or no signal.
Revised order
1. Russia (WMO): Temp fair . PPN fair .
2. USA – CFS2 : Temp good . PPN fair .
3. UKMO Contingency: Temp good . PPN good .
4. UKMO : Temp good . PPN good . PMSL good
5. USA – IRI : Temp fair . PPN poor .
6. KMA APCC : Temp missing . PPN missing .
7. JMA : Temp good . PPN fair . PMSL good
8. NMME : Temp good . PPN fair .
9. WMO multi : Temp good . PPN poor .
10. BCC : Temp good . PPN poor .
11. NASA : Temp good . PPN poor .
12. CanSips : Temp fair . PPN fair .
13. Copernicus Temp fair . PPN fair . PMSL poor
14. CMCC Temp good . PPN fair . PMSL poor
15: DWD Temp good . PPN fair . PMSL poor
16. EC Temp good . PPN fair . PMSL fair
17 JMA Temp good . PPN fair . PMSL poor
18 UKMO Temp good . PPN fair . PMSL fair
19. MF Temp good . PPN fair . PMSL poor
20 NCEP Temp good . PPN fair . PMSL poor
21 ECCC Temp: good . PPN fair . PMSL poor

ECMWF mnthely graphics good signal for drier June but not widespread enough.

WMO low res data:
BoM Temp fair . PPN fair .
Can Temp fair . PPN poor .
DWD Temp fair . PPN fair .
KMA Temp good . PPN fair .
MOSC Temp poor . PPN poor .
WASH Temp good . PPN fair (good June signal) .
CMA Temp fair . PPN poor .
ECMWF Temp good . PPN fair .
UK Temp good . PPN fair .
JMA Temp good . PPN fair
MF Temp good . PPN fair .
CMCC Temp good . PPN fair .
CPTEC Temp fair . PPN poor.

D: Text Forecast for SW England

Remainder of Summer 2023 (August)

Temperature: Anomalies suggest around 1 deg C above normal, virtually all models above normal.

Rainfall: Highest probs are for near normal rainfall, suggestion of above normal for northern and western pasrts of the region.

August climate: 1981 to 2010 average daily mean temperature 16 or 17°C in main urban areas also locally east of the moors and more widely in Somerset, 13 to 15 Celsius elsewhere. Average 1981 to 2010 rain 40 to 80mm but over the moors, typically 125-150mm.

Autumn 2023 (September October November) limited data.

Temperature: A milder than average Autumn is most likely, consistent across models.

Rainfall: Probably wetter than average for the season. Month to month detail unreliable but hints at a drier start and wetter end to the season..

Winter (December 2023 January and February 2024) limited data

Milder than normal winter overall although December could see near normal temperatures. Rainfall average or above for the season but with a chance that December and / or February could see longer drier spells. Snow probably again below average so any accumulations more likely to be across the moors.

Winter Climate: 1981-2010 average temperature values for lowland areas 7°C in the West and 5°C in the East. Rainfall; Dec and Jan typically wetter than February. 1981-2010 Autumn average 300-400 mm lowlands but 200-300 mm areas to E of Dartmoor. Snow climatology less than 5 days lying snow over lowland areas 5 to 10 hills, say hills around 200 metre elevation – one in three years have no lying snow.

E: Caution.

F: References.

SST anomaly NOAA Remote Sens. 2014, 6(11), 11579-11606; doi:10.3390/rs61111579

IRI statistics: Mason, S.J. and L. Goddard, 2001: Probabilistic precipitation anomalies associated with ENSO. Bull. Amer. Meteor. Soc., 82, 619-638.

UK climate details see: http://www.metoffice.gov.uk/public/weather/climate/

NMME information: http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-12-00050.1

CFS2 info

‘Copernicus Products’ as listed in the C3S or CAMS Service Product Specification or any other items available through an ECMWF Copernicus http://climate.copernicus.eu

International seasonal monthly data from WMO

Climate data from The Met Office UK and NCEP USA

Contains public sector information licensed under the Open Government Licence v3.0.

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