Climate review and Experimental Long Range Forecast for SW England. October 2021.

Published 17 October 2021.

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1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea are significantly generally warmer than climatology for the time of year.

Tropical Atlantic is above average and is forecast to remain warmer than average through to at least Spring 2022 (See Met Office graphic below).

The East Pacific has larger cold anomalies than last month. Forecasts suggest that tropical Pacific Sea Surface Temperatures are likely to cool further to a significant La Nina state for the Winter before approaching a neutral state in Spring/Summer 2022. Meanwhile the Indian Ocean, W and SW Pacific have well above average temperatures for the time of year.

Nino 3.4 CFSv2 and NMME ensemble forecasts.

The North Atlantic Oscillation index (500hPa index shown below) turned negative more or less as forecast in late September and is forecast to remains negative for the next two weeks though with reducing confidence and strength. The negative NAO is consistent with a blocked or non mobile pattern which can be anticyclonic or cyclonic over the UK depending on the location of the “blocked” high and low pressure centres but it might also relate to less deep low pressure systems across the North Atlantic.

The UK at present is heading towards a more mobile Atlantic pattern more like a positive phase of the NAO although this may not last.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

October up to the 17th has been warmer and perhaps slightly drier than average (1981-2010) with near or a little above average sunshine. Temperature anomalies are around 2 deg C so far..

2021 UK Met provisional Temperature and Rainfall anomalies for July to September 2021 are shown below: Temperature has been mostly above average although the South of England was colder in August. Rainfall deviated from the long term average (1981-2010) across the W of Scotland which was drier than average with parts of the south of England being wetter than average.

UKMO Top row: Temperature anomalies. Lower row: Rainfall anomalies

To illustrate the difference between 1981-2010 (top row) and 1990-2020 (lower row) in the 30 year climate periods, both are shown in the graphic below. Temperature and rainfall anomalies for September 2021 and the year to September are shown below.

UK River flows in September 2021 were near average and ground water remains above average in the East of the region. Details can be found in the September 2021 Hydrological Summary

Data as of 17th October show near normal river values across of the SW but with some locations (in orange) showing below average values.

Reservoir levels, according to SW Water, were fairly high across SW England as of 10th October 2021.

Global Flood Awareness (updated to version 3) October forecast for the period October to January 2022 indicate average flood risk for SW England. River flow forecast shown are blue for above normal river flow and grey near average.

2021 Atlantic hurricane season Started 22 May 2021. Data from Wikipedia as of 17th October 2021.

Wikipedia data summary: Total depressions 20, Total storms 20, Hurricanes 7, Major hurricanes (Cat. 3+) 4.
Estimates for total fatalities 159 total and damage $69.5 billion (2021 USD) which may be the fourth costliest tropical cyclone season on record. Global (Pacific and Indian Ocean) fatalities amounted to 518.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is changed to “winter” mode as shown by the 50hPa and 10hPa analysis for the 16th and the T+24 hour forecast. The polar stratospheric vortex is forecast to become unstable due to stratospheric warming.

In the Southern Hemisphere there is a strong and fairly stable stratospheric vortex with a well established Ozone “hole”. Data shows the size of the “hole” is currently above average with large scale ozone depletion having taken place.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for November 2021 to February 2022. There is a hint from CFSv2 data for a less mobile patterns across the Atlantic for November and December followed by a more zonal type.

B: Lower Troposphere:

Selection of model solutions for November 2021 to February 2022 using October data, are shown below.

Top row temperature anomaly and lower row precipitation anomaly.

Source Data WMO low resolution super ensemble for the winter December 2021 to February 2022.

Top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

Individual members of the WMO super ensemble

Full graphics for the November can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing the output of seasonal models for July August and September based on June 2021 data for the UK and Ireland.

For graphics and details see Verification review July August September

Summary – 19 June 2021 –
Temperature most likely near normal or slightly above normal for the three month season. Scotland and Ireland more likely normal and highest chance for above normal in S/SE England.
Rainfall for the season probably below average in the S/SE of UK, in terms of rain days, and normal in the N and NW. Some indication for a wetter than average September especially in the north. Overall rain total for the three month may end up near average perhaps below in the south but thundery showers unlikely to be predicted by seasonal models and can easily tip the balance to wetter.

Comment: Temperature was above average but the north had stronger anomalies than the south and the south was below average in August. Rainfall gridded for UK and countries show below average rain but due to rainfall in July some spot locations were above normal.

Scoring will attempt to state good, fair, poor or no signal.
TEmperature marked fair if monthly lower value for August no shown otherwise most have above average and NCEP text uses 1991-2020 hence normal = above normal in previous 30 year period.

Comment: Looking for above average temperatures, below average rain and above average pressure.

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

2: Forecast.

Remainder of Autumn 2021 (November).

Near normal or slightly milder than average temperatures seem likely with near normal or slightly below normal rainfall.

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 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 2021 / 22 (December January February)

Temperatures across SW England are likely to be slightly milder than average this winter although December may see values close to average which would be a change from recent months. Rainfall probably above average overall but December could be drier than average with January and February wetter than average. Below average snowfall is most likely, which mostly limits snow to the Moors although December has a slightly increased risk of snow showers.

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.

Spring (2022 March April May)

Overall milder than average temperatures but with lower anomalies in May. Rainfall for the season probably close to average values but some longer drier spells are possible although models do not agree which month could be drier.

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

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. 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

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

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 2021.

Published 19 September 2021.

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic, North Sea and Med sea are significantly generally warmer than climatology for the time of year.

Tropical Atlantic is near or slightly above average and is forecast to remain warmer than average through the remainder of 2021 and through to February 2022 (See Met Office graphic below).

Colder sea temperatures around Japan are most likely due to a number of storms which have affected the area. The East Pacific has cooler anomalies than last month. Forecasts suggest that tropical Pacific Sea Surface temperatures may cool further to a significant La Nina state for the Winter before approaching a neutral state in Spring 2022.

The North Atlantic Oscillation index (500hPa index shown below) had been slightly positive since early September but is forecast to turn negative again in about a week. The negative NAO is consistent with a blocked or non mobile pattern which can be anticyclonic or cyclonic over the UK depending on the location of the “blocked” high and low pressure centres. Indications are not strong in either direction and the blocks so far have been fairly week allowing some mobility to occur although the forecast is for a slightly strong negative NAO to develop.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

September up to the 18th has been significantly warmer and drier than average (1981-2010) with near average sunshine. Temperature anomalies to date have been over 2 deg C.

Summer (June July August) 2021 UK Met provisional Temperature and Rainfall anomalies are shown below: Temperature has been mostly above average although the South of England was colder in August. Rainfall deviated from the long term average (1981-2010) the W of Scotland much drier and the SE of England wetter.

To illustrate the difference between 1981-2010 (top row) and 1990-2020 (lower row) in the 30 year climate periods the Europe and Global temperature anomalies for Summer 2021 are shown below. Whilst much of the globe and Europe has seen positive anomalies this summer the UK area has been closer to the “new” average.

UK River flows in August 2021 were above average across parts of West Cornwall but near normal elsewhere. Details can be found in the August 2021 Hydrological Summary

Data as of 19th September show near normal river values across most of the SW but with some locations (in orange) showing below average values.

Reservoir levels, according to SW Water, were fairly high across SW England as of 12th September 2021.

Global Flood Awareness (updated to version 3) September forecast for the period September to December indicates average flood risk for SW England. River flow forecast shown are blue for above normal river flow and grey near average.

2021 Atlantic hurricane season Started 22 May 2021. Data from Wikipedia as of 19th September 2021.

Wikipedia data summary: Total depressions 17, Total storms 16, Hurricanes 6, Major hurricanes (Cat. 3+) 3.
Estimates for total fatalities 158 total and damage $53.498 billion (2021 USD) a considerable increase since mid August.

There were no names storms affecting the UK area.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is changing from “summer” mode towards “winter” mode as shown by the 50hPa and 10hPa analysis charts for the 18th September 1200UTC and the forecast for the 28th.

In the Southern Hemisphere there is a strong and fairly stable stratospheric vortex with a well established Ozone “hole”. Data shows the size of the “hole” is currently above average and similar to 2020 which was the 12th largest on record..

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for October 2021 to February 2022. There is a hint from CFSv2 data for a less mobile patterns across the Atlantic for October but more cyclonic patterns near the N of the UK for November and December and a more zonal type on average in January. Other models in the NMME data differs from CFSv2 data although there is some agreement for December and January.

B: Lower Troposphere:

Selection of model solutions for October to December 2021 using September data shown below.

Top row temperature anomaly and lower row precipitation anomaly.

CFSv2 using mean of 10 days model data to 7th September

Source Data WMO low resolution super ensemble below.

Top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

Ensemble mean anomalies for component members of the super ensemble – NEW Italy.

BoM Australia

Full graphics for the Winter can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Winter December 2021 to February 2022 – limited graphics.

C: Comparing the output of seasonal models for Summer 2021 (June July August) based on May 2021 data for the UK and Ireland.

For graphics and details see Verification review June July August

Original Summary – 170521 –
Suggestion of a NW/SE divide with the N and NW forecast to have temperatures nearer normal and S/SE warmer than average. Rainfall probably near or above average in the North and below average in the south – BUT – there is a fairly consistent indication for a wetter August event in the south and this may lead to higher rainfall totals for the season despite more than average dry days for southern parts. (Note model means are not able to pick up extreme hot/cold wet/dry but may give some indication of the trends).

Comment: 020921 – Completely opposite temperature split than in the forecast – very poor. Very poor rainfall forecast.

Scoring will attempt to state good, fair, poor or no signal.
Comment: Most models (but not Washington, Tokyo, Brazil, Moscow and Canada) got the ideas of above average temperatures but NOT the geographic location. There were some hints at below average rainfall often spoilt by a wetter indication for August.
1. Russia (WMO): Temp V poor . PPN V poor .
2. USA – CFS2 : Temp fair . PPN poor .
3. UKMO Contingency: Temp good . PPN fair .
4. UKMO : Temp poor . PPN poor . PMSL good
5. USA – IRI : Temp no signal . PPN no signal .
6. KMA APCC : Temp fair . PPN poor .
7. JMA : Temp poor. PPN poor . PMSL fair
8. NMME : Temp fair . PPN poor.
9. WMO multi : Temp poor. PPN poor
10. BCC : Temp good . PPN good .
11. NASA : Temp fair . PPN poor
12. Brazil: Temp fair . PPN poor.
13. CanSips : Temp poor . PPN poor .
14. IMME : Temp fair . PPN poor.
15. Copernicus Temp fair . PPN poor. PMSL poor
16. CMCC Temp good . PPN good . PMSL good
17: DWD Temp fair . PPN poor . PMSL poor
18. ECCC Temp poor . PPN poor . PMSL good
19 JMA Temp poor . PPN poor . PMSL poor
20 UKMO Temp fair . PPN poor. PMSL poor
21. MF Temp fair . PPN fair . PMSL good
22 NCEP Temp good . PPN poor. PMSL poor
23 ECMWF Temp: fair . PPN poor. PMSL good

2: Forecast.

Remainder of Autumn 2021 (October November).

Milder than average but chance that temperatures could be closer to average earlier in October. Near normal or wetter than average overall but rainfall may be below normal in October and above in November but little agreement on this detail. Some models have October wetter and November 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. October and November have similar number of rain days and totals range from around 70mm east of the moors to over 200mm over the moors.

Winter 2021 / 22 (December January February) limited data.

Slightly milder than average Winter although there might be near average values early in the winter. Rainfall above average is more likely than below average for the season with the second half of the winter could be relatively less wet/drier. Below average snowfall is most likely, which mostly limits snow to the Moors. December, however, carries a risk of wintery showers, but lying snow is still more likely over the moors than elsewhere.

Spring (2022 March April May)

First half probably milder than average then a risk of a colder than average second half of Spring. Rainfall near normal overall but with a chance of perhaps drier weather types later in Spring.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

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 2021.

Published 17 August 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology, especially so in the North and Northwest, although cooler than average values persist in an area to the SW of the UK and SW of Portugal. The North Sea, Baltic and Med are well above average for the time of year.

Tropical Atlantic is near or slightly above average and is forecast to remain warmer than average through the remainder of 2021 (See Met Office graphic below).

Colder sea temperatures around Japan follow several storms in the area after being well above normal previously. The East Pacific has similar anomalies to last month. Forecasts suggest that tropical Pacific Sea Surface temperatures may cool to a La Nina state for the Autumn and Winter before returning to a neutral state in Spring 2022.

The North Atlantic Oscillation index (500hPa index shown below) had been slightly positive for early August before turning negative. The negative NAO is consistent with a blocked or non mobile pattern which can be anticyclonic or cyclonic over the UK depending on the location of the “blocked” high and low pressure centres. Indications are not strong in either direction and the blocks so far have been fairly week allowing some mobility to occur.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

August to the 17th has been quite mixed with about 9 dry days and between 25 and 50mm of rain, which is about right for half the month. Temperatures have been a fraction below normal averaging around 16 or 16.5C. Sunshine seems to be about one third of the average, suggesting a cloudier than average month so far. (Sunshine data is limited).

May June July 2021 UK Met provisional Temperature and Rainfall anomalies are shown below: Temperature has shown marked swings from a cold May to a warmer June and July. Rainfall deviated markedly from the long term average noting the dry W Highlands of Scotland and the wetter than average S/SE of England.

UK River flows in July 2021 were above average across parts of Cornwall and South and West Devon. Details can be found in the July 2021 Hydrological Summary

Data as of 17th August shows near normal river values across most of the SW but with some locations (in orange) showing below average values.

Reservoir levels, according to SW Water, were fairly high across SW England as of 8th August 2021.

Global Flood Awareness (updated to version 3) August forecast for the period August to November indicates slightly above normal flood risk for SW England. Blue above normal flood risk, White (river in grey) normal and Orange below normal.

2021 Atlantic hurricane season Started 22 May 2021. Data from Wikipedia.

Storm timeline – active storms as of 17th August Henri, Grace and Fred.

Death toll 9 or 10, estimated cost more than $1.2 billion.

A named storm “Evert”, occurred over SW England during the 29 to 30 July 2021
Southern and south-west England experienced some unusually strong winds for the time of year from storm Evert. Winds gusted widely at over 40Kt (46mph) and was much strong in exposed locations across SW England reaching 60mph in the Isles of Scilly.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is in “summer” mode as seen by the 50hPa and 10hPa analysis charts for the 16th August 1200UTC.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for September to November 2021. There is a hint from CFSv2 data for a less mobile patterns across the Atlantic for October but more cyclonic patterns near the N of the UK for September and possibly November although NMME data differs from raw CFSv2 data showing a lack of agreement between models.

Similar plot but for December 2021 to February 2022 showing potential for increased zonal flow in February.

B: Lower Troposphere:

Selection of model solutions for September to November using August 2021 data are shown below.

Top row temperature anomaly and lower row precipitation anomaly.

CFSv2 using mean of 10 days model data to 7th August

ECMWF orange/red colours are above model hindcast average.

Data (as supplied to WMO) shown below.

Top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

Brazil

Graphics for the Autumn and Winter can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Winter December 2021 to February 2022 – limited graphics.

WMO multi model Winter

C: Comparing the output of seasonal models for 2021 May June July based on April 2021 data for the UK and Ireland.

For graphics and details see Verification review May June July

Original – Summary – 170421 –
Temperature: The three month average probable above normal, a few models suggest the north rather than the south but the majority favour the south being above normal. Monthly data suggest June nearer normal with May and July more likely above. Rainfall: Fairly good indication for below average rainfall in the first half of the season then trending above average. Overall for the three months most likely below average in S and far N, elsewhere normal. Pressure: near normal perhaps above in the south.

Comment:
Temperature: Three month average good monthly detail not correct.
Rainfall: Generally poor/misleading forecast for monthly although a few models had a drier April. For the three months overall poor.

Scoring will attempt to state good, fair, poor or no signal.
Comment: Moscow got the sequence quite well.
1. Russia (WMO): Temp good . PPN fair (but good for sequence) .
2. USA – CFS2 : Temp good . PPN poor .
3. UKMO Contingency: Temp good . PPN fair .
4. UKMO : Temp good. PPN poor
5. USA – IRI : Temp no signal . PPN poor .
6. KMA APCC : Temp fair . PPN poor.
7. JMA : Temp good . PPN poor . PMSL fair
8. NMME : Temp good . PPN fair .
9. WMO multi : Temp good . PPN poor .
10. BCC : Temp poor . PPN poor .
11. NASA : Temp fair. PPN poor .
12. Brazil: Temp poor . PPN poor .
13. CanSips : Temp fair. PPN poor .
14. IMME : Temp good . PPN fair .
15. Copernicus Temp good . PPN fair . PMSL fair
16. CMCC Temp good . PPN fair . PMSL fair
17: DWD Temp good . PPN fair . PMSL poor
18. EC Temp good . PPN fair . PMSL poor
19 JMA Temp poor. PPN poor . PMSL poor
20 UKMO Temp poor. PPN poor . PMSL poor
21. MF Temp poor . PPN poor. PMSL poor`
22 NCEP Temp good . PPN fair . PMSL poor
23 ECMWF (monthly) Temp: poor . PPN poor .

2: Forecast.

Autumn 2021 (September October November).

Milder than average but chance that temperatures could be closer to average earlier in the Autumn then milder. Near normal or wetter than average overall but rainfall may be below normal in September and/or November little agreement on this detail.

Winter 2021 /22 (December January February) limited data.

Milder than average Winter although there might be near average values early in the winter. Rainfall may be below average early in the winter but overall above average rainfall is more likely for the season with hints that February could be mild and wet. Below average snowfall is most likely, which mostly limits snow to the Moors.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

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 2021.

Published 19 July 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology except for the area west from Biscay. The North Sea, Baltic and Med are well above average for the time of year. Tropical Atlantic is near or slightly above average and is forecast to remain warmer than average through the remainder of 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific remain and show similar anomalies to last month. Forecasts suggest that Pacific Sea Surface temperatures may remain in a neutral or slightly negative state through summer and trend towards La Nina after October. The West Pacific, especially near Japan and also the Northern Indian Ocean are well above normal for mid July.

The North Atlantic Oscillation index (500hPa index shown below) has been neutral or slightly positive for much of July but is again forecast to turn negative over the next week or two, although perhaps only briefly. The negative NAO is consistent with a blocked or non mobile pattern which can be anticyclonic or cyclonic over the UK depending on the location of the “blocked” high and low pressure centres. Indications are not strong in either direction.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

Until mid month July was wetter than average in terms of the number of wet days and total rainfall for the whole month with close to average temperatures. For about a week from mid July though there has been a longer dry and very warm spell lifting average temperatures above normal for the month as a whole. Sunshine up to mid month looks to have been below average.

April May June 2021 UK Met provisional Temperature and Rainfall anomalies are shown below and illustrate the potential for extremes. Temperature swings from cold April and May followed by warmer June and Rainfall that deviated markedly from the long term average indicates the unusual times for the UK climate.

UKMO top row Temperature anomalies April to June, lower row Rainfall anomalies April to June.

UK River flows in June 2021 were well below normal except in the wetter South and SouthEast of England . Details can be found in the June 2021 Hydrological summary PDF

River levels on the 17th of July were more or less normal but starting to reduce in places

Reservoir levels, according to SW Water were fairly high across SW England as of 11th July 2021.

Global Flood Awareness (updated to version 3) July forecast for the period July to October indicates slightly above normal flood risk for SW England. Blue above normal flood risk, White (river in grey) normal and Orange below normal.

Rainfall during the severe flooding in Germany amounted to at least 100 to 200mm in 24 to 48 hours over a fairly widespread area following an already wet period. Forecast models suggest 100mm totals a few days before the event and the river flow forecast tool suggested river flows in excess of the 1 in 20 year return period but only shortly before the event.

2021 Atlantic hurricane season Started 22 May 2021. Data from Wikipedia.

Wind speeds reaching tropical depression category = 5, storm category = 5, hurricane strength 1. Total fatalities 19. Estimated damage more than 390 million USD.

No current Atlantic tropical storms as of 19th July 2021.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is in “summer” mode as seen by the 10hPa and 50hPa analysis charts for the 16th July 1200UTC.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for August to November 2021 hint at a less mobile patterns across the Atlantic for August and October but more cyclonic patterns near the N of the UK for September and possibly November.

B: Lower Troposphere:

Selection of model solutions for August to October using July 2021 data are shown below. Top row temperature anomaly and lower row precipitation anomaly.

CFSv2 mean of 10 days data to 7th July for August September October

NMME multi model ensemble data to 7th July for August September October

NASA July data for August September October

ECMWF July 2021 data

Data (as supplied to WMO) shown below, top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

BoM Australia

Graphics for the Autumn can be viewed in the July data at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Winter December 2021 to February 2022 – limited graphics.

C: Comparing the output of seasonal models for 2021 April May June based on MarchFebruary 2021 data for the UK and Ireland.

For graphics and details see Verification review April May June

Details looked for in seasonal forecast:

Temperature;. for the season the warmer June did not offset the two colder months hence below average for the season but can we see any trend colder then warmer?

Rainfall. Parts of S and SE England were above normal for the season but elsewhere the wet May was mostly offset by the other dry months.

Sunshine above average for the season

Pressure above average for the season (Slack) (April well above, May well below, June above)

Original Summary – Summary – 180321 –
Temperture: There looks to be more models suggesting near normal than typical although the main signal is for above normal with hints that this could occur later in the three months than earlier in the period.
Rainfall: Very mixed indications, possibly near normal overall. Probably some longer drier than average periods, mostly in April and more likely in the south but not a clear signal. For the three months some areas above average perhaps most likely in the north. Pressure possibly a little above average in the south.

Comment: 030721 – Although the season turned out below average the indication for warmer later was correct and the increased number of near normal solutions may have been a pointer to colder values. Reasonable indication for drier April and for some areas above normal but suggestion that this would be the north was wrong. Pressure was slightly above average for the season but not just in the south.
200hPa not enough troughing in May but CFS2 anomaly hinted at lower heights over France than in April or June.

Scoring will attempt to state good, fair, poor or no signal.
THREE MONTH SCORES
1. Russia (WMO): Temp good (model tends to be colder than others). PPN fair .
2. USA – CFS2 : Temp poor . PPN poor .
3. UKMO Contingency: NIL
4. UKMO : Temp poor. PPN poor. PMSL poor
5. USA – IRI : Temp poor. PPN fair.
6. KMA APCC : Temp poor. PPN no signal .
7. JMA : Temp poor. PPN poor. PMSL good
8. NMME : Temp poor. PPN fair .
9. WMO multi : Temp poor. PPN poor.
10. BCC : Temp poor. PPN poor.
11. NASA : Temp poor. PPN poor.
12. Brazil: Temp fair. PPN poor.
13. CanSips : Temp fair trend poor overall. PPN fair overall poor trend.
14. IMME : Temp poor. PPN poor.
15. Copernicus Temp poor. PPN poor. PMSL fair
16. CMCC Temp poor. PPN poor. PMSL good
17: DWD Temp fair. PPN fair. PMSL fair
18. EC Temp fair. PPN fair. PMSL fair
19 JMA Temp poor PPN fair. PMSL fair
20 UKMO Temp poor. PPN poor. PMSL poor
21. MF Temp poor. PPN fair. PMSL good
22 NCEP Temp poor. PPN fair. PMSL good
23 ECMWF (monthly) Temp poor. PPN poor.

2: Forecast.

Remainder of Summer 2021 (August)

Temperature above average most likely.

Rainfall uncertain but a good number of solutions suggest below average rainfall in south UK. This can easily be upset by a few thundery rain events. Hence possibly more dry days than average even if rain totals are higher.

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 2021 (September October November).

Milder than average but chance that October could be closer to average. Some western parts of the region could also be near average. Wetter than average overall. Rainfall may be below normal in one of the months but no agreement as to which month.

Winter 2021 /22 (December January February) limited data.

Milder than average Winter although there might be near average values early in the winter. Rainfall may be below average in January but overall above average rainfall is more likely for the season. Below average snowfall is most likely which mostly limits snow to the Moors.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

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. June 2021.

Published 19 June 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology except for the area centred on 50 deg North 30 deg West. North Sea, Baltic and Med are well above average for the time of year. Tropical Atlantic is slightly above average and is forecast to remain warmer than average through the remainder of 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific remain and show similar anomalies to last month. Forecasts suggest that Pacific Sea Surface temperatures may remain in a neutral state through summer and trend towards La Nina again after October.

The North Atlantic Oscillation index (500hPa index shown below) has been neutral for much of June but is forecast to turn negative over the next week or two. The negative NAO is consistent with a blocked or non mobile pattern which can be anticyclonic or cyclonic over the UK depending on the location of the “blocked” high and low pressure centres.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

Up to the 18th of June temperatures have averaged between 14 and 16 Celsius which is above average for the time of year by about a degree Celsius. June so far has only recorded less than 20% of average rainfall with typical totals ranging between 3 and 15mm. Sunshine so far looks to be a little above average.

The last three months (March April and May 2021) temperature and rainfall anomalies (shown below) illustrate the potential for extremes with an exceptionally dry April followed by an exceptionally wet May – which in places offset each other when looking at the 3 month maps. Temperature swings from mild March followed by a cold April show that it is not just rainfall that deviates from the long term averages..

UKMO temperature anomaly (top row) and rainfall anomaly (lower row)

It was not just the UK that had cold, wet and dull weather in May 2021 – the maps below ( pressure sunshine temperature and rainfall anomalies) show how widespread the event was.

River flows in May 2021 were well below normal. Details can be found in the May 2021 Hydrological summary PDF

River flows currently near average but a few are showing reductions in flow.

Reservoir levels across SW England were fairly high as of 13th June 2021 following the heavy rain in May.

Global Flood Awareness (updated to version 3) June forecast for the period June to September indicates slightly above normal flood risk for SW England. Blue above normal flood risk, White (river in grey) normal and Orange below normal.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is in “summer” mode as seen by the 10hPa and 50hPa analysis charts for the 18th June 1200UTC.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for July to September 2021 hint at a less mobile patterns across the Atlantic for July and August but more cyclonic patterns near the UK for September.

B: Lower Troposphere:

Selection of model solutions for July, August and September using June 2021 data are shown below. Top row temperature anomaly and lower row precipitation anomaly.

CFSv2 mean of 10 days data to 8th June for July August September

NMME mean of 10 days data to 8th June for July August September

Data (as supplied to WMO) shown below, top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

Beijing China

Washington USA – caution using newer averaging period in model hence may appear colder.

Graphics for the Autumn can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing the output of seasonal models for 2021 March April and May based on February 2021 data for the UK and Ireland.

For graphics and details see Verification review March April May

Details looked for in seasonal forecast:

Temperature. Below average. (March was mostly above but April and May below)

Rainfall. Very mixed three three month average some places above others below – see UKMO map – For countries as a whole: Wales above average elsewhere below. UK below average. However will be looking for indications of very dry April and very wet May

Sunshine above average due very sunny April

Pressure. Above normal. The low pressure in May did not offset the higher pressure in earlier months.

Original Summary – 190221 – Temperature: The overall indication for the Spring Season is for above average tempertures with the highest chance being in the S and E and lowest chance in the N and W. March could well see some colder spells with some models suggesting nearer average values. The strongest positive anomaly seems to be in April. Precipitation: Mixed indications suggesting near or above normal for the season across the NW and W in particilar, elsewhere normal locally below. The strongest chance of below normal being in April across the S or SW of the UK and Eire (This could be a problem with showers not being captured at model resolution). Below normal seems to outnumber the above normal solutions by about 2 to 1 but not always in the same areas – but may indicate some longer than normal dry periods are possible.

Comment. Temperature forecast was very poor. Rainfall did better suggesting long dry periods and the three month season turned out ok ‘ish but not convinced that this was more than luck. Did not capture the extreme dry April and extreme wet May. A number of models picked up the dry April ECMWF WMO CMC Brazil NMME NASA and to a limited extent KMA .

Scoring will attempt to state good, fair, poor or no signal, based on three averages.
Comment: A number of models picked up the dry April
1. Russia (WMO): Temp poor. PPN poor Wales fair England elsewhere no signal .
2. USA – CFS2 : Temp poor. PPN fair .
3. UKMO Contingency: Temp poor. PPN fair
4. UKMO : Temp poor. PPN fair PMSL poor
5. USA – IRI : missing
6. KMA APCC : Temp poor. PPN no signal .
7. JMA : Temp poor. PPN poor. PMSL poor
8. NMME : Temp poor. PPN fair.
9. WMO multi : Temp poor. PPN fair.
10. BCC : Temp poor. PPN poor .
11. NASA : Temp poor. PPN fair .
12. Brazil: Temp fair . PPN fair
13. CanSips : Temp poor . PPN poor .
14. IMME : Temp poor. PPN poor .
15. Copernicus Temp poor. PPN poor . PMSL fair
16. CMCC Temp poor. PPN poor . PMSL poor
17: DWD Temp poor. PPN fair. PMSL good
18. EC Temp poor. PPN fair. PMSL good
19 JMA Temp poor. PPN poor . PMSL poor
20 UKMO Temp poor. PPN poor. PMSL poor
21. MF Temp poor . PPN poor. PMSL poor
22 NCEP Temp poor. PPN poor. PMSL poor

2: Forecast.

Remainder of Summer 2021 (July August)

Temperature near or slightly above average for both July and August. Possibly the warmest anomalies could be in August.

Rainfall uncertain but probably above average rain totals overall. July possibly drier than August which is typical but this could be either more wet days OR a few heavy rain events for example thunderstorms.

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. July often drier than August.

Autumn 2021 (September October November).

Milder than average but some western parts could be near average. Wetter than average, especially early in the period. Rainfall may be below normal in one of the months some hints at October being the less wet month with near normal values possible.

Winter 2021 /22 (December January February) very limited data.

Milder than average Winter although February could have near average values. Rainfall may be below average in some months but overall above average rainfall is more likely for the season. Below average snowfall is most likely which mostly limits snow to the Moors.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

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. May 2021.

Published 18 May 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology although areas to the North of Scotland and to the SW of England are cooler due to lack of SW to W winds across the Atlantic. The tropical North Atlantic is forecast to remain slightly warmer than average through Summer and Autumn 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific continue to show a weakening La Nina with further warming having occurred in the West Pacific. Forecasts suggest that Pacific Sea Surface temperatures may remain in a weak La Nina or Neutral state through the remainder of 2021.

The North Atlantic Oscillation index (500hPa index shown below) has been negative since early April and is forecast to remain slightly negative or neutral for a short time before becoming uncertain. The negative NAO is constant with a blocked or non mobile pattern which has changes from anticyclonic to a more cyclonic slow moving pattern. This cyclonic pattern may slowly migrate to a more anticyclonic pattern for the UK in a week or so.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

Up to the 18th of May temperatures have averaged around 10 Celsius which is about 2 degree below the May long term average, although temperatures in the second half of May tend to be warmer than the first half. Rainfall has been well above average, perhaps over double the month average in many places due in no small measure to rainfall on the 8th 12th 13th 25th and 16th. Sunshine has also been below average so for in May.

The last three months (February March and April 2021) temperature and rainfall anomalies are dominated by the cold and very dry April, although March was also quite dry, at least in the S and E of the UK. According to the Met Office; April was exceptionally dry, provisionally the UK’s fourth driest April in a series from 1862. It was cold and the number of days of air frost across the UK was the highest in a series since 1960. It was also the sunniest April in a series since 1919.

River flows in April 2021 were well below normal. Details can be found in the April 2021 Hydrological summary PDF

River levels in SW England have since recovered due to the very wet first half of May although the dry March and April may have impacts with regards ground water levels in future months.

Global Flood Awareness (updated) System. May forecast for the period May to August indicates slightly above normal flood risk for SW England. Blue above normal flood risk, White (river in grey) normal and Orange below normal.

Reservoir levels across SW England were fairly high as of 9th May and no doubt are even higher following the heavy rain after this date.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric circulation is in “summer” mode as seen by the 10hPa and 50hPa analysis charts for the 17th 1200UTC.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for June to August 2021 hint at a less mobile patterns across the Atlantic for June and July but more cyclonic patterns near the UK for August.

B: Lower Troposphere:

Selection of model solutions for Summer (June July August) using May 2021 data (from the data source) are shown below, top row temperature anomaly and lower row precipitation anomaly. The full set of graphics can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

CFSv2 mean of 10 days data to 7th May 2021.

Selection of model solutions for summer (June July August) using May 2021 data (as supplied to WMO) are shown below, top row temperature anomaly and lower row precipitation anomaly. Left image three month mean then individual months.

WMO super ensemble using 11 countries data (DWD and Pretoria data missing)

Selection of model solutions for Autumn (September October November) using May 2021 data (from the data source) are shown below, top row temperature anomaly and lower row precipitation anomaly.

C: Comparing the output of seasonal models for 2021 February March and April based on January 2021 data for the UK and Ireland.

For graphics and details see Verification review February March April

Details looked for in seasonal forecast:

Temperature. Three month average below normal due to cold April, except in N Ireland where not cold enough in April to offset milder Feb and March.

Rainfall. Below normal thanks to very dry April and below average March after above average in February.

Sunshine Above average for season and each month except N Ireland (2 months below) and Scotland (1 month below).

Pressure. Above average for season, below average in Feb but above in March and April

\Written Summary – 160121 –
Temperature: For the three months overall the main indication is for above average temperatures or at worst near normal in western areas. Looking at the month to month detail western areas (Ireland, W Scotland, Wales and perhaps SW England, could be nearer normal with a chance of below normal in February and/or March). Precipitation: Three month overall probably normal or above normal but a chance that N Scotland could be below average. Mixed signals in the month to month variation of wetter areas but some agreement that April could be drier than preceding months.
Comment:
Temperature: Seasonal forecast not correct. Very cold April not indicated but NMME and CFS showed lower warm anomalies in April.
Precipitation: Good signal for April being a drier month – NMME, CFS2, Beijing, Brazil and to some extent Moscow, but overall indication of above average was not correct.

Scoring for the three month season will attempt to state good, fair, poor or no signal.

1. Russia : Temp fair . PPN no signal .
2. USA – CFS2 : Temp fair . PPN fair .
3. UKMO Contingency: Temp poor . PPN poor .
4. UKMO : Temp poor. PPN poor. PMSL poor
5. USA – IRI : Temp no signal . PPN no signal.
6. KMA APCC : Temp poor . PPN no signal .
7. JMA : Temp poor . PPN poor . PMSL poor
8. NMME : Temp poor. PPN fair .
9. WMO multi : Temp poor. PPN poor.
10. BCC : Temp poor . PPN good .
11. NASA : Temp poor . PPN fair .
12. Brazil (WMO): Temp poor . PPN fair .
13. CanSips : Temp poor . PPN poor .
14. IMME : Temp poor . PPN poor .
15. Copernicus Temp poor . PPN poor . PMSL poor
16. CMCC Temp poor . PPN poor . PMSL poor
17: DWD Temp poor . PPN poor. PMSL poor
18. ECMWF Temp poor . PPN poor. PMSL poor
19 JMA Temp fair . PPN poor . PMSL poor
20 UKMO Temp poor. PPN poor. PMSL poor
21. MF Temp poor . PPN poor . PMSL fair
22 NCEP Temp poor. PPN poor . PMSL poor
23 ECMWF (monthly) Temp: no signal. PPN fair

2: Forecast.

Summer 2021 (June July August)

Temperature near or slightly above average for the season. August possibly seeing the warmest anomalies and June the lowest. Most solutions suggest a less warm (compared to average) start to summer and warmer end.

Rainfall for the season uncertain but probably above average rain totals overall. The first half of summer may well be drier than average then turning wetter. Higher rain rates are typical of a warming atmosphere but may not imply an increase in the number of days with rain. Some consensus for August to be wetter than average but this could be either more wet days OR a few heavy rain events.

Autumn 2021 (September October November).

Milder than average also wetter especially early in the period. Rainfall may be below normal although at least one of the three months could be wetter although no agreement between the models but more likely September or October than November.

Winter 2021 /22 (December January February) very limited data.

Milder than average Winter although February could be near normal. Rainfall may be below average which implies below average snowfall.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

Climate data from The Met Office UK and NCEP USA

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

Review and Experimental Long Range Forecast for SW England. April 2021.

Published 19 April 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology although areas to the west of Ireland are cooler due to lack of SW to W winds. The colder Northerly types of late have resulted in cooler values in the southern North Sea despite most of the North Sea being warmer than average. The Norwegian Sea, Baltic Sea and the Med are also mostly near or above normal. The tropical North Atlantic is forecast to remain slightly warmer than average through Summer and Autumn 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific show a weakening La Nina with further noticeable warming having occurred in the west. Forecasts suggest that Pacific Sea Surface temperatures may remain in a weak La Nina or Neutral state through the remainder of 2021.

The North Atlantic Oscillation index (500hPa index shown below) has been negative recently (consistent with the blocked pattern and High pressure near the UK) and is forecast to remain slightly negative or neutral for a short time before becoming uncertain.

The positive NAO phase represents a stronger than usual difference in pressure allowing winds from the west to predominate. The position of the jet stream enables stronger and more frequent storms to travel across the Atlantic bringing more frequent milder and wetter weather types for NW Europe which in summer results in cooler temperatures.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

Up to the 18th temperatures averaged out around 7 Celsius which is about 2 degree below average for April and there have been an unusual number of frosty night/mornings. There has been 10% or less of the normal rainfall and probably more sunshine than usual too.

CPC temperature anomaly and rainfall total for 4 to 10th April 2021

Looking back at the last three months temperatures have recovered since the colder January and rainfall has been trending near ,then below average across SW England.

River flows and ground water levels in March 2021 were normal but trending lower across SW England. Details can be found in the March 2021 Hydrological summary PDF

UK based data is available in The Hydrological Outlook which provides an insight into future hydrological conditions across the UK. Detail can be found at http://www.hydoutuk.net/

Global Flood Awareness (updated) System. April forecast for the period April to July indicates slightly above normal flood risk for SW England. Blue above normal flood risk which probably mostly reflects the current ground water levels.

Reservoir levels across SW England were fairly high as of 11th April but trending lower than normal due to the dry first half of April

Atmosphere: Predictions.

A: 1: Stratosphere

North Pole stratospheric temperatures near normal or a little colder than average.

North Pole temperature at 10hPa and 30hPa

Since last month the polar stratospheric vortex has weakened and is moving towards the “summer” mode as can be seen in the 10hPa and 50hPa charts below for 1200UTC on the 18th and forecast for the 28th April.

: 2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for May to August 2021 hint at a less mobile patterns across the Atlantic for May and June but more cyclonic patterns near the UK for July but more especially August.

B: Lower Troposphere:

Selection of May model solutions using April 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

May data from WMO

Selection of forecast anomalies for May from WMO : Left to right WMO super ensemble, Brazil, UKMO, Canada, Germany, Japan, France, China, Russia. (see http://www.weather-info.co.uk/wxsvc/seaslatest.html for full sequence)

Selection of Summer (June to August) solutions using April 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly. The full set of graphics can be seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Data from WMO

WMO super ensemble of 10 international models.

German Met Service (DWD)

C: Comparing the output of seasonal models for 2021 January, February and March based on December 2020 data for the UK and Ireland.

For graphics and details see Verification review 2020 Dec 2021 January February

Review of details looked for in seasonal forecast.
Temperature. For the three months together: England Wales and N Ireland were on aggregate above normal and Scotland below. Jan was cold and other months milder.

Rainfall. For the three months together: Above normal but the detail more varied especially the large areas of below average in March.

Sunshine Scotland totals above average but elsewhere below average although the month to month picture is more complex.

Pressure. South below and North above average. Higher pressure generally in March.

Results: Monthly detail poor in almost all models. DWD and to some extent ECMWF got the warming trend but all models failed to get below normal January followed by warmer Feb and Mar. Toulouse, NMME and CFSv2 got some idea of the trend in precipitation.

Scoring for the three month season will attempt to state good, fair, poor or no signal.

1. Russia: Temp poor . PPN poor .
2. USA – CFS2 : Temp good . PPN fair .
3. UKMO Contingency: Temp good . PPN good .
4. UKMO : Temp fair . PPN good . PMSL fair
5. USA – IRI : Temp no signal . PPN no signal .
6. KMA APCC : Temp good . PPN fair .
7. JMA : Temp fair . PPN poor . PMSL poor
8. NMME : Temp good . PPN fair .
9. WMO : Temp good . PPN fair .
10. BCC : Temp good. PPN good .
11. NASA – Temp fair . PPN fair .
12. Brazil: Temp fair. PPN poor. PMSL good.
13. CanSips : Temp fair. PPN good .
14. IMME : Temp good . PPN fair .
15. Copernicus Temp fair . PPN good . PMSL poor
16. CMCC Temp fair . PPN fair . PMSL poor
17: DWD Temp poor . PPN poor. PMSL poor
18. EC Temp fair PPN fair PMSL poor
18b JMA Temp poor. PPN poor. PMSL poor
19 UKMO Temp good . PPN good . PMSL
20. MF Temp fair . PPN fair . PMSL poor
21 NCEP Temp good . PPN fair . PMSL poor
22 JAMSTEC: only available for main seasons.
23 ECMWF (monthly) Temp: fair . PPN fair .

2: Forecast.

Remainder of Spring (2021 May)

The overall indication for May is for slightly above average temperatures.

Rainfall most models suggest below average rainfall in May which would be remarkable given the drier April although the end of April may well become wet.

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 each month.

Summer 2021 (June July August)

Temperature near or slightly above average for the season with June possibly seeing the warmest anomalies and August the lowest.

Autumn 2021 (September October November).

Milder than average also wetter especially early in the period. Hints that October could be a drier month.

Winter 2021 /22 (December January February) very limited data.

Milder overall and also wetter than average which implies below average snowfall.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

Climate data from The Met Office UK and NCEP USA

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

By Master0Garfield – Created using WikiProject Tropical cyclones/Tracks. The background image is from NASA [1]. The tracking data is from the National Hurricane Center’s Atlantic hurricane database, Public Domain, https://commons.wikimedia.org/w/index.php?curid=90697173

Review and Experimental Long Range Forecast for SW England. March 2021.

Published 18 March 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are generally warmer than climatology as are waters of the North Sea. Norwegian Sea, Baltic Sea and the Med. The tropical North Atlantic is forecast to remain slightly warmer than average through Summer 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific, just south of the equator, show a weakening La Nina with further noticeable warming having occurred in the East. Forecasts suggest that Pacific Sea Surface temperatures may remain in a La Nina or Neutral state through the remainder of 2021.

The North Atlantic Oscillation index (500hPa index shown below) has been slightly positive recently and is forecast to remain slightly positive for a short time before becoming uncertain.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

Up to the 17th temperatures averaged out around 7 Celsius which is slightly below the March average. There has been about 40% of normal rainfall and 60% of sunshine. High pressure was over the UK to start the month before becoming unsettled and at times windy in the second week of March, followed again by a spell of High pressure..

CPC graphic 7th to 13th March showing temperature anomalies and total rainfall in this period.

Looking back at the last three months Winter temperatures were a little colder than average across SW England and there was above average rainfall.

River flows and ground water levels in February 2021 were well above normal across SW England. Details can be found in the February 2021 Hydrological summary PDF

UK based data is available in The Hydrological Outlook which provides an insight into future hydrological conditions across the UK. Detail can be found at http://www.hydoutuk.net/

Global Flood Awareness (updated) System. February forecast for the period February to May indicates slightly above normal flood risk for SW England.

Glofas March forecast for March to June 2021. Blue above normal flood risk which probably mostly reflects the current above average ground water levels.

Atmosphere: Predictions.

A: 1: Stratosphere

Major warming in the stratosphere (see N Pole temperatures below) in January 2021 caused a reversal of the westerly flow across North America and a significant re-location of the polar stratospheric vortex towards Norther Russia. The SSW was deemed to have ended on 13th February.

The polar stratospheric vortex has strengthened into normal winter mode. Below the ECMWF 10hPa and 30hPa for 17/1200UTC and 27th March show the strong vortex relocating poleward and remaining stronger than climatology.

A: 2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for April to August 2021 hint at a less mobile patterns across the Atlantic for April and June but more cyclonic patterns near the UK for July and August.

B: Lower Troposphere:

Selection of April to June solutions using March 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

The full set of graphics can be seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Selection of Summer (June to August) solutions using March 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

CFSv2 SUMMER 2021 note there looks to be a cold bias in temperature across the N Sea in summer.

C: Comparing the output of seasonal models for 2020 December, 2021 January and February based on November 2020 data for the UK and Ireland.

For graphics and details see Verification review 2020 Dec 2021 January February

Review of details looked for in seasonal forecast.

Temperature. The North, mainly Scotland, was colder than average elsewhere mostly near average. The colder January mostly off set by above average December and February.

Rainfall. NW Highlands ended with below average rain but elsewhere values were mostly above average for the season.

Sunshine Northern areas had above average sunshine but southern areas had cloudier skies.

Pressure. Below normal for the season but above normal in N Scotland in Jan and Feb.

Temperature forecast was a little warm but got the idea of a milder February but not the cold January. Moscow output (WMO) which is often on the cold side got the idea of a colder January with near normal other months and some other models had January with smaller anomalies hinting at less mild. The colder than average season in Scotland was not indicated although the idea of above average snow in the north was correct. Above average rainfall was correct but the month to month detail was poor.

Models affected by the cold January and the lack of ability to forecast cold conditions.

Scoring for the three month season will attempt to state good, fair, poor or no signal. (E.O.E.)

1. Russia: Temp poor . PPN poor .
2. USA – CFS2 : Temp poor. PPN fair .
3. UKMO Contingency: Temp fair. PPN fair .
4. UKMO : Temp poor . PPN fair . PMSL fair
5. USA – IRI : Temp no signal . PPN no signal .
6. KMA APCC : Temp poor . PPN no signal .
7. JMA : Temp fair . PPN fair . PMSL poor
8. NMME : Temp poor . PPN poor .
9. WMO : Temp poor . PPN fair .
10. BCC : Temp poor. PPN poor .
11. NASA – Temp poor . PPN fair .
12. Brazil: Temp poor . PPN poor .
13. CanSips : Temp poor . PPN poor .
14. IMME : Temp poor . PPN poor.
15. Copernicus Temp good . PPN poor . PMSL poor
16. CMCC Temp fair . PPN poor . PMSL poor
17: DWD Temp poor. PPN poor. PMSL poor
18. EC Temp good . PPN poor. PMSL poor
19 UKMO Temp poor. PPN poor. PMSL poor
20. MF Temp poor . PPN poor . PMSL poor
21 NCEP Temp poor. PPN fair. PMSL fair
22 JAMSTEC: Temp poor. PPN good .
23 ECMWF (monthly) Temp: poor. PPN poor.

2: Forecast.

Remainder of Spring (2021 April May)

The overall indication for the April and May is for slightly above average temperatures with the strongest indication for above average values is in April.

Rainfall uncertain, probably near average overall but with some hints that April could be drier.

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 2021 (June July August)

Temperature above average for the season with June possibly seeing the warmest anomalies and August the lowest, with values closer to the average.

Rainfall for the season uncertain but probably above average rain totals. Higher rain rates are typical of a warming atmosphere but may not imply an increase in the number of days with rain. Suggestion of one month being drier than average but no agreement as to whether it could be June or August. Slightly reduced indication for a wetter August.

Autumn 2021 (September October November).

Milder than average overall but perhaps near average, or even cooler than average, in November. Wetter than average Autumn with little agreement which month if any might be drier.

Winter 2021 /22 (December January February) very limited data.

Milder overall and also wetter than average especially early in the winter but February drier and possibly colder than average.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

Climate data from The Met Office UK and NCEP USA

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

Review and Experimental Long Range Forecast for SW England. February 2021.

Published 19 February 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are mostly warmer than climatology apart from slightly cooler than average values around the UK. Norwegian Sea and Baltic Sea temperatures also remain above climatology despite the recent cold spell. The tropical North Atlantic is forecast to remain slightly warmer than average through Summer 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific, just south of the equator, show a well established La Nina although some noticeable warming has occurred in the East. Forecasts continue to suggest that Pacific Sea Surface temperatures may remain in a La Nina state through to 2021 although may be near neutral for the Spring.

The North Atlantic Oscillation index (500hPa index shown below) turned turned slightly negative early in December 2020 and has recently turned slightly positive and is forecast to remain slightly positive through the remainder of February.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

Recent Climatology – SW England

The recent cold and largely dry spell between the 5th and 14th has resulted in temperature averages being slightly below normal although this made be offset by milder SW which look like continuing until nearer the end of February when High pressure and a change in wind direction is likely. Rainfall to the 19th has been near or slightly above average and sunshine somewhat below average.

CPC graphic 7th to 13th February showing temperature anomalies and total rainfall in this period.

Looking back at the last three months, despite the colder January, temperatures have been near or a little above average across SW England and rainfall above average despite the drier November.

River flows and ground water levels in January 2021 were well above normal across SW England. Details can be found in the January 2021 Hydrological summary PDF

The forecast changes in the next month and three months can be viewed at Hydro UK http://www.hydoutuk.net/latest-outlook/

The reservoir levels in the SW of England were above the normal level as of February 7tht 2021.

Global Flood Awareness (updated) System. February forecast for the period February to May indicates slightly above normal flood risk for SW England.

Glofas February forecast for Feb to May 2021. Blue above normal flood risk.

UK based data is available in The Hydrological Outlook which provides an insight into future hydrological conditions across the UK. Detail can be found at http://www.hydoutuk.net/

Further graphics from the February outlook are available http://www.hydoutuk.net/archive/2021/february-2021/further-information-february-2021/

Atmosphere: Predictions.

A: 1: Stratosphere

JMA North pole observed temperature changes at 10hPa and 30hPa

Since then the polar stratospheric vortex has re-formed and strengthened into a normal winter mode. Below the ECMWF 10hPa and 50hPa show only limited stratospheric warming although a further weakening of the flow is evident across western Europe at 50hPa in the forecast for 28th Feb.

A: 2: Upper Troposphere

CFsv2 200hPa contours (top row) and anomaly (lower row) for March to May 2021 hint at a less mobile patterns across the Atlantic for April and May.

B: Lower Troposphere:

A selection of March to May solutions using February 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

A selection of WMO sourced March to May solutions using February 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

A selection of June to August solutions using February 2021 data can be seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing the output of seasonal models for 2020 November December and 2021 January based on October 2020 data for the UK and Ireland.

For graphics and details see Verification review 2020 Oct Nov Dec

Review of details looked for in seasonal forecast.
Temperature. Three month season slightly above normal except Norther Ireland slightly below. Nov and DEC above normal but January as much below normal as November was above. Look for colder January following milder Nov and Dec in most areas.

Rainfall. Scotland marginally below elsewhere above normal for the season. Look for November drier and then wetter.

Pressure. Overall below normal (WSW) but above normal in November, well below in December and slightly below in January except in NW Scotland were slightly above.

Comment: DWD and Tokyo had the correct temperature sequence milder start colder end. Washington, UKMO, DWD and Canada had the rainfall trend OK but were not “wet” enough with near normal suggested rather than above normal.

TABLE below is for 3 month data only. Scoring will state good, fair, poor or no signal for the three month season.
1. Russia: Temp no signal. PPN fair.
2. USA – CFS2 : Temp good . PPN good .
3. UKMO Contingency: Temp good . PPN poor .
4. UKMO : Temp fair. PPN fair . PMSL poor
5. USA – IRI : Temp no signal . PPN poor .
6. KMA APCC : Temp good . PPN no signal .
7. JMA : Temp good . PPN poor . PMSL poor
8. NMME : Temp good . PPN poor .
9. WMO : Temp good . PPN poor .
10. BCC : Temp good . PPN poor .
11. NASA – Temp fair . PPN poor .
12. Brazil: Temp good . PPN poor .
13. CanSips : Temp good . PPN fair .
14. IMME : Temp good. PPN fair .
15. Copernicus Temp fair . PPN poor. PMSL poor
16. CMCC Temp fair . PPN poor. . PMSL poor
17: DWD Temp fair . PPN poor. . PMSL poor
18. EC Temp fair . PPN poor. . PMSL poor
19 UKMO Temp fair . PPN poor. PMSL poor
20. MF Temp poor . PPN poor . PMSL poor
21 NCEP Temp fair. PPN poor . PMSL poor
22 JMA: Temp fair. PPN poor . PMSL poor
23 ECMWF (monthly) Temp: poor. PPN poor .

2: Forecast.

Spring (2021 March April May)

The overall indication for the Spring Season is for above average temperatures. March could well see some colder spells and could turn out to be near average. The strongest indication for above average values is in April although May is also likely to be warmer than average.

Rainfall uncertain, probably near average for the season but with some longer dry periods quite likely. There is a risk that March could be wetter than average with even a little snow over the moors but this could be followed by a drier April and near normal May.

Summer 2021 (June July August)

Temperature above average for the season with June possibly seeing the warmest anomalies and August the lowest, with values closer to the average.

Rainfall for the season uncertain but probably above average rain totals. Higher rain rates are typical of a warming atmosphere but may not imply an increase in the number of days with rain. June possibly drier than average but with a risk of above normal rainfall in July and/or August.

Autumn 2021 (September October November) limited data.

Milder than average but with near average rainfall.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

Climate data from The Met Office UK and NCEP USA

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

Review and Experimental Long Range Forecast for SW England. January 2021.

Published 19 January 2021.

1. Influences.

Changes in sea temperature

Atlantic sea temperatures are mostly warmer than climatology apart from slightly cooler than average values to the SW of the UK and Ireland. North Sea, Norwegian Sea and Baltic Sea temperatures also remain above climatology. The tropical North Atlantic is forecast to remain slightly warmer than average through to at least Summer 2021 (See Met Office graphic below).

Colder sea temperatures in the East Pacific, just south of the equator, show a well established La Nina and forecasts continue to suggest that the La Nina will remain active until at least Spring 2021 possibly trending towards neutral conditions for the summer months.

The North Atlantic Oscillation index (500hPa index shown below) turned turned slightly negative early in December 2020 and currently has about a 30% chance of turning positive at the start of February.

The negative NAO phase represents a weaker than usual difference in pressure North to South across the North Atlantic. Winds from the east and north-east are more frequent, bringing with them cold air, while the adjusted position of the jet stream leads to weaker and less frequent storms. As a result Europe is more likely to experience colder, less windy and drier winters during persistent El Nino conditions.

For Met Office information about the NAO see https://www.metoffice.gov.uk/weather/learn-about/weather/atmosphere/north-atlantic-oscillation

The more blocked patterns during a negative phase can produce cyclonic or anticyclonic patterns over the UK depending on where such features become slow moving.

Recent Climatology – SW England

The first ten days of January were rather cold with frequent frosts but fairly dry. After the 10th it became less cold but with some rain. To the 19th of January temperature means across SW England are about 1 to 1.5C below the longer term average and rain totals to the 19th January are only about a third of average. Sunshine hours have been close to average. This can be seen in the snapshot for the period 3rd to 9th showing widespread below average temperature and rain/snow

Looking back at the last three months, temperatures have been near or a little above average across SW England and rainfall above average despite the drier November.

Looking back at 2020 for SW England the year was warmer, wetter but also sunnier in places. It very much looks like that when rain occurred it was “heavier”. For example in the Dawlish and Teignmouth area data suggests there were more dry days than average but also more days with 10mm or more of rain.

River flows and ground water levels in December 2020 were well above normal across SW England. Details can be found in the December 2020 Hydrological summary PDF

The forecast changes in the next month and three months can be viewed at Hydro UK http://www.hydoutuk.net/files/3916/1054/7577/2021_01_HO_Summary.pdf

The reservoir levels in the SW of England were above the normal level as of January 10th 2020.

Global Flood Awareness (updated) System. January forecast for the period January to April (shown left below) indicates slightly above normal flood risk for SW England. The image on the right shows a forecast for river flow based on the North Atlantic Oscillation (NAO) implying normal to above normal river flows across parts of the SW. For details see Outlook from NAO Analogues (hydoutuk.net)

Atmosphere: Predictions.

A: 1: Stratosphere

Major warming in the stratosphere (see N Pole temperatures below) has caused a reversal of the westerly flow across North America and a significant re-location of the polar stratospheric vortex towards Norther Russia. Although further warming is expected to continue forecasts suggest the vortex may return towards the N Pole and redevelop for a time before perhaps splitting the vortex in two weeks time.

ECMWF 50hPa and 10hPa analysis 17th and forecast for 27th Jan

NW Europe NCEP forecast temperature anomaly forecast have been trending to colder values in February and possibly March over recent days and the stratospheric warming may well be part of the reason.

A: 2: Upper Troposphere

CFsv2 200hPa contours (top row) and anomaly (lower row) for Feb to May 2021 hint at a more cyclonic February across the UK the less mobile patterns for March to May.

B: Lower Troposphere:

A selection of February to May solutions using January 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

Many models seem to have a problem forecasting colder than average values so the increase in the number of models showing near normal values might imply colder values in February and perhaps early March.

A selection of WMO sourced March to May solutions using January 2021 data are shown below, top row temperature anomaly and lower row precipitation anomaly.

A selection of June to August solutions using January 2021 data

C: Comparing the output of seasonal models for October November and December based on September 2020 data for the UK and Ireland.

For graphics and details see Verification review 2020 Oct Nov Dec

Review of details looked for in the seasonal forecast.
Temperature. above average for season with November strongest for above normal after normal October. Rainfall. above average for season with November below average except N Ireland and W Scotland. Oct and Dec wet in S and E especially. Pressure. below average for season, November above average but Oct and Dec below.

TABLE below is for 3 month data only. Scoring will state good, fair, poor or no signal for the three month season.

1. Russia: Temp good . PPN mainly no signal Scotland and N Ireland good .
2. USA – CFS2 : Temp fair . PPN fair . (CFS2 monthly E3 suggested drier Nov)
3. UKMO Contingency: Temp fair . PPN no signal .
4. UKMO : Temp good. PPN poor . PMSL poor
5. USA – IRI : Temp no signal . PPN good .
6. KMA APCC : Temp poor . PPN poor .
7. JMA : Temp good – a little cool . PPN poor . PMSL poor (mean direction good)
8. NMME : Temp good. PPN fair .
9. WMO : Temp fair . PPN poor .
10. BCC : Temp fair . PPN poor .
11. NASA – Temp good . PPN poor .
12. Brazil: Temp good . PPN good . PMSL good
13. CanSips : Temp fair . PPN fair .
14. IMME : Temp good. PPN poor .
15. Copernicus Temp fair. PPN poor . PMSL poor
16. CMCC Temp fair. PPN poor . PMSL poor
17: DWD Temp fair. PPN poor . PMSL poor
18. EC Temp fair. PPN poor . PMSL poor
19 UKMO Temp fair. PPN poor . PMSL poor
20. MF Temp fair. PPN poor . PMSL poor
21 NCEP Temp good. PPN fair . PMSL fair
22 JAMSTEC: no data
23 ECMWF (monthly) Temp: fair . PPN good

Remainder of Winter (February 2021).

February may well start near normal or even slightly milder than average but there is a moderate risk of a change to be colder than average values – overall the month ending up near or slightly below average.. Rainfall is likely be near or above normal to start the month but trending drier, overall near normal totals for the month are possible. Increased risk of snow IF the change to colder types occurs.

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 for December to February less than 5 days lying snow in lowland areas 5 to 10 hills, say hills around 200 metre elevation – one in three years have no lying snow. February possibly around 2 days on average with lying snow for low ground.

Spring (2021 March April May)

After a colder than average start Spring temperatures are likely to trend above average for May. April could see values close to normal. Overall above average values are likely for the three month season.

Rainfall uncertain but probably near or a little below average for the season. There is however a risk that March could be wetter than average followed by a drier April and near normal May.

Possibly some snowfall on the moors in March.

Early indication for Summer 2021 (June July August) limited data (data from eight global systems)

Temperature slightly above average for the season although Cornwall could be near average. Rainfall for the season uncertain but majority suggest close to average values although some models have wetter/drier than average.

3. Caution.

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary can be seen at here.

4. 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

Stratospheric Diagnostics from Japan Met Agency and ECMWF via Free University Berlin

Climate data from The Met Office UK and NCEP USA

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