Climate review and Experimental Long Range Forecast for SW England. May 2022.

Published 18 May 2022.

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A: Overview

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic, North Sea, Baltic, Mediterranean and Gulf of Mexico are warmer than climatology for mid May. Parts of the Eastern Pacific are colder than climatology although other areas continue to be warmer.

The Tropical Atlantic sea temperature warmed more than expected in April but are forecast to be near or slightly cooler than average through to Autumn 2022 which is slightly less cool than the forecast issued last month. (see Met Office graphic below).

Forecasts suggest that tropical Pacific Sea Surface Temperatures (nino3.4) are likely to have similar anomalies through the remainder of Spring 2022 with weak La Nina conditions forecast to persist through the remained of 2022.

The North Atlantic Oscillation index (500hPa index shown below) turned negative in late April and for the first week of May but then turned positive. Weakly positive are forecast to continue over the next two weeks. Positive values imply weaker westerly winds across the Atlantic towards Europe or a reversal to easterlies more typical of blocked weather patterns although a weak signal is inconclusive.

Due to changes at NCEP graphics now show GEFS ensemble forecasts in the left panel and GFS operation model in the right panel.

2. Recent Climatology

SW England:

To the 18th temperatures have been a little above average despite below average sunshine and rainfall has been slightly below average in the South and East of the region but near average in the North and West.

UK:

Met Office provisional Temperature and Rainfall anomalies for February to April 2022 are shown below:

Copernicus, European temperature and rainfall anomalies and global temperature anomaly for April 2022. (30 year period 1981-2010). Spain in particular was wetter and colder than average during March.

UK River flows and ground water levels in April 2022 reflected the drier weather and were below average. Details can be found in the March 2022 Hydrological Summary

Global Flood Awareness System – GloFAS – flood risk for May to August suggests the river flood risk is near or below average across the UK. This does not include “flash” floods caused by thunderstorms.

Reservoir levels, according to SW Water, slightly below the long term average across SW England as of 8th May 2022.

B: Forecast data:

1. Stratosphere:

The stratosphere remains in “summer” mode.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for summer (June July August) 2022, although hints at a transition to lower heights for August. Suggestion of reduced zonal flow in the Atlantic west of the UK early in the summer but less so later. The higher than average heights forecast could be due to higher than average temperatures in depth through the atmosphere?.

3. Lower Troposphere:

Selection of model solutions for summer June July and August 2022 using May data are shown below.

May graphics can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly and lower row precipitation anomaly

Source Data WMO low resolution super ensemble for June to August 2022 based on April data. Full data at http://www.weather-info.co.uk/wxsvc/seaslatest.html

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

Individual members of the WMO super ensemble.

Limited graphics for Autumn (September October and November) available at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

February to April 2022 – based upon January 2022 data.

Summary – 200122 –
All models suggest above normal temperature values for the three month average. A few models have March and/or April near normal. Precipitation forecasts (often more variable and less reliable) suggest above average values across the North or NW and below average across the south or SE of the area (UK and Ireland). The strongest signal for above average precipitation is in February for western and northern areas and the strongest indication of drier than average is in March and in a few models April. The drier signal is associated with higher than average pressure.

Review of details looked for in seasonal forecast based on observations.

Temperature: Above normal but April nearer normal

Rainfall: N Scotland above or near average elsewhere wetter Feb largely offset by drier March and especially April

Sunshine: mostly above normal due to sunnier March and near average other months..

Pressure: Slightly above average (SW) but N Scotland below in Feb.

Comment on summary: Overall a good summary hinting at above average pressure and some skill pointing to the wetter and drier months. WMO did fairly well with rain sequence.

Scoring will attempt to state good, fair, poor or no signal.
Evaluation for 3 month anomalies.
1. Russia (WMO): Temp mostly good. PPN fair .
2. USA – CFS2 : Temp good. PPN fair .
3. UKMO Contingency: Temp good. PPN poor .
4. UKMO : Temp good. PPN fair . PMSL fair
5. USA – IRI : Temp good. PPN poor .
6. KMA APCC : Temp good . PPN fair .
7. JMA : Temp good . PPN fair . PMSL good
8. NMME : Temp good. PPN fair .
9. WMO multi : Temp good . PPN fair .
10. BCC : Temp good. PPN good (monthly data good).
11. NASA : Temp good. PPN poor .
12. Brazil: Temp poor . PPN poor .
13. CanSips : Temp fair. PPN fair .
14. IMME part of Copernicus no longer included.
15. Copernicus Temp good . PPN fair . PMSL fair
16. CMCC Temp good . PPN poor . PMSL good
17: DWD Temp good . PPN poor . PMSL fair
18. EC Temp good . PPN poor . PMSL fair
19 JMA Temp good . PPN fair . PMSL fair
20 UKMO Temp good . PPN fair . PMSL fair
21. MF Temp good . PPN fair . PMSL fair
22 NCEP Temp good . PPN fair . PMSL fair
23 ECCC Temp: good . PPN good . PMSL good

D: Text Forecast for SW England

Summer 2022 (June July August)

Temperatures likely to be above average for the season and possibly each month. Typical forecast anomalies are around 1 C above average. This suggests more warm days compared to an average summer but not necessarily hot.

Rainfall forecasts are inconclusive suggesting near normal rainfall for the summer overall with perhaps a majority hinting at drier than average over N France and parts of the S of England. Suggestion that July is the most likely month to be drier but a risk that June and August could be wetter more especially in western parts of SW England than in the East. Summer rainfall can be in form of thundery showers which can lead to rainfall totals being very uneven across a district. Should local rain totals be above average due to thundery showers it may not lead to an increase in the number of “wet days”.

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 2022 (September October November).

Good indication for above average temperatures with the strongest signal being for September but with a weaker signal for November. Rainfall probably above average for the season, especially in October but drier than average in November.

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 2022/23 (December January February). Very limited data.

Temperature forecasts suggest near or above average values. Rainfall forecast is for above average rainfall early in Winter and below average later. Snowfall like to be below average which means little if any snow for lower ground but some snow over 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.

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

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

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. April 2022.

Published 21 April 2022.

A: Overview

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea remain generally warmer than climatology for mid April apart from some cooling to the west of North Africa and cooler values in the eastern Mediterranean.

The East Pacific has a similar pattern of anomalies in April 2022 compared to March although the colder anomalies have become larger. Indian Ocean sea temperatures are also mostly above average for the time of year.

The Tropical Atlantic sea temperature remains near average and is forecast to remain near or a little below average through to Autumn 2022 which is slightly cooler than the forecast issued last month. (see Met Office graphic below)

Forecasts suggest that tropical Pacific Sea Surface Temperatures (nino3.4) are likely to have similar anomalies throughout Spring 2022 with La Nina conditions forecast to persist through the summer and into the Autumn of 2022.

The North Atlantic Oscillation index (500hPa index shown below) turned negative in late March and positive in mid April but is forecast to turn negative again over the next few days. Negative values imply weaker westerly winds across the Atlantic towards Europe or a reversal to easterlies more typical of blocked weather patterns.

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

2. Recent Climatology

SW England:

Temperatures in April, to the 20th, have so far been near average despite some ground frosts. Rainfall in western parts near or slightly below average but in the east of the region it has been drier than average so far. Sunshine probably slightly above average especially in eastern areas.

UK:

Met Office provisional Temperature and Rainfall anomalies for January to March 2022 are shown below: Rainfall for the period October to March has been below normal across southern parts of England.

Copernicus, European temperature and rainfall anomalies and global temperature anomaly for March 2022. (30 year period 1981-2010). Spain in particular was wetter and colder than average during March.

UK River flows and ground water levels in March 2022 were near average. Details can be found in the March 2022 Hydrological Summary

Global Flood Awareness System – GloFAS – flood risk for April to July suggests the flood risk is no better or worse than average across the UK

Reservoir levels, according to SW Water, remain fairly high across SW England as of 10th April 2022.

B: Forecast data:

1. Stratosphere:

N Pole temperature trace for 30hPa and 10hPa from Japan Met Agency is shown below.

The stratosphere is now in “summer” mode as can be seen in the 50hPa and 10Hpa graphic for the 18th of April 2022 shown below.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for summer (June July August) 2022. Suggestion of reduced zonal flow in the Atlantic west of the UK. In addition higher than average heights are forecast (which could be due to higher than average temperatures in depth through the atmosphere)

3. Lower Troposphere:

Selection of model solutions for summer June July and August 2022 using April data are shown below.

May graphics can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

Top row temperature anomaly and lower row precipitation anomaly

Source Data WMO low resolution super ensemble for June to August 2022 based on April data. Full data at http://www.weather-info.co.uk/wxsvc/seaslatest.html

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

Individual members of the WMO super ensemble.

Montreal Canada

Limited graphics for Autumn (September October and November) available at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

January to March 2022 – based upon December 2021 data.

Original Summary – 20DEC2021 –
For the three months overall temperatures averaging out above normal but January could be near average and in places colder than average with March most likely to be well above average. Precipitation for the season above average in the N and W and below in S and E. January could well see above average precipitation and this could mean an increase the risk of snow (not just for high ground) except perhaps in parts of the S/SW. Main theme for above average precip is across the NW. Uncertain as to whether February or March could see longer drier period with below average precip although slightly more models have February somewhat drier than have March drier. (Could be split across months).

Review of details looked for in seasonal forecast based on observed data:.

Temperature. Above averagre although the south of Englnd near average in January

Rainfall. Mostly below average although some parts of NW England may have been above average. Looking for a dry/wet/dry sequence for the three months.

Sunshine. Above average although February was below average in places.

Pressure. Above average although the N was below in February.

Comment: Looking for above average temperatures and below average rainfall with possibly an indication of Feb being wetter. Also above average pressure.

Comment on summary: Good temperature forecast. Rain forecast not helpful but hints at drier end of period was just about OK.

Scoring will attempt to state good, fair, poor or no signal. (No signal implies similar probabilities for above/normal/below).

Comment: Looking for above average temperatures and below average rainfall with possibly an indication of Feb being wetter. Also above average pressure.

1. Russia (WMO): Temp poor . PPN fair .
2. USA – CFS2 : Temp good. PPN poor .
3. UKMO Contingency: Temp fair . PPN fair .
4. UKMO : Temp good . PPN poor . PMSL good
5. USA – IRI : Temp fair . PPN poor .
6. KMA APCC : Temp good . PPN fairly good .
7. JMA : Temp good. PPN fairly good . PMSL good
8. NMME : Temp good . PPN poor .
9. WMO multi : Temp good. PPN poor .
10. BCC : Temp poor. PPN fair .
11. NASA : Temp good . PPN poor.
12. Brazil: Temp fair . PPN poor .
13. CanSips : Temp poor . PPN poor .
14. IMME : Temp good. PPN fair .
15. Copernicus Temp good . PPN poor . PMSL fair
16. CMCC Temp good. PPN fair . PMSL good
17: DWD Temp fair. PPN fair . PMSL good
18. EC Temp fair. PPN fair . PMSL good
19 JMA Temp good. PPN poor . PMSL fair
20 UKMO Temp good. PPN fair . PMSL fair
21. MF Temp good . PPN fair . PMSL good
22 NCEP Temp good . PPN poor . PMSL good

D: Text Forecast

Remainder of Spring (2022 May)

Strong signal from most seasonal forecast systems for above average temperature. Majority signal for below average rainfall, roughly 30% of models suggest above average. Most likely below average number of wet days away from parts of W and N Cornwall and N Devon.

Due to climate change and a warmer atmosphere, rain totals have often been higher than might be expected on wet days but the number of wet days at times can be the same or lower than average. Season rainfall forecasts are mostly in terms of amount of rain per day averaged over a month and models find it difficult to predict individual wet days. Hence a good deal of caution is needed when considering rainfall forecasts.

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 2022 (June July August)

Temperatures likely to be above average for the season and possibly each month. This suggests more warm days compared to an average summer but not necessarily hot. Possibly a drier than average June then near normal or above average rain totals for July and/or August. Not good agreement as to which month could be wetter. Summer rainfall can be in form of thundery shower outbreaks and rainfall totals can be very uneven across a district. Overall rain totals for the summer may well be above average but the number of dry days could easily be near or above average.

Autumn 2022 (September October November).

Good indication for above average temperatures with the strongest signal being for September. Rainfall probably above average for the season but some longer dry spells indicated for October and/or November which could be split between the two months.

Winter 2022/23 (December January February). Very limited data.

Temperature forecast suggest near average values with a hint at above average in places. Rainfall forecast is for above average rainfall but below average snow, except perhaps over higher ground in the north.

E. 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.

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

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. March 2022.

Published 18 March 2022.

A: Overview

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea remain generally warmer than climatology for mid March apart from some cooling to the west of North Africa.

The East Pacific has similar anomalies in March 2022 compared to February except for a colder zone just north of the equator near 140 deg West and a warmer area west of Ecuador. Indian Ocean sea temperatures are also mostly above average for the time of year.

The Tropical Atlantic sea temperature has returned to near average and is forecast to remain near or a little above average through to Summer 2022 (See Met Office graphic below)

Forecasts suggest that tropical Pacific Sea Surface Temperatures (nino3.4) are likely to have similar anomalies throughout Spring 2022 with a fairly strong La Nina. Warming to a neutral state during Summer 2022 is less certain and may result in La Nina conditions persisting for all of 2022.

Nino 3.4 CFSv2 and NMME ensemble forecasts.

The North Atlantic Oscillation index (500hPa index shown below) turned positive early in January and is forecast to remain positive over the next two weeks although with a weaker signal.

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

2. Recent Climatology

SW England:

For the first half of March 2022: the temperature has been slightly above the long term average of 7.9 Celsius and rainfall has also reached to average value for the whole month of around 69mm.

UK:

Met Office provisional Temperature and Rainfall anomalies for Winter (December 2021 to February 2022) are shown below:

Copernicus, European temperature and rainfall anomalies and global temperature anomaly for February and Winter. (1981-2010 30 year period)

UK River flows in February 2022 and ground water levels were near average. Detail can be found in the February 2022 Hydrological Summary

Global Flood Awareness System – GloFAS – flood risk for March to June suggests a normal risk of flooding in southern England but enhanced risk in Ireland and Scotland..

Reservoir levels, according to SW Water, remain fairly high across SW England as of 13th March 2022.

B: Forecast data:

1. Stratosphere:

A minor warming took place on the 5th of March and a second phase is now underway (see temperature graphic below).

The vortex is currently split and is forecast to displace and weaken further. GFS 10hPa extended range suggests this may be the start of the final warming with a transition away from the winter state. ECMWF 17/1200UTC and T+24 hour forecast illustrate this process (see graphic below).

The displacement of the vortex has split and reduced the area of lower stratospheric ozone due to increased mixing.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for April to June 2022. Suggestion of reduced zonal flow in the Atlantic west of the UK. Overall higher than average heights in may be due to higher than average temperatures.

3. Lower Troposphere:

Selection of model solutions for April to June 2022 using March data, are shown below.

Top row temperature anomaly and lower row precipitation anomaly. April to June 2022.

Source Data WMO low resolution super ensemble for April to June 2022. Data for summer can be seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

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

Individual members of the WMO super ensemble.

WMO CFSv2, NMME and NASA graphics using, March 2022 data, for Summer 2022 (June July August) can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

December 2021 to February 2022 (Winter) – based upon November 2021 data.

Original Summary – 151121 –
Winter looks likely to be milder and porbably wetter (in terms of total rain) than average. December may well see near normal temperatures (implies possibly a colder December) followed by above average values for January and more especially February. December may also be a drier than average month, although the N could see near average precipitation, followed by January and / or February seeing above average values. Snowfall probably below average except higher ground in the north.

Review of details looked for in the seasonal forecast based on observed data.

Temperature.Large area of England near normal in January but other months above average and season above or well above average.

Rainfall. looking for the south to be drier, Wales and NW Midlands/NW England to be wetter and for any indication of drier Jan/wetter Feb

Sunshine. Below average in West and above in East.

Pressure. Above average (WSW mean flow). Dec below average Jan well above Feb above in S below in N.

Comment:
The idea of a stronger signal for above average in February was correct as was the mild forecast for the season. Lower values in December were wrong. Mixed rainfall result parts of the NW were above average but the south in particular had below average rain for the season. Marked swing from Jan to Feb from drier to wetter.
DWD and UKMO got the idea of less mild in SE UK January whilst being above average in D and F. DWD also got the drier Jan and Wetter Feb to some extent.

Scoring will attempt to state good, fair, poor or no signal.
Comment: Looking for above average temps, below average rain in S and E (although if it had been a leap year the 1st March was very wet in SW England.)
1. Russia (WMO): Temp . PPN .
2. USA – CFS2 : Temp good . PPN .
3. UKMO Contingency: Temp fair . PPN fair .
4. UKMO : Temp good. PPN fair incorrect . PMSL fair
5. USA – IRI : Temp poor . PPN fair .
6. KMA APCC : Temp good . PPN no signal .
7. JMA : Temp good . PPN poor . PMSL fair/good
8. NMME : Temp good. PPN poor.
9. WMO multi : Temp good. PPN poor.
10. BCC : Temp good. PPN fair .
11. NASA : Temp good. PPN poor .
12. Brazil: Temp good. PPN fair.
13. CanSips : Temp good . PPN poor .
14. IMME : Temp good . PPN poor .
15. Copernicus Temp good. PPN . PMSL poor
16. CMCC Temp good. PPN . PMSL fair
17: DWD Temp good. PPN . PMSL poor
18. EC Temp good. PPN . PMSL poor
19 JMA Temp good. PPN . PMSL fair
20 UKMO Temp good. PPN . PMSL fair
21. MF Temp good . PPN . PMSL good
22 NCEP Temp good. PPN . PMSL poor
23 ECCC Temp: good. PPN . PMSL good

D: Text Forecast

Remainder of Spring (2022 April May)

Strong signal from most seasonal forecast systems for above average temperatures although April could be only slightly above average. Some agreement for below average rainfall across SW England in April, but with above average values in May. Recent climate change seems to result in higher rainfall totals but not always more wet days, i.e. when it rain it rains heavier but not always more often, hence rain totals for the season could be swayed by smaller number of heavy rain events.

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 2022 (June July August)

Autumn 2022 (September October November).

Limited data. Milder and wetter than average.

Winter 2022/23 (September October November). Very limited data.

February data suggested cooler wetter start to winter then milder/near average temperatures and perhaps slightly drier. March data reverses this with a milder winter especially at the start and a less mild February. Rainfall forecast also change to suggest above average rainfall but below average snow.

E. 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.

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

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. February 2022.

Published 16 February 2022.

A: Overview

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea remain generally warmer than climatology for mid February.

The East Pacific has similar anomalies in February 2022 compared to January with the NW and SW of the Pacific strongly above average. Indian Ocean sea temperatures are also above average for the time of year. In all of these areas tropical storms may be enhanced by the warmer seas.

The Tropical Atlantic sea temperature is slightly above average and is forecast to remain warmer than average through to at least Summer 2022 (See Met Office graphic below)

Forecasts suggest that tropical Pacific Sea Surface Temperatures (nino3.4) are likely to have similar anomalies through Spring 2022 with a fairly strong La Nina. Warming to a neutral state during Summer 2022 is less certain and may result in La Nina conditions persisting for all of 2022..

The North Atlantic Oscillation index (500hPa index shown below) turned positive early in January and is forecast to remain positive over the next two weeks.

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

2. Recent Climatology

SW England:

For the first half of February 2022: the temperature averaged about two and a half degrees Celsius above the long term average, rainfall was above average in western areas and near average in the east. Sunshine generally was below average.

UK:

Met Office provisional Temperature and Rainfall anomalies for November to January 2022 are shown below:

Copernicus, European temperature and rainfall anomalies. (1981-2010 and 1991-2020 30 year periods) for February 2022

Copernicus Global and European temperature anomalies (1981-2010 and 1991-2020 30 year periods)

UK River flows in December 2021 and ground water levels were near average. Detail can be found in the January 2022 Hydrological Summary

River flows have reduced since last month although ground water remains near average.

Global Flood Awareness System – GloFAS – flood risk for Feb to May suggest reduced risk of flooding in southern England.

Reservoir levels, according to SW Water, remain fairly high across SW England as of 6th February 2022.

B: Forecast data:

1. Stratosphere:

North polar stratospheric winter circulation is well established and strong as shown by the 50hPa and 10hPa analysis for the 15th and the T+240 hour forecast. At this time there is no sign of a Sudden Stratospheric Warming in a location that might impact March weather.

In the Northern Hemisphere there is some reduction in Ozone but values remain above the nominal Ozone “hole” value of 220DU. If the stratospheric vortex and its associated low temperatures remain during March then an Arctic mini ozone hole could form.

2. Upper troposphere:

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for March to May 2022. Suggestion of enhanced zonal flow in N Atlantic during March steering weather systems mostly N of UK. Overall higher than average heights in April and May me be due to higher than average temperatures but at less ridging in May.

3. Lower Troposphere:

Selection of model solutions for Spring 2022 using February data, are shown below.

Top row temperature anomaly and lower row precipitation anomaly. March to May 2022.

Source Data WMO low resolution super ensemble for the Spring 2022. Data for summer can be seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

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

Individual members of the WMO super ensemble. Spring 2022

WMO CFSv2, NMME and NASA graphics using, February 2022 data, for Summer 2022 (June July August) can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing previous output:

November 2021 to January 2022 – based upon October 2021 data.

Original Summary – 171021 –
The three month average is most likely to be above average but some models suggest near average values are possible in November and December with a few models suggesting below average values in December at least in parts of the UK. Precipitation three month average probably above average but number of models suggest that the first half of winter and possible December could see below average totals at least in parts of the UK and Ireland. The WMO super ensemble mean indicates no preference between above/normal/below indicating the lack of agreement between model output. Snow risk may be slightly enhanced for northern areas.

Review of details looked for in the seasonal forecast.

Temperature. Three month season above normal all areas, look for S being above in December and North in Nov and Jan.

Rainfall. Three month season below normal all areas except far NW Scotland. Look for December nearer average and locally above in parts of England and Wales.

Sunshine. N Ireland below normal. Elsewhere mixed near normal in Nov below in Dec and above in Jan.

Pressure. Above normal but below in December

Comment:
General signal for above average temperature was correct. Precipitation forecast was incorrect for the season although the idea of below average start was correct but did not suggest drier January.
Good monthly precipitation sequence (WMO graphics) by China, fair signal by Russia and Australia.

Scoring attempts to state good, fair, poor or no signal for THREE MONTH mean.

1. Russia (WMO): Temp fair (cool) . PPN Fair but not dry enough.
2. USA – CFS2 : Temp good . PPN poor (overly wet).
3. UKMO Contingency: Temp good . PPN poor (overly wet).
4. UKMO : Temp good . PPN fair. PMSL poor
5. USA – IRI : Temp fair . PPN fair.
6. KMA APCC : Temp good . PPN fair .
7. JMA : Temp good . PPN good . PMSL good
8. NMME : Temp good . PPN poor (overly wet) .
9. WMO multi : Temp good . PPN fair (overly wet) .
10. BCC : Temp good . PPN good (slightly wet).
11. NASA : Temp poor (cool) . PPN poor .
12. Brazil: Temp good . PPN poor (overly wet).
13. CanSips : Temp good . PPN poor (overly wet) .
14. IMME : Temp good . PPN fair (overly wet) .
15. Copernicus Temp good . PPN fair (overly wet) . PMSL poor
16. CMCC Temp good . PPN no signal . PMSL poor
17: DWD Temp good . PPN no signal . PMSL poor
18. ECMWF Temp fair . PPN no signal . PMSL good
19 JMA Temp fair. PPN fair. PMSL good
20 UKMO Temp fair . PPN no signal . PMSL poor
21. MF Temp poor . PPN no signal . PMSL fair
22 NCEP Temp good . PPN no signal . PMSL good
23 ECCC Temp: fair . PPN poor . PMSL poor

D: Text Forecast

Spring (2022 March April May)

Strong signal from most seasonal forecast systems for above average temperatures with largest positive anomalies possibly in March. Hint that April could be only slightly above average. Unusually strong agreement for below average rainfall across SW England in March and possibly in April, but with above average values in May. Recent climate change seems to result in higher rainfall totals but not always more wet days, i.e. when it rain it rains heavier but not always more often hence rain totals for the season could be swayed by smaller number of heavy rain events.

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 2022 (June July August)

Temperatures likely to be near or above average for the season suggesting more warm rather than hot days compared to an average summer. Possible a drier than average June then near normal or above average rain totals for July and August but with August suggested as having more rain. Summer rainfall can be in form of thundery shower outbreaks and rainfall totals can be very uneven across a district.

Autumn 2022 (September October November).

Limited data. Milder and wetter than average.

Winter 2022/23 (September October November). Very limited data.

Cooler wetter start to winter then milder/near average temperatures and perhaps slightly drier.

E. 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.

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

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. January 2022.

Published 20 January 2022.

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea remain mostly warmer than climatology for January.

The East Pacific has similar anomalies in January 2022 compared to December 2021 with the NW and SW of the Pacific strongly above average. Indian Ocean sea temperatures are also above average for the time of year. In all of these areas tropical storms may be enhanced by the warmer seas.

The Tropical Atlantic sea temperature is slightly above average and is forecast to remain warmer than average through to at least Summer 2022 (See Met Office graphic below).

Forecasts suggest that tropical Pacific Sea Surface Temperatures are likely to have similar anomalies through Spring 2022 with a fairly strong La Nina. Warming to a neutral state in Summer 2022 is less certain. Indian Ocean sea temperatures are also above average for the time of year.

The North Atlantic Oscillation index (500hPa index shown below) turned positive early in January, which was not as suggested by earlier forecasts. The pattern is forecast to be fairly neutral / uncertain over the next two weeks but with a trend to possible positive state by the end of January.

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

January started unsettled with a series of weather systems crossing the UK and predominantly southwest or west winds. Higher pressure across mainly the south of the UK brought drier spells and some night frosts although not especially cold air. Temperatures across SW England to the 19th average out above normal by between a half and two degrees Celsius with western areas seeming the later anomalies. Rainfall in the west has been a little below normal and in the east about half of what might be expected. Sunshine has probably been a little below average so far in January 2022.

21 UK Met provisional Temperature and Rainfall anomalies for October to December 2021 are shown below:

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

Copernicus, Global and European temperature and Europe rainfall anomalies. (1981-2010 30 year period) for December 2021 and January to December.

UK River flows in December 2021 and ground water levels were near average. Detail can be found in the December 2021 Hydrological Summary

Data, as of 20th January show near normal but mostly falling river values across of the SW and with some locations (in orange) showing below average values.

Reservoir levels, according to SW Water, were fairly high across SW England as of 16th January 2022.

A: 1: Stratosphere

North polar stratospheric winter circulation is well established as shown by the 50hPa and 10hPa analysis for the 19th and the T+240 hour forecast. At this time there is no sign of a Sudden Stratospheric Warming starting.

In the Northern Hemisphere there is some reduction in Ozone but values remain above the nominal Ozone “hole” value of 220DU.

Percentage difference in Ozone compared to average.

A2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for February to May 2022. Suggestion of enhanced zonal flow in February and Western Europe ridging in March. Overall higher than average heights in April and May me be due to higher than average temperatures?

B: Lower Troposphere:

Selection of model solutions for Spring 2022 using January data, are shown below.

Top row temperature anomaly and lower row precipitation anomaly. February to May 2022.

Source Data WMO low resolution super ensemble for the Spring 2022. February data seen at http://www.weather-info.co.uk/wxsvc/seaslatest.html

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

Individual members of the WMO super ensemble. Spring 2022

DWD Germany

Seoul Korea

CFSv2, NMME and NASA graphics using, January 2022 data, for Summer 2022 (June July August) can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing the output of seasonal models for October November December based on September 2021 data for the UK.

For graphics and details see Verification review October November December

Review of details looked for in seasonal forecast based on the observed data.

Temperature. Above normal overall but November normal.

Rainfall. Below average mainly due to dry November although N Scotland probably above normal

Sunshine. Below average, November near average

Pressure. above normal overall but December below.

Original Summary – Summary – 190921 –
The main signal is for above normal temperatures for the season perhaps with reduced anomalies across the south of the UK and elsewhere in December. Rainfall very mixed signals almost as many drier than average as wetter than average. Potential for wetter than average highest in the N and W and lowest in the S and E which represent a typical weather type. There is a suggestion of periods of dry weather – and periods of wet weather but no agreement as to which month this applies – may suggest some extremes. Sea level pressure may be above average for the season.

Comment:
Temperature: DWD KMA got the sequence fairly well. Most got the above average for season, less good were Canada, Brazil, France, Washington WMO data set.
Precipitation: The three month sequence with dry November was best captured by: NASA DWD BoM with the overall signal of below average best captured by: Canada DWD Brazil Russia and to some extent UKMO

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

D: Forecast.

Remainder of Winter (February 2022)

Temperatures across SW England are likely to be milder than average in February. Rainfall most likely above average although a chance that parts of the south and east of SW England could have near normal rainfall. Any snow mostly limited to the Moors – if any.

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 (2022 March April May)

Overall milder than average temperature with larger anomalies in March and May. Rainfall for the season uncertain but probably near or above average rain totals but with March possibly being drier than average. Recent climate change seems to result in higher rainfall totals but not always more wet days, i.e. when it rain it rains heavier but not always more often.

Summer 2022 (June July August)

Limited data but suggestions are for near or a little above average temperature. Possible a drier than average June then near normal or above average rain totals for July/or Augusts.

Autumn 2021 (September October November).

Very limited data. Milder and wetter than average but possible drier in September.

E. 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.

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

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. December 2021.

Published 20 December 2021.

1. Influences.

Changes in sea temperature

Sea temperatures in the Northern Hemisphere Atlantic and North Sea remain mostly warmer than climatology for the time of year.

The Tropical Atlantic sea temperature 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 similar anomalies in December compared to November 2021 with the NW and SW of the Pacific strongly above average. Forecasts suggest that tropical Pacific Sea Surface Temperatures are likely to have similar anomalies through January with a fairly strong La Nina before warming to a neutral state in Summer 2022. The tropical Indian Ocean sea temperatures are also above average for the time of year.

The North Atlantic Oscillation index (500hPa index shown below) turned negative as forecast for the latter part of November but has since been oscillating between positive and negative. This oscillation may continue but with the chance of a stronger negative state at the turn of the year.

A 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.

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 first half of December saw changeable weather across the UK with winds predominantly from a westerly point. This helped keep temperatures between 1 and 2 degrees above the 1981-2010 average. Skies were often rather cloudy (reduced sunshine hours) but with pressure being slightly above average, across the south of England, rainfall totals have been lower than might have been expected.

For the period September to November 2021, temperatures have been mostly above average although the South of the UK had closer to normal values in November. Rainfall deviated from the long term average (1981-2010) in many areas due to the wet October and an unusually dry November.

2021 UK Met provisional Temperature and Rainfall anomalies for September to November 2021 are shown below:

November, Global and European temperature and rainfall anomalies. (1981-2010 30 year period).

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

Data, as of 20th December, show near normal but mostly falling river values across of the SW and with some locations (in orange) showing below average values.

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

Global Flood Awareness (updated to version 3) December forecast for the period December 2021 to March 2022 indicate average flood risk for SW England. River flow forecast shown are blue for above normal river flow and grey near average.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric winter circulation is well established as shown by the 50hPa and 10hPa analysis for the 15th and the T+240 hour forecast.

In the Southern Hemisphere the the Ozone “hole” is dissipating. There are indications of a lower ozone associated with the north polar vortex but this vortex is much less stable over the long term.

Top row: Southern Hemi Ozone. Lower row: Northern Hemi Ozone.

2: Upper Troposphere

CFSv2 200hPa contours (top row) and CFSv2 anomaly (middle) and NMME (lower row) for January to March 2022. There is a hint of a less mobile pattern across the Atlantic in January and for the more zonal flow to be displaced slightly north during February and March.

B: Lower Troposphere:

Selection of model solutions for January to March 2022 using December data, are shown below.

Top row temperature anomaly and lower row precipitation anomaly.

ECMWF JFM

Source Data WMO low resolution super ensemble for the January to March 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

Canada JFM

Graphics using, December 2021 data, for Spring 2022 (March April May) and Summer 2022 (June July August) can be viewed at http://www.weather-info.co.uk/wxsvc/seaslatest.html

C: Comparing the output of seasonal models for September October November based on August 2021 data for the UK.

For graphics and details see Verification review September October November

Review of details looked for in seasonal forecast based on the observed data.

Temperature: Above average for the season but with near average values in the south in November.

Rainfall: In many areas the wetter October was cancelled out by the drier November. Overall will be looking for a drier than average signal for the season and hints to wetter in the far N and parts of NW England/SW Scotland.

Sunshine: Below average in N and W and above average in some eastern areas.

Pressure: mostly above average in the south.

Original Summary – 170821 –
Main theme seems to be for near or slightly above normal temperatures for the season. Some hints at larger positive anomalies in either September or October. Rainfall quite mixed indication but there are more drier solutions than wet ones for the season especially for southern UK. Overall near average rainfall for the season seems likely but with chance of some longer dry periods most likely early in the Autumn and most likely in the S and E. Models differ as to which month could be the wettest/driest.

Comment: Good indication for above average and even for lower anomalies later in the season. Rainfall good hint at drier than average

Comment: Brazil, Washington and NMME had possibly the best precipitation indication. NMME, UKMO, French, WMO combined and Brazil did ok with temperature sequence.

Result summary:

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

2: Forecast.

Remainder of Winter 2021 / 22 (January February)

Temperatures across SW England may end up slightly milder than average when combining Jan and Feb but there looks to be a risk that January could have near or a little below average temperatures. (Models seem to have a problem with picking out a colder month in a sequence hence the suggestion of near normal in some of the output could imply colder.)

Precipitation: January probably below average at least for a good part of the month but then turning wetter. Below average snowfall is most likely, despite a colder January because of a milder February. Snow mostly limited to the Moors although January has a slightly increased risk of light snow.

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.

Spring (2022 March April May)

Overall milder than average temperatures with bigger anomalies in March and May although April may see nearer average values. Rainfall for the season uncertain but probably above average totals with March and May being the wetter months. Recent climate change seems to result in higher rainfall totals but not always fewer dry days, i.e. when it rain it rains heavier.

Summer 2022 (June July August)

Limited data but early suggestions are for near average temperatures, below average rain days but near or above average rainfall total in places – variable due to summer rain being more convectively driven.

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. November 2021.

Published 18 November 2021.

1. Influences.

Changes in sea temperature

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

Tropical Atlantic sea temperature 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 slightly larger cold anomalies than last month with the NW and SW of the Pacific strongly above average. Forecasts suggest that tropical Pacific Sea Surface Temperatures are likely to cool further to a strong La Nina state for the Winter before warming to a neutral state in Spring/Summer 2022. The tropical Indian Ocean sea temperatures are also above average for the time of year.

The North Atlantic Oscillation index (500hPa index shown below) remained negative for a little longer than forecast last month and although is now weakly positive the forecasts suggest a return to negative state.

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 first half of November has seen milder than average temperatures (roughly a two degree anomaly) with average or below average sunshine, consistent with cloudier skies. Rainfall has been below average with some parts of the SW having less than a tenth of the months rain, so far, which is perhaps compensating for the higher rain totals in October.

2021 UK Met provisional Temperature and Rainfall anomalies for August to October 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 parts of SW England due to the wet October. Although rain totals in October where high in places the number of wet days was about average at least in parts of Devon.

Global and European temperature anomalies for October and the year Sept 2020 to October 2021 and European area rainfall anomalies are shown below. Data with reference to 1981-2010 30 year period.

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

Data as of 16th November 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 7th November 2021.

Global Flood Awareness (updated to version 3) November forecast for the period November 2021 to February 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 16th November 2021.

Wikipedia data summary: Total depressions 21, Total storms 21, Hurricanes 7, Major hurricanes (Cat. 3+) 4.
Estimates for total fatalities 161 total and damage $70.5 billion (2021 USD) which may be the fourth costliest tropical cyclone season on record.

The 2021 Atlantic hurricane season had above-average tropical cyclone activity. It is also the second year in a row, and third overall, in which the designated 21-name list of storm names was exhausted. The current season will end on November 30, 2021.

Atmosphere: Predictions.

A: 1: Stratosphere

North polar stratospheric winter circulation is well established as shown by the 50hPa and 10hPa analysis for the 15th and the T+240 hour forecast.

In the Southern Hemisphere the strong stratospheric vortex is beginning to “wobble” causing the Ozone “hole” to start to weaken. Data shows the size of the “hole” remains above average with large scale ozone depletion having taken place. There are some indication of a lower ozone area associated with the north polar vortex but this vortex is much less stable over the long term.

2: Upper Troposphere

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

B: Lower Troposphere:

Selection of model solutions for December 2021 to February 2022 using November 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

France

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

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

For graphics and details see Verification review August September October

Original Summary – 170721 – Roughtly 30% of solutions suggest near normal temperature for the season but the main signal is for above normal values. Hints at a trend to lower or cooler anomalies as the season progresses. Rainfall slightly more below normal solutions than normal with much fewer above normal solutions. Trend to increased wetter solutions later in the period but models differ as to September or October being wetter. Summary: possibly warmer and drier than average for the season.

Comment: Good summary and some idea of trend to wetter later.

Temperature: DWD got the correct temperature sequence. CFS2 late in July also signalled cooler in south for August. BCC also had good temperature sequence.
Most models got above normal for three mouths average except WMO Washington, France, Russia and Brazil. UKMO Contingency overly warm for August.
Rainfall: UKMO Contingency good rain signal

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

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

2: Forecast.

Winter 2021 / 22 (December January February)

Temperatures across SW England are likely to be slightly milder than average this winter season. December though may see values close to average which would be a change from recent months and could well signal colder than average values for a time. January and or February are likely to be above average. Models seem to have a problem with picking out a colder month in a sequence hence the suggestion of near normal could imply colder.

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. The signal for a drier start to Winter and wetter later has been consistent but which month could be the wettest month has less agreement.

Spring (2022 March April May)

Overall milder than average temperatures but with bigger anomalies in March and lower anomalies in May. Rainfall for the season uncertain but probably above average totals with March and / or May being the wetter months. Recent climate changes seem to lead to higher rainfall totals but not always fewer dry days, i.e. when it rain it rains heavier.

Summer 2022 (June July August)

Very limited data but early suggestions are for near average temperature and below average rainfall – best taken as more dry days than average because of higher rain rates when rain does occur and often showery in nature so very variable from place to place.

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. October 2021.

Published 17 October 2021.

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.

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.

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.

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.

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. 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.

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.