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

Published 18 May 2021.

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1. Influences.

Changes in sea temperature

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

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

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

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

Recent Climatology –  SW England

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

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

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

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

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

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

Atmosphere: Predictions.

A:  1: Stratosphere

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

2: Upper Troposphere

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

B: Lower Troposphere:

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

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

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

WMO super ensemble using 11 countries data (DWD and Pretoria data missing)
BoM Australia
Brazil Met Service
Canada Met Administration
BCC China
European Centre
Meteo France
Japan Met Agency
Korean Met Administration
Russia (Moscow data)
UK Met Office
USA Climate Prediction Center

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

WMO super ensemble AUTUMN
NMME AUTUMN

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

For graphics and details see Verification review February March April

Details looked for in seasonal forecast:

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

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

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

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

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

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

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

2: Forecast.

Summer 2021  (June July August)  

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

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

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 2021  (September October November).

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

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


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

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.

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 20146(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.

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

Published 18 March 2021.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

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

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

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

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

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

Recent Climatology –  SW England

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

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

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

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

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

River flow from climate forecast

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

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

Atmosphere: Predictions.

A:  1: Stratosphere

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

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

A: 2: Upper Troposphere

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

B: Lower Troposphere:

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

CFSv2 April to June
NMME April to June
NASA April to June
ECMWF April to June
UKMO April to June
WMO super ensemble April to June

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

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

CFSv2 SUMMER 2021 note there looks to be a cold bias in temperature across the N Sea in summer.
NMME SUMMER 2021
NASA SUMMER 2021
ECMWF SUMMER 2021
WMO super ensemble for SUMMER 2021
Beijing for SUMMER 2021
Australia BoM for SUMMER 2021
Germany DWD for SUMMER 2021
Canada for SUMMER 2021
Korea KMA for SUMMER 2021
France for SUMMER 2021
UKMO for SUMMER 2021

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

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

Review of details looked for in seasonal forecast.


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

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

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

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

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

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

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

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

2: Forecast.

Remainder of Spring  (2021 April May)

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

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

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

Summer 2021  (June July August)  

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

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

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 2021  (September October November).

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

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


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

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.

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 20146(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.

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

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

Published 19 February 2021.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

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

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

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

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

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

Recent Climatology –  SW England

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

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

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

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

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

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

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

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

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

River flow from climate forecast

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

Atmosphere: Predictions.

A:  1: Stratosphere

Major warming in the stratosphere (see N Pole temperatures below) in January 2021 caused a reversal of the westerly flow across North America and a significant re-location of the polar stratospheric vortex towards Norther Russia.

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

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

A: 2: Upper Troposphere

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

B: Lower Troposphere:

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

NMME Spring 2021
CFSv2 Spring 2021
ECMWF Spring 2021
NASA Spring 2021

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

WMO super ensemble 11 models combined
Beijing Spring 2021
BoM Australia Spring 2021
Brazil Spring 2021
DWD Germany Spring 2021
ECMWF Spring 2021
Canada Spring 2021
Korea Spring 2021
Japan Spring 2021
France Spring 2021
UKMO Spring 2021
USA CFS2 Spring 2021

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

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

For graphics and details see Verification review 2020 Oct Nov Dec

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

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

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

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

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

2: Forecast.

Spring  (2021 March April May)

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

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

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 2021  (June July August)  

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

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

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 2021  (September October November)  limited data.

Milder than average but with near average 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 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.

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 20146(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.

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

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

Published 19 January 2021.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

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

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

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

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

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

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

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

Recent Climatology –  SW England

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

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

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

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

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

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

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

Atmosphere: Predictions.

A:  1: Stratosphere

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

ECMWF 50hPa and 10hPa analysis 17th and forecast for 27th Jan
JMA North pole observed temperature changes at 10hPa and 30hPa

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

A: 2: Upper Troposphere

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

B: Lower Troposphere:

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

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

NMME
CFS2
ECMWF
NASA

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

UKMO
WMO super ensemble
Beijing China
BoM Australia
Brazil
Germany
Canada
Korea
France

A selection of  June to August solutions using January 2021 data

NMME
NASA

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

For graphics and details see Verification review 2020 Oct Nov Dec

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

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

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

Remainder of Winter (February 2021).

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

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

Spring  (2021 March April May)

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

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

Possibly some snowfall on the moors in March.

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.

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

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

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.

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 20146(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.

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

Review and Experimental Long Range Forecast for SW England. August 2020.

Published 21 August 2020.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

ssta08

Atlantic equatorial sea temperatures look warmer than climatology as area area around the UK, in the N Sea, Norwegian Sea and Baltic. The North Atlantic west of Britain has seen a reduction the the cooler than average areas and the Artic Circle shows  very strong positive anomalies. Higher than average sea temperatures in the Gulf of Mexico may aid the development of current potential storms 13L and 14L.

Colder sea temperatures in the East Pacific just south of the equator show the La Nina has strengthened.

tna_anom_20200801

The tropical north Atlantic is forecast to remain slightly warmer than average through to at least January 2021 (See Met Office graphic above).

In the Atlantic, 2020 so far ( Wikipedia link for details. ) there have been 14 tropical depressions 11 tropical storms and 2 hurricanes resulting in 45 deaths and nearly six billion US dollars worth of damage. One tropical storm resulted in no electricity  to homes parts of New Jersey, USA, for a week due to trees falling over power lines.

21f3aca3b79ecb29985205d49291aed2

Time line above and tracks below

1280px-2020_Atlantic_hurricane_season_summary_map

In the Pacific sea temperatures continue to trend towards cooler / La Nina conditions which may now last until the mid Spring 2021 before returning to neutral conditions.

nino08

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) turned positive at the start of August and heralded the drier and warmer weather. The index turned negative in mid August a forerunner of more unsettled and cooler weather. The trend is for this to revert back to positive later in the month but for how long?

nao08

Recent Climatology –  SW England

August to the 20th: Temperatures have been running over two degree above the long term average across the SW thanks to the very hot spell in the first half of the month when temperatures reached into the mid thirties Celsius.

The month had been drier than average until heavy rain fell on the 14th and more especially the 19th. These two days accounted for a months average rainfall. The recent heavy rain with thunderstorms led to flash flooding in, for example, Exeter and Barnstaple. In addition unseasonably windy conditions brought high seas to coastal areas in recent days (19-21 August) in association with storm Ellen and its parent Atlantic depression.

The week 9 to 15th gives a reasonable indication of the extent of the hot weather.au9to1508

The earlier part of the summer (June and July) showed near average temperatures after a warmer June and cooler July, but mostly above average rain (except the SE of England)  despite a drier July in the south.

climsum08

River flows in July 2020 were near normal across the SW and groundwater levels were above normal in the eastern parts of SW England. Details can be found in the July 2020 Hydrological summary PDF 

river08

The reservoir levels in the SW of England (16th August) were close to average.

res08

Global Flood Awareness System. August forecast has near normal flood risk for southern parts of UK (Orange below normal Blue above).

glo08

Atmosphere: Predictions.

A:  1: Stratosphere

Stratosphere remains in summer mode as shown by the 50hPa chart for 20th August.

ecmwf50a12

A: 2: Upper Troposphere

CFSv2 200hPa contours for September to November 2020  shown in top row along with the anomalies from CFS (middle row) and the NMME anomalies (lower row). Forecast of above normal heights more especially in the western Atlantic and southern Europe implies more changeable weather for the UK especially the in the north.

z200SON0820

B: Lower Troposphere:

A selection of  September to November solutions using August 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly. (WMO graphics not available at time of writing).

NMMEson08

NMME

cfsson08

CFS2

NASASON0820

NASA

ECESON082020

ECMWF

For the Winter period December 2020 to February 2021.

NMMEdjf08

NMME winter

cfsdjf08

CFSv2 winter

NASADJF0820

NASA winter

ECEDJF082020

ECMWF winter

If the WMO graphics become available they will be added to the weather-info site. 

C: Comparing the output of seasonal models for May June July 2020, based on April  2020 data.

For graphics and details see Verification review 2020 May Jun Jul

Temperature: Reasonable indication for above average values although signal for slightly below average July was missed except in NCEP and DWD models.
Rainfall: Rain forecast fairly poor. UKMO and DWD got some idea of the sequence at least in S of UK.

Scoring is for whole season and will attempt to state good, fair, poor or no signal (similar probs for above normal, normal and below normal).

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

 

2. Forecast. SW England.

Autumn 2020 (September October November) 

Temperature are likely to be above the 30 year average (1981-2010) for the season and may be above average for each month although September might be nearer average.

Rainfall above average rainfall is likely for the season although October in some models is drier than average in places but perhaps not the SW of England.

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 (2020 December 2021 January February).

A milder than average Winter in indicated as well as each month being milder than average. Caution models tend to be poor at picking colder types.

Mixed rainfall indications but Winter probably having above average rainfall and below average snowfall. Some hints that December and/or February could be less wet.

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

Spring  (2021 March April May) limited data.

Milder than average temperatures seem likely with near normal rainfall.

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

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

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

Climate data from The Met Office UK and NCEP USA

Review and Experimental Long Range Forecast for SW England. July 2020.

Published 19 July 2020.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

170720ssta

Equatorial sea temperatures look warmer than climatology as is part of the N Sea, Norwegian Sea and Baltic sea temperature. The North Atlantic west of Britain has become much cooler than average although the western side of the Atlantic is warmer than average. The colder than normal sea temperatures to the west of the UK produces below average temperatures in August in some models, assuming winds are from a westerly direction.

Colder sea temperatures in the East Pacific just south of the equator show the La Nina has strengthened.

tna_anom_20200701

The tropical north Atlantic is forecast to remain very slightly warmer than average through the remainder of 2020 (See Met Office graphic above).

No more Atlantic tropical storms are forecast for the remainder of July but there have been six tropical storms in the Atlantic/Gulf of Mexico area this season but no hurricanes. Names are Arthur, Bertha, Cristobal, Dolly, Edouard and Fay. – Wikipedia link to details.

In the Pacific sea temperatures continue to trend towards cooler / La Nina conditions which may now last until the end of Spring 2021 before  returning to neutral conditions.

170720nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been negative since late June and is forecast to remain so over the next few weeks which suggests a colder and wetter period may develop/continue across the N and E of Europe.

170720nao

NAO background information see the Met Office NAO information.

Recent Climatology –  SW England

July to 19th Temperatures have been running slightly below average across the SW with other parts of the UK seeing cooler values. Sunshine also looks a little below average but rainfall has been well below average. Further north in the UK rainfall has been above average in places.

jul0720

NCEP EU area temperature anomaly and rain total 5 to 11 July

Previously April to June had been warmer than average and drier in most places although June 2020 was very wet across the SW.

AMJ0720

River flows in June 2020 were normal and reflected the wetter month. Groundwater levels were above normal. Details can be found in the June 2020 Hydrological summary PDF 

river

The reservoir levels in the SW of England (12th  July) showed 75% storage which is close to average.  Burrator was down to 47% in May but recovered during the wet June.

res

Global Flood Awareness System. July forecast has near normal flood risk for southern parts of UK (Orange below normal Blue above).

glo

Atmosphere: Predictions.

A:  1: Stratosphere

After a long period (during winter and spring) with a strong polar vortex the Stratosphere settled into summer mode around the end of April and remains with an easterly circulation as shown by the 30hPa chart for 18th July.

ecmwf30a12

A: 2: Upper Troposphere

CFSv2 200hPa contours for August to October 2020 are shown (top row) along with the anomalies from CFS (middle row) and the NMME anomalies (lower row). Forecast of above normal heights through the period although in September lower anomalies may occur near the UK.

z200ASO0720

B: Lower Troposphere:

A selection of  August to October solutions using July 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

170720nmme

NMME

170720E3

CFS2 E3 data

NASAASO0720

NASA

ECEASO072020

ECMWF

In the WMO data white areas are where the probabilities of below/normal/above are similar hence there is no overall signal. Precipitation forecasts over the UK end up with no signal because the wet models cancel out the dry forecasts showing there is no agreement between the models.

WMOASO072020

WMO super ensemble 11 models.

UKMOASO072020

UKMO

MONTASO072020

CMA

BOMASO072020

BOM

TOKASO072020

JMA

The available selection, including plots for Autumn and Winter, can be seen at the weather-info site. 

C: Comparing the output of seasonal models for April May June 2020, based on March  2020 data.

For graphics and details see Verification review 2020 Apr May Jun

Temperature: the main thrust for above normal temperatures was correct though if anything understated. Areas of normal or below normal were limited.
Rainfall: Below average rainfall was correct for the season. Monthly variation hard to find in the models but NMME and ECMWF did quite well.

2. Forecast. SW England.

Remainder of  summer 2020  (August) 

Temperatures in August probably near normal, perhaps cooler near northern and western coasts and a little warmer than average in southern and eastern parts of the region.

August is likely to be drier than average although there is a hint of nearer normal rainfall in N Cornwall and NW Devon. There is a typical summer risk that locally thundery outbreaks may upset totals in a few locations.

August climate: 1981 to 2010 average daily mean temperature 16 or 17°C in many areas, a little cooler over the N coastal areas of Devon and Cornwall  to 16 or 17°C  and a few degrees cooler over the moor. Locally over 17C in parts of Somerset.  Average rain in August typically 60 to 80mm, but 40 to 60mm in places especially East of the moors and in Somerset. Locally over 100mm across the moors.

Autumn 2020 (September October November) 

Overall near or a little above average temperature seems likely, especially later in the season. Rainfall very mixed indication, most models have some longer dry periods but suggest September could be wetter in many areas but near normal in the SW . Overall signal is for near normal rain although eastern parts of the region could be drier than average.

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 (2020 December 2021 January February) limited data.

A milder than average winter in indicated although February could see temperatures nearer average. Very mixed rainfall indications but Winter could end up near average although the first half of winter might be wetter than the second half.  Below average snowfall is again likely.

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.

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

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

Climate data from The Met Office UK and NCEP USA

Review and Experimental Long Range Forecast for SW England. June 2020.

Published 19 June 2020.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

ssta03

Equatorial sea temperatures look warmer than climatology as are the N Sea, Norwegian Sea and Baltic sea temperature. The North Atlantic west of Britain remains mostly near or cooler than average towards North America. Colder sea temperatures in the East Pacific just south of the equator show the La Nina has strengthened.

tna_anom_20200601

The tropical north Atlantic is forecast to remain very slightly warmer than average through the remainder of 2020 (See Met Office graphic above).

No more Atlantic tropical storms are forecast for the remainder of June but there have been three tropical storms in the Atlantic/Gulf of Mexico this season. Names are Arthur, Bertha and Cristobal – see Wikipedia link to details.

In the Pacific neutral El-Nino conditions are likely to continue to trend towards cooler / La Nina conditions until later in the Autumn 2020. The GFDL model reverts to neutral or El Nino conditions rather faster than most models with the consensus being La Nina or neutral conditions into winter.

nino06

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been  roughly neutral since mid May and is expected to remain so over the next few weeks.

nao06

NAO background information see the Met Office NAO information.

Recent Climatology

June to 18th has seen temperatures near average after a very warm or even hot start to the month. Rainfall has been well above normal (typically 80 to 90mm locally double this over some hilly areas due to thundery outbreaks. Sunshine rangled from below average in in parts of Cornwall to near average further east (limited data).

Spring 2020 recorded above average temperatures (March was near normal) and well below normal rain although February was very wet and March had nearer normal rainfall.

2020MAMT2M

May temperatures were above average across much of the globe but there were some colder spots including a good part of Northern Europe.

EZuuhI2XQAENQNg

River flows in May 2020 reflected the drier Spring although groundwater levels were above normal. Details can be found in the April 2020 Hydrological summary PDF 

river06

The reservoir levels in the SW of England (14th  June) showed 77% storage.  Three of the main reservoirs are at 75 to 82% capacity but Burrator was down to 47%. The very wet 18th and night of 18th/19th will no doubt lift these values.

Global Flood Awareness System. June forecast has near normal flood risk for southern parts of UK (Orange below normal Blue above).

glofas06

Atmosphere: Predictions.

A:  1: Stratosphere

After a long period with a strong polar vortex the Stratosphere settled into summer mode around the end of April and remains with an easterly circulation as shown by the 30hPa chart for 18th.

ecmwf30a12

A: 2: Upper Troposphere

CFSv2 200hPa contours for July to September 2020 are shown (top row) along with the anomalies from CFS (middle row) and the NMME anomalies (lower row). Forecast of above normal heights through the period.

z200JAS0620

B: Lower Troposphere:

A selection of  July to September solutions using June 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

In the WMO data white areas are where the probabilities of below/normal/above are similar hence there is no overall signal. Precipitation forecasts over the UK end up with no signal because the wet models cancel out the dry forecasts showing there is no agreement between the models.

WMOJAS062020

WMO

UKMOJAS062020

UKMO

TOULJAS062020

Meteo France

MOSCJAS062020

Russia

ECLWMOJAS062020

ECMWF

Other models

cfs2son06

CFS2 USA

son06nmme

NMME USA

NASAJAS0620

NASA 

The full selection, including plots for Autumn and Winter, can be seen at the weather-info site.

C: Comparing the output of seasonal models for  March April May 2020, based on February  2020 data.

Most models got the idea of above average UK temperatures but not the nearer average March. Dry signal could have been stronger but some ideas about the NW being the least dry was good.

For graphics and details see Verification review 2020 Mar Apr May

2. Forecast. SW England.

Remainder of  summer 2020  (July August) 

Slightly above average temperatures are expected for the summer season with higher anomalies possibly in the second half of the summer.

Very mixed rainfall patterns but an indication for a wetter than average July and a near normal August although the east could be drier than average. Summer rain can be showery or thundery in nature with wide variations in rain days and rain totals across a region. It is not clear of above average rain means more wet days or just some days with higher rain total which has been a feature of recent years.

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 in July typically 60 to 80mm, but 40 to 60mm in places especially East of the moors and in Somerset. Locally over 100mm across the moors. August slightly small areas with the lower rain totals due to July often being drier than August.

Autumn 2020 (September October November) 

Overall above average temperature seems likely, especially later in the season. Rainfall very mixed indication, most models have some longer dry periods but do not agree which month might be the drier or wetter month. Overall signal is for near normal rain although eastern parts of the region could be drier than average.

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 (2020 December 2021 January February) limited data.

A milder than average winter in indicated although February could see temperatures nearer average. Rainfall could end up near average but at least one moth is likely to be wetter than average and again some longer drier spells are suggested but little agreement as to when. Below average snowfall (snow chiefly over the moors) is most likely.

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.

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

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

Climate data from The Met Office UK and NCEP USA

Review and Experimental Long Range Forecast for SW England. May 2020.

Published 19 May 2020.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

170520ssta

Equatorial sea temperatures look warmer than climatology as are the N Sea and Baltic sea temperature. The North Atlantic west of Britain remains near or cooler than average towards North America but have warmed relative to average closer to the UK.

tna_anom_20200501

The tropical north Atlantic is forecast to remain very slightly warmer than average through Spring and Summer 2020 (See Met Office graphic above). The first Atlantic Tropical Storm “Arthur” developed off Florida but will weaken soon.

arthur

In the Pacific neutral El-Nino conditions are likely to trend towards cooler / La Nina conditions during Summer and into early Autumn 2020. The CFSv2 model looks quicker than most of the other ensemble systems of the NMME in completing this transition. The timing of the change from El Nino to La Nina might impact on the Atlantic hurricane season, El Nino tending to depress the formation of Atlantic Tropical Storms.

170520nino

Met Office Atlantic tropical storm forecast for June to November 2020 issued 19 May 2020: “The most likely number of named tropical storms (winds of at least 39 mph) predicted to occur in the North Atlantic during the June to November period is 13, with a 70% chance that the number will be in the range 9 to 17. The 1981-2010 long-term average is 12.

The most likely number of hurricanes (winds of at least 74 mph) predicted to occur in the North Atlantic during the June to November period is 7, with a 70% chance that the number will be in the range 5 to 9. The 1981-2010 long-term average is 6.

The most likely number of major hurricanes (winds of at least 111 mph) predicted to occur in the North Atlantic during the June to November period is 3, with a 70% chance that the number will be in the range 2 to 4. The 1981-2010 long-term average is 3. 

Note: Tropical Storm Arthur occurred in May 2020 and is therefore outside the period covered by this prediction (June-November).”

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been mostly negative since then end of March and is forecast to be roughly neutral over the next few weeks.

180520nao

NAO background information see the Met Office NAO information.

Recent Climatology

May to 18th has seen temperatures near average on the whole but with well below normal rainfall (5 to 15mm) and above average sunshine.

Because of the very wet February running average for the three months is above average.

190520clim

River flows in April 2020 reflected the drier January and February conditions and groundwater has largely recovered to above normal values in all areas. Details can be found in the April 2020 Hydrological summary PDF 

190520ground

The reservoir levels in the SW of England (10th  May) showed 89% storage.  Three of the main reservoirs are at over 90% capacity but Burrator is down to 68%.

res

Global Flood Awareness System. May forecast has a surprisingly high risk for southern parts of UK and may be because of high ground water following the very wet February. (Orange below normal Blue above)

190520glow

Atmosphere: Predictions.

A:  1: Stratosphere

After a long period with a strong polar vortex the Stratosphere settled into “summer” mode around the end of April.

strat

A: 2: Upper Troposphere

FSv2 200hPa contours for June to August 2020 are shown (top row) along with the anomalies from CFS (lower row). Forecast of above normal heights through the summer period.

z200JJA0520

B: Lower Troposphere:

A selection of  June to August solutions using May 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

White areas are where the probabilities of below/normal/above are similar hence there is no overall signal for this period from the WMO data.

WMOJJA052020

WMO 

UKMOJJA052020

UKMO

TOKJJA052020

JAPAN

MOSCJJA052020

MOSCOW

ECLWMOJJA052020

ECMWF

NASAjja0520

NASA

0520nmmejja

NMME

0520E3JJA11may

CFS2 E3 data

The full selection can be seen at the weather-info site.

C: Comparing the output of seasonal models for  February, March and April 2020, based on January 2020 data.

There were some good indications for above average temperatures and the drier trend. NASA was one of the few monthly anomalies that picked out the near normal March and only UKMO and perhaps to lesser extent ECMWF picked the very much milder April.
CFS2 and NMME indicated drier for April as did Brazil and to a lesser extent Toulouse – some others did but were mostly drier throughout so rejected if did not get wet start to season.

For graphics and details see Verification review 2020 Feb Mar Apr from January

2. Forecast. SW England.

Summer 2020  (June July August)  limited data

 The main theme is for above normal temperatures although some indication that they may only be slightly above. August and possibly June could have the higher anomalies in the south. Rainfall very variable monthly detail from the models but probably below average for the season except perhaps in the North. Hints at August being above average in places, mainly in the south.

Slightly above average temperatures are expected for the summer season with higher anomalies possibly in the second half of the summer

Very mixed rainfall patterns but an indication for a drier than average June and July but possibly a wetter August. Summer rain can be showery or thundery in nature with wide variations in rain days and rain totals across a region.

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 2020 (September October November) limited data.

Overall above average temperature, especially later in the season. Rainfall  may be below average early in the season followed by a wetter October although indications from models are quite mixed.

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 (2020 December 2021 January February) very limited data.

A milder than average winter in indicated although February could see temperatures nearer average. Rainfall could end up below average but January looks to be wetter and February drier. Below average snowfall (snow chiefly over the moors) is most likely.

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.

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

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

Climate data from The Met Office UK and NCEP USA

Review and Experimental Long Range Forecast for SW England. April 2020.

Published 17 April 2020.

GDPR statement: Please note that the author of this blog does not set cookies but the host “wordpress.com” sets multiple cookies which are outside of the authors control. You can view their cookie policy here. 

1. Influences.

Changes in sea temperature

150420ssta

Equatorial sea temperatures look warmer than climatology as are the N Sea and Baltic sea temperature whereas the North Atlantic west of Britain remains near or cooler than average.

170420tna

The tropical north Atlantic is forecast to remain very slightly warmer than average through Spring and Summer 2020 (See Met Office graphic above).

170420nino

In the Pacific neutral or weak El-Nino conditions are likely to trend towards cooler / La Nina conditions during Summer and into early Autumn 2020. The CFSv2 model looks quicker than most of the other ensemble systems of the NMME in completing this transition. The timing of the change from El Nino to La Nina might impact on the Atlantic hurricane season, El Nino tending to depress the formation of Atlantic Tropical Storms

University College London forecast issued 7th April 2020 suggests that the Atlantic hurricane activity in 2020 may be 25% above the long-term norm: Intense Hurricanes=3 (70 year average 3) Hurricanes=8 (70 year av 6) Tropical Storms=16 (average 12). Met Office outlook available in May.

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been mostly negative since then end of March but is forecast to be roughly neutral over the next few weeks.

170420NAO

NAO background information see the Met Office NAO information.

Recent Climatology

April to the 16th has been very mild with temperature anomalies between 2 and 3 Celsius although cold easterly winds held windward coastal sites lower. It has also been extremely dry with only 3 to 6mm (1 to 4%) of the normal month rain. Rainfall totals were more than doubled on the 17th by a band of rain that moved north from France bringing 5 to 15mm of rain.

170420jfmclim

River flows in March 2020 reflected the very wet conditions in February followed by nearer normal rain in March with high river flows in most areas except for Aberdeenshire. It is perhaps a surprise that groundwater in eastern England is still below average. Details can be found in the March 2020 Hydrological summary PDF 

070420river

The reservoir levels in the SW of England (12th April) showed 95% storage. All main reservoirs are at over 90% capacity.

120420res

Global Flood Awareness System. April forecast (high) risk for early part of the forecast decreasing through to July 2020 and largely reflects the well above average rain in February and early March.

170420glofas

Atmosphere: Predictions.

A:  1: Stratosphere

A second phase of significant warming occurred at 10hPa and more recently down to 30hPa as the very persistent stratospheric polar vortex slowly warms out.

170420jmastrat

ECMWF 10 and 30hPa 16/1200UTC data shows that despite ongoing warming the polar stratospheric vortex is reluctant to be eroded completely but forecast for the 26th shows than warming out is almost complete and the transition to summer mode should take place by the end of April.

160420stratec

A: 2: Upper Troposphere

CFSv2 200hPa contours for May to August 2020 are shown (top row) along with the anomalies from CFS (lower row) and NMME (middle row). Suggestion of  above normal heights through the period.

0420z200mjja

B: Lower Troposphere:

A selection of May to July solutions using April 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

White areas are where the probabilities of below/normal/above are similar hence there is no overall signal for this period from the WMO data.

WMOMJJ042020

WMO combined multi model ensemble 

UKMOMJJ042020

UKMO

TOULMJJ042020

Meteo France

MOSCMJJ042020

Russian Met Centre

MONTMJJ042020

Canada

ECLWMOMJJ042020

ECMWF

BOMMJJ042020

BoM Australia

SEOUMJJ042020

Korea Met Agency

A selection of June to August solutions using April 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

NMMEJJA0420

NMME Summer 2020

CFS2JJA0420

CFS2 summer 2020

NASAJJA0420

NASA summer 2020

ECEJJA042020

ECMWF summer 2020

UKMOJJA042020

UKMO summer 2020

The full selection can be seen at the weather-info site.

C: Comparing the output of seasonal models for January, February and March 2020, based on December 2019 data.

Observed three month period was above average but did anyone get the trend to cooler/near normal in March?

Forecast temperature summary was good for the three month forecast with some idea of less mild in north later.

Observed rainfall for the three month period was above average but largely due to a very wet February, January and March were near or below average across the UK.

Rainfall was OK with the above average indication but not the drier east of UK in Jan and Mar. The seasonal total rain swamped by the very wet Feb.

For graphics and details see Verification review 2020 Jan Feb Mar from December 2019

2. Forecast. SW England.

End of Spring 2020  (May) 

Most models suggest above average temperatures for May.

Precipitation is uncertain but most models suggest  drier than average.

May climate: 1981-2010 average mean temperature 11 or 12°C. Average 1981 to 2010 rain typically 60 to 80mm. Locally as low as 40mm in parts of E Devon and over areas of Somerset but 100 to 150mm over the moors.

Summer 2020  (June July August)  limited data

Slightly above average temperatures are expected for the summer season with July suggested as the month least likely to have above normal values (a change from last month which suggested June rather than July).

Very mixed rainfall patterns but an indication for a drier than average June but possibly wetter July. August solutions split between wetter and drier. Summer rain can be showery or thundery in nature with wide variations in rain days and rain totals across a region.

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 2020 (September October November) limited data.

Overall near or above average temperature and above average rainfall is suggested for the season but no agreement for any particular month to be wetter or drier.

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

Winter (2020 December 2021 January February) very limited data.

A milder than average winter in indicated with near or above average rainfall and below average snowfall (snow chiefly 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.

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

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

Climate data from The Met Office UK and NCEP USA

Review and Experimental Long Range Forecast for SW England. March 2020.

Published 20 March 2020.

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1. Influences.

Changes in sea temperature.

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Noticeable changes in the Atlantic include a much larger area of cooler than average North Atlantic sea temperatures to the west of the UK and Eire also a much warmer area near the equator between Africa and South America. The North Sea, Baltic and Med remain above normal.

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The tropical north Atlantic is forecast to remain very slightly warmer than average through Spring and Summer 2020 (See Met Office graphic above).

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In the Pacific neutral or weak El-Nino conditions are present but forecasts suggest conditions are likely to trend cooler during Summer and into early Autumn 2020 – see CFSv2 and NMME multi model ensemble forecast above.

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been mostly positive since early December 2019 and is forecast to remain slightly positive over the next week before trending negative at the end of March which might hint at a colder start to Spring.

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NAO background information see the Met Office NAO information.

Recent Climatology

March, to the 19th, has been slightly cloudier, milder and wetter than average.

Winter, as can be seen in the graphics below, has been very mild and in most places wet due to a very wet February.

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River flows in February 2020 reflected the very wet conditions with high river flows in most areas apart from Aberdeenshire. It is perhaps a surprise that groundwater in eastern England is still below average. Details can be found in the February 2020 Hydrological summary PDF 

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The reservoir levels in the SW of England (15th  March) showed 97.5% storage. The less than 100% value is due to Colliford as the the other main reservoirs are at 100% capacity.

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Global Flood Awareness System March forecast (high) risk through to June 2020 largely reflects the well above average rain in February and early March. The risk reduces from late April or early May.

Atmosphere: Predictions.

A:  1: Stratosphere

A second phase of significant warming is occurring at 10hPa and to some extent at 50hPa but from unusually low temperature values.

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ECMWF 10 and 50hPa 18/1200UTC data shows that despite ongoing warming the polar stratospheric vortex is reluctant to be eroded completely.

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A: 2: Upper Troposphere

CFSv2 200hPa contours for April to August 2020 are shown below (top row) along with the anomalies from CFS (middle row) and NMME (lower row). Suggestion of  enhanced Atlantic jet for April towards or just north of the UK imply unsettled types but possibly higher pressure further south.

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B: Lower Troposphere:

A selection of April to June solutions using March 2020 data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

White areas are where the probabilities of below/normal/above are similar hence there is no overall signal for this period from the WMO data. Problems with the WMO web site in South Korea has made access to this data difficult.

APRIL TO JUNE 2020

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UKMO

CPTECAMJ032020

Brazil Met Service

DWDAMJ032020

German Met Service

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Canadian Met Service

BOMAMJ032020

Australian Met Service

If they become available further examples from WMO will be added to the weather-info site.

ECEAMJ032020

ECMWF

NASAAJM0320

NASA USA

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CFS2 USA

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NMME USA

SUMMER JUNE TO AUGUST 2020

ECEJJA032020

ECMWF

NASAJJA0320

NASA

190320CFS2JJA

CFS2

190320NMMEJJA

NMME

C: Comparing the output of seasonal models for December 2019,  January and February 2020, based on November data.

Observed Temperature. Well above average for the season and each month.

Forecast temperature:  Most models forecast the above normal temperatures but perhaps not the detail.

Observed Rainfall. Above average all areas thanks to an exceptionally wet February. January was the relatively less wet month.

Precipitation Forecast: Above average rainfall was forecast but the much wetter February was not well forecast with some models suggesting a less wet month.

Observed Pressure. Below average but near or slightly above in far South.

Pressure Forecast was correct.

For graphics and details see Verification review 2019 Dec 2020 Jan Feb from Nov data.

2. Forecast. SW England.

Spring 2020  (April May) 

Some models suggesting near normal temperatures for April and perhaops early May and then above normal but models seem not to be able to reliably predict colder months. The near average signal may imply a colder than average April.

Precipitation is uncertain but probably a drier than average period in April and possibly early May before a return to near normal rainfall amounts.

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 2020  (June July August)  limited data

Near or perhaps only slightly above average temperatures are expected for the summer season with June suggested as the month least likely to have above normal values. Very mixed rainfall patterns but an overall indication for a drier than average summer, although August could be wetter than average.

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 2020 (September October November) limited data.

Overall above average temperature and rainfall is suggested for the season but  September could be drier than average.

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 2020 (2020 December 2021 January February) very limited data.

Another milder than average winter in indicated with near average rainfall resulting in below average snowfall (snow chiefly 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.

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

Stratospheric Diagnostics from Japan Met Agency and Free University Berlin

Climate data from The Met Office UK and NCEP USA