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

Published 17 August 2021.

1. Influences.

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Changes in sea temperature

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

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

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

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

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

Recent Climatology –  SW England

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

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

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

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

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

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

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

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

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

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

Track map to 15th August.

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

Atmosphere: Predictions.

A:  1: Stratosphere

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

2: Upper Troposphere

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

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

B: Lower Troposphere:

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

Top row temperature anomaly and lower row precipitation anomaly. 

CFSv2 using mean of 10 days model data to 7th August
NMME multi model
NASA
ECMWF orange/red colours are above model hindcast average.

Data (as supplied to WMO) shown below.

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

WMO multi model ensemble mean
Beijing CMA

Brazil

DWD Germany
CMC
Russia
Korea
Japan
France
UK Met Office

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

Winter December 2021 to February 2022 – limited graphics.

WMO multi model Winter

NMME multi model Winter.

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

For graphics and details see Verification review May June July

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

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

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

2: Forecast.

Autumn 2021  (September October November).

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

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) limited data.

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

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. December 2020.

Published 18 December 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

Apart from a semi permanent cooler area, centred near 55 North 30 West, Atlantic sea temperatures are mostly warmer than climatology as as are sea temperatures around the UK, Norwegian Sea and Baltic.

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

Wikipedia states that: ” The 2020 Atlantic hurricane season was the most active and the seventh costliest Atlantic hurricane season on record. In addition, it was the fifth consecutive above average Atlantic hurricane season from 2016 onward. The season featured a total of 31 (sub)tropical cyclones, all but one of which became a named storm. Of the 30 named storms, 13 developed into hurricanes, and six further intensified into major hurricanes, with one, Hurricane Iota, attaining Category 5 strength on the Saffir–Simpson scale.[nb 1] It was the second season to use the Greek letter storm naming system, the first being 2005. Of the 30 named storms, 12 made landfall in the contiguous United States, breaking the record of nine set in 1916. The season was also the fifth consecutive season in which at least one Category 5 hurricane formed. During the season, 27 tropical storms established a new record for the earliest formation by storm number. This season also featured a record 10 tropical cyclones that underwent rapid intensification, tying it with 1995.[2] This unprecedented activity was fueled by a La Niña that developed in the summer months of 2020.”

Wikipedia track map 2020

Colder sea temperatures in the East Pacific, just south of the equator, show the La Nina is well established and forecasts suggest that the La Nina will remain active until at least Spring 2021.

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) turned positive in late October but turned slightly negative early in December.

The positive NAO phase represents a stronger than usual difference in pressure between the two regions. Winds from the west dominate, bringing with them warm air, while the position of the jet stream enables stronger and more frequent storms to travel across the Atlantic. These support mild, stormy and wet winter conditions in northern Europe

The negative NAO phase represents the reverse with a weaker than usual difference in pressure. 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.

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 were such features become slow moving. There is a chance that higher pressure will become established across the SW of England over the Xmas period and possibly last into the New Year but this is rather uncertain.

Recent Climatology –  SW England

December to the 17th has been very slightly milder than the 1981 to 2010 average and has been slightly wetter in the east but much wetter in Cornwall and West Devon. Sunshine has been slightly below average so far in December.

Autumn temperatures have been near or a little warmer than average and rainfall was slightly below average for the season.

River flows and ground water levels in November 2020 were near normal across SW England. Details can be found in the Novembver 2020 Hydrological summary PDF 

The reservoir levels in the SW of England were about normal of December 13th 2020.

Global Flood Awareness (updated) System. December forecast for the period December to March (shown below) indicates slightly above normal flood risk for SW England with typical river flood values as seen every two to five years (see lower section of graphic).

Atmosphere: Predictions.

A:  1: Stratosphere

Data from December 15th shows polar vortex established at 50 and 30hPa but with some warming occurring leading to a more complex stratospheric pattern and probably a relocation of the polar vortex to just north of Norway in a week or two. This may start to impact the weather patterns nearer the surface in January. It is possible that this could be the start of a significant stratospheric warming which could result in a colder January/February though this is too early to tell.

The temperature trace below indicates that temperature in the stratospheric polar region is cold enough for Polar Stratospheric Cloud formation which is implicated in Ozone depletion. This may be something to watch out for in the North polar region next Spring. http://www.weather-info.co.uk/ozone.html

A: 2: Upper Troposphere

CFsv2 200hPa contours (top row) and anomaly (lower row) for Jan Feb and March 2021 hint at a more cyclonic January and possibly February across the UK area possibly suggesting low centres could be steered further north than normal in the the remaining Winter months.

B: Lower Troposphere:

A selection of  January to March solutions using December 2020 data are shown below, top row temperature anomaly and lower row precipitation anomaly. 

NMME JFM tends to be overly warm
CFS2 E3 data JFM tends to be overly warm
ECMWF JFM
NASA JFM

WMO data. Three month average then separate months. Low resolution data.

WMO super ensemble JFM 12 members
Beijing JFM
BoM Australia JFM
Brazil JFM
Germany JFM
Canada JFM
Russia JFM
S Korea JFM
Japan JFM
France JFM
UK JFM
USA JFM

SPRING (March April May) 2021

WMO super ensemble MAM
NMME MAM
CFS2 MAM
NASA MAM
ECMWF MAM

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

For graphics and details see Verification review 2020 Sep Oct Nov

Review of details looked for in seasonal forecast.
Temperature. Looking for the West to be near normal and the East above normal also for a milder November in monthly detail.

Rainfall. Mixed three month pattern with above normal in NW and SE but areas below normal SW England Wales N Midlands NE England and far N Scotland. Looking for October signal to be wetter and other months drier.

Good temperature forecast but perhaps not the stronger anomalies in November. Rainfall fair in that overall values above normal but failed to get any detail. Pressure reasonable signal.

TABLE below is for 3 month data only:
Scoring will attempt to state good, fair, poor or no signal based upon
temperature being normal (fair) or above average (good). Rainfall above average and pressure below average. Errors and omissions excepted.

1. Russia: Temp fair – a little cool but reasonable sequence. PPN fair .
2. USA – CFS2 : Temp fair . PPN poor .
3. UKMO Contingency: Temp fair but overly warm . PPN fair .
4. UKMO : Temp good . PPN poor . PMSL good
5. USA – IRI : Temp no signal. PPN no signal .
6. KMA APCC : Temp fair . PPN no signal.
7. JMA : Temp good sequence but a little cool. PPN fair . PMSL good
8. NMME : Temp fair too warm. PPN good .
9. WMO : Temp fair. PPN poor .
10. BCC : Temp fair. PPN poor .
11. NASA – Temp good – got the milder November. PPN poor – almost reverse of actual .
12. Brazil: Temp Poor way to cold. PPN fair .
13. CanSips : Temp poor . PPN very good .
14. IMME : Temp fair . PPN fair.
15. Copernicus Temp fair. PPN fair. PMSL good
16. CMCC Temp fair . PPN poor . PMSL fair
17: DWD Temp good. PPN fair . PMSL fair
18. EC Temp fair. PPN poor . PMSL poor
19 UKMO Temp good . PPN fair. PMSL good
20. MF Temp poor . PPN poor . PMSL fair
21 NCEP Temp fair . PPN good . PMSL good
22. JAMSTEC: Temp good . PPN fair .
23 ECMWF (monthly) Temp: fair. PPN poor . PMSL

2. Forecast. SW England.

Remainder of Winter ( January and February 2021).

January temperatures are likely to be near normal; and there is a chance of below normal values for a period but by February milder than average values are more likely.

Rainfall indications are rather mixed but there is a reasonably strong indication for above average rainfall in January which could also mean above average snowfall, chiefly over the hills and moors. In February near normal rainfall is likely but perhaps above normal in western areas and below to the east of the moors with 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.

Spring  (2021 March April May)

Milder than average temperatures seem likely for the season although March and April could see values close to normal and May could be significantly milder than average.

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

Possibly a little 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 six global systems)

Temperature slightly above average for the season. Rainfall for the season near average but drier than average in June and July followed by a wetter than average 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.

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

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.

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.

160320ssta

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.

tna_anom_20200301

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

180320nin34

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.

190320nao

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.

190320djf

190320winter

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 

1903river

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.

190320res

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.

190320strat1

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

190320strat2

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.

z200AMJja0320

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

UKMOAMJ032020

UKMO

CPTECAMJ032020

Brazil Met Service

DWDAMJ032020

German Met Service

MONTAMJ032020

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

190320cfs

CFS2 USA

190320nmme

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

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

Published 24 February 2020 (delayed due laptop failure).

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.

210220ssta

Changed map. Now using 5km rather than 50km sea temperature anomaly data

North Atlantic sea temperatures remain above average apart from a cooler section in Mid Atlantic to the west of Ireland.  The southern North Sea and the Baltic as well as Arctic area show values well above average.

tna_anom_20200201

The tropical north Atlantic was again analysed as slightly below normal but is forecast to remain very slightly warmer than average through Spring and early Summer 2020 (See Met Office graphic above). The forecast has been a little quick to lift temperatures over recent issues.

0220nino34

In the Pacific neutral or weak El-Nino conditions are present but forecasts suggest conditions are likely to trend cooler during Summer 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 or so but trending lower before mid March.

0220nao

NAO background information see the Met Office NAO information.

Recent Climatology

February (to 23rd) has been very mild across the south of the UK with temperatures running about two degrees above average and in places over double the normal rainfall.

0220clim

Given the February data, Winter (Dec to Feb) will turn out to have been unusually mild and wetter than average.

River flows and groundwater in January 2020 reflected the much wetter conditions in December and will no doubt be above average following the rain in February. Groundwater in eastern England shows signs of recovery. Details can be found in the January 2020 Hydrological summary PDF 

0220ground

The reservoir levels in the SW of England (16th  February) showed 92% storage. The less than 100% value is due to Roadford and Colliford as the the three other main reservoirs are at 100% capacity.

res0220

Global Flood Awareness System February forecast risk through to May 2020 largely reflects the well above average rain this winter.

0220glofas

Atmosphere: Predictions.

A:  1: Stratosphere

The polar stratospheric vortex moved east and reduced due to a significant warming event, as shown by the 10hPa temperature plot at the North Pole but this was quickly reversed as the vortex strengthened again becoming an unusually strong circulation.

strat1

ECMWF 10 and 50hPa 23/1200UTC data shows the strong vortex. Changes over the following 10 days may result in a reversal of the stratospheric wind over Europe early in March. This in turn implies a less mobile weather pattern could develop later in March at least over southern UK, although this development is not clear cut.

The stratospheric low temperatures and the static nature of the vortex recently has again allowed a reduction in total column Ozone to values just above the nominal “Ozone Hole” number of 220DU. The chart below shows the departure from average of the total column ozone.

o3current

A: 2: Upper Troposphere

CFSv2 200hPa contours for March to May 2020 are shown below (top row) along with the anomalies from CFS (lower row). Suggestion of  enhanced Atlantic jet for March across the northern part of the UK imply unsettled types but this risk reduces for April and May.

z200MAM0220

B: Lower Troposphere:

A selection of March to May (Spring) solutions using February 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 super ensemble (BoM, CMC, Moscow, DWD, CPTEC, Seoul, Washington, Tokyo, Toulouse, ECMWF) UKMO,  Beijing and Pretoria not available from WMO but are available elsewhere.

WMOMAM022020

WMO multi ensemble

UKMOMAM022020

UKMO

MOSCMAM022020

Russia

ECLWMOMAM022020

ECMWF

BOMMAM022020

Australia

Further examples from WMO are available at the weather-info site.

NASAMAM0220

NASA

nmmemam0220

NMME Spring

mam010220e3

USA CFSv2 E3 version Spring 2020

Selected June to August summer graphics.

nmmejja0220

NMME summer 2020

NASAJJA0220

NASA summer

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

UK area based on September 2019 data.

Temperature:
Good signal for above average temperature for the season BUT very few models suggested a colder November. NASA had a good trend and NMME had lower anomalies for November increasing in subsequent months.
Rainfall:
Generally poor indication for drier areas month to month. Overall signal for a wetter than average three months was OK but detail was poor.

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

2. Forecast. SW England.

Spring 2020  (March April May) 

Models seem not to be able to reliably predict colder months (eg forecast for November), so despite a strong signal for above average temperatures for the season a near normal or  colder than average spell seems possible some time in March/April. This idea would fit with the changes expected in the stratosphere.

Precipitation for the season as a whole is uncertain but probably a drier than average period in March/April. then a return to near normal rainfall amounts. fewer than average wet days.

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 slightly above average temperatures are expected for the summer season but  August values could be closer to normal.  Rainfall patterns very mixed but the wetter than average solutions for the season as a whole look to outweigh the drier ones. No reliable indication for any month being especially drier.

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 October could be drier and colder than average according to two out of the three available models.

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. 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

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

Published 17 January  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.

170120ssta

North Atlantic and North Pacific sea temperature anomalies continue to show above average values although both areas, roughly between 40 and 60 degrees North, show some cooler well mixed areas probably due to due to storms. The North Sea is slightly above the long satellite term average.

tna_anom_20200101

The tropical north Atlantic was analysed as slightly below normal but is forecast to remain very slightly warmer than average through Spring and early Summer 2020 (See Met Office graphic above).

In the Pacific neutral or weak El-Nino conditions are present and forecasts suggest conditions are likely to remain similar over winter then trend cooler during Summer 2020 – see CFSv2 and NMME multi model ensemble forecast below.

150120nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been positive since early December 2019 – implying a milder, wetter, winter 2019/2020. However ensemble forecasts show a trend to a negative phase in about a weeks time which fits in with forecast for high pressure to develop over the UK. The forecast shown in the December review suggested a negative NAO but in practice the diagnostic remained positive (just).

150120nao

NAO background information see the Met Office NAO information.

Recent Climatology

The first half of January has seen temperatures well above average, the anomaly to the 17th being between plus 2 and plus 3 Celsius, although colder temperatures to come may reduce this for the month as a whole. Rainfall has been above average with some places already close to the January total and sunshine looks to have been below average.

Temperature and rainfall anomalies for October to December 2019 are shown below. A  summary for the Teignmouth and Dawlish area is available here.

ONDtemp

CET

Central England temperature series updated to Min January 2020

Despite the mostly drier October, for the three months rainfall was above average across SW England

ONDppn

Europe anomalies for 2019 are shown below.

year2019

River flows and groundwater in December reflect the much wetter conditions though it is interesting to see that groundwater in eastern England remains low. Details can be found in the December 2019 Hydrological summary PDF 

170120river

The reservoir levels in the SW of England (12th January) show 86% storage, which is above normal for the time of year. The less than full percentage seems to be due to Roadford and Colliford with the three other main reservoirs being at capacity.

170120res

Global Flood Awareness System January risk forecast through to April 2020 largely reflects the well above average rain in November and December.

170120glo

Atmosphere: Predictions.

A:  1: Stratosphere

The North Polar stratospheric vortex, after its weakening and migration east in Nov/Dec, returned over the pole and became very strong with very low temperatures near the centre.  Further warming incidents may again move the vortex centre eastwards over the next few weeks.

150120

The stratospheric low temperatures (eg: below minus 80 Celius at 50hPa) and the strength and static nature of the vortex over recent weeks has allowed a reduction in total column Ozone to values just above the nominal “Ozone Hole” number of 220DU.

170120ozone

The transfer east of the North Polar stratospheric vortex may allow greater mixing and redistribution of the ozone over the next month.

A: 2: Upper Troposphere

CFSv2 contours for February March and April are shown below (top row) along with the anomalies from CFS (middle row) and NMME (lower row). CFSv2 in particular suggest enhanced Atlantic jet for February and March across the northern part of the UK.

z200FMA0120

B: Lower Troposphere:

A selection of February to April solutions using January 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 super ensemble (BoM, CMC, Moscow, DWD, CPTEC, Seoul, Washington, Tokyo, Toulouse, ECMWF) UKMO,  Beijing and Pretoria not available in time for this publication from WMO but are available elsewhere.

WMOFMA012020

WMO 10 model composite ensemble

BOMFMA012020

BoM – one of the colder solutions.

WASHFMA012020

CFS2 – Washington – tends to be warm

TOULFMA012020

MeteoFr 

Further examples from WMO are available at the weather-info site.

nmmefmam0120

NMME  Feb to May

ECEFMAM012020

ECMWF Feb to May 

 

NASAFMAM0120

NASA Feb to May

Summer 2020

nmmejja0120

NMME June July August 2020

NASAJJA0120

NASA June July August

C: Comparing how well the models did for October, November December 2019.

UK area based on September 2019 data.

Temperature:
Most models were overly warm but there was a good indication of a much milder December although the colder November and to some extent October was not well forecast. Models that got colder values did not get the upturn in December. NASA got the trend reasonably well.
Rainfall:
Month to month detail was poor although some indication in NMME data was good. For the season WMO gave a hint at wetter in SW UK and Eire.

For graphics and details see Verification review Oct Nov Dec 2019 from Septemberg forecasts.

2. Forecast. SW England.

Remainder of Winter  (February 2020) 

The indication for a milder than average February remains the main signal but there is uncertainty in evolution of any significant stratospheric warming which might lead to a less mobile (westerly) pattern and hence nearer average or even cold solutions for a time later in the month.

February could be less wet than earlier winter months with nearer average rainfall, perhaps above average in exposed western areas and drier than average east of the moors.

Risk of snow mainly for the moors and temporary in nature.

February Climate: 1981-2010 Temperature; average temperature values for lowland areas 5 or 6°C but over 6°C in West Cornwall. Rainfall;  February. 1981-2010 average 80-100mm mm lowlands but 60-80mm in areas to E of Dartmoor and 40-80mm East of Exmoor. Over the Moors 100-250mm. .

Winter Climate: 1981-2010 average temperature values for lowland areas 7°C in the West and 5°C in the East. Rainfall;  January typically wetter than February. 1981-2010 Winter 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 2020  (March April May) 

Near or slightly above average temperature for the season but in some models March and in others May is indicated as being a less mild month (relative to its average). Precipitation uncertain but probably near or a little above average but perhaps fewer than average wet days.

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

Slightly above average temperature but possibly nearer normal in August. Rainfall uncertain but indications for near or perhaps slightly above average for the season overall though some longer drier periods suggested sometime in the July/August period but probably not a whole calendar month.

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) early indications with minimal data.

Slightly above normal or normal temperatures and near normal rain though hints at drier October.

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. 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