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

Review and Experimental Long Range Forecast for SW England. December 2019.

Published 18 December  2019.

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.

161219SSTA

North Atlantic and North Pacific sea temperature anomalies continue to show above average values although the North Atlantic roughly between 40 and 60 degrees north shows some well mixed areas due to Atlantic storms with cooling in eastern parts to the west of Europe.

tna_anom_20191201

The tropical north Atlantic is forecast to remain very slightly warmer than average through Spring 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 from about late Spring 2020 – see CFSv2 and NMME multi model ensemble forecast below.

1219nino

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 if maintained could lead to colder weather types for the UK.

1219nao

NAO background information see the Met Office NAO information.

Recent Climatology

The first half of December has seen above average rainfall across SW England, except perhaps in the far West of Cornwall were values have been near or even slightly below average. Temperatures have also been slightly above average, again except for the far West of Cornwall which has been near average.

Temperature and rainfall anomalies for Autumn 2019 are shown below. A more local summary for the Teignmouth and Dawlish area is available here.

1219clim

Europe anomalies for Autumn 2019 are shown below.

map_SON_anomaly_Europe_ea_hydro_201909-201911_v01

 

River flows and groundwater in November reflect the much wetter conditions though it is interesting to see that groundwater in eastern England in November had still not recovered to normal. Details can be found in the November 2019 Hydrological summary PDF 

1219riverflow

The reservoir levels in the SW of England (15th December) show 82% storage, which is above normal for the time of year.

151219reslev

Global Flood Awareness System December forecast through to March 2019 largely reflects the well above average rain in November and early December.

1219glowfas

Atmosphere: Predictions.

A:  1: Stratosphere

The North Polar stratospheric vortex shifted east (relative to 00Deg W), as shown by the ECMWF 50hPa and 10hPa charts for 1200UTC on the 8th December. This led to a reversal of the stratospheric winds over North America and may be contributing to the recent colder types in that region. The vortex has started to edge back towards the pole as shown in the plot for the 17th December 2019, with an associated strengthening of the stratospheric winds and of the vortex.

Further warming is occurring and this may lead to another reshaping and displacement of the vortex over the next few weeks. This suggests there is some risk of a sudden warming leading to a change in European weather types in mid to late January. Current seasonal forecasts do not suggest a change persistent colder types at present.

1812196strat

Plot of 10hPa GFS model zonal wind history and forecast (Source @HannahAttard)

1219strathattard

A: 2: Upper Troposphere

Combined NCAR and CFSv2 200hPa averaged monthly mean height contours and anomalies (below).

Period January to March 2020. Indication of above normal heights throughout with marked ridging in February and hints at stronger than average Atlantic jet in March.

z200JFM1219

Period March to May 2020. Indication of above normal heights throughout but with hints at stronger than average Atlantic jet in March and April.

z200MAM1219

B: Lower Troposphere:

A selection of January to March 2020 solutions using December 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, UKMO, Seoul, Washington, Tokyo, Toulouse, ECMWF) Tokyo, Beijing and Pretoria missing but Tokyo and Beijing data is available on their respective web sites.

WMOJFM122019

WMO super ensemble

UKMOJFM122019.png

UKMO

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

ECEJFM122019

ECMWF  Jan to March 2020

nmme12JFM

NMME Jan to March 

E3JFM

CFS2 E3 (mean of 10 days model output) for January to March 2020

NASAJFM1219

NASA January to March

Spring 2020

ECEMAM122019

ECMWF for Spring 2020

NASAMAM1219

NASA for Spring 2020

nmme12MAM

NMME for Spring 2020

Summer 2020

NASAJJA1219

NASA for summer 2020

nmme12JJA

NMME Summer 2020

For SW England there remains a consensus for above normal temperatures and for above normal precipitation through the remainder of Winter and into Spring though less consensus for summer rainfall.

C: Comparing how well the models did for the Autumn, September to November 2019.

Poor temperature forecasts. BoM and perhaps Tokyo hinted at cooling trend but not colder than average. Most models failed to get colder signal. Rainfall signal for wetter in south was good but models in general were poor with only a few hinting at the drier Scotland.

For graphics and details see Verification review Autumn 2019 from August forecasts.

2. Forecast. SW England.

Remainder of Winter  (January and February 2020) 

Increased uncertainty due to changes in stratosphere.

The indication for a milder than average winter as a whole remains the main signal. Some hints that February could be nearer normal.

Precipitation for the winter as a whole is likely to be above average with some hints that parts of January or February could be less wet but no consistent indication. Given that the first half of winter has been wetter than average it seems likely that a drier period is on the cards although this could be temporary.

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

The signal for windier than usual conditions continues but with pressure near normal or even above normal close to the south of the UK this may be a feature of the weather further north and may be less evident in January.

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) 

Above average temperature for the season but in some models May continues to be indicated as being a less mild month (relative to its average). Precipitation uncertain but probably near or a little above average.

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

Summer 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.

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. 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. November 2019.

Published 17 November  2019.

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.

141119ssta

North Atlantic and North Pacific sea temperature anomalies continue to show above average values although the North Atlantic roughly between 50 and 60 degrees north shows some well mixed areas due to Atlantic storms.

tna_anom_20191101

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

In the Pacific neutral or weak El-Nino conditions continue and forecasts suggest conditions are likely to remain similar over winter and and probably through to Spring 2020 – see CFSv2 and NMME multi model ensemble forecast below.

201911nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has recently turned positive which if maintained implies a milder, wetter, winter 2019/2020. However it is  far from clear that this will be the case and the majority of the enesmeble forecast show a dip to a negative phase over the next week or two.

201911nao

NAO background information see the Met Office NAO information.

Recent Climatology

The first half of November has been wetter than average with only on or two days with no measurable rain. Rain totals range from over 100mm in some western and hilly areas to 50mm in the east, that’s over 90% of the typical November rain in western areas.  Temperature means have been around 7 or 8 Celsius which is above half a degree or so below the 1981 to 2010 average and it has been cold enough for sleet over some higher hills and snow over the moors giving a covering. Sunshine has typically been below average.

Temperature and rainfall anomalies for June to October are shown below. Please note you can view the Teignmouth and Dawlish summary here.

201911clim

Europe anomalies over the last 12 months November 2018 to October (Copernicus data), shown below, show the UK and Scandinavia with below average temperature in an otherwise above average region. Southern UK has also been wetter than average.

2019year.png

Meanwhile October global temperatures show a warming trend compared to 1981 to 2010 average.

201910globe

River flows and groundwater in October reflect the wetter conditions but groundwater in eastern England has still not recovered to normal. Details can be found in the October 2019 Hydrological summary PDF 

201910river

The reservoir levels in the SW of England (10th November) show 76% storage, above normal levels for the time of year.

201911res

Global Flood Awareness System has been upgraded but data starting in November is not yet available.

Atmosphere: Predictions.

A:  1: Stratosphere

North Polar vortex forming in the Stratosphere is in winter mode as shown by the ECMWF 50hPa chart for 1200UTC 15th November 2019. There are signs of warming causing the vortex to split relocate eastwards and this might result in a less mobile Atlantic pattern which may develop in mid December. This is not born out by long range forecast at present. Plot of 10hPa GFS model zonal wind shown below the 50hPa plots.

16111950hpa

u_65N_10hpa_gefs

GFS forecast for 10hPa showing marked weakening of zonal wind associated with weakening or movement of the stratospheric vortex. Thanks to @HannahAttard.

A: 2: Upper Troposphere

NMME (top) and combined NCAR and CFSv2 200hPa averaged monthly mean anomalies (middle) compared to CFS2 forecast height contours (lower row) for the period December 2019 to February 2020, based on November data, Indication of above normal heights throughout but with hints at stronger than average Atlantic jet.

z200DJF1119

For Spring 2020, again above normal heights with less  signal for enhanced jet flow.

z200MAM1119

B: Lower Troposphere:

A selection of December 2019 to February 2020 solutions in low resolution from WMO using November data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

White areas are area 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, UKMO, Seoul, Washington, Tokyo, Toulouse, ECMWF) Beijing and Pretoria missing but Beijing data is available on their web site.

WMONDJ112019

WMO super ensemble

UKMONDJ112019

UKMO seasonal

BOMNDJ112019

BoM seasonal – along with Moscow represents the two colder solutions.

ECLWMONDJ112019

ECMWF seasonal DJF 

WASHNDJ112019

Washington seasonal 

The complete set of graphics including NASA and NMME graphics is available at the weather-info site.

Fewer models for Spring 2020

NASAMAM1119.png

NASA seasonal March April May 2020 (Nov 2019 data)

201911E3spring.png

CFS2 E3 data seasonal forecast Spring 2020 data November 2019.

201911nmmespring

NMME data November 2020 forecast for Spring 2020.

For SW England there remains is a strong consensus for above normal temperatures and for above normal precipitation at least through winter.

C: Recent results for (August to October 2019):

Temperature forecast for above normal for the season were OK although some output may be a little warm and the less warm September was not well forecast. Many precipitation forecasts were poor but the overall trend  to wetter types was suggested especially for SW England although the month to month detail was poor.

Comparison graphics can be seen at the verification page for July August September 2019

More recently models were slow to pick up a colder first half of November but may recover the average in the second half of the month.

2. Forecast. SW England.

Winter  (2019 December 2020 January February) 

Increased uncertainty due to changes in stratosphere.

The indication for a milder than average winter remains the main signal. Only two models suggest a colder season and one or two indicate less mild months, notably February.  Precipitation is likely to be above average with some hints that February could be less wet but no consistent indication for any specifically drier month. Below average snowfall is more likely than above average. The signal for windier than usual conditions continues but with pressure near normal or even above normal close to the south of the UK this may be a feature of the weather further north.

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 2020  (March April May) limited data

Above average temperature for the season but in some models May is indicated at being  a less mild month (relative to its average). Precipitation uncertain but probably near or a little above average early in the season but less strong indications for later in the season.

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 temperatures but possibly near normal for August. Rainfall uncertain but some indications for a drier August with overall rainfall near or perhaps slightly above average.

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

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 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. October 2019.

Published 16 October  2019.

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.

1019SSTA

North Atlantic and North Pacific sea temperature anomalies continue to show above average values although the area between Newfoundland and Ireland shows some well mixed areas. The tropical north Atlantic is forecast to remain warmer than average through to at least Spring 2020 (See Met Office graphic below).

tna_anom_20191001

In the Pacific neutral or weak El-Nino conditions continue and forecasts suggest conditions are likely to remain similar through to Spring 2020 – see CFSv2 and NMME multi model ensemble forecast below.

1019nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has recently been in a negative phase but is forecast to turn slightly positive within a week or two. A positive phase, if maintained, implies a milder wetter winter 2019/2020.

1019nao

NAO background information see the Met Office NAO information.

Recent Climatology

October to date has been wetter than average with only on or two days with no measurable rain and in some places rain every day. Temperature though continue above average.

Temperature and rainfall anomalies for July to September are shown below. Please note you can view the Teignmouth and Dawlish summary here.

10JAS

Europe anomalies over the last 12 months (September 2018-2019 Copernicus data).

map_12month_anomaly_Europe_ea_hydro_201909_v01 (1)

Global temperature anomaly over the last 12 months (2018-2019 Copernicus data).

map_12month_anomaly_Global_ea_2t_201909_v01[1]

 

River flows and groundwater in August reflect wetter month but for parts of the E/SE of England drier types have left significantly low river flows and groundwater values. Soil moisture deficit is extensive across much of England and Wales . Details can be found in the Septem 2019 Hydrological summary PDF 

1019river

The reservoir levels in the SW of England (13th October) show 66% storage which was above normal levels for the time of year.

1019res

Looking ahead (October to January) the experimental product from the Global Flood Awareness System (Version 2) suggests reduced flood risk for the SW over the next few months although local flash flooding would not be included in this. This seems at odds with the seasonal forecast output (shown later) which suggests increased rainfall.

1019glofas

Atmosphere: Predictions.

A:  1: Stratosphere

North Polar vortex forming in the Stratosphere which is moving into winter mode as shown by the ECMWF 50hPa chart for 1200UTC 15th October 2019.

1019strat

A: 2: Upper Troposphere

NCAR and CFSv2 200hPa averaged monthly mean forecast height (contours) and anomaly (lower row) for the period November 2019 to February 2020, based on October data, shows above normal heights throughout but with hints at stronger than average Atlantic jet in December and possible February 2020.

1019200hpa.png

B: Lower Troposphere:

A selection of November 2019 to January 2020 solutions in low resolution from WMO using October data are shown below. Three month season and individual months, top row temperature anomaly and lower row precipitation anomaly.

White areas are area where the probabilities of below/normal/above are similar hence there is no overall signal for this period from the WMO super ensemble which includes UKMO, DWD, CMC, BoM, Seoul, Washington, ECMWF, Toulouse, Brazil.

WMONDJ102019

WMO super ensemble

UKMONDJ102019

UKMO

BOMNDJ102019

BoM one of the few colder solutions

ECLWMONDJ102019

ECMWF

the complete set of graphics is available at weather-info site.

Graphics For the winter period December 2019 to February 2020

1019NMMEDJF

NMME 8th October WINTER

1019NASADJF

NASA Winter

1019ECMWFDJF

ECMWF winter

1019E3CFS2DJF

CFS2 (E3 data) 8th October. Winter.

For SW England there is a strong consensus for above normal temperatures and for above normal precipitation.

C: Recent results for (July to September 2019):

Temperature forecast for above normal for the season were good although some output may be a little warm. Many precipitation forecasts were poor but the overall trend  to wetter types was suggested although the month to month detail was poor.

Comparison graphics can be seen at the verification page for July August September 2019

2. Forecast. SW England.

Remainder of Autumn 2019  (November)

November is likely to see above normal temperatures and normal or above normak rainfall.

November climate: 1981 to 2010 average mean temperature 8 or 9C°C.  Average 1981 to 2010 rain 60 to 100mm East of the moors, 100-200mm west of the moors but over 250mm over the moors. 

Winter  (2019 December 2020 January February) 

The indication for a milder than average winter remains the main signal although hints at December being nearer normal with the largest anomalies compared to the average being later in the winter.  Precipitation is likely to be above average with no clear indication for any specifically drier month. Below average snowfall is more likely than above average. Possibly increased number of gales.

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 2020  (March April May) limited data

Above average temperature for the season but May could be a less mild month. Precipitation uncertain  but probably near or above average though some hints that March could be drier.

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

Summer 2020  (June July August)  very limted data

A warmer and possibly drier than average summer is possible.

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. 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. July 2019.

Published 19 July 2019.

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.

150719ssta

Due to the recent settled and at times very warm weather, sea temperatures around the UK (and in the Mediterranean) have strongly recovered being above normal in the latest data. Sea temperatures around Greenland and Alaska are notably above average.

Tropical Atlantic has continued to warm and is forecast to remain slightly warmer than average – see Met Office graphic below:

tna_anom_20190701

In the Pacific weak El-Nino conditions have become weak and may now become neutral or even slightly La Nina this Autumn – see CFSv2 and NMME multi model ensemble forecast below. This may impact on the number of Atlantic tropical storms which are reduced during El Nino years. The latest forecast from Tropical Storm Risk (University College London) call for near normal numbers of Atlantic storms but stress the uncertainty with regards El Nino changes.

nino340719

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been in a negative phase since later April 2019 which for the summer period translates to a colder/wetter phase for the UK and June reflected the wetter type in many areas but with temperatures near normal or slightly above. In July this has also been the case in Scotland but not further south. Recent NAO forecasts suggest a (possibly temporary) change to a positive state with drier and warmer types more likely.

NAO0719

NAO background information see the Met Office NAO information.

Recent Climatology

Despite a colder first half of June the warmer period at the end of the month led to near normal mean temperatures for most parts of the SW. Up until the 18th of July it has been dry with only about 1% of typical July rainfall. Data from the main SYNOP station show above average sunshine but a mean temperature of 17 Celsius which is near average, despite some very warm days. Probably parts of the SW have had warmer than average values once all the data is available early in August.

temp

Met Office mean temperature anomalies Autumn 2018, Winter, Spring and June 2019

PPN0719

Met Office rainfall anomalies Autumn 2018, Winter, Spring and June 2019

Because of the June rainfall 12 month totals to end of June are close to average although but temperature is above average as shown by the Copernicus graphic below.

map_12month_anomaly_Europe_ea_hydro_201906_v01

riverflows

River flows in June reflect the wet month although annualised rates are below average more details including ground water can be found  in the  June 2019 Hydrological summary PDF 

Soil moisture content was still below normal over parts of the SW at the end of June and the dry first half of July is not likely to have helped.

sm0719

The reservoir levels in the SW of England (14th July) show 73% storage which is slightly close to a normal July level.

resevoir

Looking ahead the experimental product from the Global Flood Awareness System (Version 2) suggests reduced flood risk for the SW over the next few months although local flash flooding would not be included in this.

GLOFAS0719

Atmosphere: Predictions.

A:  1: Stratosphere

Stratosphere is in summer mode as shown by the ECMWF 50hPa chart for 1200UTC 18th July 2019.

50hpa0719

A: 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row) for the period August to November 2019 based on 7th July show above normal heights throughout and it is not until February that some below normal heights are indicated over the north of Scotland.

z200ASON0719

CFS2 200hPa mean and anomaly August to November

z200DJF0719

CFS2 200hPa mean and anomaly December 2019 to February 2020

B: Lower Troposphere:

A selection of August to October 2019 solutions in low resolution from WMO using July data. Three month season and individual months. Top row temperature anomaly and mid row precipitation anomaly.

White areas are area where the probabilities of below/normal/above are similar hence there is no overall signal for this period from the WMO super ensemble which includes DWD, CMC, BoM, Moscow, Seoul, (CPTEC missing data), UKMO, Washington, Pretoria, Tokyo, ECMWF, Beijing and Toulouse seasonal models.

WMOASO072019

WMO super ensemble August to October

The super ensemble has an indication for above normal temperature but no agreement in the precipitation detail.

Some examples from individual centres are shown below. Full list can be seen at the seasonal forecast page.

UKMOASO072019

UKMO ensemble August to October

WASHASO072019

Washington NCEP WMO ensemble August to October

NMMEASON

NMME multi model ensemble August to November

NMMEDJF

NMME multi model ensemble December 2019 to February 2020

There are a few models that suggest colder and wetter periods in the August to October period but not the majority.

A summary for SW England from all the models for August to October looks roughly:
Temperature: 70% above normal, 20% normal 0% below normal and 10% no signal.
Rainfall:  15% above normal, 30% normal, 20% below normal and 35% no signal.

No signal = similar probs for above/normal/below

Additional model graphics can be seen at the seasonal forecast summary

C: Recent results for (April to June 2019):

Some good pointers to temperature anomaly and cooler signal in some models but the overall above average forecast for the season was correct. Some good indications from some models for a wetter June in England and in May for Scotland but idea of drier end to season was not correct, although the very end of June was dry and warm.

Most precipitation forecasts were poor.

Comparison graphics can be seen at the verification page for April May June 2019

2. Forecast. SW England.

Remainder of Summer 2019  (August) 

August is likely to see near or above normal temperature. There are slightly more solutions in favour of a drier than average month than those for a wetter one but thunderstorm rain rates could lead to some very wet days in a few places.

Higher temperatures may lead to shorter periods of heavier rain but fewer wet days which has been a pattern in recent years.

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 2019  (September October November) limited data. 

Overall the season is likely to see above normal temperatures, possibly nearer normal in September and much milder later in Autumn.

Rainfall is likely to be below normal for the season, especially in the S and E of the region perhaps nearer normal elsewhere. Little agreement as to which month could be wetter but some hints that it could be 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.

Winter 2019  (December January February) limited data. 

The indication for a milder than average winter remains the main signal. Rainfall is likely to be above average although there are hints that December and / or February may be less wet in parts of the S and E of the region. Below average snowfall more likely than above average.

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

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 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