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. 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. September 2019.

Published 18 September 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.

ssta09

Except for a cooler area around Spain and to the north of Scotland the Atlantic continued to warm above the long term average. Cooler water can be seen near ther Bahamas following recent tropical storms. In general the tropical area is forecast to remain slightly above average through to Spring 2020.

tna_anom_20190901

In the Pacific neutral or weak El-Nino conditions have become establish and are likely to remain through the remainder of Autumn, into Winter and spring  – see CFSv2 and NMME multi model ensemble forecast below.

nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has recently been in a positive phase and the recent dip is forecast to be short lived with a return to a positive phase withing a week or so. A positive phase, if maintained implies a milder wetter winter 2019/2020.

noa0919

NAO background information see the Met Office NAO information.

Recent Climatology

September, so far (18th), has been about half a degree warmer than average with near or slightly above average sunshine and 30 to 45% of monthly rainfall.

Temperature and rainfall anomalies for Spring and Summer are shown below.

climate09

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 August 2019 Hydrological summary PDF 

river09

The reservoir levels in the SW of England (9th September) show 60% storage which is close to or slightly above normal levels.

res09

Looking ahead (September to December) 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.

glofas

Atmosphere: Predictions.

A:  1: Stratosphere

Stratosphere is in summer mode as shown by the ECMWF 50hPa chart for 1200UTC 17th September 2019.

50hpa

In the Antarctic region there has been a sudden stratospheric warming resulting in an early demise of the ozone hole leading to a record short lived ozone hole. The graphic below slows the extent of the ozone hole on the 16th September 2019  with associated 50hPa temperature and contour heights. The ozone being well above normal

shemioz

A: 2: Upper Troposphere

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

200hpa09

B: Lower Troposphere:

A selection of October to December 2019 solutions in low resolution from WMO using September 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 DWD, BoM, Seoul, CPTEC Brazil, UKMO, Washington, Pretoria, Tokyo, ECMWF, CMC and Toulouse seasonal models.  DWD and Beijing are missing.

WMOOND092019

WMO super ensemble

UKMOOND092019

UKMO

WASHOND092019

Washington CFS2

BOMOND092019

BoM Australia

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

Graphics For the winter period December 2019 to February 2020

09nmmedjf

NMME DJF

09CFS2E3djf

CFS2 DJF

NASADJF0919

NASA DJF

ECEDJF092019

For SW England there is good agreement for above normal temperatures and for normal or above normal precipitation. However precipitation forecasts are often misleading and a shift northwards of the wetter zone as in ECMWF may lead to lower rainfall values.

C: Recent results for (June to August 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 a trend to wetter types was suggested although the month to month detail was poor.

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

2. Forecast. SW England.

Remainder of Autumn 2019  (October November)

Overall the season is likely to see above normal temperatures with each month probably having above average values.

Rainfall forecasts slightly favour above normal rainfall for the season, perhaps with a less wet October then a wetter November but this is not clear.

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. 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. 

Winter  (2019 December 2020 January February)  limited data

The indication for a milder than average winter remains the main signal although February may see closer to normal values with December having the largest anomalies compared to the average.  Precipitation is likely to be above average especially in December, and possibly parts of January, although February may see nearer normal. Below average snowfall is 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.

Spring 2020  (March April May) very limited data

Above average temperature for the season but May could be a less mild month. Precipitation uncertain  but possible near average although Pparts of April or May could be drier.

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

3. Caution.

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

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

4. References.

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

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

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

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

CFS2  info

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

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

International seasonal monthly data from WMO

Stratospheric Diagnostics from Japan Met Agency and Free University Berlin

Climate data from The Met Office UK and NCEP USA

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

Published 23 August 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.

2019augssta

Except for an area between 10 and 40 degrees West, just south of 50 deg North the Atlantic continues to warm above the long term average and the tropical area is forecast to remain slightly above average through the turn of the year into 2020.

tna_anom_20190801

In the Pacific weak or neutral El-Nino conditions have become establish and are likely to remain similar through the Autumn and Winter period – see CFSv2 and NMME multi model ensemble forecast below.  The latest forecast from Tropical Storm Risk (University College London) along with NCEP have slightly increased the number of expected Atlantic tropical storms for the remainder of the period.

201908nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been in a negative phase for much of the period since April 2019. This translates for the summer period to a colder/wetter phase for the UK as indicated by the wet June. Recent NAO forecasts have moved to a positive phase and are forecast to remain positive at least in the short term suggesting drier and warmer types are more likely but if a positive phase was maintained it would lean towards a milder wetter winter?

201908nao

NAO background information see the Met Office NAO information.

Recent Climatology

August so far (23rd) has been wetter than average, slightly warmer but with less sunshine –  leading to a warmer than average summer. The temperature and rainfall anomalies from Spring onward are shown below.

201908temp

201908rain

The picture for rainfall is more mixed but many places will probably end up with above average rain for the the summer season. A few parts of the SW may be close to average depending on the rain total in August –  see the June + July anomalies below.

201908jjrain

River flows and groundwater in July reflect that drier month. More details can be found in the July 2019 Hydrological summary PDF 

201908riverflow

201908ground

The reservoir levels in the SW of England (18th August) show 65% storage which is close to or slightly above normal August level.

201908resev

Looking ahead (Aug to Nov) 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.

201908glofas

Atmosphere: Predictions.

A:  1: Stratosphere

Stratosphere is in summer mode as shown by the ECMWF 50hPa chart for 1200UTC 22nd August 2019.

20190850hpa

A: 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row) for the period September to November 2019, based on 8th August data, show above normal heights throughout the Autumn but with hints at strong Atlantic jet (on average) developing for November.

z200SON0819

B: Lower Troposphere:

A selection of September to November 2019 solutions in low resolution from WMO using August 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, BoM, Seoul, CPTEC Brazil, UKMO, Washington, Pretoria, Tokyo, ECMWF,  and Toulouse seasonal models. Moscow, Beijing and CMC missing.

WMOSON082019

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

Data from NASA

NASASON0819

UKMO

UKMOSON082019

ECMWF

ECLWMOSON082019

JAPAN

TOKSON082019

NMME Autumn 2019

08NMMESON

NMME Winter 2019/20

08NMMEDJF

For SW England, data from  Japan Canada and Germany suggest near normal temperatures but all other models suggest above normal temperatures this Autumn but rainfall forecast are much more varied.

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

Temperature forecast for a warming trend to above normal for the season were good although some output may be a little warm. Many precipitation forecasts were poor but a trend to wetter types was suggested although not specifically the much wetter June.

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

2. Forecast. SW England.

Autumn 2019  (September October November)

Overall the season is likely to see above normal temperatures, again hints at being slightly above normal in September then much milder later in Autumn.

Rainfall forecasts slightly favour above normal rainfall for the season, perhaps with a less wet start in September and a wetter end of Autumn but this is not clear. Some linger drier periods are suggested but no agreement as to when (may straddle a month and be missed by monthly anomalies)

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 2020 January February)  limited data

The indication for a milder than average winter remains the main signal. Precipitation is likely to be near or above average although there are hints that parts of the S and E parts of the S and E of the region may have normal or below average values. Below average snowfall is 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.

Spring 2020  (March April May) very limited data

Above average temperature for the season but May could be a colder month. Precipitation near average or below but May could be wetter than 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.

 

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

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

Published 18 June 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.

170619ssta

Due to the recent unsettled and rather cool weather the sea temperature around the UK (and western Mediterranean Sea) is mostly a little below the average along with much of the North Atlantic (40 to 55North).

Tropical Atlantic seems to be warming and is forecast to remain warmer than average – see Met Office graphic below:

tna_anom_20190601

In the Pacific weak El-Nino conditions have continued and are expected to persist as indicated by CFSv2 and NMME multi model ensemble forecast (shown below).

180619nino

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) returned to slightly positive from mid April after the first negative phase period for some time but shortly after went and remained negative. For the summer period this translates to a colder/wetter phase for the UK.

180619nao

NAO background information see the Met Office NAO information.

Recent Climatology

In the SW of England, June  has been wetter, colder and cloudier than average. Main station SYNOP data to the middle of June showed the average temperature anomaly to be around minus 1 C with rainfall between 20 and 50% above average and sunshine only a third of average. This represents a significant change from overall warmer and drier weather of the last six months. Seasonal models historically have been poor at picking out a change to colder types.

170619temphist

Winter and Spring temperatures have been above normal and rainfall mostly normal or below across SW England.

170619rainhist

River flows were showing below normal values in the east of the SW Region although groundwater seems near normal in the May report. The wet weather in June is likely to lifted river levels somewhat.

170619riverflowmay

Full details can be found in the  May 2019 Hydrological summary PDF 

The reservoir levels in the SW of England (16th June) show 80% storage which is slightly below the normal June level, but recovering.

060619reslev

The June experimental product from the Global Flood Awareness System (Version 2) was not available on the 18th.

Atmosphere predictions.

A:  1: Stratosphere 

17061950hpa

Remains in summer mode as shown by the ECMWF 50hPa chart for 17th June 1200UTC.

A 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row) for the period July to November 2019 based on 7th June data, show mostly above normal heights but perhaps imply a slightly enhanced jet in mid Atlantic during October and more especially in November though perhaps to west of Uk.z200SON0619

B: Lower Troposphere:

July to September 2019 solution in low resolution from WMO . JAS and individual months. Top row temperature anomaly, mid row precipitation anomaly and lower row PMSL 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, UKMO, Washington, Pretoria, Tokyo, ECMWF, Beijing and Toulouse seasonal models.

WMOJAS062019

WMO July to August

UKMOJAS062019

UKMO JAS and monthly anomalies

nasa0619

NASA June 2019 to Feb 2020 Temp and Rain anomaly

nmme1

NMME July to November 2019 top row temperature lower row rain rate anomaly.

NMMEDJF06


NMME December 2019 to Feb 2020 top row temperature lower row rain rate anomaly.

There are several models that suggest colder and wetter summer but not the majority.

A summary from all the models for July to September looks roughly:
Temperature: 50% above normal, 31% normal 19% below normal.
Rainfall:  50% above normal, 28% normal, 22% below normal.

Additional model graphics can be seen at the seasonal forecast summary

C: Recent results for the Spring (March to May 2019):

Most models forecast above normal temperatures but NCEP, CANSIPs and JMA captured the trend for a less mild May.
Precipitation: Good indication that March could be wetter and some idea that the season could be wetter in places but was incorrect about the south/SW. Signal for below normal in places was correct but as usual exact location was not predicted well.

Comparison graphics can be seen at the verification page for Spring 2019

2. Forecast. SW England.

Remainder of Summer 2019  (July August) 

A warmer than average summer for the season is still more likely than not despite a colder two thirds of June.

Overall the balance has shifted towards above normal rainfall for the season.Models remain mixed at which month could be drier or wetter. However some longer dry spells seem likely over the next two months.

Higher temperatures may lead to shorter periods of heavier rain but fewer wet days which has been a pattern in 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 2019  (September October November) limited data. 

A warmer September, then milder than normal each month and for the season.  Still looks likely that the Autumn could start drier in September then end with a wetter November, hence overall average or below average rain for the season.

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) minimal data. 

Milder than average throughout. Near or above average rainfall for the season. 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