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

Published 19 July 2019.

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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

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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

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

Published 21 May 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.

sst0519

Despite sea temperatures around the UK being above average.,much of the northern Atlantic is somewhat below average as is parts of the Mediterranean.

atltrop0519

UKMO tropical N Atlantic forecast sea temperature

The forecast Atlantic tropical sea temperature (shown above) continues to suggest a warming trend although this has been reluctant to occur.

In the Pacific weak El-Nino conditions continue, see CFS2 and NMME multi model ensemble forecast below. Current forecasts are mostly slightly less warm, a more marginal El-Nino.

ninosst

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) continued a negative phase which in summer would suggest colder / wetter condition for the UK. There is roughly a balance of models suggesting wetter verses drier but the majority suggest warmer.

nao0519

NAO background information see the Met Office NAO information.

Recent Climatology

In the SW of England, main station SYNOP data to May 1800 20th shows the average temperature anomaly to be around -1 C with below average rain and near average sunshine hours. tempanomn

Winter and Spring temperature until recently though have been above normal and rainfall for the last 12 months mostly normal or below.

climat rain 05

River flows are again showing below normal values in the east of the SW Region although groundwater seems near normal in the April report.

riverflow04

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

The reservoir levels in the SW of England (12th May) show 86% storage which is slightly below the normal May level.

reslev1205

The experimental product from the Global Flood Awareness System (Version 2) based on early May ECMWF seasonal forecast for May to August 2019. The system does not suggest an enhanced flood risk for SW England.

glofas

Atmosphere predictions.

A:  1: Stratosphere 

The stratospheric has reverted to “summer” mode as shown by the ECMWF 30 and 10hPa images below for 1200UTC on the 18th..

ecstrat0519

A 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row).

z200jja0519

Generally above normal heights are forecast by CFS2 system for the summer months.

 

B: Lower Troposphere:

June to August 2019 solutions in low resolution from WMO . JJA and individual months. Top row temperature anomaly and lower row precipitation anomaly. Above normal orange/reds below normal in blue shades.

wmojjamulti0519

WMO multi model ensemble probabilities JJA

ukmojja0519

UKMO ensemble probabilities JJA

ecjja0519

ECMWF JJA probabilities

nmme0519jja

NMME JJA 

e3son0519

CFS2 JJA (E3 data)

For the summer; Data from Australia BoM, Brazil, South Africa and Russia suggest below normal summer temperatures but the vast majority of solutions suggest above normal values for the season and each month. Rainfall solutions are more evenly balanced between the wetter and drier solutions.

For the Autumn.

e3son0519

Autumn NMME data

e3son0519

Autumn CFS2 E3 data

C: Recent results for the period February March and April:

Continuing on from recent reviews temperature forecast were fairly good but rainfall forecast were generally poor. Verification page for February to April 2019

2. Forecast. SW England.

Summer 2019  (June July August) 

A better than average summer is more likely than a less good summer.

A warmer than average summer for the season is likely and probably each month is likely to be above normal too.

Models are mixed at which month could be drier or wetter. Howver some longer dry spells seem likely. Overall near normal rainfall seems likely but uncertain as to whether it is the number of dry days or the rain total that will be lower/higher. 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 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 2019  (September October November) limited data. 

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

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. Wetter start to winter then ending below average in February. Below average snowfall.

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

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 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. April 2019.

Published 21 April 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.

180419ssta

The sea temperature around the UK and across much of the North Atlantic is similar to last month being fairly close to the seasonal normal or a shade warmer/cooler in places.

The Met Office diagnostic for the tropical Atlantic (shown below) was near normal with a trend to above normal values in the majority of the ensemble solutions.

tna0419

In the Pacific weak El-Nino conditions have continued, see CFS2 and  multi model ensemble forecast below but current forecasts are mostly slightly less warm.

nino0419

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) returned to slightly positive (warmer wetter phase for UK) from mid April after the first negative phase period for some time.

noa0419

NAO background information see the Met Office NAO information.

Recent Climatology

In the SW of England, main station SYNOP data to April 1800 20th shows the average temperature anomaly to be around +0.7 C, but zero in the east. Rainfall between 60 and 90% of average with about 55% of normal sunshine hours.

tempsummary

The mean temperature over the last six months has been above average except for January (which was near average). February was exceptionally mild and followed on from a warmer than average summer 2018.

Rainfall was above average in SW England during March (mainly until 17th). For the six month period October to March south parts were slightly above average but northern parts remained below the long term 1981-2010 average.

rainfall

The recent wetter periods helped river flow recover from the lows in January but river flows were reported as slightly below average. Ground water in the east of the region remains normal but eastern parts of the UK have less good water resource levels.

riverflow

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

The reservoir levels in the SW of England (14th April) show 88% storage which is slightly below the normal April level.

reslevel14

The experimental product from the Global Flood Awareness System (Version 2) based on early April ECMWF seasonal forecast for April to July 2019. The system does not suggest an enhanced flood risk for SW England.

Glofas0419

Atmosphere predictions.

A:  1: Stratosphere 

The stratospheric polar vortex re-established and became unusually strong. Much colder than normal temperatures were recorded, especially at 10 and 30hPa.

npole0419

Temperatures have recovered and it looks like the polar vortex will transition to “summer” mode by early or mid May as seen by the ECMWF forecast (dated 18th April) and shown below.

strat0419

A 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row).

z2000419

Some indication of more troughing just west of the UK but overall weaker than normal jet flow may be lead to more blocked patterns. Uncertain location of higher pressure which may be further east for periods.

B: Lower Troposphere:

Selection of May to July 2019 solutions in low resolution from WMO (not all data available at date of issue) . Top row temperature anomaly and lower row precipitation anomaly. Above normal orange/reds below normal in blue shades.

mjjsum0419

Three month average anomalies sourced from WMO up to 20 April 2019

Above normal temperatures are indicated but data from Australia and Russia are the exception with a below normal temperature forecast. Rainfall patterns less clear cut with the cooler wetter output (2) slightly outnumbered by the near normal/uncertain (6) and drier solutions (3).

MtoAugE3

CFS2 (E3 data) 1st April for May to August

NMME140419JJA

CFS2 (E3 data) 124th April May to August

Although temperature forecasts from CFS2 (E3 data) show consistent positive anomalies the rainfall anomalies are in less good agreement between model runs.

NMME0419MJJA

NMME data 9th April for May to August

C: Recent results for the period January February March:

Temperature mostly fair indication (scale no indication poor fair good). Signal for the milder February was confused by the colder indication due to a sudden stratospheric warming which although blocked patterns developed the flow remained mild rather than colder easterly.

Rainfall was fair at best and many models were poor. Month to month forecasts were poor. Pressure was slightly above average so at best only a partial signal. Better models seemed to be NMME and Japan.

2. Forecast. SW England.

Remainder of Spring 2019  ( May) 

Milder/warmer than average temperature is forecast by most models May in the SW of England.

Rainfall forecasts suggest than May could be drier than average (few models suggest wetter).

Spring climate: 1981-2010 average mean temperature 9 or 10°C but a few degrees cooler over the moors. Roughly  May 11 or 12°C. Average spring 1981 to 2010 rain 200 to 300mm lowest values in E Devon and over parts of Somerset. May roughly 80-150mm over the moors, 60-80mm elsewhere but 40-60mm locally to the East of Dartmoor and over large parts of Somerset and Dorset.

Summer 2019  (June July August) 

A better than average summer is more likely than a less good summer.

Warmer than average summer although temperatures in August may be closer to normal.

Models are mixed at which month could be drier or wetter. Overall near normal rainfall seems likely but uncertain as to whether it is the number of dry days or the rain total that will be lower/higher. Higher temperatures may lead to shorter periods of heavier rain but fewer wet days which has been a pattern in recent years. Indications of some linger dry spells.

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 2019  (September October November) limited data. 

Warmer September then milder than normal, monthly and for the season.  Could start drier in September then  end with a wetter November hence overall 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. Wetter start to winter then ending below average. Below average snowfall.

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

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 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. March 2019.

Published 15 March 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.

140319sst

The sea temperature around the UK and across much of the North Atlantic is similar to last month being fairly close to the seasonal normal, a shade warmer/cooler in places.

The Met Office diagnostic for the tropical Atlantic (shown below) was near normal with a trend to above normal values in the majority of the ensemble solutions.

150319tropatl

In the Pacific weak El-Nino conditions have continued, see CFS2 and  multi model ensemble forecast below.

140319ninot

An interesting feature is the sea temperature anomaly to the west of Panama. The cold tongue is caused by up-welling of colder salty water which is probably due to the spread west of lower salinity water by persistent easterly winds.

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been slightly positive (warmer wetter phase for UK) since early January and the index is likely to remain in a positive phase over the short term. Longer term there are signs of a disruption in this pattern.

150319nao

For NAO background information see the Met Office NAO information.

Recent Climatology

In the SW of England, March main station SYNOP data to 0600 15th shows the average temperature anomaly to be around +1.5 C, rainfall between 100 and 110% of average with about 40% of normal sunshine hours.temp150319

Temperatures over the last six months have been near or above average with February exceptionally mild and follows on from a warmer than average summer 2018.

Rainfall was above average in SW England during November and December 2018 otherwise the nine months from June 2018 has seen normal or below normal rainfall for most parts.

climrain1503

The wetter period in the first half of February 2019 helped river flow recover from the lows in January but river flows were reported as slightly below average.

river1503

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

The reservoir levels in the SW of England (10th March) show 87% storage which is below the normal winter level.

resevoit1503

The experimental product from the Global Flood Awareness System (Version 2) based on early March ECMWF seasonal forecast for April to June 2019. The system does not suggest an enhanced flood risk for UK currently and suggest lower than normal river flows are possible.

150319glofas

Atmosphere predictions.

A:  1: Stratosphere 

The stratospheric polar vortex re-established and became unusually strong. Much colder than normal temperatures were recorded, especially at 10 and 30hPa.  30hpaRecent forecasts (ECMWF shown below) suggest a new area of warming is likely to develop and this may well be the final warming prior to the change to a “summer” pattern. This may fit in with some forecasts of more blocking patterns and the lower than average river flow forecast shown by Glofas.

50hpa

A 2: Upper Troposphere

CFSv2 200hPa monthly mean forecast height (contours) and anomaly (lower row).

150319cfs200Z

Some indication of enhanced jet in April with a SSW jet possibly steering lows further N over or to N of UK on average. More generally ridged pattern for May and June but less of a signal for July and August.

B: Lower Troposphere:

Selection of Spring (April May June and some July August) solutions. Top row temperature anomaly and lower row precipitation anomaly. Above normal orange/reds below normal in blue shades.

1503ECj

ECMWF monthly

CFS2E30319

CFS2 E3 monthly

NMME0319

NMME monthly 

Selection of models UKMO, Australia, Russia, France, Canada and Germany. Left image season April to June then separate months. Top row temperature anomaly and lower row precipitation anomaly.  Russia and Australian colder and wetter most others warmer drier after a wetter start and possible end of the period April to August. Other models available at web link.

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C: Recent results for the winter period December January February:

Temperature mostly fair indication (scale no indication poor fair good)  but signal for the milder February was confused by the colder indication due to a sudden stratospheric warming which although blocked patterns developed the flow remained mild rather than colder easterly. Rainfall good indication for December but poor overall for the season being wetter than average. Pressure was above average so at best only a partial signal. Better models seemed to be NMME and Japan.

2. Forecast. SW England.

Remainder of Spring 2019  (April May) 

Milder than average temperatures continue for both for April and May in the SW o England.

Rainfall totals normal to wetter than normal in April but trending to drier than average in May.

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

Summer 2019  (June July August) 

Warmer than average summer although temperatures in August may be closer to normal.

Overall near or below normal rainfall seems likely but uncertain as to whether it is the number of dry days or the rain total that will be lower. Higher temperatures may lead to shorter periods of heavier rain but fewer wet days which has been a pattern in recent years.

Several models suggest a drier than average June and possibly July although some suggest August rather than July to be drier. Probably an increased risk of at least normal rainfall later in the summer. Overall monthly details is inconsistent but the idea that the start of summer could be the drier period seems well supported although this is different to February data.

Chance of reduced river flows and reservoir levels causing some concerns.

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 2019  (September October November). 

Warmer September then milder than normal, monthly and for the season.  Could start drier in September then  be a wetter than average start to Autumn in the SW but then near or even below normal rainfall possible for for October or November.

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

Winter 2019  (December January February) minimal. 

Milder than average throughout. Wetter December then below average rainfall hence a drier than average winter. Below average snowfall.

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

3. Caution.

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

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

4. References.

SST anomaly NOAA Remote Sens. 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 2018.

Published 17 December 2018

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.

sstanom131218

The sea temperature in the North Sea remains above normal and temperatures in the N and E Atlantic (west of the UK) slow slightly less of a cool anomaly compared to last month. The sea temperature remains above normal south of 50 deg north and west of 20 deg West across to Florida but is cooler near the equator.

tna_anom_20181201

UKMO December 2018 Tropical North Atlantic SST forecast

The tropical North Atlantic SST has been below the forecast value from last month but is forecast to return to near average. In the Pacific the El Nino is well established (see graphic below) and is forecast to remain through to Autumn 2019.

171218elnino

The dominant IRI statistical predictor for UK rainfall based on the Pacific sea temperature anomalies for the winter season is shown below. Probabilities shown are for “near normal” precipitation, which is the category which has higher probs than either below or above normal.

elninonormal

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) has been swapping between a positive and negative and is forecast to continue to oscillate over the next month but with no strong signal for a negative phase. See below.

171218nao

For NAO background information see the Met Office NAO information.

Recent Climatology

In the SW of England data to December 16th shows temperatures above average by over two degrees, above normal rain and well below average sunshine. November also saw well above average temperatures although earlier months were nearer average. Rainfall in November was above average but the longer term rain total remains lower than normal (see below).

171218clim

Recent rainfall has boosted soil moisture and the forecast (GFS) is for more rain to come in December hence increases in soil moisture.

171218soilm

Rover flows in November reflect the reflect the wetter November and December although rivers in the east of SW England were still lower reflecting the longer term rainfall deficit.

161218riverflow

Ground water has improved to near normal see details in the November Hydrological Summary which can be viewed here – November 2018 summary PDF 

The reservoir levels in the SW of England (9th December) show 69% storage which is a big increase since last month due to the wetter November and first half of December.

161218res

The experimental product from the Global Flood Awareness System (Version 2) based on early December ECMWF seasonal forecast for December to  March. To date this system has not be a useful guide. The current EC seasonal forecast does not suggest well above average rain hence no or very low flood signal.

161218glofas

Atmosphere predictions.

A:  Stratosphere and Upper Troposphere

The stratospheric polar vortex was well establish with temperatures in line with the normal variations but in the last week or so marked warming has begun leading to a forecast re-positioning of the polar vortex and a forecast stratospheric wind reversal over the USA an d Pacific. It is not yet clear if this reversal/weakening of the stratospheric wind flow will extend to the UK area but it at least seems probable. THIS MAY HAVE STRONG IMPACT on the forecast for the remainder of the winter but as yet models only suggest N America surface temperature cools markedly in January compared to earlier forecasts (to well below normal) and that N/NE Europe and Russia becomes colder than normal in February.

151218ecstrat

ECMWF 50hPa forecast data 15th December 1200UTC

Note not all seasonal models cover events in the stratosphere but UKMO CFS2 and ECMWF certainly have layers into the stratosphere. A sudden stratospheric warming is more often than not (but not always) followed by a change of type for the UK weather to a more blocked pattern with possibly colder easterly types.

CFS2 200hPa 8th December 2018 data for the January to March 2019 period continues to suggest above normal heights across the S of the UK and  imply enhanced Atlantic jet flow in January suggesting disturbed weather.

091218cfs2z200JFM

CFS2 Jan to March 2019 mean 200hPa height and anomaly forecast.

091218cfs2z200MAM

CFS2 March to May 2019 mean 200hPa height and anomaly forecast.

For the Spring period there is a hint of below normal 200hPa heights in March over NE Uk may imply more cyclonic N or NW flows then above normal heights return.

B: Lower Troposphere:

Graphics for January to March 2010 –  comparison of ECMWF NMME and CFS2(E3 version). Top row are temperature anomaly and lower row rain rate anomaly. Red/oranges are above “model hindcast” normal and blue below.

ECJFM122018

ECMWF December data monthly forecast temp and rain anomaly JFM 2019

 

E3JFM1218

CFS2 December data monthly forecast temp and rain anomaly JFM 2019 

NMMEJFM1218

CFS2 December data monthly forecast temp and rain anomaly JFM 2019 

In most of the output there are indications for above normal temperature and rain in the SW of UK for the three month period though with differing ideas of which month could be drier.

For the March to May period comparison graphics are shown below:

ECMAM122018

ECMWF December 2018 data for March to May 2019

E3MAM1218

CFS2 (E3) December 2018 data for March to May 2019

NMMEMAM1218

NMME December 2018 data for March to May 2019

Near or slightly above normal temperatures are indicated and some agreement that April could be drier than normal.

C: Recent results:

Typically models over forecast the temperature positive anomaly and have poor matches to rainfall distribution over the UK. A look at how “good” seasonal forecasts have been can be seen at the review page.

2. Forecast.

Remainder of Winter (January and February 2019).

161218 – Caution marked stratospheric warning occurring/forecast to occur next two weeks which might impact the remainder of winter forecast and change to colder easterly types.

Main consensus is for near or above average temperatures for January but nearer normal in February and perhaps even slightly colder than average.

January is likely to be wetter than average with average snow risk. February probably nearer normal rainfall but with an increased snow risk especially for the moors.

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 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 2019  (March April May) based on less data.

Possibly near normal or a colder than average March then recovering to milder than average temperatures for the season, with May probably the month with the strongest signal for above normal temperature.

A wetter than average season is likely with increased snow risk for March, mainly over the hills. April could be the drier of the months with May 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.

Summer 2019  (June July August) based on very limted data.

Another warmer than average summer with slightly above normal rain although the number of wet days may be below average and there is some indication that June could be 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.

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

ECMWF seasonal monthly data from weather.us

Stratospheric Diagnostics from Free University Berlin

Climate data from The Met Office UK and NCEP USA.

Review and Experimental Long Range Forecast for SW England. November 2018.

Published 17 November 2018

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.

151118sstanom

The sea temperature near and to the East of the UK remains above normal but is likely to cool as strong easterlies develop over the next few days. The northern North and Northeast Atlantic is below normal as are the Great Lakes given how warm it was in this area at the end of October.

SST171118

The tropical Atlantic is trending to near normal and in the Pacific the El Nino is established as can be seen in the above plots.

The dominant IRI statistical predictor for UK rainfall based on the Pacific sea temperature anomalies for the winter season is shown below. Probabilities shown are for “near normal” precipitation, which is the highest category.

elninonormal

The North Atlantic Oscillation index (shown by a 500hPa index in the image below) had been mostly in a positive phase as forecast turned sharply negative near the end of October and after a recover is forecast to again turn sharply negative: see below.

171118nao

Conditions applicable to a persistent negative NAO are shown by the Met Office graphic below:

nao_lo_winter_pr_tas2

However the persistence of a negative NAO is not yet certain. For NAO background information see the Met Office NAO information.

Recent Climatology

Temperatures during September and October in SW England were near average following an unusually warm summer and so far November has been well above average but due to the cold spell about to start may well end up near average. Rainfall in September and October was mostly a little below average and followed a drier than average summer. November is currently near or a little above average rainfall so may well end up slightly above average.

171118climate

Despite recent rainfall soil moisture remains below normal across SW England.

171118soilm

Rover flows in October reflect the longer term drier period.171118riverflow

Groundwater levels in Eastern parts of SW England are near normal and the November outlook (below right) suggest the main problem areas are further east.

171118groundwater

The October Hydrological Summary can be viewed here – October 2018 summary PDF 

The reservoir levels in the SW of England (11th November) show 55% storage which is a slight increase since last month due to the wetter start to November.

171118res

The experimental product from the Global Flood Awareness System (Version 2) based on early November ECMWF seasonal forecast for November to February.

141118glofas

Atmosphere predictions.

A:  Stratosphere and Upper Troposphere

The N Pole stratosphere is cooling in line with normal variations.

50mbnhlo

The polar vortex formed in October and has migrated SW of the pole. Forecasts show a splitting of the vortex and reduced stratospheric flow over Europe for a time before reforming again after about a week. This is illustrated in the 50hPa forecast sequence shown below.

16111850hpa

FS2 200hPa data (as supplied to NNME data set October 2018) for the December to February 2019 period continues to suggest above normal heights across the UK. for both December and January there are signs of enhanced jets suggesting stormy spells at least for the north of the UK.

CFS2 200hPa 7th Nov 2018 data (missing from NNME data set) for the December 2018 to February 2019 period continues to suggest above normal heights across the UK during the winter period. Anomalies imply enhanced Atlantic jet flow suggesting disturbed weather for northern UK in particular during December and the far north in February.

200z

CFS2 mean 200hPa contour and anomaly forecast Dec Jan Feb.

B: Lower Troposphere:

The Copernicus multi model ensemble has been upgraded with the addition of models from Italy and Germany adding to ECMWF, UKMO and MeteoFr. The winter forecast is shown below.

Capanoms112016

Copernicus Temperature mean anomaly forecast 

CapanomsPPN112016

Copernicus Rainfall mean anomaly 

CFS2 (E3) 10 day mean of model output for the winter months (December January and February). Oranges/red are above “model normal” blues are below.

E3DJF1118L

NMME mean of model output for the winter months (December January and February). Oranges/red are above “model normal” blues are below.

NMMEDJF1118

ECMWF mean of model output for the winter months (December January and February). Oranges/Purple are above “model normal” blues are below.

ECDJF112018

There is good agreement for above normal temperatures in December and an indication than anomalies could be lower or negative in February. Rainfall is much more variable but a signal for wetter December may offset less wet month to follow.

For Spring graphics see seasonal latest.

C: Recent results:

A review of how useful forecast have been can be seen at the review page.

For the period August to October using July 2018 data the following marking was given (good/fair/poor/no signal) for the UK.

Original text Summary – Good – Slightly optimistic temperature but idea of the west trending to normal was good as was the idea of higher than average pressure. Rainfall trend towards normal was fair and the idea of the of the north becoming above normal was good. 
1. Russia: Temp fair . PPN poor .
2. USA – CFS2 : Temp good . PPN fair .
3. UKMO Contingency: Temp fair . PPN good .
4. UKMO : Temp poor . PPN poor . PMSL poor .
5. USA – IRI : Temp no signal . PPN good .
6. KMA APCC : Temp fair . PPN fair .
7. JMA : Temp fair . PPN good . PMSL fair
8. NMME : Temp fair . PPN good .
9. IMME – Temp fair . PPN fair .
10. BCC – Temp fair . PPN fair .
11. NASA – Temp poor . PPN fair .
12. Brazil: Temp fair . PPN good PMSL fair .
13. CanSips : Temp fair . PPN poor .
14. SAWS: not available
15. Copernicus Temp good . PPN no signal . PMSL good
16. EC Temp good Temp fair . PPN no signal . PMSL poor
17. MF Temp fair. PPN fair . PMSL fair
18. JAMSTEC:
19: KMA: Temp fair . PPN fair. PMSL poor
20: ECMWF (monthly) Temp: fair PPN: fair

Last winter most seasonal forecast output based on November data, was poor.

2. Forecast.

Winter 2018/9  (December January and February).

Main consensus is for near or above average temperatures for the season but starting off milder than average and ending less mild and perhaps even slightly below normal.

Rainfall likely to be near or above normal for the season with the wetter month compared to average being December.

Below average snowfall is likely with the highest risk of snow possibly late in the winter and 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.

Spring 2019  (March April May) based on less data.

Possibly near normal or a colder than average March then recovering to milder than average temperatures for the season.

March may be wetter than average with increased snow risk. April and May probably near normal or a little 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.

Summer 2019  (June July August) based on very limted data.

Another warmer than average summer with above normal rain although the number of wet days may be below 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

ECMWF seasonal monthly data from weather.us

Stratospheric Diagnostics from Free University Berlin

Climate data from The Met Office UK and NCEP USA.