Experimental Long Range Forecast for SW England

February 2016 to May 2016 and Summer 2016. Published 18 January 2016.

This attempt at a Regional Forecast for SW England is based on Long Range experimental forecasts for the period February through to May 2016 plus some early data for Summer 2016. Prepared using available data up to 18 January 2016. The summary forecast aims to test if any usable regional forecast can be made from internet model data. The forecast should not be used for any other purpose. A brief verification summary for UK and Eire is routinely published at http://www.weather-info.co.uk/wxsvc/Verification.html

Features that might impact on the Seasonal Forecast.

Sea Temperatures.

anomnight.1.14.2016

NOAA/NESDIS night time sea temperature anomaly 14 Jan 2016

North Atlantic remains below normal although sea temperatures near the UK are above normal, especially in the southern North Sea. El Nino warm anomalies continue to dominate the East Pacific but this is predicted to weaken as shown below.

IRI El Nino probabilities

IRI El Nino consensus probability forecast issued early Jan 2016

IRI rainfall statistical probabilities for March April May during an El Nino Event are shown below but due to expected weakening of the El Nino probabilities for the summer month are not shown.

IRIelninoMAM

IRI Spring (MAM) precipitation probabilities for drier, wetter and normal during El Nino.

 Stratospheric changes.

An area of Stratospheric Warming is forecast to move east over the Pacific and across N America. So far this winter season the warming has not progressed and has weakened. If the forecast is correct and the Polar Vortex in the upper atmosphere is relocated then there is a chance of a change which might impact the weather types in Europe during February bringing the chance of cold easterlies into the UK. To date this possible change to the UK weather types has not been forecast by the climate models and must be considered a low risk.

ecmwf50f120

Example of ECMWF forecast at 50hPa Valid 12Z 27th Jan 2016 – Free University Berlin

 

Forecast anomalies at the jet level.

NMME_CFS2_z200_comp

NMME and CFS2 200hPa anomalies Feb to Aug 2016

Despite above normal heights increased zonal jet strength indicated for a time April and May though weakening and transferring north over the NE Atlantic especially by June.

Experimental Long Range Forecast for SW England.

Remainder of Winter (February 2016):

February 2016 is likely to be unsettled for the UK as a whole but just a little less so in the SW. Temperatures across the SW of England are likely to be milder, possibly much milder, than average. This still allows for some colder intervals but suggests that frost and snow may occur less often than average. Rather cloudy weather may be implied by the milder type especially in western areas. Rainfall; rather mixed indications but probably above normal, mainly in the west but with a chance of below normal rainfall to the East of the moors and in the East of the region. In terms of the number of rain days (0.2mm measured in 24 hours) these may be above normal in the west but parts of Torbay to the Exmouth area and areas to the East of the Moors may be a little drier than normal.

(Typical February 1981-2010 values for average mean temperature across lowland areas 6 or 7°C in West Cornwall, 5 or 6°C in most coastal and urban areas but a little lower over parts of N and E Devon, central Somerset and inland Dorset. Average rainfall 100-250mm over hills and moors, around 50mm over parts of Somerset, 70mm East of Dartmoor around Exeter area and 90mm in other coastal and low lying parts of the Southwest. Rain days (0.2mm) 16 to 18 in west and 12 to 14 in the East. Snow climatology less than 1 or 2 days lying snow for lowland areas up to 10 days over the higher parts of Dartmoor).

Spring (March April and May) 2016:

Unsettled with low pressure often over or crossing the UK but some intervals of higher pressure possible in May. On average the temperature is likely to be above normal with March and May more likely to be above normal than in April which could be nearer normal. Rainfall mostly above normal possibly more so in March and April than in May

(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 300 mm lowest values in E Devon and over parts of Somerset.)

Summer  (June July August) 2016 limited data.

Temperature near normal but with a chance of above normal mean values although cooler Atlantic Sea temperatures may result in reduced maximum temperature especially in the west. Some model data hint at average temperatures being above normal but not the maximum and minimum values. The strongest indication for above normal temperatures is in July.

Rainfall is likely to be below normal in June and more especially in July but perhaps not in August although this detail is quite uncertain. The hint at drier types is a change from last months data.

 (1981 to 2010 average mean temperature 14 or 15°C in many areas to 16 or 16°C in main urban areas, locally east of the moors and more widely in Somerset – average max temps 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)

 

Caution:

Experimental Long Range Forecasts do not have a good success rate. The data used for the above forecast summary and brief verification of previous Long Range Forecast summaries can be seen at   http://www.weatherservice.co.uk

References:

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

http://www.mdpi.com/2072-4292/6/11/11579

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

http://dx.doi.org/10.1175/1520-0477(2001)082<0619:PPAAWE?2.3.CO;2

UK climate details see:

http://www.metoffice.gov.uk/public/weather/climate/

 

 

 

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