SW England Experimental Long Range Forecast – October 2015

SW England Seasonal Forecast November 2015 to May 2016 – 18 Oct 2015.

This attempt at a Regional Forecast for SW England is based on long range experimental forecasts from November through to Spring 2016 and has been prepared using data up to 16 October 2015. The summary forecast aims to test if any usable forecast can be made.

The forecast should not be used for any other purpose.

A comment about October. The onset of a very unsettled period looks like being in the latter third of the month rather than around mid month which was signalled in some earlier UK forecast summaries.

190915 – looking at 30 day model runs it seems possible that the wetter than normal period might start mid to late October.   http://www.weather-info.co.uk/wxsvc/seasSEP2015.html

170815 – fair agreement for move to wetter period in second half of this 3 month periods (SON) and for temps to recover a little especially in E and S though still with the risk of below normal values (especially N and W) due to cold Atlantic Sea temps. http://www.weather-info.co.uk/wxsvc/seasAUG2015.html

A brief verification summary is routinely published http://www.weather-info.co.uk/wxsvc/Verification.html

Changes to Atlantic Sea Temperature.


The mid North Atlantic Sea Temperatures remain below normal but as can be seen from the above sequence there is a hint that the temperatures slightly less so. Model forecasts however keep an area of below normal temperatures for the winter season and into Spring 2016 which may continue to impact on the UK temperatures. On the left image the El Nino warm across the E Pacific can be clearly seen.

The strong El Nino is forecast to remain well into 2016.

Comparison of model temperatures Nino3.4 Pacific Ocean – source IRI

The statistical impact of a strong El Nino on the UK weather is disputed/unclear, however, the IRI study of El Nino impact on rainfall is included below for comparison.


IRI Winter (DJF) precipitation probabilities for drier, wetter and normal during an El Nino event

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

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

Experimental forecast for SW England.

November 2015:

There is a consistent indication for a very unsettled month with winter depressions bringing above normal rainfall, perhaps very wet conditions, accompanied by windy periods. Temperatures are on average likely to be near normal perhaps with milder than normal nights. (1981-2010 averages; Rainfall below 100mm for parts of SE Devon and low lying Somerset, 100-150mm for many other areas but much higher totals over the hills and moors. Temperature mean typically 7 or 8 C but a little higher over S and W facing coastal areas and 5 or 6 C over higher ground).

Winter 2015/16 (Dec Jan Feb): 

Probably a “typical winter” for SW England plenty of rain and not much snow. No significant indication for an unusually cold winter.

Perhaps less frequent low pressures crossing Atlantic towards UK from around the middle period of January compared to the very unsettled start of winter, although low pressure types are more likely to continue predominate than high pressure. Temperature mean probably near or a little above normal in December and parts of January, though still with a risk of slightly lower than average values in western areas at least by day. Temperatures in the remainder of January and for February near normal rather than above but may turn colder than normal late in February. (Typical winter average 1981-2010 values for lowland areas 7°C in the West and 5°C in the East).

Precipitation probably above normal in many areas to start winter but nearer normal later in winter, hence overall above normal. (Dec and Jan typically wetter than February in any case. 1981-2010 Autumn average 300-400 mm lowlands but 200-300 mm areas to E of Dartmoor). Snow risk near normal (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). Number of snow lying days over moors near normal overall less in December and a little more in January or February.

Spring 2016 (Mar Apr May):

Hints at a colder than average start to Spring, possible the colder months later in Feb through to early or mid April then recovering to above normal so may end up near normal for the three month period. The possible colder start could lead to an increased risk of late winter/early spring snowfall chiefly over the moors.

Precipitation indications are quite mixed but near normal overall seems the most likely. There are some indications of slightly above normal in the west during March and below normal rainfall in eastern parts of SW England for April and May. To date the forecast models do not support the El Nino statistics for a wetter than normal Spring across SW England.

(Average 1981 to 2010 rain 200 to 300 mm. Temp 9 or 10°C, roughly Mar 7 or 8°C Apr 8 or 9°C  May 11 or 12°C)

Caution experimental long range forecasts do not have a good success rate. The data used for the above forecast summary and brief verifications of previous summaries can be seen at   http://www.weatherservice.co.uk


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. doi:


UK climate details see: