Winter 2010/11 Forecasts

I don't as a rule issue long range forecasts. At best they can only indicate general trends over a multi-week period and at worst they are misconstrued and taken out of context by the media and general public.

However, with prevailing synoptic trends continuing in a similar vein to last year it does look like for the British Isles it'll be another cold and snowy winter, though maybe less extreme than last winter. I don't see any return to frequent mild, wet and windy southwesterly weather, but I think cold spells will be more broken than we experienced last year. However, such cold spells look like setting in earlier - it was not until December that I saw my first air frost of the autumn in 2009. And with an earlier start to winter we may also see an earlier arrival of Spring. Though that's a long way off. Chances of a white Christmas somewhere or other in Britain look quite high at this stage, insofar as the second half of December will probably see some snowy weather at some point. The nature of LRFs is that we cannot be any more specific - whatever some may try and tell you.

Anyway, the main point of this posting is to list the various other winter forecasts as I come across them, to help with evaluation come March.

The Met Office do not issue their long range thoughts derived from the GloSea4 computer model any more, although early indication from the September run suggest they would be slightly favouring a milder than average winter. In fact probably similar to what they said last year (which as we know, still gave a 1 in 5 probablity of colder than average). I'll update my thoughts on this once I've seen the October run.

Brian Gaze at The Weather Outlook has issued his initial thoughts although his full forecast will not be out until November. Brian does have a reasonably good track record at LRFs and his thoughts for this winter concur fairly well with mine at this stage. Significantly he explains the rationale behind his forecast and the type of synoptic situation expected.

Our view at the current time is that winter 2010/11 is likely to bring colder than average conditions to the UK again, with the risk of heavy snowfall and severe frost affecting much of the country at times. However, the actual pattern of the winter may be different to last year, with the cold tending to come more from the east or south east rather than the north east. In this scenario the heaviest snow often occurs in the boundary zone between the cold dry air from the east, and the mild and moist air trying to push in from the Atlantic. With this pattern we expect the most persistent cold in eastern England and Scotland with temperatures falling as low as -15C overnight, and at times remaining sub zero during the day, but with the chance of heavy snow in western regions and Northern Ireland. We expect the worst of the wintry weather to come during January and the first half of February.

“I am currently expecting winter 2010/11 to be colder than average again in the UK. Although cold spells may be less sustained than last year, some very sharp spells of wintry weather are likely to bring heavy snow falls and sharp frost. The battleground between cold continental air and mild Atlantic air may well shift around close to the UK. In the UK the heaviest falls of snow often occur when mild and wet air from the Atlantic runs into dense cold and dry continental air. This can lead to the formation of heavy and slow moving bands of sleet and snow. So I wouldn’t be surprised to see some locations in the west of Britain and Northern Ireland having significant snowfalls, but the coldest weather is likely to persist for longer in eastern Britain. The core of the cold may well be slightly further east than last year, and this is also likely to give much of mainland Europe below average temperatures. If this occurs the alpine ski resorts may have another good season, although cold conditions on their own don’t ensure this because unless some mild and moist air gets into the mix, it often remains too dry for the heavy snow needed. “ Forecast background The initial winter forecast is based on data from seasonal forecasting models, historic weather pattern matching, and recent UK temperature trends.

(Press Release issued 14th October)

Jonathan Powell at PWS has also issued a forecast but without any rationale and with less synoptic explanation, making it more open to interpretation.

December: Chilly, some wintry weather around.

A chilly but dry start to December with some dry and bright weather around, but also some rain - amounts of which are not expected to give cause for concern. Through mid-month, high pressure consolidates, so expect a run of dry weather, which will combine chilly and bright daytimes, with clear and crisp nights, leading to sustained frost and fog activity, some of which will persist throughout the day, predominantly inland and in more so valley locations. During the final segment of December, unsettled weather chiefly affecting the higher ground across the eastern and north-eastern side of the UK, and possibly higher ground pushing westward for a time, may well deliver a White Christmas.

January: Mainly dry start, wintry weather developing.

A cold but dry start to January, quite raw at times, with a continuation of dry and bright conditions by day, with some sharp night frosts, particularly inland. By mid-month, with the cold theme continuing, sleet and snow showers will become increasingly more widespread, with moderate falls of snow possible, which have the potential to cause disruption - particularly for eastern and upland regions. PWS will continue to assess how the detail of the expected snowfall develops, but confidence is high that this eventuality will occur. January ends with dry and bright conditions alternating with periods of wintry weather, with the north and northeast again most likely to experience the worst of the conditions, with the south and west seeing more of a rain/sleet combination for the most part.

February: Bitterly cold month, wintry weather.

Another largely cold start to another month, with the ongoing threat of wintry conditions, in the form of organised bands of rain, sleet, and snow, interspersed with drier and brighter weather. Through mid-month, the likelihood and confidence of more widespread and disruptive snowfall increases, most likely once again to the north and east, with for a time, the south and west affected too, and some level of disruption can be expected. PWS will continue to monitor this segment of the forecast. By late month, although the cold conditions show signs of receding somewhat, further wintry weather especially to the north and east cannot be ruled out, with the south and west more likely to see a rain/sleet mix.

(Press Release 30th September)

The Net-Wx Forecast produced by Stewart Rampling has now been released and can be read in full here . It's a very well put together forecast with plenty of explanations - other forecasters might like to take note! In summary it reads:

Anomalously cold ocean temperatures in the Tropical Pacific or ‘La Nina’ conditions have become well established. There is a high probability that these conditions will intensify over the coming months and become one of the strongest La Ninas on record.

With a strong coupling between the atmosphere and ocean signal, global weather patterns are very likely to be ‘forced’ by a strong La Nina with dominant high pressure centres in the northern Pacific and in the North Atlantic.

La Nina winters have a variable influence on the weather in Europe although we anticipate no sustained extremes of cold and the emphasis on dry, settled weather. Some wintry weather is however expected, particularly during mid to late December an early January.

Temperatures are likely to be close to or slightly below average with the coldest weather (relative to long term averages) centred over France and Iberia, the south-east of the UK closest to this cold. Compared to many winters of the last two decades, this coming winter would probably be regarded as cold although not of the same degree as last year or 2008/9.

With the monthly breakdown:

December

• High pressure likely to be centred to the north-west of the UK with winds from the north-west with northerly interludes.
• Temperatures likely to be below average, the largest departure of the three months compared to long term averages with the coldest temperatures in the south-east.
• Rainfall likely to be much below average.

January

• Large area of high pressure in the central Atlantic gradually edging towards the UK although an unsettled phase likely with potential for snow, particularly in western areas.
• Likely to be cold to start with fog and frost persistent.
• Rainfall below average.

February

• High pressure centred over the UK with a lot of settled weather.
• Temperatures likely to be slightly above average although surface temperatures may be depressed by fog and cloud.
• Rainfall likely to be much below average.

The October run of the MetO's GloSea4 model has now been completed and looking at the data my impression is that there is a higher probablity of this winter being drier than average with no strong indication of temperature, though more likely above average than below average. The most noticeable signal is for below average pressure across the eastern mediterranean - something to watch out for.

Joe Bastardi from Accuweather has now published his thoughts:

TUESDAY 11 P.M.

THE WINTER OUTLOOK FOR EUROPE

EUROPE

In 2003, the fierce heat wave centered in France was replaced by a chilly October, and when winter came, much of Europe was warmer than normal. However., the area that was near normal to a bit below was close to where that heat wave was then eastward through southern and southeastern Europe.

This year's August heat wave, like 2003, coming off an El Nino winter the year before, was over Russia and into central Europe. October has been cold in much of this area, and guess what, the winter will be most fierce from Euro-Russia into the Alps. Russian temps as much as 3C below normal for the winter are possible, 1-2 C below normal westward into the Alps. THIS INCLUDES THE BALKANS INTO NORTHWESTERN TURKEY, SORRY TO MY FAN CLUB THERE (I love all of you!!) But I should have been better in my description. I like above-normal snow in much of this area. Most of northwestern Europe will be near to a little below normal (up to 1C below normal) while northern and central Scandinavia, Scotland and Ireland are near or a bit above normal.

Snowfall will be above normal across much of Europe with heaviest in the Alps into Russia, perhaps a bit below normal in northern areas.

To sum up, a severe winter looks to be on table from the Alps into Russia, but winter in Great Britain and Ireland will not be as severe as last year.

Globally. Opposite of last year, the globe will be cooling considerably and temps by spring should be running near or below normal. This trend will probably make 2011 the coolest year since the late 1990s. Arctic sea ice will continue to recover from the 2007 lows, with the summer ice melt season next year probably returning ice to pre-2006 levels.

(that's Tuesday 19th October)