Lomondsnowstorm's Winter Forecast 09/10

[LomondSnowstorm]

LomondSnowstorm's Winter Forecast 09/10

Factors to Consider

Firstly, the current ENSO situation is a major factor to consider during this winter. The latest weekly anomaly for Nino 3.4 is +1.7, which means we are in a moderately strong El Nino phase, though this looks set to weaken slightly through the coming winter. This means that the likelihood of a cold or very cold winter are weakened, although perhaps less so than normal with a moderate/strong el nino as this one is west-based.

As has already been said on this forum by GP and Chionomaniac, the Sea Surface Temperatures have been showing signs of a slightly negative NAO, which would, if it occured, lead to more blocking to our north and therefore to an increased chance of colder weather.

Another major factor is the Easterly QBO, which, combined with low sunspot activity, appears to increase Stratospheric Warming at high latitudes, which again leads to more blocking and increased cold. Current Stratospheric temperatures are above average, increasing the chances of a colder spell in the next 2-4 weeks.

I'm sure I have not covered all the factors involved but I feel that I cannot explain them adequately enough and will instead refer you to the brilliant preliminary winter forecast by Glacier Point http://www.netweathe...r-forecast;sess=.

December

Currently, the beginning of December looks rather cool and unsettled, with some frost and possible snow across the north of the country from northwesterly winds.Maximums around this period varying from 4-6^oC in northern Scotland to 8-10^o C across southern Britain with Minima as low as 0 ^o C in central England and -4 ^oC in the Central Highlands in clearer skies. Rainfall will be generally above average in western Scotland and Cumbria but will be close to or slightly below average in the southeast of the UK. Towards the middle of the month I expect a change to milder conditions, with low pressure centred to the west of the UK bringing rain to western parts but with generally more settled weather towards the northeast. Temperatures ranging from 7-11^oC across the UK with rainfall highest in the south and west. The run up to Christmas, I believe, will continue with the unsettled theme, and we will perhaps see a return to the cooler weather seen at the beginning of the month. Christmas day will be cool, with temperatures around 4 ^o C in the north and 8 ^oC further south. Although confidence at this stage is very low, some snow showers may fall in northern parts, although any showers further south will be mainly of rain. The end of the month may bring a more settled spell of weather courtesy of a mid-latitude high, although this will be short-lived. The CET for this month will be around 5.5 ^oC, moderately about the 1961-90 average.

January

The month will begin with the high pressure giving way to atlantic low pressure, with yet more rain, this time across all areas. Temperatures will vary from cool to very mild across the period, with the main feature of the weather being above average rainfall for all parts. The middle of January looks like being rather mild for a time, with southerly winds and fohn effects giving northern Wales and the Moray Firth temperatures peaking at 15 ^oC. The last third of the month looks totally different though, with a major stratospheric warming event and a significantly weaker El Nino bringing significant heights building south west from siberia, bringing a northeasterly across the UK. Significant snowfall from convective showers is possible across all eastern areas, but in particular Tyneside and Aberdeenshire, which could see accumulations up to a foot. Channel lows could also bring major snowfall to parts of the southwest on a par with last winter. Daytime temperatures will struggle to get much above freezing in most places, with highs of just -1 ^oC on the snow covered east coast. Minima could reach -15 ^oC as high pressure builds in from the east, giving drier but still very cold conditions. Overall, I believe the CET will be around 3.5-4.5 ^oC, depending on the severity and length of the cold snap. This is around both the 61-90 and 71-00 averages, although this will disguise both an exceptionally mild and cold spell.

February

February will begin on a cold note, with frosty nights and daytime maxima of 2-4 ^oC at best in the south. Towards the end of the first week, though, atlantic lows will move toward the British Isles and come up against high pressure, bringing a band of frontal snowfall right across the UK. More accumulations are possible, this time across the west of the UK, as the milder air slowly wins through. The middle of the month will then bring a more zonal period of weather, will more above average rainfall across the UK and temperatures recovering to double figures in some areas. The end of the month looks like bringing a return to colder conditions from another easterly, though this time snowfall will be confined to southeastern Britain with dry and cloudy conditions dominating further north. February looks like being the coldest month, with a CET of around 3 ^oC, around 1 ^oC below average. Overall the winter looks like being around 4.5 ^oC, around average, although it will feel cold compared to recent winters. Snowfall will be around or above average in most parts, with only northwestern Scotland failing to see hugely significant snowfall. Rainfall will be well above average in southwestern Britain, while most other regions will see close to average rainfall. This forecast is partly based on the trends of the CFS model but also on my own thoughts and interpretations of the factors listed at the top. Please bear in mind that this is the first LRF i've attempted so try not to be overly critical, though comments are welcome.

CW

Edited November 17, 2009 by LomondSnowstorm

[Paul]

Thanks LS, interesting forecast

We'll be amalgamating everyone's forecasts so we can watch them as we move through the winter.

[mcweather]

Thanks for your work on this LS. It is certainly the sort of winter I could live with.

[Methuselah]

Thanks for that, LS...Well explianed and all. Good luck! :lol:

[Stuart]

Good Luck

[LomondSnowstorm]

thanks for the positive feedback

[Backtrack]

Nice forecast mate. Good job

[SteveB]

Thanks LS,

Looks like your calling for an average winter.

[LomondSnowstorm]

Thanks LS,

Looks like your calling for an average winter.

Pretty much, average, fairly zonal for the most of it but with a good cold spell late January. Not too disimilar to Backtrack's forecast really!

CW

[LomondSnowstorm]

Perhaps time for me to be brave enough to call my forecast 'bust' - I got the exceptional cold spell right, just at the wrong time, from the wrong source and with all the CETs totally wrong (except perhaps February)! Oh well, this winter has been a learning curve for everyone, and I'm glad I at least had a go at the forecast - seeing as how no one got it exactly right, I'm not too unhappy with this, but GP and BFTP were much closer to the mark I feel.