Countdown to Christmas, white or not
Blog by Jo Farrow
Issued: 16th December 2014 11:18
Updated: 16th December 2014 11:45

Countdown to Christmas, white or not

Christmas Day is only 10 days away now. To quote Elf, SANTA!!!!!!!!!

Whenever there is a screaming headline about some extreme weather in the next season to come, I am often asked, how far ahead you can really forecast. Answer -5 days. Met Office has got a brand new super computer and so the 6 to 10 day period is now firming up with its output.  Hence the excitement of Dec 16th putting us into that section. Beyond that, forecasts are more about themes and trends than being able to say, it will rain, snow, be sunny in Birmingham on January 22nd at 3pm

Still day 9 or 10 is a long way off, and when looking at a deterministic output (one solution) there is still a lot of scope for change. But even so, it’s the chance of a white Christmas, have to have a peek. Book makers are currently varying from Edinburgh and Glasgow 2/1, Aberdeen just lower than that and Birmingham and Cardiff 5/1, although I did find 5/2 for Scotland cities and 7/1 for Penzance. At the start of December, Norwich airport was 8/1 which is looking a much better bet on today’s charts.  The odds always fall once it actually snows, regardless of the forecast. Headlines of “odds slashed on a white Christmas” as London moves from 7/1 to 6/1 earlier this week seem to just be a bookmaker’s publicity dream to take more money off punters.

So the GFS chart for Christmas Eve 00z, Santa is out there and this chart shows a favourable tail wind for him to whizz to the UK from the North Pole. Remember on 1000-500mb thickness charts, the 528 line is a rough rule of thumb for snow. So northern Scotland and the islands could see snow showers and through Christmas day as that low to the north pulls away, the north winds could sweep down the east coast of Britain, perhaps bring a flake or two to Norfolk?? That’s cold air for the north and east. Southwest, forget it.

The GFS ensemble mean chart shows the Low in the NE further away with the milder Atlantic flow having more influence over the UK = less chance of snow.

The Met Office have already issued a press release to say that their models are showing pulses of mild then cold air sweeping the UK around Wednesday Thursday next week. It looks windy with rain, which if cold enough could turn to snow. Like this week where we see cold air, then a mild midweek and back to a chilly Friday, next week will be wavering about like that. So the further north you are the more chance you have of seeing some snow. It really doesn’t look like anyone is going to get a beautiful crisp, Christmas card scene, unless you are up a Scottish mountain. But let’s not deviate from the excitement of a bit of wet snow falling.

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The CFS has us all in a mild S or SW flow, so no snow, let’s ignore that one

ECMWF shows a cold flow for north-eastern parts of the UK, which could include snow with a low away to the NE and high pressure near the Azores, much like on Monday this week

We have to wait 2 more days for the Netweather MR (NMM12) to show its Christmas charts. And at least there are some charts that are out do have hints of flow from the north. Showers can easily flow to N.Ireland, through the North Channel to NW England, Wales, through the Midlands, in a strong enough NW wind they have been known to reach Greater London. Eastern England might see lines of wintry showers flow down the North Sea, it’s just Penzance that isn’t looking like a good bet at the moment

Keep an eye on the Santa Shaker, he’s fun. Scotland in with a chance, southern England not.

Further updates to come

Netweather Forum threads on the go –
The GFS countdown to Christmas 2014 in Forecasting Model Discussion
White Christmas 2014 in Weather discussion and chat


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