Isolated Frost

EC op at 192, elongated lp system to the east bringing in east to north-west winds over the UK, a rather rare synoptic in its alignment. Cold as well, with snow shrs on high ground in the north and north-east. Indeed we must urge caution, but the net result was near record lows for many eastern and south-eastern parts of England, with some large snowfalls in the SE in early February. The effects of the SSW dramatically altered the NH pattern, ask Europe.

GFS 06z sees the warmth penetrate into the upper vortex at 10hpa by 7th January- as chiono notes, it's very much SSW territory- hopefully the upcoming runs can maintain this trend for a warming around 7th-9th January.

Very, very cold in northern parts of Scotland and the northern isles from the 25th to the 27th. Spreading south into much of Scotland and northern England by the 26th. The likelyhood is that it will be a very transient event but could deliver big for some northern areas with a strong N/NW wind accompanied by a local trough. GFS 06z suite provides the northern isles with -14c 850s for 27th 06z, and much of Scotland by this period is under -10c 850s. -6c 850s spread into London and the south, including south Wales by 27th 09z, and -9c 850s reach Lincolnshire by 27th 12z. It looks like it could well turn very cold in an abrupt arctic airstream from the 26th to the 27th. A very short window of opportunity, but plenty of snowfall likely in the far north, and potentially further south at times on the 27th. There is also the small signal for wintry precip from a breakdown late on the 27th/early on the 28th.

ECM consistent with it's expected temps- at 240 (30 Dec), looking at roughly -9c as the highest temp around, v close to breakdown warming- latest GFS suite consistent with a strong prolonged warming 192 onwards, with 0c and 5c being passed at 10hpa, and zonal 10hpa winds across the arctic, with a squeezed vortex around svalbard at 100hpa we see the mean vortex over siberia, with an elongated ridge moving energy into svalbard/scandi, symptoms shown by the current nwp, notably the ec op

A mighty stratospheric stand-off, with the warming attempting to crack the core... and in the next few days I think the clock will stop ticking and start ringing, times up, pv...

http://forum.netweat...perature-watch/? edit: the above is the 2010-11 one (2 seasons ago), but I think the first one is below, the 2009-10 one http://forum.netweather.tv/topic/57364-stratosphere-temperature-watch/

vortex has had a tooth or two knocked out... no sub 500 air at 240- a very 'blocky' arctic profile as we enter a new year- plenty of cold bubbling just to the north, but not quite the substantial cold on our shores just yet

December colder than February in Durham! The warming trend continues though, and that is the general point with these averages.

Pretty cold for Scotland, with upper temps passing 0c for only a 24-36hr interlude in the 240hr run, and plenty of -4c and below incursions. On a W/NW flow with plentiful Am/Pm incursions, there is a lot of snow to be had on high ground, and at times on lower ground as well. Expect some sunshine to come of it as well under a more showery regime than the current one. Just because there is not notable blocking around Greenland---Scandi, doesn't mean we can't have some cold and snowy weather, this time though, Scotland and the north mostly enjoy it, maybe that's why it's so glum around here!

-35c uppers touch Svalbard on a bitter, long stretched northerly for Christmas eve. Only around -25c uppers for Christmas day on the island. Incredible surge of arctic air.

Heavy snow/sleet moving into Scotland and Northern Ireland on christmas night, plentiful snow shrs for Scotland, Northern Ireland and NW England (mostly high ground) on Boxing day as well.

10c at D14 on the latest GFS 0z suite-

It's getting cold as the polar vortex shifts energy dramatically over the next few weeks. At D5, the EC op has -30c uppers touching Svalbard.. Merry christmas on Longyearbyen

Really interesting synoptics atm Displaced bartlett hp split over Greenland and Siberia! Displaced Icelandic low in Scandinavia? Anyway... Bye bye vortex- the canadian heights (the ones that wouldn't been conductive to any colder weather), long stretch northerlies with an elongated lp section to the NE of us- this isn't going to be your typical mild pattern, definitely cold-orientated, especially for those further north

Very interesting. Drizzle/low cloud from the E/SE on Friday, potential light snow/sleet shrs on Saturday, especially over Northumberland and on high ground (Cheviots, North Pennines at times). Feel very bitter with temps at day around 1-2c on Saturday, with a breeze from the E and some wintry precip. Turning progressively, but slowly milder from Sunday onwards- Christmas could be wet and windy from the W, shortwave ridden and downpours, cooler from the NW, cold and cloudy from the S or even a tad wintry from the SE, no chance of prediction from the volatile NWP (op and ens!)

GEFS goes with the Op flow for the most part- -8c uppers into Scotland for Saturday, -6c uppers in for Friday morning.. it's very positive oop norf

SE flow off the continent.. extremely cold temperatures across many areas, especially in the se of England for christmas day- Don't expect the GFS op to be a mild outlier in comparison with the GEFS, the 850s will be similar but the airflow could well be markedly different.. on the operational however it is clear the Scandinavian/Baltic blocking high has beaten the Atlantic

Thatcher would have loved this, a real north-south divide. ...anyway, GFS op and ECM op both looking very similar up until D4/D5- so increasing support for the easterly scenario over Scotland. The shortwave core o/ England from D3 onwards is yet to be known, but with some southward adjustments over the next few days, SE Scotland and NE England can join in the (wintry) fun. Snow and sleet from Friday to Sunday in the far north and north-east of Scotland, mainly snow on high ground (Highlands, Borders at times), this could spread into the Cheviots, North Pennines and inland SE Scotland/NE England on Saturday.

For me it seems the window the opportunity for snow shrs in N/NE Scotland and parts of the Borders is Thursday onwards, with the UKMO and ECM earlier op signal indicating the highest probability around Friday evening/Saturday- especially across the N Isles and NE Scotland. The modelling of the main shortwave feature- which is attached to the trough due west is interchangeable and it's current position according to the UKMO op would provide snow shrs through much of Scotland, especially the east on Saturday- with the chance of snow shrs on Cheviots and North Pennines above 150m. The likelyhood of rain is also quite strong across many southern and midland areas- along with N Ireland and Wales towards the latter stages of the week. All in all, the 12z output has strengthened the likelyhood of snow shrs from the E/SE above an elongated shortwave on Friday, Saturday and potentially Sunday for parts of Scotland and northern England. The main source of precip will be convective in more northern parts, this associated with snow, whilst other precip will be more frontal and more likely to be less wintry. As with more zonal outbreaks, the upcoming 7 days look like being cool, colder than average for much of Scotland and at times northern England, whilst being more average elsewhere. The best chance of any milder weather will be across the south and west- and with the Iberian +ve heights after D4 (in line with Cohen ssw composites but shhh), and a weak mean trough stable to the west and south-west, it looks distinctly average for the time being, the signs of change are nearby and they don't favour rampant zonality and widespread mild weather... Appreciate the upcoming synoptics, it's all weather!

Heavy snow across ne scotland, moving into other parts of Scotland at times on Friday and Saturday according to the EC op solution this morning- parts of high ground in north england may also see some snow come Saturday- breakdown on Sunday, strong signal for a snow to rain event- with a south/south-east flow in most eastern areas.

Well the vortex would be well maintained (as in survive) well with the forecasted warming on the 18z- as well as the lack of cold moving into the cold core- plenty of opportunity for change though and the ECMWF is coming into 'warming' territory now. -21c at 240- hopefully tomorrow's 12z pulls that further

Snow into NE Scotland at D5- another solution, and another unresolved matter to come across, I am more interested in the pv reaction to the strat-tropo feedback in further fi and following ensembles- definitely trending away from mild, especially in the north (parts of Scotland always were below 0c in terms of 850s)

under 1c = 1% 1c-2c = 5% 2c-2.5c = 5% 2.5c-3c = 15% 3c-3.5c = 30% 3.5c-4c = 20% 4c-4.5c = 15% 4.5c-5c = 5% over 5c = 4% imo

Unfortunately the 10hpa temp at 360 is max -2c, yesterdays 12z had it at about 9c at 384- so perhaps the warming is now seeing it's dilution begin ? However, the latest run shows the vortex energy in Novaya Zemlya at 384- and it's notably warmer across NE Canada/Greenland- that would be more conductive to something at home

Indeed the GFS 0z downgrades the 384 warming from 14c to 4c at 10hpa- hopefully the trend is just a freak for now, mind you, the 0z would eventually get very near, it seems under-progressive in comparison to previous runs.