An unusually warm, wet December ends cold, frosty and largely dry while January opens increasingly cold, with biting northerly. The northerly, packing 30 to 50+mph gusts shall usher in increasingly heavy and frequent snow showers. Low level accumulations of 5-10cm and 10-20, locally 30+ over high, exposed ground. A yellow snow and ice warning is in effect across the Highlands through the opening days of the New Year.
Winds will be noticeable in strength and feel!
Met model
The snow threat is most pronounced for the North and Central Highlands while the Central Lowlands is sheltered. NW England and N Wales as well as Eastern Scotland and England could well see snow through the opening weekend as winds fluctuate N, NW, NE.
GFS snow depth projection for the end of Thu, Fri, Sat.
Met model
GFS total snowfall through Thu 8th. Snow could fall across MOST of Europe!
850 temps will be in the -10 to -12C range through the weekend resulting in ‘ice days’ certainly where snow lies in the North but potentially as far south of south-central even SE England and Wales.
Very cold air won’t be confined to UK as seen below…
GFS temp anomaly 06z Sun 4th
06z Mon 5th
Overnight temps will almost certainly fall below -10 in places with a chance of -15 to -18C rivaling last winter’s UK winter low of -18.9C recorded in Altnaharra last January.
This cold spell comes when just 2 weeks ago, it wasn’t seen by the models. I believe there’s been somewhat of a hand off from stratosphere to tropics. The strat warming late November favoured a cold North America/warm Europe and effects of this stretched polar vortex from Siberia to Canada led to an increase in zonality across the Atlantic. Now that the stratospheric dynamics have changed, the effects of an amplified MJO phase 8 is now showing as well as increased blocking from upper stratosphere down into the troposphere as seen from the below Polar Cap Height (PCH) plot below from Giuseppe Petricca.
The response is clear to see when looking at the MJO/AO/NAO and resulting 500mb pattern.
GFS temp anomalies
CFSv2
How long and strong this imminent cold spell shall be remains to be seen. The pattern favours some notably low day/night temps especially early next week and in terms of potential flip back to an Atlantic regime, models are hinting at that as early as Tue/Wed 6/7th Jan. I am not so sure we’ll flip back quite as early.
There’s a lot of uncertainly regarding the end of week 1 into week 2 with a few options on the table. 1) A brief push of milder followed by the return of an arctic northerly, 2) the cold holds firm allowing Atlantic moisture to creep in providing snowier times for a snow starved south is possible too 3) the mild wins altogether.
I see a return of the Atlantic towards mid month. While the MJO isn’t noticeably creeping into the warmer or stormier phases but more the null phase for now (could change later Jan) I’m well aware of the strengthening stratospheric polar vortex and sure, it may not couple quickly with the lower strat or trop but I think stronger zonality makes a return later Jan.
The ECMWF mean zonal wind hints at more disruptions, albeit minor at this stage.
January overall
Both GFS & ECM ensembles show a textbook Greenland to Arctic block with cold Europe next 30 days!
The Verdict
I have to say I’m struggling with timing. Does this cold hold longer or depart earlier? I shall stand by my winter forecast (decent shout for Dec) for an average to COLDER than average January for most of Europe including UK & Ireland… However, a cold or very cold first half I believe will be replaced by a milder mid to late month…
FEATURED IMAGE CREDIT: Chris Booth
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