January was, like many recent months, a tale of two halves with cold first half followed by less cold 2nd half. I say less cold because it wasn’t entirely mild. Some days a little above, some a little below and many nearer average and that should make for a slightly colder than average following the cold start, fitting nicely with my monthly outlook.
While it was a little colder with decent snowfall in the North of Scotland and some in other parts of the UK and Ireland, albeit far patchier, rainfall was above average for the UK and Ireland as a whole, however while it was very wet in the SW, S and E of the UK, the NW was drier than average all thanks to the pressure pattern with low southwest and high northeast which forced rainfall to frequently affect S and E facing upslopes.
The cold first half to January was driven more by MJO rather than polar vortex. While there was weakening of the PV late November, the stretching of the high altitude circulation was oriented in a way to favour frequent shots of arctic air into North America rather than Europe. While cold in E US/Canada in December it was mild in W Europe and that temperature pendulum flipped into in early January then flipped back late January.
At the close of December into the New Year, the MJO passed through phases 6-7-8 allowing the build-up of pressure across the pole and Greenland which allowed arctic air south across much of Europe.
The stratospheric polar vortex so far this winter hasn’t favoured Europe but that might change in February and if so, during the 2nd half.
Note the sharp deceleration in the mean zonal wind at 10mb as per latest ECM.
Note the now vs 15th, even 23rd temp anomaly at the lower 50mb level. The warming is oriented more central Eurasia across the pole and down over Greenland into Atlantic, POTENTIALLY splitting the cold pool in a way which favours less Atlantic influence by pushing the storm track further south and pooling the cold more over W Europe. Lot’s of IFS, BUTS, MAYBES!
Early February Model Conflict
Before any real affects even remotely affect our atmosphere from happenings way up within the stratosphere (remember the 10-15 day lag) the ongoing wet setup looks to persist into the start of February. However according to the ECM the cold that’s never been far from our northeast horizon looks to steadily break free and begin to trickle it’s way across the North Sea and across N UK, perhaps becoming more noticeable week 1 into week 2, even at that it’s back and forth with milder air affecting S UK. The GFS keeps a stronger, slightly milder Atlantic influence.
The ECM increases snow chances to increasing lower levels over Scotland later week 1 while staying mild in far South simply due to winds bending more easterly drawing on some colder continental air we’ve not been able to tap.
Even in the short lead time (by ensemble standards) of the next 7 days there’s a difference over the UK between GFS and ECM ensembles.
GFS is warmer than ECM. Bitterly cold across N/E Europe.
This process of more of an easterly becoming more pronounced looks more mid to late month IF and it’s a big if, we see coupling between stratosphere and troposphere and exactly the type of warming and even at that, there are other factors which need to align.
Week 2 and 3 off GFS and ECM
ECM
What’s apparent is the trend to colder into middle Feb for UK and Ireland followed by a back off later. It’;; be interesting to see if the trend to colder pushes deeper towards the back half of the month in conjunction with stratospheric projections which modelling aren’t grabbing on yet or their not grabbing on for a reason?
Here’s the month of Feb on the whole for 500s and temp anomalies.
Here’s the CFSv2
Both AO and NAO are projected to remain firmly negative for the forseeable.
The 3 models all show a VERY cold Northern Europe but when it comes to UK, it’s difficult to know what side of the mild vs cold line we shall be on. GFS and CFSv2 arguably hold us on the milder side.
The questions are, how far south shifted will the storm track get beneath the block over top? Do we merely repeat the 2nd half to January or do we finally see that dam break, aided by a stratospheric warming. There’s so much on the table which could deliver pretty much both extremes as well as the in between.
Could the MJO have a detrimental influence while strat more favourable?
MJO albeit weak look to drift through phases 1 into 2, 3
Sure Phase 1 looks good but 2, 3? Lower heights. Must be said that the surrounding waters are cooler in Feb than Dec and so too is atmosphere overall.
So do I buy into the potential of a more favourable significant weakening of the stratospheric polar vortex and hands down go for a cold Feb which would be first in 3 years or hold to my winter idea and nagging feeling of milder than average. I’m torn. This pattern has the potential to deliver our first ‘Beast from the Beast’ since Feb 2021, yes Feb 2021 following on the a Major SSW or NOTHING like Feb 2025. There’s actually a greater chance of a Beast due to Europe being cold this time around.
The Verdict
Ok, I am going to call for a near average February in a line from Ireland/UK southeastwards to Italy, to the north and east MUCH Colder than average, south and southwest milder than average and VERY WET!
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