December 2022 marks a significant turnaround to what’s been a warm year. In fact the warmest year on record many parts of Europe including UK.

December 2022 has been a distinct tail of two halves with a very cold first 15 days followed by much milder 2nd half. The month featured the deepest December -AO/NAO and coldest days and nights since December 2010. It’s the only colder-than-average month for the UK of the year.

December 2022 temp anomaly

The month ended with a neutral AO and firmly positive NAO which has led to a record warm end to the year.

The final day of 2022 and first of 2023 was marked by big contrasts. Despite an overall mild, Atlantic dominated pattern, Scotland remains in the air cold north side of the jet stream with an ongoing snow and ice risk. To the south of the SW to NE oriented jet stream and low pressure, much of England and Wales has endured frequent spells of wind and rain along with distinctly spring-like mildness of 10-14C.

500mb height anomaly

Jet stream

With a trough extending southwards west of the UK and strong high over south-central Europe and a powerful jet stream in between, temperatures have been record warm with low 20s over Iberia, even near 18-20C in parts of Germany and Poland.

Highs on Dec 31

Big range over the UK on Dec 31.

Cold start to 2023 in north, mild to the south.

Fresh snow to open the year across the north.

Happy New Year everybody! ? ? A little fresh covering of snow to open 2023! pic.twitter.com/B34cVhx8Kk

— MarkVoganWeather.com ?? (@MarkVogan) January 1, 2023

A snowy start to the new year in Carrbridge pic.twitter.com/pkmxNsVMrQ

— Highlandweather (@highlandweather) January 1, 2023

Nice snowy scenes at Loch Morlich this morning following the overnight fall. pic.twitter.com/Uz14sUy52J

— Highlandweather (@highlandweather) January 1, 2023

Beautiful morning here in Braemar, Aberdeenshire where's the snow continues to fall @metoffice @SeanBattyTV @highlandweather @Meopham_Weather @BBCNorthEast @BenPhilip_ @philippetrieTV pic.twitter.com/3qblfVPHY7

— Braemar, Ballater and Deeside Weather Page (@Alonso2012F) January 1, 2023

January projection

So January opens warm for most almost ALL of Europe except Scotland!

With a strong Atlantic jet stream and high over the continent, this is driving an overwhelmingly warm pattern but what’s next?

I blame the MJO for both delivering the cold (phases 7, 8 and 1) and now the mild (phases 2, 3, 4 and 5).

However, the models show the MJO returning to the typically colder phases we saw back at the beginning of December.

Does the return of phases 7, 8 into 1 mean the return to a highly blocked and cold pattern like we just saw? It’s possible but there no guarantee. The reason why? The parameters within the atmosphere shift as we progress through the season. What gave early may have a different response mid and late winter so nothing’s clear cut.

As it stands, I don’t see a particularly locked in cold pattern for West or Northwest Europe through at least the first 10, possibly 15 days of January.

According to the GFS ensemble, the AO looks to be heading negative while NAO remains mainly neutral…

With regards to the polar vortex, we’ve seen a weak tropospheric vortex but stronger stratosphere. Looks like we start January with a strong coupling between troposphere and stratosphere which is currently driving the strong zonal jet which in turn is driving moist, maritime air across the USA as well as UK and Europe.

I believe the first 2 weeks of January is mainly Atlantic driven with mixture of mild and cold, often unsettled. Question is whether we see a response from the eastward propagating MJO and what happens with the polar vortex.

The models are firming up on a strong warming from Siberia towards North America which is stretching and pushing the vortex towards eastern North America, Greenland and Canada.

Regarding purely the stratosphere, until we see more warming straight towards Greenland with a possible split, I fear a similar situation to what we saw back in 2014 which observed extreme cold driving south over North America. The increased thermal gradient corresponding to a strengthening of the Atlantic jet stream and this drove one storm after another across the UK. Positioning of these lows would determine a mild or cold outcome.

My hunch is a relatively mild first half to January followed by colder second half with MJO forcing higher latitude blocking (Scandinavia). Remember that even if we see a true SUDDEN STRATOSPHERIC WARMING, the response to the 500mb pattern wouldn’t come till at least the last 10 days of January. This month, like December is likely to be driven by the Pacific drivers (MJO, PNA, EPO, WPO)

The CFSv2 500mb height anomaly suggests high over Europe, trough over Atlantic but doesn’t rule out Scandinavia blocking which could drive east winds.

The possible 8-12th flip from low to high heights over the pole could increase ‘spells of colder conditions’ for the UK.

CFSv2 precip and temp anomaly for Jan. Warm but wet NW Europe away from Scotland.

 

JANUARY 2023: AVERAGE TO SLIGHTLY ABOVE AVERAGE TEMPERATURES FOR UK, IRELAND AS WELL AS SOUTHERN EUROPE, COLDER SCANDINAVIA.

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