Following a colder-than-average December and only colder month compared to average in 2022, January will wind up slightly above average. A warm opening 10 days and cold following 10, the final 7 days looks to tip the balance on the slightly above average side…

Based on a non-development of a sudden stratospheric warning or SSW, the mild outweighing cold in January was expected. I anticipated the madden julian oscillation or MJO while favourable for cold in December was unlikely to favour cold in January with a major reversal in the high latitude pressure pattern.

That being said, the cold which initially focused on Scotland mid-January with significant snowfall then focused over England and Wales while it warmed big-time across Scotland.

Forecast v Reality!

Extract from the 2022-23 winter forecast

DECEMBER 2022

A cold month looks likely with a maturing cold pattern week 1 into week 2 as blocking establishes over Greenland and air masses grow colder through the mid latitudes.

Winds could veer from easterly week 1 to north, northeast week 2 as the Greenland high becomes more dominant than the Scandi high.

How cold it gets depends upon snow cover as well as light winds and clear sky and of course the depth of cold within the air mass but potential is there for significant cold week 2, possibly week 3 and that would take us towards the Christmas period.

How long the cold pattern holds during December is a tough call but I suspect a moderation possibly towards Christmas for UK and W Europe. The return to phases 1, 2 possibly 3 are cold phases but sometimes a particular pattern can take charge of itself and can be hard to break.

December 2022: Colder than average northern Europe (including UK and Ireland), warmer south

What happened!

December was below average for the UK, Ireland and Northwest Europe while South and Southeast was above average as per my prediction. A significant cold spell between Dec 1-17th produced the UK’s lowest maximum temperature since 2010 with -9C recorded at Braemar, Aberdeenshire. The same site also recorded the lowest temperature of -17.2C.

During the cold spell, the first significant snowstorm in several years (for December at least) hit London and the Southeast. Ice days were recorded even in central London during this episode.

As expected, a warm-up occurred in the week running up to Christmas and held through New Year for England and Wales. Scotland hung on to somewhat colder conditions with spells of snow for some.

December 2022 as expected was a colder-than-average month.

Considering what was expected and timing along with impacts and intensity of the predicted chill… SKILL SCORE 9 out of 10.

Extract from the 2022-23 winter forecast

JANUARY 2023

January is a tough one. The big question will be the MJO and perhaps more so the stratosphere. Do we see the upcoming high latitude blocking weaken the polar vortex at 10mb? If so, does this lead to any sort of strat warming? If that happens we could see a renewed cold pattern developing but it depends on when (if) that warming occurred.

At this time I will suggest a period of milder conditions early to mid January for UK and NW Europe with return to a +AO/NAO. Perhaps a return to colder conditions week 3 and 4.

A threat of an SSW event occurring late December could reinforce a colder flip in January but it’s all about timing.

The GFS ensemble certainly sees strong warming over Siberia but how much pressure does this put on the vortex in Dec?

Based on no SSW event during December, I will aim for a mild first half to January and therefore…

January 2023: Average to above average temperatures over NW Europe including UK, Ireland, colder southeast Europe.

What happened!

Without the assistance of an SSW early (as expected), a significantly mild theme opened the first 10 days of the month and year for most of Europe including UK and Ireland but with the exception of far N Scotland. Here, colder air held on bringing a continued snow and ice threat. Elsewhere, temperatures held above or well above average, especially on New Year’s Day and during the opening week of the month and NY.

A shift to colder occurred around mid month, initially affecting Scotland then ALL UK. Sub-freezing days and nights and frequent spells of snow which built up over the course of a week, made for a notable return of winter following the mild first 10 days which broke records on mainland Europe.

Scotland bore the brunt of the northerly blast initially with many Highland areas witnessing a steady building of snow cover to depths of between 10-30cm.

https://twitter.com/highlandweather/status/1615395920568254492

https://twitter.com/highlandweather/status/1615287332965580800

While less snow fell further south, harsh frosts began to set in.

Images from space just before the thaw over Scotland. As can be seen, much of Northern Ireland had a decent snow cover too! Sorry for forgetting you, NI!!

Southern Scotland, Northern England…

A significant up-side down flip occurred over the UK. After a week, Scotland dramatically warmed due to the arrival of mild WSW winds. However, for England and Wales, the cold strengthened beneath a stable high pressure system which saw the development of an inversion. While days struggled to reach 0C in the South, a rapid thaw was in full swing over Scotland. A switch from highs holding steady between +2 and -2C widely, lows -3 to -6, locally -10C to days of +8-12C, locally 16C at Aberdeen.

https://twitter.com/highlandweather/status/1617895515898908673

https://twitter.com/highlandweather/status/1617908356047568897

Even Greater London struggled to get above freezing by day while nights fell to -10C. Heathrow Airport witnessed an overnight minimum of -8.6C, the lowest since 2010 and lowest for January since 1987.

https://twitter.com/metoffice/status/1617448910271963136

https://twitter.com/danholley_/status/1617451565589086209

Heavy snow for the near continent. Here was parts of the Netherlands…

https://twitter.com/weerenradar_nl/status/1616392719525634048

During the final week of the month, mild returned for all. As for Europe, it turned colder towards months-end but as a whole, it was a warmer than average month except for Iberia.

Considering how the month panned out for UK, Ireland and Europe, given timing of warm followed by cold but overall warmer Europe with no cold southeast continent. SKILL SCORE… 7.5 OUT OF 10…

Interestingly, based a temperature anomaly chart for the last 60 days, the below chart courtesy of Weatherbell.com suggests the UK and Ireland are among the few in Europe to have in fact experienced a colder-than-normal December, January when combined! Iceland really stands out.

February 2023 Verdict?

With a predominantly stalled phase 3 MJO combined with -PNA and +WPO/EPO teleconnection and no SSW (only a minor warming and PV displacement), the first half of February is unlikely to be particularly cold. That being said, there’s questions with regard to week 2.

The models appear to be in pretty good agreement that the opening week of the month sees a trough over Hudson Bay slide east to Greenland after a spoke of the tropospheric PV swings through the NE United States. The downstream effect pumps the Azores high and builds it north over the UK.

There’s 2, possibly 3 scenarios regarding week 2! 1) how much amplitude does the trough exiting NA have as it positions over Greenland and 2) does the UK high get pushed north towards Scandinavia rather or east.

The 3rd is that the high refuses to shift north or east and may anchor overhead…

Systems riding the northern flank of the Azores-UK high will bring ups and downs in temperature to particularly Scotland with frequent spells of wind and rain whereas most of England, Wales and Ireland remain drier than normal. If scenario 3 occurs then cold low level air could become trapped beneath the high resulting in a similar situation to January where it remains drier, clearer but also cooler for England and Wales with night frosts compared to a more changeable, milder Scotland, Northern Ireland IF the high doesn’t move away from the UK.

2 of the 3 outcomes would provide almost opposite types of weather as a more northerly positioned high could sees winds flipping easterly whereas a high over central Europe could promote a very mild SW tropical-maritime flow. Scenario 3 is a bit of both but without the east wind.

The jury is still out with regards to week 2 but as for 3 and 4, well that depends on whether the MJO decides to continue progressing eastwards through the Indian Ocean, even Maritime Continent and into the West Pacific or remain stuck further west. If it was to progress east, I suspect a greater chance of high latitude blocking returning and increased chances for a slowing of the westerlies and more intrusions from north or east. If that was to happen then more ideas I put out way back at the beginning of December could be well and truly on… COLDEST OF THE WINTER IS ON THE TABLE!

Another factor needing to be considered is the ongoing stratospheric warming and displacement of the polar vortex. While a major SSW looks unlikely through February, we do have an ongoing series of MINOR warmings which could still increase the probability of either high latitude or a Greenland/Scandinavian blocking pattern developing through the final 10 days of the month. A full fledged MAJOR cannot be ruled out! If that were to happen then we could see a possible 2018 or 2013 situation for the very end of February and more so, March which could present a ‘delayed spring’.

Either way, we have several options on the table which would make it somewhat foolish (for now) to write off this winter.

CFSv2 for week 1 & 2 shows the eastward progress of the trough/ridge as discussed above but there’s uncertainly over amplification and northward progress…

There are models including ECMWF which supports late month blocking over the top, whether this is from the MJO, flip from + to – in the WPO/EPO or +PNA or indeed the strat warming, who knows. You never know, perhaps a cold pattern doesn’t show at all. Anything is possible I think given the complexity of the atmospheric and it’s competing drivers with origins over the Pacific basin.

FEBRUARY 2023: Average to above average for UK, Ireland and Scandinavia, possibly colder than average across South and Southeast Europe!

FEATURED IMAGE: lochiegirl @lochiegirl

Tags: featured, monthly-outlook