Europe January 2024 Outlook

Written by on December 29, 2023 in Rest of Europe, United Kingdom & Ireland with 0 Comments

December follows October and November as being a very wet month. It started cold and dry then turned very mild but also very wet. Christmas to New Year has seen it turn somewhat colder and snowier, especially in the north.

The month overall coincides quite well with my December Outlook (scoring 8 out of 10)

First week of December 2023

Credit: Weatherbell

1-28th December 2023

Credit: Weatherbell

A look back at December 2023

My Weather Station Stats for December 2023

MAX TEMP: 14.1C MIN TEMP: -9.0C WETTEST DAY: 40.69 mm PEAK GUST: 73.4 kph WET DAYS: 24 DRY DAYS: 7 MAX PRESS: 1024 mb MIN PRESS: 975 mb TOTAL RAIN: 170.60 mm AVG Temp: 3.9C

Reasoning behind another ‘good monthly forecast’

In mid to late November we had an amplified phase 1 into 2 MJO which resulted in a firmly -AO/NAO pattern with cold Europe.

As expected however, the MJO continued to progress eastwards in the tropics but rotating through the warmer phases of 3, 4, 5 and 6.

So, as the cold arrived it also left and the jet stream over both Pacific and Atlantic wakened pushing a lot of warm, moisture rich air across North America as well as Europe.

My thinking was that towards the all important Christmas-New Year period, IF the MJO happened to continue it’s eastward rotation back in to phases 7, 8 and 1, then the return of colder was likely.

We are back in phases 1, albeit the colder air has been fighting warmth across much of Europe (as expected) and we find a north-south split over the UK as well as the continent…

Note it’s becoming more amplified into 1.

Correlation

After briefly entering the ‘null’ or less amplified state, it’s once again becoming stronger (more amplified equates to more influence towards the pole). Due to the previous comment, I would expect a slackening off of the polar jet over both ocean basins and a renewed period of large-scale height rises into the higher latitudes once again with return of the -AO/NAO.

Lo and behold…

Here’s the extended GFS ensemble

Note the height change over N Pacific and Atlantic as jet streams weaken and flip from negative to positive.

Day 0-7

Credit: Weatherbell

Day 7-14

Credit: Weatherbell

Day 14-21

Credit: Weatherbell

Day 21-28

Credit: Weatherbell

2m temperature anomaly

Day 0-7

Credit: Weatherbell

Day 7-14

Credit: Weatherbell

Day 14-21

Credit: Weatherbell

Day 21-28

Credit: Weatherbell

ECMWF Ext 30-day

Credit: Weatherbell

Credit: Weatherbell

Credit: Weatherbell

I believe the active phase 1 response only properly impacts the 500mb pattern as we progress through week 1 of January and the ‘colder’ push only kicks in between 6-8th January, maturing mid month say from 10-20th January with either a continuation of the chill or a bit of a pull back to milder.

Sudden Stratospheric Warming?

As for what’s happening within the 10mb or upper stratosphere, the strong Eurasia to pole warming has begun.

The question is twofold, 1) do we see such a deceleration of the mean zonal winds to a point of reversal (constituting a true sudden stratospheric warming event) 2) If so, is the result a displacement, split or collapse of the polar vortex? These are all important questions, I believe we see either a major displacement or splitting of the PV rather than complete collapse.

Keep in mind that even with a Major SSWE, 70% of these result in significant UK/Ire/W Europe cold.

What actually is a Major SSWE? It’s a strong warming or wave breaking within the stratospheric layer which causes a slowing down of the mean zonal winds which circle the cold vortex usually spinning above the pole.

The strong warming from outwith the arctic forces the cold PV core to become displaced and as we’re observing now, is leaning towards the N Atlantic and Europe hence the widespread observation of nacreus or polar stratospheric clouds.

This warming if strong enough can force a 50C temperature rise over the polar region with the ‘wave breaking’ becoming strong enough for the typical west to east winds to flip back on themselves and reverse. The warming within the stratosphere causes the stratospheric layer to expand which then forces the troposphere beneath to contract. This contraction of the tropospheric layer then forces pressure to build within the 500mb level or within the lowest 18,000ft of the atmosphere ultimately triggering a -AO and often -NAO. The whole process if stratosphere-troposphere coupling is successful takes bitter cold out of the stratosphere into the troposphere and then away from the arctic towards the equator.

IF and it remains an if, we see a Major SSWE and all of the above happens, the response comes typically 2 WEEKS after the zonal winds have reversed. It takes time for all the energy to propagate downwards through the lowest two layers of Earth’s atmosphere.

There could well be somewhat of a baton exchange between cold phases of the MJO (explained above) and SSW continuing if not strengthening a cold pattern for Eastern North America/W Europe.

The very wet conditions during particularly October and early November may have been a hint at the cold spell to end November, begin December and I wonder whether the most recent spell of very wet weather could be yet another hint at a coming cold pattern?

Conclusion

I suspect Atlantic resistance through the first week to 10 days but as heights are expected to build between Scandinavia, Iceland and Greenland I would think the jet pushes further south into France or Iberia. This should allow intrusions of polar or cold continental air to slide down from north or northeast presenting increasing threats of snowfall and colder conditions.

All in all I suspect a Slightly Colder & Drier Than Average January is Likely for the UK/Ireland and all of Northern Europe including Denmark, Northern Germany & Poland, Baltics & Scandinavia Inc Finland and Russia, Warmer & Wetter Across S Europe

FEATURED IMAGE CREDIT: Kairo Kiitsak

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