It’s been quite the autumn and winter so far with excessive rains, swings back and forth of cold and warm as well as multiple storms.

10 named storms since 1 Sept through January

Name	Date named	Date of impact on UK and/or Ireland and/or Netherlands
Agnes	25 September 2023	27 – 28 September 2023
Babet	16 October 2023	18 – 21 October 2023
Ciarán	29 October 2023	1 – 2 November 2023
Debi	12 November 2023	13 November 2023
Elin	9 December 2023	9 December 2023
Fergus	9 December 2023	10 December 2023
Gerrit	26 December 2023	27 – 28 December 2023
Henk	2 January 2024	2 January 2024
Isha	19 January 2024	21 – 22 January 2024
Jocelyn	22 January 2024	23 – 24 January 2024

Back in August we had 2 named storms from the previous season with just 4 for the entire 2022-23 season compared to 10 so far this season.

A-Z of UK storm names 2022/23

Name	Date Named	Date of impact on UK and/or Ireland
Otto	16 February 2023 (named by DMI)	17 February 2023
Noa	12 April 2023 (named by Météo-France)	12 April 2023
Antoni	4 August 2023	5 August 2023
Betty	18 August 2023	18 – 19 August 2023

As a likely consequence of El Nino and record warm Atlantic SST’s, it would appear that the October through December 2023 period will go down as the wettest on record for the UK, one of Ireland’s wettest and likely northern France too.

2023 saw the wettest July-December period on record for the UK as a whole (dating to 1890).

71% of 800 gauging locations in England & Scotland had notably or exceptionally high flows in December, compared to the monthly norm

????River flows on 2 Jan (UK Water Resources Portal) pic.twitter.com/XErMLhLRTq

— UK Centre for Ecology & Hydrology (@UK_CEH) January 5, 2024

Over 50% more rainfall than normal over the 4-month period.

As well as El Nino (possibly a strong positive Indian Ocean Dipole also), a strong Greenland block (-NAO) with active south displaced jet stream is another likely contributor. A further south (warmer source) storm track taps more moisture.

December 2023: Cold Start, Followed by Mild, Tease At The End!

Courtesy of some minor strat warming in Oct/Nov and more importantly an active phase 7-8-1 MJO, we observed winter’s first cold spell ending November, beginning December. The AO/NAO as expected responded.

Temp anomaly to open December and winter!

It was a decent cold spell lasting about a week, however, built into the winter forecast, it was well anticipated that the MJO wouldn’t hang around in the cold/blocky phases of 7-8-1 and was destined for phases 4-5, arguably the mild which arrived 6/7 Dec and lasted through the 20/25th may have been somewhat enhanced by El Nino/+IOD and possibly some earlier strengthening of the strat polar vortex. No doubt the warm Atlantic played a role too.

While mid-December turned very mild on both sides of the Atlantic, flipping the temp anomaly for Europe on it’s head and presenting North America with one of it’s warmest December’s on record, MJO continued it’s eastward journey back into more favourable colder phases. By entering phases 6-7, this brought a somewhat snowier theme and atmospheric fight between Christmas and New Year.

Overall, December was wet and slightly warmer than average for most of Europe except the north.

FORECAST v REALITY

What was said about December:

While blocking should continue over Greenland and Arctic, the Atlantic for the most part should continue to dominate Western Europe through at least through mid-month bringing milder than average temperatures after a cold start.

There’s a question mark with regards to the run-up to Christmas and New Year. I suspect the MJO may attempt at a return towards phase 7, eventually shifting into 8 and 1. This increases a return to colder for UK and Ireland and so I wouldn’t be surprised to see moderate chances of some snow, especially for Scotland.

Overall, Average to ABOVE Average temperatures for UK/Ire, Colder for Scandinavia and east Europe, warmer Iberia, France. Wetter for southern UK/Ireland, Drier Northern and this goes for Europe (dry north/wet south)

December 2023 in the United Kingdom had an average temperature of 5.8C ,+1.6C above normal.
Average precipitation was 188.6mm ,+48% above normal.

2023 as a whole had an average temperature of 9.97C, +0.83C above normal and was the SECOND warmest year on record. https://t.co/Knv2uOXbHY

— Extreme Temperatures Around The World (@extremetemps) January 3, 2024

SCORE: 8 out of 10

January 2024: Bookend Mild, Cold Middle!

January opened largely mild for UK and Ireland but extremely cold up in Scandinavia. It was arguably one of the coldest start’s to a new year on record for Norway, Sweden and Finland.

The first 4 days of January 2024 averaged 8.2C in Central England. Effortlessly very mild and it's not just because of the nights, even the maxima are almost 5C above 61-90 average. pic.twitter.com/fnn0CFqqlx

— Snowbie ❄️ (@SnowbieWx) January 6, 2024

Pattern Change As High Replaces Low then Retrogression Up to Greenland…

Beyond the opening few days of 2024 with wind and almost a month’s worth of rain falling on southern UK, a renewed burst of powerful jet stream winds exiting the southern USA helped set the wheels of a significant pattern change in motion.

The rapid deepening of a hurricane-force depression over the Northwest Atlantic forced high pressure on the other side of the Atlantic to strengthen. In fact one high near the Azores hooked up with another over southern Scandinavia and these merged to become one, promoting a 1046 high over Scotland.

That hemisphere-wide pattern change can largely be attributed once again to an active MJO pulse entering the western hemisphere which in turn drove heat north, reshaping the upper pattern within the mid to high latitudes.

The stronger the MJO, the more influential it can be all the way into the arctic. I believe the amplified phase 7-8-1 MJO coincided with a stratospheric warming late December to drive this hemispheric pattern switch.

That 1046 high over Scotland did two things. Pushed warm Atlantic air into Scandinavia on it’s northern flank and by doing so, pushed out the intense cold pool which brought days of -40. The cold then cycled around the base of the anticyclone and swept westwards across central and into western Europe.

This prompted the shut down of the extremely wet pattern over Western Europe but also commenced a colder setup.

Around 13/14 January, the high retrograded WNW away from the UK and up over Greenland opening the door to arctic winds which swept south. These winds brought heavy snow throughout Scotland down to the southern Highlands.

As forecast in both winter forecast as well as January forecast, the period of 10-20 January was likely to see the coldest of winter. A widespread 6-12 inches of snow lay while Dalwhinnie fell to -14C.

A lack of snow cover away from the Highlands yes but overnight lows of -6 to -10C across the Midlands and South, even reaching the Channel coast saw S England’s coldest JANUARY nights since 2010. Had a system which brought a swathe of heavy rain, sleet and snow across N France been further north, overnight minimums of -10 to -15C would have easily been achieved given the 850mb temps as low as -10C and snow cover.

14-19 January (core of cold spell and worst of winter so far)

9-19 January

1-19 January

Beyond the 20th January, the warm pattern returned with a vengeance throughout the mid latitudes! MJO as predicted all the way back to the end of December was going to repeat December and head back through phases 3-4-5 and hello to the UK storms again, likely enhanced by El Nino and warm Atlantic etc.

The below mean sea level pressure anomaly courtesy of the GFS ensemble extended for the final 7 days of January is/was a textbook phase 4-5 MJO signature with strong +AO/NAO. A complete 360 from the previous week to 10 days!!

This promotes a blowtorch throughout the mid latitudes… RECORD WARMTH North America, Europe, Asia!

OPPOSITE past 14 days!

What a beautiful correlation between amplified tropical forcing (MJO) essentially driving the global pattern.

Think of the positive AO/NAO as phase 4-5 and negative 7-8-1.

Enhanced Aleutian/Icelandic troughs mirroring each other are flooding the continents with Pacific and Atlantic air respectively…

Past 7 days!

1-31 January

Finally, after some tremendous pressure thrown at the stratospheric polar vortex (especially from below), we did indeed see a brief REVERSAL of the MEAN ZONAL WINDS at 10hpa. This constitutes a true Major SSWE (Major Sudden Stratospheric Warming Event).

I believe this almost constant pressure from warming will and has filtered into the lower stratosphere and troposphere… See February Forecast below…

FORECAST vs REALITY

What was said about January:

January has the potential to see an increased snow and cold threat for Western Europe as blocking may strengthen either up over Greenland or Scandinavia in response to both MJO and strat warming.

I am going to suggest a moderate January cold spell. The cold may start as early as Dec 20th or as late as Jan 2-4th and may last 10-16 days before a pull back during the 2nd half of the month. The Atlantic is likely to return with warmer, wetter weather.

There’s also a growing possibility that January sees strong to major warming of the stratosphere early/mid January. The potential impacts of this if it was to occur would come towards the end of the month and more likely early February.

Overall, average to below average temperatures with cold first half followed by milder 2nd half.

January 2024 in the United Kingdom had an average temperature of 3.8C which is 0.1C below the 1991-2020 normal.
A new national record heat was set at the end of the month.
For CET (Central England) the average matched the 1991-2020 norm. https://t.co/ayvm7Xc6yv

— Extreme Temperatures Around The World (@extremetemps) February 2, 2024

SCORE: 8 out of 10

Here was the past 60-day temperature anomaly from about a week ago! Period from 24/25th November to 24th January.

Notice how it’s warmed given the level of warmth in the past week…

My Weather Station Stats for January 2024

MAX TEMP: 14.2C MIN TEMP: -8.3C WETTEST DAY: 13.49 mm PEAK GUST: 88.2 kph WET DAYS: 15 DRY DAYS: 16 MAX PRESS: 1044 mb MIN PRESS: 954 mb TOTAL RAIN: 63.50 mm AVG Temp: 3.1C

SNOW STATS: DAYS WITH SNOW COVER: 5 CONSECUTIVE: 5 MAX DEPTH: 9″

Does Warm To Very Warm End to January Right Off February Cold?

While many have thrown in the towel on winter, based on the past week or even before it began, I always believed this was a winter of extreme swings but with a lean to MILD for the 90-day period. It was always going to be a unique fight of several ocean and atmospheric drivers competing against each other. Question was, what would win? Strong El Nino coupled with record warm global ocean and atmosphere or east based QBO, modoki El Nino, favourable MJO phases etc?

Your more ‘typical teleconnections’ I think have become less useful over the past few winters given just how warm the Atlantic has become. While there’s no denying our warmer world, one cannot deny that it can still get cold. Warmer Atlantic and warmer world certainly makes record warmth MUCH easier to come by as we’ve seen just this week, however there’s much more to it.

Despite the somewhat hemisphere-wide blow torch we have to end January commence February, there’s somewhat of a loaded cold weight I think is ready to drop!

My beloved MJO is back in the favourable cold phases of 7 and attempting to limp into 8. This is almost exactly where it was back at the end of November.

Keep in mind the ocean has cooled and the atmosphere is different commencing February compared to December.

Based on MJO alone and what we’ve seen happen already, then the current +AO/NAO warm pattern is living on borrowed time.

However, we have something else…

Here’s a fantastic graphic produced by Richard Traut (contributor to GavsWeatherVids).

Note the weakened mean zonal wind prior to BOTH December and January’s cold spells. (weakening of the mean zonal winds mean weakening of the polar vortex)

Note the strongest weakening and brief reversal 10-14 days ago!

Check out the LATEST 70hpa (lowest level of the stratosphere) temp/pressure profile.

Now look at the below 500mb pattern for February off the CFSv2 verses the above 70hpa profile. Similar?

AO appears to tank while NAO is only neutral but I expect this to correct in the coming days.

Based on the return of MJO phase 7 into 8 combined with the strongest warming/weakening of the polar vortex and the lower stratosphere already reflective of a strong northerly blocking pattern, it’s only time till the North America and Europe highs lift north and northwest and replaced by troughs.

It’s likely to be a bumpy, stumbly, stuttery transition given the level of warmth courtesy of the MJO phase 4-5, that’s really done a work.

December started cold, January was colder than December and I stand by my forecast issued at the end of November that February still delivers the coldest of winter. The month opens mild to warm for much of the mid latitude NH and between 5-10th but as positive heights replace negative within the arctic in response to the strat warm/MJO. The N France/S UK ridge reflective of MJO phase 6 will pull WNW similar to that of January prior to the last cold spell.

For cold, like January, it’s 10-20th February is period to watch. The opportunity is there for a MAJOR cold outbreak for both US and Europe INCLUDING UK and Ireland MID-LATE MONTH!

GFS ensemble trends cold between 7-10 Feb.

I suspect the models will trend colder in the coming days and I believe the longest and strongest cold of winter is ahead mid/late month…

TIME WILL TELL…

Average to Below average UK/Ireland

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