Following a record warm, dry summer, November and autumn will go down as warm and wet.

Europe 2m temp anomaly

Sep

Oct

Nov

This follows what has been a record warm year-to-date for UK as well as Europe.

Hints back in September of what was coming in December?

The pattern triggered by the phase 6, 7, 8 MJO/late season tropical development in early/mid Sep brought the UK’s coolest 2nd half to September since 2012 and has returned for early/mid December.

Bastardi of Weatherbell has stated for years that very wet November’s for the UK can often lead to cold December’s. 2009 and 2010 are prime examples.

https://twitter.com/MarkVogan/status/1598349728307200001

The AO/NAO is tanking to the strongest negative in 12 years!

Looks likely that it’s a gradual process to cold as Europe remains relatively mild and so east winds aren’t cold enough to bring snow to low levels. Beast from the east’s almost never happen this early in the season, 2010 was quite exceptional.

Week 1 sees east wind (Scandi high), week 2 northeast wind (Greenland high) and this could present the coldest air and increase low level snow chances, week 3 could see a pattern shift with return of Atlantic air but it depends upon how anchored this Greenland block becomes and how much cold air is in the pattern.

The below shows the block focusing directly over Greenland week 2.

The cold pattern has potential to grip hard mid-month, especially if it turns snowy.

GFS ensemble has the cold intensifying through next week after a gradual trend downwards in temp.

The models have some impressively cold air over the UK mid month with persistent ‘waves’ of polar air sweeping south around the Greenland high.

Snow forecasting is a tricky one but as the air mass grows colder, so snow chances at all levels increase. The GFS suggests an expanding snow cover mid month.

My feeling is that the MJO rotating back into phases 1, 2 and 3 brings a shift to milder in the run-up to Christmas.

The GFS ensemble indicates at 50mb (lower stratosphere) a cool pool flipping warm above Greenland (block) with cold over N America & Europe, this would be mirrored at 500mb. However the cool pool returns to Greenland by 312hrs possibly suggesting the return of a Greenland trough N Am/Europe high.

Initial

168hrs

312hrs

Note the westward shift of the block and supportive of the above…

The GFS ensemble MJO forecast suggests change later in the month.

Models have been known to shift blocking highs too fast however and it’s ultimately impossible to say how long as well as strong this incoming cold pattern will be. You never know, it could be gone in 10 days, then again it could grow worse as the month progresses bringing a snowy Christmas to many.

December is likely to be a colder-than normal month throughout Northern Europe, warmer across the south and through the Med Basin.

Tags: featured, monthly-outlook