Europe February 2021 Outlook

Written by on February 1, 2021 in Rest of Europe, United Kingdom & Ireland with 0 Comments

It’s been an interesting winter so far with frequent spells of snow and frost, albeit frustrating across southern Britain.

However, following a colder than normal January for at least the northern UK (near normal for south) and prospects of a cold to very cold February, the 2020-21 winter may in fact wind up below normal for at least half of the UK.

Although not extreme, the cold pattern has been quite persistent allowing many inland loch’s to freeze over like this one (Loch Morlich).

We of course witnessed the major sudden stratospheric warming event back at the turn of the year, I believed the response from this would come in the traditional 10-15-day lag time but it’s been delayed and likely only now beginning to show it’s hand. That being said, we’ve seen frequent northern blocking providing frequent Arctic intrusions but with the presence of a still strong Atlantic zonal jet. The weak polar vortex has forced a southerly displacement of the jet stream providing an air mass battleground over the UK. While the Atlantic has recently managed to drive temps 12-14C across southern parts, the arctic air always managed to hang on over Scotland where snow has been frequent and continue to pile up above 200m.

While it’s been a mix at low levels, frequent snowfall is building an increasingly deep snow pack within Scotland’s mountains above 2-400m as can be seen here from the Black Isle looking over to Ben Wyvis

The delayed downward energy transfer in response to the SSWE has been slow, even strange, ultimately preventing the shut down of the Atlantic as upper winds from stratosphere into troposphere didn’t truly reverse, hence a -NAO with still strong Atlantic influence. This delayed response from the SSWE may have been caused by a masking effect from the La Nina and or the MJO.

Here is a nice brief explanation as to why the SSWE hasn’t impacted the low altitudes of the atmospheric in the typical time frame…

1/2 part tweet by Judah Cohen

1/ Why is this #PolarVortex disruption different from all other polar vortex disruptions? First are the twirls & loop-de-loops in this event’s polar cap geopotential height anomalies. Yellow arrows show where they go up & blue arrows where they go down. Normally they only go down

2/ Here is the “dripping paint” plot of the AO (similar to PCHs) from Baldwin and Dunkerton 2001 and it shows how the maximum anomalies propagate or drip down. I can think of at least four important differences for the current event and I will likely discuss in the next blog.

In the below cross section of the NH polar vortex, you can’t help to notice the deep reds extending right down to 1000mb as we enter THIS WEEK. This, albeit delayed IS THE RESPONSE to that SSWE.

February’s opening week likely sees our pattern transition as additional Atlantic fronts sweep into the UK and Ireland from the SW. While these systems push ENE, the cold is intensifying and expanding over Scandinavia.

The focus of ‘prolonged snowfall’ over the upcoming couple of days looks to be across NE England, Southern Uplands and Highlands where a foot of additional snow may occur above 200m. It could be very mild across southern Ireland, England and Wales. while remaining cold for Scotland, N Ireland. Would could see 2-4 inches of snow at lower levels over N/NE England as well as the Central Lowlands. but the end of tomorrow (Tue).

Credit: wxcharts.com

Credit: wxcharts.com

Credit: wxcharts.com

Things look to get more interesting from Thursday on wards as heights build WEST and north of the British Isles, this puts pressure on the expanding cold pool over the north and northeast continent and begins to force the cold reservoir westwards underneath the high, eventually (hopefully) reaching the UK by the weekend/early next week.

The GFS ensemble 5-day increments nicely see this classic -AO/NAO pattern evolve at 500mb. Note the Greenland and mid-Atlantic ridge join bringing the all important shut down of the Atlantic.

Day 1-5

Credit: Tropical Tidbits

Day 6-10

Credit: Tropical Tidbits

Day 11-15

Credit: Tropical Tidbits

While there remains a lot of model variance, this folks is a cold pattern and has potential to go to the extreme with frequent heavy snow spreading east-west aboard strong, bitter easterly winds blowing straight out of Siberia.

GFS ensemble 2-metre temp anomaly

Day 1-5

Credit: Tropical Tidbits

Day 6-10

Credit: Tropical Tidbits

Day 11-15

Credit: Tropical Tidbits

CFSv2 for February overall.

500mb

Credit: Tropical Tidbits

2-metre temp anomaly

Credit: Tropical Tidbits

While individual model runs are to be taken with a pinch of salt, I must admit I like what the GFS is printing out for early next week with heavy snow piling into over southern Britain in the midst of a mature long-fetch easterly.

Credit: wxcharts.com

Credit: wxcharts.com

This could plaster London.

Credit: wxcharts.com

and provide images like these…

Credit: NASA

Follow the isobars all the way back to Russia…

Credit: wxcharts.com

The all important train tracks of solid snow cover extending from UK back to Russia allows minimal weakening of the cold.

Credit: wxcharts.com

This would certainly be a bonified beat from the east.

GFS 850mb temps

Credit: wxcharts.com

Credit: wxcharts.com

Credit: wxcharts.com

The UK has not observed a -18C since December 2010. I expect to see a couple of nights below this value this month.

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