We know it’s turning cold through this weekend but I want to break down the details and the question I ask is how cold will it get early next week across the UK and Ireland? In the post yesterday I spoke of the incredible 850mb temperatures depicted by the model with the latest run of the ECMWF perhaps even colder than last night with -10 to -15C air at 5,000 feet COVERING the UK and Ireland by Monday. If that occurs as the model says, this would certainly be the coldest air mass of the entire winter but there is competition within the atmosphere from top to bottom at this transitionary time of the year.

This mid-level layer has a tougher time transferring this bitterly cold air down to the surface at this late time of year when the sun angle is much stronger than say a month ago.

In saying that, I am confident that most areas of the UK as well as interior Ireland, even if there is sunshine, will have a hard time getting much above 1-2C. Sheltered areas may stay at -2 or -3C during the day. Even this weekend, just as the colder air begins to invade, those easterly winds are going to start biting with wind chills ranging from -2 to -5C across Northern and Central Britain.

Check out this streamline chart off the GFS which nicely depicts where are air is coming from during late Sunday. This is driving the frigid mid-level air across the UK and Ireland, setting the stage for what may be one of the coldest 3 day periods in 10 to 20 years over the UK.

Here’s the latest 850mb temps off the ECMWF

48 hrs (Sat)

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72 hrs (Sun)

96 hrs (Mon) Now that is quite amazing!!

114 hrs (Tues)

Air temperatures during Sunday will widely range from 0 to 3C and by Monday -2 to 1C, factor in any breeze out of the east and wind chills will be lowest of winter, impressive given we’re going to be into the 2nd week of March.

As for nighttime temperatures, we could see lows of -2 to -4C with wind and or cloud but if we manage to see clear skies, temperatures despite a breeze may still manage to get down to -4 to -11C. Clear skies and light enough winds and we would see the coldest night of winter!

Here’s the GFS forecasted 2 metre temperatures for Sunday through Tuesday.

Sunday 12z (12pm) temps

Sunday 18Z (6pm) temps.

Monday 6z (6am) temps

Monday 12Z (12pm) temps

Tuesday 6z (6am) Minimum..

These are expected temperatures from the somewhat more conservative GFS, the ECMWF supports even colder. Notice these are in F, in C readings by night widely drop to between -5 to -7C with pockets nearer -10C.

This end game scenario very much fits my idea all the way back to last autumn when I was building my winter forecast package. The winter of 2009-10 was my primary analog due to similarities in the summer, autumn pattern and similar SST’s, ENSO index, the wet summer and the bias towards a negative NAO signal. I always believed the second half of this winter would be tougher than the front end with February and March outliers with potential to cause trouble and sure enough February has been coldest and we now face a significant March cold blast, one which could be worst in at least 10, perhaps 20 years. March 2010 proved quite wild with severe frosts and snow, lets see if early next week challenges the bitter blast experienced back in March 2010..

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