It may be the first day of astronomical spring but it’s anything but spring-like. Amazing how opposite this is compared to last year on both sides of the Atlantic (see yesterday’s post), in fact I am seeing some tweets making mention that the UK’s long standing Central England Temperature or CET which combines the temperature for all of Britain is running below that of January and January was below normal! Now that is pretty impressive.There are two main reasons for this cold. One the -NAO which has directed the cold from Scandinavia towards the UK but with an unusually deep negative AO (which drives arctic air out of the polar region into the mid-latitudes), this has aided in bringing mid-winter level cold our way. According to Dr Jeff Masters, the Arctic Oscillation has reached a value of -5.2 today (March 20) which in fact is the second lowest March value since records began back in 1948. This explains a lot as to why we’re so chilly and with a significant recovery needed, the cold isn’t going anywhere despite the time of year.

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I certainly don’t see any milder weather through the rest of this month and it may take well into April before the NAO/AO returns to neutral or positive. Once that happen, expect spring to arrive.As forecasted back at the weekend, following a very snowy and disruptive first half to the week, conditions are settling with a cold surface high building in before a system tries to spread moisture into Irekland and eventually the UK on Friday. As the coldest air aloft slides over the deep and widespread Scottish snowcover, clearing skies and light winds tonight promises for a bitterly cold late March night, we may take another run at the coldest temperature of the winter. Back last week Aboyne, Aberdeenshire hit -13C and while the BBC are shooting for -10C, with a more expansive and deeper snowpack, I think it’s possible to see just as cold again tonight with towns a cities dipping to between -2 and -5C despite a lack of snow but where there’s snow, expect -8C or lower IF it’s clear.

Here’s the GFS surface chart for tonight. Note the lack of moisture overhead with the 522 thickness line mainly south of Scotland.

Here’s the 850mb temps for tonight.

Note the -10 to -15C line covers the deep snowpack across Grampian and Aberdeenshire, this is most likely to see where the coldest surface temperatures tonight, again if skies are clear.

As for Friday, a ton of mositure associated with an Atlantic frontal system will spread in from the southwest affecting Ireland and then Devon and Cornwall before sweeping across much of the UK. While heavy rains impact Ireland and south and southwest England and South Wales, expect snow to break out further north.

Here’s the surface and precip chart at 42 hrs.

Here’s the latest GFS snow projections through 72 hrs (Saturday), overdone, maybe but we could see a significant snow event, a 4th in 10 days for the UK.

What About Next Week?

The one good aspect about next week’s forecast is that our pattern appears to calm down in terms of storminess, however the cold continental air mass remains strong, in fact we may have an even colder air mass in place next week compared to what we have just now. So with higher pressure supporting sunnier skies and daytime surface temperatures responding nicely to the late March sun, nights however look bitterly cold with hard to severe frosts likely to continue.

Here’s the latest ECMWF upper chart and 850 temps through next week.

Sun

Tue

Thur

Sat

Here’s the latest AO ensemble and you can see how deeply negative it really is.. note the spite back to positive at the beginning of April, if this happen then there’s your break in this pattern with spring’s arrival!

As stated already, there doesn’t appear to be any warmth on the way through at least the remainder of March into April. This most certainly means a cold first half of spring but this is the kind of pattern which can flip quick and so it wouldn’t surprise me if we see a sharp incline with both NAO/AO with a decent warm-up come mid to late April for both the UK and USA.

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Tags: arctic oscillation, march cold, UK March cold