April 2021 will go down as a notably cold and potentially record dry month, all thanks to a very stubborn, stuck blocked pattern. It’s the persistency in the chill and rain starved pattern that’s been very impressive. Dry April’s aren’t uncommon for the UK but a cold, dry April is. The chill came is two forms, firstly, the blast of arctic air then chilly high pressure. While it’s been a month of relentless overnight frosts, days have gradually warmed.
The below visible satellite image from April 5th clearly shows the potent polar front and ‘cloud streets’, (representative of pure arctic air) sweeping south over the UK behind it.
April 2021 Highlights (as of 28th)
On April 5, as bitter arctic air swept south, the air at 850mb above Keflavik Airport, Iceland measured -20.5C. Said to be the coldest air at this level and location during April since 1968.
The 505dam thickness value crossed Lerwick, Shetland. This was the lowest thickness to pass over British airspace which the arrival of the record breaking Beast from the East on February 28, 2018.
During the arctic outbreak between April 2nd-10th, frequent snowfall and accumulation occurred for many.
This was the view out of my bedroom window in Invergordon, Ross-shire at around 5pm on April 9.
The depth of snow observed in Lancashire this morning would be impressive even in mid winter never mind April! https://t.co/jkeIFjidP0
— MarkVoganWeather.com (@MarkVogan) April 11, 2021
On April 6, just a week after recording an all-time March high of 24.8C, Beauvais, France plummeted to -6.9C, setting a new April record low.
Impressive freezing temperatures in #Italy in which is undoubtedly the coldest spell ever recorded in April. Temperatures plunged to near -10C in Tuscany and Umbria Regions at 200m-300m of elevations smashing monthly records by wide margins. pic.twitter.com/oxgQkX4U7A
— Extreme Temperatures Around The World (@extremetemps) April 9, 2021
On April 6, Loch Glascarnoch, Ross-shire only managed to reach 0.7C for a maximum.
The below image is of my car beside the village of Evanton, Ross-shire (beside the Cromarty Firth) on the morning of April 6.
On the morning of April 7, a low of -7.5C occured at Benson, Oxfordshire which was England’s lowest April minimum since 2013, this was later broken several times.
The -9.4C minimum recorded at Tulloch Bridge, Highland was the UK’s lowest April reading since 2013. The -9.4C is not only the UK’s coldest for April since 2013 but a joint daily record low with 1958! Also UK’s first daily record low since 2013 also.
We've just had our coldest April morning on record in Bishopton, Isle of Harris, Tyndrum, Strathallan and Islay. Lowest temperature last night was -9.4C at Tulloch Bridge – extreme, but still a bit off the all-time April record of -15.4C recorded in 1917 in Dumfries and Galloway. pic.twitter.com/PHGaj3ixJ6
— Sean Batty (@SeanBattyTV) April 12, 2021
For the first 17 straight morning’s of April, Loch Glascarnoch, Ross-shire recorded 0C or lower.
Aboyne, Aberdeenshire observed 18 straight morning of 0C or lower between March 31-April 17th.
Diurnal swing of 22.2C at Aboyne yesterday. From -7.3 to 14.9.
— MarkVoganWeather.com (@MarkVogan) April 17, 2021
On April 5, Slovenia set a new national April record with a minimum of -20.6C at Novi Vasi na Blokah. This surpasses the previous national record of -20.4C set in 1956.
10cm of snow in Belgrade this morning, which is new RECORD for the month of April, station operates since 1888! Previous record was 7cm achieved in both 1996 and 1997.
Few photos this morning from northern suburb of Belgrade (lowest area of city), so less snow here. pic.twitter.com/DyRfdovV0e— Milos Milic (@skomimaster) April 7, 2021
So Far Germany Seeing COLDEST APRIL IN 104 YEARS, Second Coldest Since 1881, Snowiest Since 1986 https://t.co/0RDAU8hLwx
— Pierre L. Gosselin (@NoTricksZone) April 18, 2021
Europe temperature anomaly through April 25.
As of 28th, the Met Office has declared that April 2021 has been the ‘frostiest’ since records began back in 1960 with an average of 13 air frosts for the UK, surpassing the previous record of 11 set in 1970.
Current provisional frost figures across the UK in April (days):
UK – 13
England – 12
Southern England – 11
Northern England – 14
Wales – 11
Scotland – 16
Northern Ireland – 8
The full weather statistics for April 2021 will be available at the end of the month.
Here is the temperature departure from normal throughout the UK and Ireland as of April 26. These are impressive values given this represents almost the entire month and usually the 2nd half to a cold start is much warmer and often washes out any significant negative departures.
While low pressure sinks south over the UK today and tomorrow bringing some rain, several sites remain absent of measurable rainfall since the end of March and could go through the entire month of April without anything.
Here are the rain departures as of April 26.
Seriously dry so far this month, with no county seeing more than 7mm of rain. Here are the @metoffice stats for the 1-21 April @itvwestcountry pic.twitter.com/tQr4YPPrER
— ITV – Charlie Powell (@ITVCharlieP) April 23, 2021
Turning colder
The current low tracking south will introduce colder air again and through the final few days of the month, may push the monthly mean temperature anomaly down a bit.
GFS has snow return next 72 hours over the Cairngorm Plateau.
More places next 240 hours.
The GFS ensemble is adament and has been for a solid week or so that the opening 1-2 weeks of May are on the chilly side. In fact if the model is correct and I believe it is, we may have a very cool 1st half to May or indeed May overall.
Well well well, look what the CFSv2 has for the month. Not often you see the CFSv2 showing a colder-than-normal month!
A chilly May makes sense given the amplification of the MJO through phases 1 and 2.
This amplification of the MJO in favorable phases along with ‘late’ final stratospheric warming should help reinforce the already developing -A0/NAO pattern.
The final stratospheric warming now looks likely to take place tomorrow, according to the GFS – with 10 hPa 60°N zonal-mean winds switching to easterlies once more, and the Arctic stratosphere becoming dominated by the summertime anticyclone. pic.twitter.com/sB0PU1np5h
— Simon Lee (@SimonLeeWx) April 25, 2021
The models show a textbook Greenland block and twin troughs either side, although the CFSv2 doesn’t see an eastern US trough. This may correct.
This May is going to be interesting in terms of rainfall as well as potential chill. Remember back to last spring, both April and May were dry and RECORD sunny. Unlike this year SO FAR, both April and May 2020 wound up warmer than average thanks to surges of summer heat. But let’s not forget the spells of cool too, it’s just the heat far outweighed the cool.
Warmth is something you’d kind of expect if you get a record sunny as well as dry month. This spring may be dry but COLD if modelling and my hunch bares fruit.
SUMMER FORECAST COMING UP SOON, STAY TUNED!!
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