Two polar opposite ends to winter - 2018 and 2019
When I am writing this post in February 2022, it will have been the fourth anniversary of the 'Beast from the East' from 2018 and the third anniversary of the exceptional warm period from February 2019. These aren't particularly special anniversaries by any means but due to interest, I thought a blog looking at and comparing the two periods would be intriguing to some. We can get years contrasting with one another in different weather regimes and extremes from time to time in the UK & Ireland. Some examples that come to mind are March 2012 and March 2013, Christmas 2010 and Christmas 2011 as well as July 2006 and July 2007. However, one of the most extreme and notable examples of this happening was by far the change from February 2018 to February 2019. These periods were textbook polar opposites of each other. One was severely cold and the other was exceptionally mild and even warm for the time of year.
Before directly comparing the two, let's give a brief overview of the periods in question.
The 'Beast from the East' as dubbed by the mainstream media, whilst being a term known for years and used in previous periods such as the failed December 2012 easterly, was a period of severely cold and snowy weather at the end of February and beginning of March 2018. This was brought in by unusually cold polar continental air via easterly winds and a massive Scandinavian anticyclone named Anticyclone Harmut by the University of Berlin as part of Adopt-a-Vortex. A major sudden stratospheric warming occurred on 12th February 2018 and the zonal mean zonal winds at 60N 10hPa in the stratosphere reversed to an extreme level with a perfect split of the stratospheric polar vortex at its roots and was ideal to providing extreme cold to Eurasia. This indeed was what followed with a very quick tropospheric response by only 10 days later when we seen the first signs of pressure rising over Scandinavia developing into a proper anticyclone and the winds became easterly by the 23rd February in the UK and Ireland. At this time, forecasts were becoming more certain that we were going to get a direct hit from the easterly whilst on previous days, models like the ECMWF were persistently predicting that high pressure to the north would be too far south for a direct hit. The BBC were very conservative with a cold week ahead being forecast with a couple of wintry showers. Met Éireann issued its first advisory on the 23rd of some very notable wintery weather to come and be prepared. The severe continental air reached eastern parts of England later on the 25th February and the first snow showers appeared. Showers became more widespread each day and by the 28th, there was plenty that kept coming and going before Storm Emma approached from the southwest on 1st March. Record low maximum temperatures were set on the 28th February and 1st March. Storm Emma brought deep drifting to the southwest of the UK and south/SE regions of Ireland with the biggest snowfalls here since 1982 being achieved. For the time of year, 2018 brought the coldest weather since 1785 according to the long-term Central England Temperature series.
Although less benign by comparison in terms of impacts, the end of February 2019 was equally or even more remarkable than 2018. Very mild southerly to southeasterly winds along with long spells of unbroken sunshine allowed temperatures by day to respond highly during the final week of February 2019. Daily and national records in the UK were being broken left right and centre from the 21st. 25th February 2019 was the first time in recorded history that 20°C has been achieved in meteorological winter in the UK and was 2 weeks earlier than the prior earliest 20°C. 26th February meanwhile seen the first 21°C and 21.2°C at Kew Gardens on this day is over 1.5°C higher than the previous February record. Initially, nights were very mild especially in the north setting a record for February high minimum in Scotland on the 23rd with a cloudy tropical maritime southwesterly airflow. However, with the unbroken clear skies and light winds, nights were relatively chilly during the warmest part of the spell so daily mean temperatures weren't exceptionally high and February 2019 whilst a very mild month wasn't as mild as February 1998. The mean maximum temperature for February 2019 however was the warmest on record - UK monthly mean temperatures go back to 1884.
Compared to 2018, the February 2019 spell was likely aided by a sudden stratospheric cooling event that occurred through February and March 2019. There had been a major sudden stratospheric warming event with a reversal in early January 2019 but impacts from it were negligible in the UK and Ireland.
The graph below compares daily UK mean temperatures for February and March 2018 and 2019. Data is courtesy of the Met Office and has been collated from Starlings Roost Weather. Using this data, 1st March 2018 and 2019 had a mean temperature difference of 11.0°C whilst both 28th February and 2nd March had a difference of 10.0°C.
Let's take this comparison a step further by comparing the daily mean maximum temperatures (see second graph). In this instance, the mean maximum temperature between 26th February 2018 and 2019 is as much as 14.0°C whilst 27th February difference is 13.4°C. Each day between 25th February and 2nd March inclusive has a mean maximum temperature difference of at least 10°C between 2018 and 2019. The national mean maximum temperature for 28th February 2018 was only -2.0°C whilst 26th February 2019 was 16.1°C - the coldest and warmest days of their respective periods. Both periods were opposite ends of the spectrum in terms of how extreme they were for mean temperature.
Here is an overview of the maximum temperatures across the UK and Ireland on 28th February 2018 and 26th February 2019, maps via Starlings Roost Weather. 28th February 2018 featured widespread ice day conditions across both isles whilst 26th February 2019 had maximum temperatures widely in the mid to high teens and even the low 20s locally including the prior mentioned record maximum temperature of 21.2°C in Kew Gardens.
The maximum temperature did not rise above -4.7°C at Tredegar (Gwent) on 1st March 2018 which was a new national low maximum temperature record for the UK beating -4.6°C at Cassley (Sutherland) on 2nd March 2001. Ireland had its first observed March ice days in a digitised series since 1942 with Cork Airport not getting above -1.7°C all day on 1st March. Although very elevated and exposed, Cairngorm had a maximum temperature of -13.1°C on the 28th February which combined with the windchill from the easterly wind here gave a feels-like temperature of -30°C! Even for Cairngorm, this is exceptional. Most places had their first ice days since early 2013 or December 2010.
What's probably most unbelievable though is that in terms of daily mean maximum temperature, 28th February 2018 was the UK's coldest day since December 1995! It was colder than any day in 2010. However, in December 2010, very low maximum temperatures lasted for at least a week compared to only a few days in 2018 so they're not 1:1 comparable. Daily mean maximum temperature records go back to 1960 and it was the coldest February day in the series. Mind that this is a national mean and does not account for regional variation where say February 1991 might have colder maximum temperatures in the southeast of England for example.
The table below shows the temperature records set in the UK during the February 2019 spell. Not only did the UK and England set a maximum temperature record for February and winter, Wales and Scotland also seen their highest February temperature on record. Scotland set a new high minimum temperature record too for the UK. Scotland's maximum temperature record broke a record from all the way back in February 1897 whilst the others were more recent in either February 1990 or 1998. How recent the prior record was shouldn't take away from the exceptional nature of this spell however especially given the fact how much the February 2019 spell deviated from previous record warm February spells.
In Ireland, some station records were set but the national record of 18.1°C at Phoenix Park (Co. Dublin) from February 1891 stayed intact with February 2012's 18.0°C at Cahore (Co. Wexford) being the closest the country has come to breaking the record. The country's highest in 2019 was 17.6°C at Delphi Lodge (Co. Mayo) on the 25th.
There is no doubt that both the February 2018 and 2019 spells were remarkable and will be remembered for many more years to come. Both provided exceptional weather for the UK and Ireland for the time of year. One was severely cold and snowy whilst the other was more benign for impacts besides some local wildfires but statistically was phenomenal for high maximum temperatures. For year to year contrasts in the UK and Ireland, it doesn't get more textbook than late February 2018 and 2019.