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Beast from the East - February/March 2018

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I thought I would start off this thread for people to add information about the Beast From The East this year all in one thread so that it is easily found.

- Jamie

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I was planning on sharing my weather article on the event here tomorrow considering today's was November/December 2010 🙂

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This pic shows what the last BFTE did, that's a road, it's up to a meter deep. One week later!

The drifts were something I don't remember seeing before.

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Some more pics from the event but from Co. Kildare in Ireland - THE place to be for it. So many awesome scenes and so many pics to look at.

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The main cause of the Beast From the East 2018 event was a phenomena called Sudden Stratospheric Warming. 

What is Sudden Stratospheric Warming?

A sudden stratospheric warming is a phenomena where the stratospheric temperatures rise by a very large amount in a short period of time like a couple of days. In a typical Winter, several minor warming events in the stratosphere tend to occur but sometimes, you can get a major warming event here which does not have a pattern or sequence to foretell us when we can expect one. Major warming events have occurred in multiple consecutive years such as 2006 to 2010 but there have been multiple consecutive years without one too such as 1992 to 1998. The contrasts between orography (the study of the formation of mountains) and land sea temperatures cause long Rossby waves in the troposphere (the layer of the atmosphere where weather takes place). The Rossby waves travel upward to the stratosphere and dissipate here which causes the zonal winds to decelerate and warming of the Arctic occurs. 

A major warming event within the stratosphere can either displace, split or obliterate the Polar Vortex. Displacing involves the Polar Vortex going to another location where it would not normally be. Usually, the Polar Vortex lies over the Arctic Circle disallowing cold from filtering down into the mid-latitudes. A split involves the Polar Vortex dividing into two or more vortices with each being in a different location. An obliteration involves the Polar Vortex being non-existent in the stratosphere where the layer is just warm all around with little to no colder than average anomalies being seen. 

Canadian Warming events can occur too. These involve the dramatic rises in stratospheric temperature to occur over Canada rather than the Arctic itself. These kind of stratospheric events tend to take place within the period from mid November to early December but as seen from 2018, they can take place outside of this period.

It takes minimum 9-14 days (approximately 2 weeks) for a tropospheric response from the stratospheric warming to take place usually but can take up to 2 months. For example, the February 1981 SSW was followed by a cold end to April with a snowstorm across England or the January/February 1963 SSW made the 1962-63 severely cold Winter more prolonged into February. It's difficult to say when this response occurs exactly and it's also difficult to say when the effects run out of power because the effects can happen multiple times through the Winter and early Spring season such as in March 2013 following the January 2013 SSW when a cold spell took place from March 10th to 13th with a brief milder shot on the 15th into the 16th. However, another cold spell happened afterwards lasting to the 7th April. It is therefore very important we look out for changes in our usual zonal pattern following a SSW event.

With all the explanation of what a sudden stratospheric warming event is behind us, let's talk about the February 2018 SSW event or should I say, events because remarkably, two SSW events took place during the month. 

On 9 February 2018, two pools of warmer than average temperatures at 10hPa in the stratosphere appeared with one to the southwest of Greenland and the other to the east of Russia. These combined with one another by the latter part of the 10th causing the Polar Vortex to split with one going over the northwest of Canada and the other to the east of Europe. By the 12th and 13th, temperatures in the stratosphere rose by at least +40c with the pool of warm anomalies to the west of Greenland rising to around -8c which is very warm for the stratosphere. These anomalies gradually cooled down somewhat for a few days before another rise took place over Canada on the 17th February. The temperatures here rose even further than the previous warming event mentioned above rising up to a balmy -4c. The first major warming event was a Polar Vortex split which in of itself was unusual because a split has occurred very few times before, two examples of which were January 1985 and January/February 1991. January 1985 was far similar to 2018's one than 1991 and that was followed by a very cold and snowy spell in the middle of the month two weeks after the event had initially occurred. This gave us an indication that something was down the line for our weather after up to that point what had been overall a rather average Winter temperature wise with some cold and mild fluctuations. The second major warming event was a Canadian Warming which has never occurred in February since stratospheric records began in 1951 so was very unusual to see and there was no historical occurrence to base it on what we could expect following it, it had to be nowcasted. As time got closer, it was revealed that the zonal winds reversed a second time which is likely caused by this Canadian Warming but of course with nature, you'll never get a true answer, we can only theorise. The stratosphere took its time for temperatures to go back to average and in fact, we had to wait 'til mid-March for this to happen at 30hPa so the stratosphere was severely disrupted for a very long time meaning the Spring pattern in the Northern Hemisphere was to have a long delay. Zonal wind speeds had reversed to nearly -40 m/s around mid-February and again for a second time near the end of the month. At this time of year, the zonal wind speeds should be around 20 to 30 m/s so this was of huge abnormality. The below chart showing the mean zonal wind speeds at 10hPa in the stratosphere from June 2017 to May 2018 courtesy of Hannah A. Attard reveals just how extreme the zonal wind reversions were - see the huge downward spikes in February. I'd also like to highlight the downward spike in mid-March on the chart. This was followed by the Son of the Beast from 17-19 March which brought more unseasonably cold conditions and heavy snowfalls, especially on the 18th March. However, the spell was not as severe as the Beast From the East because it was shorter and solar radiation was more intense. Therefore, the snow tended to melt quicker. 

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IMG_9443.thumb.JPG.393bcac0e5562283a08502e5fb8b5d23.JPGThis was the first bit of heavy snowfall that actually settled over my town of Herne Bay.

Got around 2cm of snowfall from this one heavy snow shower.

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oh boy, do i have some images for you guys. this is the 28th Feb

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