NZstorm wrote: ↑Thu 01/03/2018 17:44
I am always amused at the various media explanations to how tornadoes form
A rotating column of wind draws in cloud droplets, making a region of intense low pressure visible. They are formed in the same way as a tornado building around this localised area of intensely low pressure and are typically associated with the formation of cumulonimbus thunderclouds.
It looks like I will have to eat a little humble pie after complaining about the 'hype' circulating about the recent cold spell in late Feb/early March as it did have an effect on a significant minority of the population and continues to do so despite ending a few days ago. The worst of the snow arrived as the month changed to March so I will start a new thread for Spring when I get the chance. Many places in England and Wales remained sub zero from the 26th Feb to 2nd March and most areas saw at least some snow.
Here in Hythe we had a 15 minute heavy snow shower on the afternoon of Tuesday 27th February that left a dusting and most of this persisted through the next day despite some strong sunshine - see photo below.
The final CET for February was 2.9*C (-0.8*C) and the final EWR was just 50mm which is 77% of the monthly average.
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Wednesday 28th February was a particularly cold day over the UK with the highest reported temperature nationwide being just 1.7*C which was recorded in Katesbridge - which is in Co Down, Northern Ireland. There were some very low maximums in all countries with the lowest recorded at Met Office sites being:
England - max of -4.7*C at Spadeadam (Cumbria)
Wales - max of -4.8*C at Lake Vyrnwy (Powys)
Scotland - max of -4.9C at Braemar (Highlands)
Northern Ireland - max of -2.1*C at Killylane (Co Down)
Whilst not national records for the month of February, they are very low for the last day of the month. The maximums listed are for the standard 0900 - 0900 period.
The 28th also delivered the lowest temperatures of the month with -11.7*C recorded at South Farnborough (Hampshire) and -11.4*C at Ravensworth (N Yorks).
The snow that fell in the last three days of February was mostly in the form of showers which developed as the cold air from the continent crossed over a much warmer North Sea (SST's around 6-8*C). Some of these showers formed in bands (due to local convergence) so that certain places in the east received frequent showers and a decent covering of snow, whilst places only a few miles away got next to nothing - and obviously the orientation of the windflow dictated the position of these snow bands. As an example, in the ENE wind on Wednesday 28th February a band of snow showers persisted along the entire length of the English Channel for the whole day with nearly all the snow falling into the sea. The line did have subtle changes in orientation and this gave a decent snowfall to the Channel Islands and parts of the far SW of England including the Scilly Isles.
The worst affected areas (from the snowfall) were limited to the east of the UK (apart from the areas mentioned above) with parts of East Anglia and SE + NE England seeing the greatest snow depths. Some places recorded level depths up to 25cm by the 28th Feb, although drifting was making some of these measurements difficult in more northern areas. The snow was falling at temperatures between -2*C and -5*C so was dry and powdery. The link below gives an idea of the snowfall in parts of East Anglia:
February turned out to be a colder than average month despite being on the mild side for much of the time. The intense cold in the last few days dragged the average down sufficiently to turn the anomaly negative. It was also drier than average.
The winter (Dec, Jan, Feb) as a whole was a little colder than average and a little drier than average. The interesting statistic is that it was evidently the second sunniest winter on record since such records began in 1929 - it was just a little less sunny than 2015 evidently. I am not sure how much of this is fact or more to do with the change to electronic sensors from the old Campbell-Stokes glass balls. The Met Office have provided the usual stats for both February + the winter in the link below.
The funnel cloud video is an interesting one. A number of sightings were reported and based on the comments made by these observers and radar images from the day, it appears that the funnel ran along the coastline to the south of the town of Brixham in the NE to ENE flow. It was also observed from the town of Paignton, which is a little further to the north. There are no confirmed reports of ground contact so it has been classified as a funnel cloud, but it could have been either a tornado or waterspout or indeed both depending on how close to the coast it was. It is certainly unusual for a funnel cloud to be observed when the air temperature was around freezing point, but the much warmer seas in the English Channel may be an important ingredient. Similar phenomena have been observed on the Great Lakes during lake effect snow events.
Simon Culling wrote: ↑Sat 17/03/2018 00:15
The funnel cloud video is an interesting one. A number of sightings were reported and based on the comments made by these observers and radar images from the day, it appears that the funnel ran along the coastline to the south of the town of Brixham in the NE to ENE flow. It was also observed from the town of Paignton, which is a little further to the north. There are no confirmed reports of ground contact so it has been classified as a funnel cloud, but it could have been either a tornado or waterspout or indeed both depending on how close to the coast it was. It is certainly unusual for a funnel cloud to be observed when the air temperature was around freezing point, but the much warmer seas in the English Channel may be an important ingredient. Similar phenomena have been observed on the Great Lakes during lake effect snow events.
Yes, it was interesting to see a funnel cloud reported in such a cold environment. Almost certainly a waterspout as there is no heat source over land in February. There would have been a surface boundary along the coast to generate the vorticity.
Thanks for the soundings link, NZstorm. I was not aware of this site and to have forecast soundings for about 10 locations in the UK will be very useful.
With regard to the funnel cloud, as you have said it is much more likely to have formed over the warm (relatively) coastal waters of the English Channel which would have had an SST of around 7/8*C at this time, although the water close to the coast would have been a little cooler. It is a pity that no observations from that coastal strip have been reported - although the weather was not good at the time with heavy snow showers, a 25mph+ ENE wind and a temperature just south of 0*C.
The Met Office have produced an excellent summary of the cold spell in late Feb/early March, and it can be viewed here:
Some low thickness levels were recorded at the end of February over all of the UK and the attached sounding for Herstmonceux (on the Sussex coast in southern England) is for 00:00GMT on Wednesday 28th February and it shows a thickness level of just 508 DAM. Maps for the rest of Europe show the locus of this cold pool to be over southern Sweden at this time where the thickness is shown at 498 DAM.
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