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Winter 2009 / 2010 in Western Europe?

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Author Topic: Winter 2009 / 2010 in Western Europe?  (Read 27847 times)
martinastro
Martin Mc Kenna
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« Reply #225 on: January 07, 2010, 10:09:21 pm »

19Z Update

UK Remains in a firmly blocked scenario this evening with a major polar trough extension stretching from the Arctic circle to Iberia.  An Omega block of high pressure persists in the Atlantic effectively blocking Atlantic systems from moving towards the UK.   Major North Atlantic Jet is way south nr 40N , where it will remain for the next several days.  The Atlantic ridge disrupting over the next 36hrs and developing a cutoff high nr the Faeroes with a surface inflexion lying from the Faeroes to Scandinavia.  The assoc deep layer trough will perform a complex disruption proces with a deep largely cutoff vortex forming over the Western Med with a trough extending NW towards the UK. a filament of vorticity and a NE Jet Streak coming SW to enhance this block with a new centre forming over NW FRance and heading WNW on Sunday and Monday...   High pressure becoming anchored over Scandinavia with time.  A bitterly cold easterly wind is likely to affect the UK over the weekend making it feel very raw. However with more cloud around the extreme overnight lows will become confined to Scotland.

Discussion

The North Sea vortex has come SW and is currently filling nr SE Kent.  SHowers are continuing to affect areas largely east of the Meridian with some heavy ones coming into Yorks and Kent at present - 2-5cm in places overnight.  Winds mostly offshore across London and the SE at present, however the situation over the next 24hrs becomes more straightforward with a ENE wind becoming established and becoming quite strong with a biting wind chill developing across the South and SE.  This wind allowing North Sea showers to come further inland across the SE, Winds allowing some weak ones to get as far as 1W in the Midlands and CS England, further minor accumulations in places.

Temps are going to become very low in places tonight, though temps in the SE more dependent on cloud and wind than last night - hence likely to be higher than last night. However across Scotland and the North of England winds are very light and temps are plunging. Temps -14C to -18C possible across Scotland tonight.  Whether the Magic Media -20C is breached is another question.

Saturday sees further Snow showers spreading inland across Central and Southern Parts giving another cm in places but more likely a dusting.  The Key theme for Sat is the strong ENE winds and increasing cloud cover giving lots of Snow grains and light snow showers.  It will feel bitterly cold in the East and South with the wind.  Sunnier further north, but bitterly cold.

We still have problems on Sunday and Monday.  The process which develops the potential snow is not straightforward, it seems to relate to an upper air disturbance forming over N France and drifting west, at the same time moisture at 700mbs or so drifts west assoc with frontal activity currently developing in assoc with the Mediterranean low pressure system, the developing upper level trough and low enhances this as it moves West over the South of England and N France.  The Questions are , How extensive, How much and How far north...  The 12Z GFS is less keen (as it generally has been) on much snow developing it has 1-4cm generally between 00Z sunday and 12Z monday across parts of England and Wales (excl the snow showers in the SE tomorrow) a few spots seeing a little more.  However both the UKMO GM and the ECM continue to produce more activity, UKMO having 5-7cm developing by 12Z Monday from East Wales down to CS England and Wessex.  ECM has a few spots with even higher totals.  Therefore confidence on this aspect remains quite low.  Winds easing in the south by Monday.

Into the Middle of next week - there is good agreement on low pressure moving NE towards Ireland and High pressure trenched in over Scandinavia with a very cold low level airmass in place across Britain and much of Northern Europe.  The 12Z GFS breaks this down easily, however its 06Z run didnt and frankly is all over the place with its ensemble after the 13th. The UKMO bring a front into ther SW and then shear it SE but this produces more snow in the SW, Wales  and Wessex with another 5cm in places by T+144. The ECM doesnt get precip much further than the SW before the Scandi High intensifies to over 1040mbs and infact has a 1050mb centre over Sweden by T+240, a easterly / COntinental flow persists across the UK. 

The ECM guidance remains largely consistent along with its ensemble.  It appears to be performing really quite well at the moment and I will be interested in seeing its performance once its resolution is increased even more (to 16KM) at the end of Jan.  It remains the clear leader in last 2 weeks performance stats

Paul Blight
UKww Manager - Education/Warnings
Associate Fellow Royal Meteorological Society
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