UK meteorology

Blademonkey said:
Dull and damp, all good things come to an end! :(
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Possibly quite showery tomorrow in the unstable airmass behind the fronts, on particular if we have any diurnal heating of the ground from sunlight which warms the boundary layer (first few dozens of metres of the air column) and thereby makes it buoyant.

On a not unrelated subject, though I am by no means knowledgeable in physics (I'm mathematically inept if nothing else), I do enjoy the Youtube channels fron Nottingham University, including the channel devoted to physics, and I thought I'd embed a new video of theirs on thunderstorm formation:
 
chrisbell said:
Possibly quite showery tomorrow in the unstable airmass behind the fronts, on particular if we have any diurnal heating of the ground from sunlight which warms the boundary layer (first few dozens of metres of the air column) and thereby makes it buoyant.
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To the above point, here's tomorrow's forecast FAX, with the low still to the west of the UK and troughs in the cool, unstable north-westerly airmass:
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Malcolm has posted a short analysis of the GEFS (American) and EPS (European) anomalies:
Last night's NOAA and this morning's GEFS and EPS medium term anomalies indicate quite an amplified pattern.

Upstream low pressure over the Arctic, ridging western North America and a quite intense vortex northern Canada with associated trough negatively inclined across Iceland/UK/ western Europe all the way down to north Africa, This trough complimented by high pressure in south east Europe ridging north west through Scandinavia.

Thus, although there is quite a strong westerly upper flow leaving North America south of the vortex, and around the Atlantic high pressure, it hits the buffers in the eastern Atlantic when it meets the aforementioned trough/ridge axis.and diverges tending to leave the UK in a weak W/SW upper flow. This portends a quite complex and slow moving evolution dominated by a slack low pressure area in the vicinity of the UK, thus changeable weather, with temps a little below average but perhaps creeping up towards the end of the period as the trough weakens. As always the det. runs will need to sort the details of all of this.

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Another short post that is of particular interest to me from a regional perspective:
Interesting to note that the METO have issued a heavy rain warning for East Anglia and SE England Sunday evening through Monday.

Saturday midday there is a neutrally aligned upper trough just to the west of the UK coming under some pressure from the Bermuda high ridging to the west. Thus on the surface the UK in a very slack gradient with low pressure concentrated to the south.



The trough comes under further pressure over the next 24 hours and starts to realign south of the UK thus the surface low and associated fronts become more organized and start tracking NE though France.into the southern North Sea.



This realigning of the upper trough and development of the Surface low continues through Monday



Obviously what is crucial here is the precise track of the low and fronts and in view of the warning may well be close enough. I'll post yesterday evening's fax charts but again obviously need to see today's updates.

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Malcolm's thoughts for the 27th:
Today

A very wet day for England and Wales as the low and associated fronts tractkeast across southern England before clearing into the North Sea later tonight. Elsewhere across N. Ireland and Scotland, and even northern England isolated showers, perhaps thundery.



Saturday

Cloudy and quite cool across central and eastern England with patchy rain whilst brighter elsewhere with isolated showers in the light winds. The neutrally aligned upper trough to the west stretching a fair way south and is about to play an important role over the next couple of days.



Sunday

A generally dry day but the upper trough is being realigned as it comes under pressure from the high pressure ridging to the west and the block to the east and it spawns a surface low over France which is becoming a major feature by 1800.and is developing rapidly as it moves north into the North Sea. The key here is how far west will it track as it is accompanied by heavy rain and quite likely northerly gales.





Similar theme through Monday before the low moves east so certainly quite a cool and wet period for eastern and south eastern areas with even the possibility of some snow on the higher ground in the south. But just to repeat this is according to the gfs and there is still some uncertainty about how far west it will track


Continuing uncertainty with the track of the low Monday with the ecm keeping central Channel longer and the front running straight up the country.

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FAX chart:

1 - Developing occlusion associated with surface low over southern UK
2 - Triple point, where cold front catches-up wityh the warm front and occludes as in the Norwegian Cyclone Model
3 - Upper cold front
4 - Developing low in base of longwave trough, though this won't affect us
5 - More lows forming in eastern Canada as part of the vortex, which may be strong enough to flatten any ridging of the Azores high.
 

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Malcolm's post for 29th part 1:
Today

Sunshine and showers in the north whilst cloudy with patchy rain/drizzle in the south but more particular in central and eastern areas. But by early evening more persistent rain will have reached the far south east from the wave that has formed over France and is moving NNE.





Overnight and through Monday the low and associated fronts will continue to track into the North Sea with a fair amount of rain falling south east of a line Hull-Portsmouth accompanied by strong winds, gale force along the coast in exposed areas, There still remains some doubt on how far west the rain will spread (these charts are simply the WRF take on it) and there is also the possibility of some wet snow on the higher ground





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Part 2:
Tuesday should be not too bad with sunny intervals and showers but the next frontal system, courtesy of the upper trough swinging round the Atlantic ridge, is approaching western Ireland by 1200 and continues east through the afternoon and evening affecting western areas by 00z



Wednesday portends to be quite a wet and windy day as the front moves SE across the country clearing the far south east by 1800. Behind the front sunny intervals and showers. Worth pausing here I feel to take a quick look at the 850mb temp distribution (different airmasses) and the upstream energy flows because as far as I can see it's down to the interaction and phasing of these that is going to dictate th weather over the weekend.





So keeping this in mind Thursday tending towards a N/S split, quite windy with showers in the north, drier and sunnier in the south

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Malcolm has posted something shorter today than normal:
Once the low has cleared east overnight tomorrow will not be a bad day, dry and quite sunny, for most but active frontal systems are rapidly approaching from the west and by 1800 are already impacting Ireland and the Western Isles with a freshening wind and rain. A welcome contrast from today in the south east.



The front and rain traverse the country on Wednesday but quite slow to clear the south east, as a ridge pushes north east in it;s wake introducing drier weather.



But this ridging north east towards the intensifying European high pressure to the east is still relatively fragile under continuing pressure from the energy exiting North America so although the southern half of the UK is tending dry and warmer over the next couple of days the far north west remains unsettled and cooler. Albeit this is relative and generally the temps are on the up.







Need to leave it there but to put it in a fuller context this morning's 2-7 GEFS anomalies. (and a reminder of course that this just the GFS.

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