UK meteorology

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chrisbell
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Part 2:
Wednesday sees the start of the transition with developments in the western Atlantic but the immediate effect closer to home is to realign our high cell which becomes more influential, thus winds abating in the north and resulting in a generally fine day with sunny intervals and relatively warm. Still some patchy rain across the west coast of Scotland





By Thursday the transition is well underway with the trough over the eastern seaboard initiating rapid amplification of the subtropical high in the western Atlantic which in turn facilitates the trough and cold air to plunge south to the north of Scotland. So that by midday the cold front is just about across the north coast of Scotland. Thus rain will spread down the west coast and to N. Ireland during the afternoon whilst the rest of the country again remains dry with sunny intervals.








Overnight and through Friday the cold front will track south reaching the south by the afternoon leaving in it's wake much colder air in a very strong northerly wind which could touch gale force in the north and north east. In this very unstable air frequent heavy showers will develop which will be wintry in the north with snow on the high ground and possible even at low levels. It goes without saying it will feel very cold.








And the NH profile at T120 sums it all up


 
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chrisbell
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Malcolm's view on Saturday 27th part 1:
Changeable weather over the next few days with temps remaining below average

The 500mb and surface analysis for midnight

Squally showers overnight, of snow over the high ground in Scotland but rain and rain/hail in the N. Ireland and and coastal regions of Wales and England. Note the Pembroke Dangler in the south west. These will tend to die out over N Ireland and Scotland during the day and become more concentrated along the east, south east coasts and central southern England as the wind veers somewhat. Elsewhere after a very frosty start very crisp and sunny but feeling very cold.




Showers continuing in the east overnight as the wind also continues to veer with the ridge edging across in the north. A widespread frost by morning

The ridge becomes more influential through Sunday but still very breezy in the south and once again showers of rain/hail. possibly some sleet, concentrated over eastern regions. Another very cold day but generally the wind has abated so less wind chill
 
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chrisbell
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Part 2:
By Monday the changes that have been mentioned in previous posts are underway with the amplification of the subtropical high in the western Atlantic forcing the next upper trough south east that also serves to reinforce the European ridge to the east of the UK At the same time activating the low pressure to the south where a wave has formed on our old front over south east France. All of which results in calm and bright, but still cold, day for most with a few showers lingering along the east coast.





By Tuesday both troughs are caught in the pincer movement of the amplifying ridges and thus any longitudinal movement ceases resulting in the aforementioned wave over France, deepening and tracking north into the southern North Sea. This will bring strong winds and possibly heavy rain to eastern regions but, obviously, the precise track of the low is the key to the extent of this.Whilst this going on elsewhere another dry and cold day after a frosty start





By Wednesday the North Sea low has filled and tracked north to be off the Norwegian coast and the Atlantic trough has taken closer order with a slack low pressure area to the south west and a waggly front up the Irish Sea. All resulting in patchy rain/showers in the west and dry with sunny intervals elsewhere and still cold





And the NH profile at T120


 
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chrisbell
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New chap doing relatively frequent short-range posts in the Netweather forum (he's actuslly one of the moderating team):
The 12z models showing fairly good agreement in the general evolution out to T168hrs.

As posted in the short term thread we see that small but quite active low over Scotland whip down the north sea early next week and showing over the low countries by Tuesday .This bringing quite a cold northerly in it's rear.

GFS chart T120hrs



Some snowfall probably over the far north and can't be ruled out over higher levels towards the east as the winds turn on shore mid-week although most will just see an unpleasant spell of chilly rain.

The general idea is the high starts then to topple and recede south west as the jet goes over the top and cuts back into Europe.This turns the quite cold flow to north east and then east and then the winds drop off as the high settles across the UK again.

Temperatures after recovering a little around this week end fall off again as the polar air moves south early next week and will likely remain just below or around average.

We are pretty close to a really good northerly early next week but the high is wobbling around just too close and again the coldest plunge goes into Europe.

T168hrs



The ongoing trend of further cold air driving south through the Scandi.trough continues to top up the European cold pool. We are starting to see the cut back of the jet under the block which was not apparent a couple of days ago so these are trends to watch to enable the UK to turn properly cold instead of being on the periphery.
 
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chrisbell
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Back to Malcolm's posts:
Outlook - Unsettled, quite windy at times, and becoming colder as the influence of the high cell wanes
The NH 500mb and surface analysis for midnight and the 0500 surface chart.

A cloudy and mild start to the day with some patchy rain around central England and Wales at the moment as the cold front continues to drift south during the morning. Further north frequent showers over western Scotland. But more persistent rain will arrive here, and to regions a little further south, by late morning and track east through the afternoon, albeit becoming intermittent, courtesy of the warm front associated with the system tracking rapidly east from southern Greenland, Still mild but becoming quite windy in Scotland.

The rain will then pep up over Scotland through the evening and then further south as the triple point passes close by and the cold front starts tracking south east. Meanwhile the rest of the country stays cloudy, but mild, in the warm sector.

Through Sunday the cold front will continue to track south thus essentially splitting the country with cloudy warmer air south of it and windier with some heavy showers in the north as the wind veers more northerly introducing much cooler air.
 
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chrisbell
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Part 2:
Overnight the cold front quickly clears the south coast so Monday a much quieter day, cloudy with perhaps some sunny intervals, but much less wind as wind courtesy of a transient ridge. But by early evening patchy rain will start effecting western regions as a warm front, associated with a another low near the southern tip of Greenland, edges east.



Some light patchy rain/drizzle on Tuesday as the weakening warm front crosses the country but very mild in the warm sector.The one slight complication is the cold front waves a tad so perhaps some more persistent rain over Scotland for a time



On Wednesday the subtropical high amplifies in mid Atlantic which diverts the little complex frontal structure south east over Scotland which will track south during the day bringing patchy rain to most areas with snow on the high ground in Scotland. At the same time introducing cooler air once again as the wind veers.



And the NH profile for T120

 
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chrisbell
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Today's posts from Malcolm, as a colder, polar airmass arrives:
Part 1
Outlook - the colder weather has arrived and will stick around a while

The NH 500mb and surface analysis for midnight





As can be seen, the colder air has arrived everywhere apart from the far south where the cold front is just clearing.with some rain still around. So a frosty and cold start to the day with some showers along north and eastern regions which could be of snow. These will hang around during the day but the wind will ease as the ridge moves in leaving a sunny and cold day in most places.



The showers will die out during the evening leaving a clear and cold night with a widespread frost by morning. But by 06 cloud and rain from the approaching occlusion will be effecting western regions



The front will edge east through Friday along with the precipitation which will be a mix of rain, sleet and snow, the latter more prevalent on the higher ground but perhaps lower as well in north western regions. Another cold day.





The weakening front will continue to edge east overnight Friday and through saturday so patchy rain around, still likely to be of snow on the high ground, but slightly less cold

 
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chrisbell
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Part 2:
But overnight Saturday and through Sunday an occlusion associated with a shallow low around Iceland has tracked south east and this will bring some wintry showers with, particularly in the north west. At the same time an eye must be kept on developments to the west and a major trough has tracked east from Canada and is around the tip of Greenland.



The trough tracks east overnight and by 12 Monday the associated fronts are approaching north west Scotland and by evening a belt of rain will be effecting northern and western regions, likely snow over the higher ground in Scotland, as the front(s) track south east



And the NH profile for T120

 
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chrisbell
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Malcolm's post for today part 1:
Outlook - remaining cold and unsettled

The 500mn and surface analysis for midnight and the 0300 surface chart



There is a widespread, quite severe, frost this morning which lead on to a sunny and cold day in eastern regions. But a belt of rain associated with the occlusion is already effecting N. Ireland and south west Wales and England. This will track east during the day with perhaps some snow flurries on the moors in the south west but more likely on the higher ground in Wales and the north west of England



Through this evening and overnight the patchy rain, sleet and snow will spread to all areas except norther Scotland , the snow more likely in the north, so not as cold tomorrow morning as today.



 
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OP
chrisbell
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Location
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Part 2:
This is pretty much the story for Saturday with norther Scotland remaining cold and dry but the main area of the rain will move east but some heavy showers will spring up behind which could be heavy in the south west



This frontal system will clear over night Saturday but a cold front associated with a low tracking north of Iceland will move south east down the country on Sunday giving some snow on the high ground in Scotland but patchy rain further south as it weakens.



On Monday , after a quiet start to the day, it will become increasingly windy with gales in exposed areas and heavy rain and snow (mainly in the Scotland) will spread south east on a cold front associated with a complex low over Iceland



This situation continues through Monday evening and early Tuesday but from this point the scenario becomes more complex as the the subtropical high pressure amplifies in mid Atlantic and the filling trough is forced down across the UK as the cold front slips into the North Sea. And this is all connected to the trough tracking up the east coast of the US. There are still doubts about how this will precisely pan out.





And the NH profile at T120

 
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