UK meteorology

Count of Undolpho said:
Hey when you have to keep up with all the intrigue and general shenanigans that goes on in Castle Undolpho you have to be on your toes. Not easy marrying wealthy widows, hounding to their deaths and then attempting to extort wealth from their daughters you know.
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Sounds like something you'd find in a Bram Stoker novel.
 
Count of Undolpho said:
Hey when you have to keep up with all the intrigue and general shenanigans that goes on in Castle Undolpho you have to be on your toes. Not easy marrying wealthy widows, hounding to their deaths and then attempting to extort wealth from their daughters you know.
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Don't tell us ... and then you have breakfast and a close shave !

JohnnyO. o/
 
I must mention that the change in model output for next week has been dramatic over the past 24 hours. It's gone from being a significant cold spell with snow for many to being extremely mild - I would be surprised to see daytime temperatures in the mid-teens in the south.
 
Blademonkey said:
You would or wouldn't?.... Mid teens.
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Sorry BM - that should have been "...wouldn't be surprised..":oops:
Here's the usual post:
Over the next couple of days the weather is relatively simple to sum up. A low is drifting around in the east in the region of the southern Baltic whilst high pressure persists west of Ireland. Ergo the UK is under a cold NW/N airstream with wintry showers, sometimes heavy, along the coasts and in the north whilst the spine remains relatively dry and sunny. Cold everywhere with a widespread frost tomorrow morning.



By Thursday the high pressure has ridged north east across the Faeroes which initiates the low in the east to track south west into Holland and thus veering the surface wind north east which will concentrate the wintry showers (quite likely of snow) along the coast and a little inland. Always the chance of the odd trough or two in the flow to give some more concentrated precipitation periods. As the ridge moves south over the UK Thursday evening and into Friday the showers follow suite and become concentrated in the far south east before dying out on Friday. So a cold week with Thursday probably the coldest day with max temps ranging from 2C-4C (just a guide)



Over the weekend the UK stays under the influence of the eastern quadrant of the high pressure and thus a different airmass to earlier so temps rising to around average and dry for most areas The overall pattern still indicates a split flow out of North America but the high cell in the eastern Atlantic remains dominant for a few days on this run.



The high continues to hang on during the beginning of next week but is coming under extreme pressure from the twin attacks of the upstream energy and by Weds midnight is starting to succumb which results in quite fascinating surface analysis.



Quite surprisingly, leaving aside the fine detail, the ecm is not a million miles from the gfs. Even by T192 the analysis is in the same ball park with the high pressure centred to the south east with the UK in it's NW quadrant with the twin troughs to the NE/SW Thus continuing dry with temps around average until the trough to the west becomes more organized and begins to make inroads.At this end of the run this is, as always, subject to revision.

These evolution's do to some extent support last night's anomalies with the weakening of the ridging north west into Greenland before the transition in the later period and more amplification upstream in North America

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Further to explain why the outputs are shifting, Netweather's chief forecaster has made a rare forum post to explain that, with the jet divided into two different 'arms' - one north of the UK, one south of us, and unusually high pressure over the Pole (a negative AO, or Arctic Oscillation), the models cannot decide how far east of west the blocking high in the Atlantic will be, whether it'll drift over us and then sink south to its usual position over south-eastern Europe, and how much of the currently fairly weak jet stream energy leaving the US east coast heads into the northern arm, and how much into the southern arm. All this is leading the models to swing erratically from one possibility to another, all against the backdrop of an imminent linking between the stratospheric and tropospheric sections of the polar vortex and a likely pattern change in the position of longwaves troughs and ridges due to La Nina. You can see the divided jet over us in the output in his quoted post below:

The meandering southern and northern branches of the split jet stream over N Atlantic sector causing plenty of uncertainty and low confidence with model guidance in the medium range ... because they can't seem to resolve where to place the ridge between the two branches and where the southern and northern arms meet this side of the Atlantic.



GFS blows up lows on the northern arm on the 00z then drops them on the 06z in the same timeframe, and along the southern arm it can't decide how far east to move the lows toward Europe, combine that with cold arctic air being pushed south from the pole by the -AO height pattern developing. It turns into rather a roller coaster of evolutions on each new run!
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chrisbell said:
Further to explain why the outputs are shifting...
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Just to illustrate the point, the second run of the American GFS model for the day has switched back to cold and possibly snowy set-up:
gfsnh-0-264.png

Although these colours aren't showing temperatures (rather, geopotential heights), that is a cold set-up.
 
Does that make any sense? I know it goes partly beyond what I've covered in my 'lecture' posts, but most of it is to do wit the vortex and longwave ridging and troughing of the jet, both of which I've covered (perhaps might be an idea to check back on some of those posts if you're uncertain?)
 
chrisbell said:
Does that make any sense? I know it goes partly beyond what I've covered in my 'lecture' posts, but most of it is to do wit the vortex and longwave ridging and troughing of the jet, both of which I've covered (perhaps might be an idea to check back on some of those posts if you're uncertain?)
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Yes Chris, it makes perfect sense, the weather could go this way or that! Cold or not so cold, have still got my long johns on standby and wellington boots are in use for dog walking as vey wet under foot. :) P.
 
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