UK meteorology

The Global Wind Map is interesting today - a clear separation running across the UK.
That's at 1000hPa (approximately ground level) and 850hPa (lower troposphere) - if you set it to 500hPa (upper troposphere, where the Jet lies) that apparent separation disappears, and the strong zonal jet becomes evident.
 
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Risk maps for Doris from Netweather:
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Yay @ Chris ... Now those illustrations I appreciate ! Not only do they make sense, but, best of all, for oncey Dumbarton is clear of the projected worst hit areas. Way to go.

JohnnyO. o/
I've not seen them very often from the Netweather forecasters before. Unfortunately, I'm under the centre of the eastern end of the highest wind risk area...:eek:
 
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New amber warning for snow from the Met Office:
Issued at: 21:07 on Wed 22 Feb 2017

Valid from: 02:00 on Thu 23 Feb 2017

Valid to: 18:00 on Thu 23 Feb 2017

Heavy snow is expected on Thursday. Local accumulations at low levels of around 3 cm are possible, but accumulations of 10 to 20 cm above around 100 metres are likely, with 20 to 30 cm falling on hills above 300 metres. This will lead to disruption to transport and perhaps power supplies. The warning has been updated to include a greater part of the Central Lowlands.

As storm Doris moves eastwards across central parts of the UK on Thursday a spell of heavy snow is expected on its northern flank. This will accompanied by strong winds with drifting of snow possible. There is some uncertainty over the track of Doris and therefore over the extent of snowfall, but confidence is now higher for disruptive snow to affect the amber area.
 
Slightly concerning regarding the possibility of a sting jet is that the warm front is wrapping back around the rear of the low, allowing dry air from higher up (see dry conveyor in previous lesson) to enter the circulation, as seen here on water vapour satellite (dry air is darker in this rendering):

dorisWV2202.png.1c9b5d5a0e73d90d72fdf908a9086ffe.png


This GIF shows dry air in red overunning the moist air below, and the wave in the polar front jet has already started cyclogenesis, as can be seen by the so-called Baroclinic Leaf, a roughly leaf-shaped are of cloud on visible radar which develops in the longwave trough at the end of the sequence:
output_unC014.gif.3d295c0b34f293dc9fe131c2f64b299f.gif


Finaly, the following forecast GIF shows the predicted jet stream over the next few hours:
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Latest analysis from Netweather's senior forecaster is that Doris is now exiting the jet to the left (as I explained previously) in the diffluent longwave trough. She should undergo explosive cyclogenesis over the next few hours as she approaches Ireland.
 
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Not sure that it's quite ' explosive cyclogenesis ' here, however Doris has been farting flurries of driving sleet/snow here overnight, however am pretty sure we're missing the worst so far. Hope you're doing okay further south Chris.

JohnnyO. o/
 
Heavy rain last night but loads less wind than Wednesday night (excepting Cara my 6yo who I could hear singing the Whizz Pop song from The BFG at stupid o'clock this morning). Pretty still and mild at mine this morning, 8°C. Started livening up when I got to Leeds though, quite an exciting weather week really especially now I understand what's happening (mostly!!).
 
Not sure that it's quite ' explosive cyclogenesis ' here, however Doris has been farting flurries of driving sleet/snow here overnight, however am pretty sure we're missing the worst so far. Hope you're doing okay further south Chris.

JohnnyO. o/
I think you're too far north the get the full effects of the explosive cyclogenesis, Johnny. Getting damn windy here - I'm just going to update myself and I'll post new info.
 
International Space Station image showing the swirl of cloud to the far south of Doris over the Bay of Biscay - Chrbourg visible top right:
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Latest Met Office FAX chart, valid 6 a.m. UTC (note occlusion bent back under the centre, but, fortunately, no break of the cold front):
20170223.0716.PPVA89.png

Netweather forecasters now consider sting jet unlikely, but injuries have been reported in the north-west (a man blown off his feet incurring head injuries) and elsewhere.

Latest European satellite image shows dry air swinging around the swirl of cloud and entering the low from the west:

1.4
 
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