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Convective/Thunderstorm Discussion : 2019 and Winter 2020
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Storm Forecast
Valid: Tue 23 Jul 2019 06:00 to Wed 24 Jul 2019 06:00 UTC
Issued: Mon 22 Jul 2019 21:21
Forecaster: DAFIS
Levels 1 and 2 were issued for parts of France and the UK for large hail, severe wind gusts, and excessive precipitation.
A level 1 was issued for parts of Ukraine, Russia, and Belarus mainly for excessive precipitation and large hail.
SYNOPSIS
An intensifying ridge in W Europe brings exceptionally warm air masses up to the UK and the North Sea, and a jet stream builds on its forward flank, curving east towards South Scandinavia and Poland. At the same time, two troughs are forming on the west and east side of the ridge, leading to an Omega Blocking. Downstream from these two troughs, we expect DMC events mostly covering a large part of E Europe on Tuesday 23/07. Moreover, storms are also expected in Spain and NE Portugal, which may produce locally severe wind gusts.
DISCUSSION
.... France and UK ....
The advection of very warm air masses over France with up to 25oC at 850 hPa will create a strong cap extending north up to the UK, so we do not expect surface-based convection to use the fat CAPE profiles aloft, where very steep lapse rates create about 2.500 J/kg CAPE. Nevertheless, late in the afternoon and early night of Tuesday a short-wave trough is forecast to reach the west coasts of France and the UK, with strong PVA. Current thinking is that the unstable air masses in extreme NW France and SW UK will penetrate the cap, given the strong synoptic lift, and will lead to severe weather events. The exact time of convective initiation is questionable, but any storm that will form inside the level-1 and 2 areas will be able to produce severe wind gusts, large hail and locally excessive precipitation. A jet-streak of 20-30 m/s that will cross SW UK increase the threat level for severe convective wind gusts and large hail. In France, NWP models (for e.g. GFS, AROME, ICON) show CAPE values exceeding 2.000 J/kg with strong low/mid-level helicity, suggesting that storms may quickly become supercells and very large hail is possible near the coasts of Normandy and Brittany, but according to IFS storms will stay offshore. After midnight the storms will continue propagating N-NE over the UK, mostly elevated. In the early morning of Wednesday 24/07 the main threat will be excessive precipitation in central parts of the UK.0 -
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PukkaStukka wrote: »I'm in Cornwall at the moment. Should I order in beer and popcorn for tomorrow night??
Ok, none of you replied. So I ordered plenty of beer and lots of popcorn. By all accounts It'll be a cracker here. 0 -
PukkaStukka wrote: »Ok, none of you replied. So I ordered plenty of beer and lots of popcorn. By all accounts It'll be a cracker here.
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Latest bbc news 24 forecast graphics does have a few storms heading north affecting east wexford and east Wicklow and probably eventually Dublin (though the graphic jumped past the timeline for that and moved onto Scotland)
So the question remains,is there hope?
I'll be up and about in the small hours hopefully and if theres anything going on,will do a live broadcast on the Arklow weather Twitter
(shameless plug) 0 -
UK Met Office weather chart for midnight tonight:
I'd still not rule out some thundery showers breaking out around then as that weak cold front (we don't need strong cold fronts to trigger storms at this time of year) moves into that very moist plume that will be still running up along the east coast. Of course the risk will always be low, and I may be offering nothing but a false hope, but who knows... These type of situations are never as clean cut as the computer models might or might not show.New Moon
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Latest bbc news 24 forecast graphics does have a few storms heading north affecting east wexford and east Wicklow and probably eventually Dublin (though the graphic jumped past the timeline for that and moved onto Scotland)
So the question remains,is there hope?
I'll be up and about in the small hours hopefully and if theres anything going on,will do a live broadcast on the Arklow weather Twitter
(shameless plug)
To hell with the models, I am more interested in what your folkish intuition is? What does your gut tell you?New Moon
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After the recent thunderstorm bust a few weeks back, with promising charts and model outputs, I'm reminded of the old saying "a watched kettle never boils."
Over the years as I recall, the best and most spectacular thunderstorms have occured with very little fanfare and taken everyone by surprise.
Therefore I'm now very reluctant to get in any way excited at the forecast of thunder until I can actually see the forks and hear the thunder.
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Rapid ECM 06Z showing a fair chance of thunderstorms breaking out in the SW this evening and up along the W as the evening goes on. Showing some chance along the S and SE coasts as well perhaps as the front crosses the country. This run of all the models showing the front move the furthest inland and with the most chance of rain but most of it staying off shore as the chart below shows. ECM I reckon has been doing very well with these set ups recently in that it is about the best at handling elevated storms . Interesting to see if this verifies.
Nice areas of convergence in the SW and W and off the NW. Good levels of DLS.
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