By Nick F
Storm & Convective Forecast
Issued 2018-08-06 21:33:50
Valid: 07/08/2018 00z to 08/08/2018 00z
THUNDERSTORM OUTLOOK - TUESDAY 7TH AUGUST 2018
North Atlantic upper trough will begin to amplify S and SE across the far west of Britain during Tuesday, with a strengthening upper flow across the UK – as SWly jet stream shifts S and E across the UK. Ahead of the jet streak, a weak surface cold front will progress slowly east, to lie North York Moors - West Sussex by 00z Weds. A very hot, humid and increasingly unstable airmass ahead of the cold front across SE England and East Anglia is forecast to destabilise and produce thunderstorms in the evening here before the front clears through and introduces cooler and more stable air.
… SE ENGLAND and E ANGLIA …
Surface-based CAPE will build up through the day due to surface heating of humid plume in conjunction with lapse rates steepening in association with advection north of EML (elevated mixed layer) aloft. However, this surface instability is likely to remain capped. However, a shortwave in the strengthening flow aloft will move NE from Bay of Biscay area in the morning crossing NW France in the afternoon. The increased lift by the shortwave along NW edge of hot and humid plume over France and SE UK combined with increasing mid-level instability as dry air intrusion punches NE overlapping plume, is forecast by many models to break out thunderstorms across Brittany and Normandy by early evening, before spreading / expanding NE across SE England then East Anglia through the evening.
Thunderstorms are likely to be elevated, though 40-50 knots of 0-6km shear forecast will allow storm organisation into clusters, perhaps even an MCS passing over parts of Kent and eastern E Anglia, so there is potential for strong storms that may bring locally intense downpours leading to flash-flooding, isolated hail, strong wind gusts and frequent cloud-to-ground lightning. These storms should clear away NE into the North Sea after midnight.
Issued by: Nick Finnis
A new thread for all things convective around the UK going into the summer of 2018.
Old thread here:
Convective weather relating to Europe should go into here:
A chance of a few thunderstorms this week with central and southern parts of England and Wales looking most at risk. Although Monday is now moving into the reliable timeframe it is still too early to discuss specifics for the week as a whole. It is likely though that this week will provide some thundery showers or storms for a few of us. An easterly flow will probably favour more western areas for home grown storms, but elevated storms from the continent could also affect southern and south-eastern areas at times.
Not sure if we have a thread open yet for storms as we haven't really had one yet..
Here is my post this Morning on the first to effect Southern England
A shiny new thread as we head into the second half of July and the mid point of the summer.
What a summer it has been. We started the summer with a lot of thunderstorms as June came in with a bang. Unfortunately as June came to a close and we moved into July the temperatures dropped and so did the storm risk. The most thundery early June I can remember has been balanced by the poorest early July I can remember. This looks like it is all set to change though as temperatures rise and summer returns.
Temperatures are already rising across the south and this building warmth and humidity will spread northwards through the early part of the coming week, with the heat likely peaking on Tuesday. The first 30c is very likely this week. The increasing heat and humidity also looks likely, on current modelling, to culminate in the possibility of some dramatic thunderstorms.
The thoughts of Weather09 in the previous thread provide a good view of what we could expect from current modelling, seen on page 140 of the thread. The very high CAPE values being modeled for Tuesday are unlikely to be realised with strong ridging. It is currently late Tuesday night into Wednesday the period of interest (subject to change of course). Pin pointing an area to be at risk at this range is pointless.
I am thinking this thread is going to get busy with lots of excitement, forecasts and thoughts regarding what is likely to happen, even what you are hoping will happen. I am hoping it will be busy with lots of reports of thunderstorms and convective activity by the middle of this week and beyond. I think most of us would not want to see it fill up with "why do I always miss out", "nothing here", "wishing for no storms" or other moaning posts that should be in the correct moaning thread like the one below.
Good luck to all those that want a storm.
A chart showing MLCAPE for early Wednesday, just to get the excitement flowing
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