UK meteorology

Clouds are gathering as I type showing the effects of increased atmospheric moisture and buoyancy as the cold front moves in (see earlier in this thread for diagrams and descriptions of how cold and warm fronts affect the profile of the air column).
Here's the first part of Malcolm's post from this morning:
Today is the last day of the current hot spell as a more changeable and cooler regime sets in but it quite likely will not go quietly in the south east. Before getting to more detail the current NH profile





At the moment a fair bit of cloud across n. England, Wales and the south west associated with the weakening cold front that is gradually moving south east and some bits and bobs of rain in the far north west from the occlusion.





The cold front is really the major player today as it will again be hot to the south and east of it with the cooler air behind. Thus another very hot day in parts of the south east which will not only trigger some storms but be in the firing line of an unstable low feature tracking north west from France during the evening which could well produce some quite intense outbreaks before clearing into the North Sea.The storms obviously could occur anywhere but probably east of a a line the Wash to west Sussex. Elsewhere cooler with showers in the west and the cold front should clear the east coast in the early hours of Wednesday. The sequence:











So by Wednesday everyone is in the cooler westerly airflow thus a bright sunny day with showers which could well be heavy and concentrated at times in the north and west.








 
Part 2:
As was mentioned in a post last evening a wave forms near Coruna by 00 Thursday and this develops quite rapidly and tracks north east through France into the North Sea during the day accompanied by an area of heavy rain En route this impacts the south east of the UK











By Friday the Atlantic is revving up and a warm front associated with a complex area of low pressure brings patchy rain to western regions





By Saturday the complex area of low pressure is more organized and the low is centred over N. Ireland and, in conjunction with the associated fronts, has brought wet and windy weather to most of the UK. Not unusually the far south east excapes and in fact is pleasantly warm.





The NH profile at T120


 
Worse storms over the Continent:
An outbreak of intense severe storms seems likely across N France and BeNeLux this evening - supercells with very large hail, damaging winds and tornaadoes possible! Storm clusters overnight while the activity spreads towards NW Germany: H/t severe-weather-EU


 
Netweather's chief forecaster has produed a Storm and Convective forecast for this evening:
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

Synopsis
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.
 
Met Office has a Yellow "Be Aware" warning for this evening:
Thunderstorm
Between 16:00 Tue 7th and 03:00 Wed 8th

Thunderstorms are likely across east and southeast England.
What to expect
  • There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost
  • Where lightning strikes or flooding occurs, there is a chance of delays and some cancellations to train and bus services
  • Spray and sudden flooding could lead to difficult driving conditions and some road closures
  • There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes, hail or strong winds
 
BTW, in the Netweather post, an elevated mixed layer refers to the leading edge of the cooler, drier air at height (upper levels of the troposphere) associated with the cold front. It is mixed, in that the cooler air is fairly homogenous in and of itself, but it lies above the hot, moist airmass currently over this area (I''m sweating as I type!) and is not yet mixed with that hot, humid airmass (hence it is described an an elevated layer).
 
Looking at my pine cone (alright - BBC weather) and with my finger in the air, it looks like the heatwave is reaching its end. A fresh breeze blowing in my Lincolnshire village tonight and a drop of 4 degrees C by tomorrow. No real sign of rain though and the temperature looks to be running around 2-3 degrees C above average for a good while yet. All good - hopefully a forthcoming trip to Rome won't come as too much of a shock, plus I've tomatoes to ripen and, if the trend continues into autumn, an October break in Norfolk should be pleasant :)
 
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