Nick F

Evening, I'm back my my two pennies worth. Early elevated storms breaking out Saturday morning northwards from English Channel across CS England and forming a line on into Midlands and perhaps N England, the line moving swiftly NE to N and E England through morning. This won't be the cold front, rather likely a lobe of vorticity streaming NNE interacting with 16-18C theta-w plume advecting north. But more of intetest from a severe perspective is post cold from area of storms models develop across western England / Welsh Borders which then look to organise, perhaps into an MCS by evening, as left exit of strong jet streak arrives from SW. Given 1000-1500 j/kg CAPE forecast and 30-40 deep layer shear, these storms could be severe with large hail IMO. SEVERE THUNDERSTORM WATCH - SAT 08 JULY 2023 Issued 2023-07-07 21:11:01 Valid: 07/07/2023 2100 - 09/07/2023 0600 Forecast Details An upper level low and collocated surface low will be slow-moving centred just the west of Ireland on Saturday. A plume of warm and humid air continues to advect north across the British Isles ahead of the low to the west heading into Saturday. The plume will become increasingly unstable from the south on Saturday, as areas of vorticity moving northeast across Britain, surface convergence and later a shortwave trough and left exit of a jet streak moving NE create lift of warm / moist plume – supporting heavy showers and thunderstorms to develop and spread NNE across the British Isles. In more detail: plume characterised by theta-w values of 18C is forecast to arrive tonight across S England from France and will be inherently unstable with steep mid-level lapse rates. Although there is still some uncertainty, as is often the case with destabilising plumes over the UK, models loosely agree on developing showers and elevated storms over English Channel and pushing into central S England in the early hours of Saturday within axis of higher theta-w plume moving north, likely in response to a lobe of vorticity moving north and wind convergence. A line of elevated storms then looks to extend quickly north along lobe of vorticity streaming north through plume from CS England to N England during Saturday morning before the line then moves NE towards the east coast of England and into E Scotland through the morning and into the afternoon. Some localised flooding and locally frequent C-G lightning is possible with this activity. It’s also possible that a separate area of rain and linear convection with isolated lightning will develop along the cold front following this activity, the front reaching N and E England during the afternoon. Post-cold front environment across England will still be warm and moist, with dew points of 15-17C forecast, surface heating of moist air beneath increasingly cold air in the mid-levels advecting NE is forecast to yield 1000-1500 j/kg SBCAPE from CS/SW England across Welsh Borders, Midlands to NW England by afternoon. This strong instability combined with N-S breeze convergence in the same areas and an upper shortwave trough ahead of left exit of strong jet streak both moving northeast causing larger scale ascent, are forecast to support the development of surface-based thunderstorms, perhaps initially developing from SW England up through Welsh Borders to NW England, before storms organise into clusters or perhaps upscale into an MCS, given 30-40 knots of deep layer shear, which tracks NNE across N England and on over Scotland through the evening. Given storms are likely to organise given strong CAPE, favourable shear and increasing divergence aloft, perhaps one or two supercells can’t be ruled out during initial storm development, there is a risk of localised large hail (2-4cm), strong wind gusts, intense rainfall leading to flash-flooding and frequent cloud-to-ground lightning. A severe storm risk area has been highlighted for N and W England – where these severe risks look possible. Storms will tend to clear away north across far N of England during the evening and Scotland overnight – where they will tend to wane. Issued by: Nick Finnis

UK Severe Convective & Storm Forecast - Issued 2023-07-07 21:11:01 Valid: 07/07/2023 2100 - 09/07/2023 0600 SEVERE THUNDERSTORM WATCH - SAT 08 JULY 2023 Click here for the full forecast

A detailed look at a brief plume of heat and humidity today followed by a thundery breakdown on Saturday, with warnings now issued for thunderstorms tomorrow. View the full blog here

UK Severe Convective & Storm Forecast - Issued 2023-07-05 06:39:24 Valid: 05/07/2023 0600 to 06/07/2023 0600 THUNDERSTORM WATCH - WEDS 05 JULY 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-07-04 07:13:54 Valid: 04/07/2023 0600 - 05/07/2023 0600 THUNDERSTORM WATCH - TUES 04 JULY 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-07-03 08:51:52 Valid: 03/07/2023 0900 to 04/07/2023 0600 THUNDERSTORM WATCH - MON 03 JULY 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-07-02 06:34:59 Valid: 02/07/2023 0600 to 03/07/2023 0600 THUNDERSTORM WATCH - SUN 02 JULY 2023 Click here for the full forecast

Recent trends from weather models for the first half of July are for low pressure to remain close by with unsettled conditions and average temperatures, in contrast to July last year. View the full blog here

UK Severe Convective & Storm Forecast - Issued 2023-06-28 21:27:46 Valid: 28/06/2023 2200 to 30/06/2023 0000 THUNDERSTORM WATCH - THURS 29 JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-26 12:37:23 Valid: 26/06/2023 1300 to 27/06/2023 THUNDERSTORM WATCH - MON 26 JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-25 00:30:46 Valid: 25/06/2023 0000 to 26/06/2023 0000 SEVERE THUNDERSTORM WATCH - SUN 25 JUNE 2023 Click here for the full forecast

06z GFS still indicating severe thunderstorms possible on Sunday Midlands northwards - as a sharp upper trough and preceding surface cold front move eastwards and engage high theta-w airmass . Lightning Wizard, which uses GFS, shows significant tornado parameter and supercell composite areas over Midlands to NE England. E Mids to Lincs and up through S, E and N Yorks looks prime area for severe weather looking at CAPE and the severe parameters mentioned.

UK Severe Convective & Storm Forecast - Issued 2023-06-22 06:19:42 Valid: 22/06/2023 0600 to 23/06/2023 0600 THUNDERSTORM WATCH - THURS 22 JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-21 06:21:22 Valid: 21/06/2023 0600 to 22/06/2023 0600 THUNDERSTORM WATCH - WEDS 21ST JUNE 2023 Click here for the full forecast

Feels rather sticky now than sun is out, despite breeze, plenty of fuel for surface-based storms further north

Think that's it south of Cambs and Suffolk, though can't rule out a stray heavy shower

Had a close CG earlier - my water butts are full up now too. 20230620_070053.mp4 chance of severe storms, perhaps a few supercells, over parts of E England today, more in my Severe Thunderstorm Watch here: Severe Convective Weather & Storms Forecast - Netweather.tv WWW.NETWEATHER.TV here's a few charts of parameters that suggest a severe risk. High theta-w / high CAPE, some DL and LL shear (note significant tornado parameter) Lincs could be prime position

Had a close CG earlier - my water butts are full up now too 20230620_070053.mp4

UK Severe Convective & Storm Forecast - Issued 2023-06-20 08:18:47 Valid: 23/06/2023 0900 to 24/06/2023 0600 THUNDERSTORM WATCH - TUES 20TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-19 07:59:03 Valid: 19/06/2023 0600 - 20/06/2023 0600 THUNDERSTORM WATCH - MON 19TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-18 08:18:47 Valid: 18/06/2023 0600 to 19/06/2023 0600 THUNDERSTORM WATCH - SUN 18TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-17 07:55:13 Valid: 17/06/2023 0600 - 18/06/2023 0600 THUNDERSTORM WATCH - SAT 17TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-16 07:48:52 Valid: 16/06/2023 0600 to 17/06/2023 0600 THUNDERSTORM WATCH - FRI 16TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-12 06:01:31 Valid: 12/06/2023 0600 - 13/06/2023 0600 THUNDERSTORM WATCH - MON 12TH JUNE 2023 Click here for the full forecast

UK Severe Convective & Storm Forecast - Issued 2023-06-11 07:25:45 Valid: 11/06/2023 0600 to 12/06/2023 0600 THUNDERSTORM WATCH - SUN 11TH JUNE 2023 Click here for the full forecast