Storms and Convective discussion - 16th June 2021 onwards

[Ben Sainsbury]

6 minutes ago, offerman said:

Have storms forecast here but nothing on radar even showing as yet 

You're looking at 1-2pm onwards before we start seeing any deep convection taking place :), some models don't start initiating until 3-4pm.

[sparky1972]

morning all, hopefully lots of you will see a storm or  2 over the next cpl of days, not looking overly great here, very cloudy, light rain and feeling fresh but here is hoping for later.

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Sat 03 Jul 2021 - 05:59 UTC Sun 04 Jul 2021

ISSUED 07:25 UTC Sat 03 Jul 2021

ISSUED BY: Chris/Dan

Broad upper trough will extend from the North Atlantic across the UK/Ireland on Saturday, to the north of the main jet activity which will run across Iberia and the Mediterranean. The subsequent cooling aloft atop a moist boundary layer (dewpoints of 14-17C, locally higher in East Anglia) will create a widely unstable environment in many areas, with the potential for deep convection and scattered showers/thunderstorms in numerous places.

Initially in the morning a PVA lobe will lift northwards across England and Wales, creating broad ascent with showery outbreaks of rain - with the potential for embedded convection to enhance rainfall intensity. As this early rain clears, increasing insolation and surface heating will help yield as much as 1,000 J/kg MLCAPE in places with forecast profiles revealing an incremental decrease in RH with height. For the most part, winds will be fairly unidirectional with height with only a slight increase in speed - the net result is fairly weak shear (generally 10-15kts), however stronger upper-level flow over eastern England could aid in better organisation/longevity of cells here with a greater potential for marginally-severe hail and perhaps an isolated tornado, especially where vorticity stretching occurs as updrafts move over existing low-level convergence. Particular focus on Norfolk and perhaps Lincolnshire, where a SVR has been introduced for the risk of hail locally up to 2cm in diameter.

In general, the slow storm motion coupled with any backbuilding could result in local flash flooding - this appears greatest over Devon and Somerset where a persistent convergence zone aligned near-parallel with the steering flow could result in multiple cells running over similar areas, giving locally very high rainfall totals. As a result a SVR has been introduced for the heightened threat of flash flooding, especially given the terrain and catchment response in the area.

A gradual weakening trend is likely through the mid-late evening, however PVA lifting north across northern England and southern Scotland may continue to aid development here for a time into the night hours. Otherwise, the main focus during the overnight period turns once again to the English Channel (and eventually southern England) as another PVA lobe encourages broad lift and areas of showery rain to develop - and again there will be the risk of a few isolated lightning strikes given weak/skinny CAPE.

http://www.convectiveweather.co.uk/forecast.php?date=2021-07-03

 

[Liam Burge]

13 minutes ago, offerman said:

Have storms forecast here but nothing on radar even showing as yet 

I don't think storms are meant to initiate until this afternoon (around 1pm).

[Liam Burge]

18 minutes ago, Summer Sun said:

Day 1 Convective Outlook

VALID 06:00 UTC Sat 03 Jul 2021 - 05:59 UTC Sun 04 Jul 2021

ISSUED 07:25 UTC Sat 03 Jul 2021

ISSUED BY: Chris/Dan

Broad upper trough will extend from the North Atlantic across the UK/Ireland on Saturday, to the north of the main jet activity which will run across Iberia and the Mediterranean. The subsequent cooling aloft atop a moist boundary layer (dewpoints of 14-17C, locally higher in East Anglia) will create a widely unstable environment in many areas, with the potential for deep convection and scattered showers/thunderstorms in numerous places.

Initially in the morning a PVA lobe will lift northwards across England and Wales, creating broad ascent with showery outbreaks of rain - with the potential for embedded convection to enhance rainfall intensity. As this early rain clears, increasing insolation and surface heating will help yield as much as 1,000 J/kg MLCAPE in places with forecast profiles revealing an incremental decrease in RH with height. For the most part, winds will be fairly unidirectional with height with only a slight increase in speed - the net result is fairly weak shear (generally 10-15kts), however stronger upper-level flow over eastern England could aid in better organisation/longevity of cells here with a greater potential for marginally-severe hail and perhaps an isolated tornado, especially where vorticity stretching occurs as updrafts move over existing low-level convergence. Particular focus on Norfolk and perhaps Lincolnshire, where a SVR has been introduced for the risk of hail locally up to 2cm in diameter.

In general, the slow storm motion coupled with any backbuilding could result in local flash flooding - this appears greatest over Devon and Somerset where a persistent convergence zone aligned near-parallel with the steering flow could result in multiple cells running over similar areas, giving locally very high rainfall totals. As a result a SVR has been introduced for the heightened threat of flash flooding, especially given the terrain and catchment response in the area.

A gradual weakening trend is likely through the mid-late evening, however PVA lifting north across northern England and southern Scotland may continue to aid development here for a time into the night hours. Otherwise, the main focus during the overnight period turns once again to the English Channel (and eventually southern England) as another PVA lobe encourages broad lift and areas of showery rain to develop - and again there will be the risk of a few isolated lightning strikes given weak/skinny CAPE.

http://www.convectiveweather.co.uk/forecast.php?date=2021-07-03

 

Somerset is gonna be washed away haha

[TJS1998Tom]

Of course Lincolnshire is in a severe warning when I'm not there. Should be interesting to see how it pans out on radar at least 

[Petorious]

Just as I'm about to drive up to North Wales for a couple of days! Couldn't make it up

[The PIT]

Not expecting anything here the nail in the coffin could well be the low temperatures they've actually dropped a bit.

I'll think I'll wash the car while it's raining saves a little on water.

[wimblettben]

Although most of the uk is expecting something we are right to the side of the warning area so will probably miss out again.

[CalmBeforeTheStorm]

Very murky here in saxilby , near Lincoln, hard to imagine anything will kick off ! Fingers crossed though good luck everyone 

[Liam Burge]

It's very sticky here in Somerset.

[Dangerous55019]

Morning everyone

Is the great storm drought of 2021 about to be broken? I do hope so. ??

I’ve just had this update from the U.K. Meto app!

Anyway… As always good luck to everyone today and tomorrow with this. ?⛈

[viking_smb]

11 hours ago, Flash bang flash bang etc said:

Aren’t laptops portable?

Yes, and the answer is no, i'm not chasing.

[wimblettben]

Just now, Dangerous55019 said:

Morning everyone

Is the great storm drought of 2021 about to be broken? I do hope so. ??

I’ve just had this update from the U.K. Meto app!

Anyway… As always good luck to everyone today and tomorrow with this. ?⛈

Not expecting much based on their warning then given the fact that we are not even in the warning area.

[Argyle10]

Hi, have posted here in a while

CW have me in a slight today but is this likely to happen? 

Edited July 3, 2021 by Charlie Harnett
Spelling

[Flash bang flash bang etc]

Look at cloud breaks for clues to the developments later on - which at the moment doesn’t offer a great prognosis for the midlands, as any clear spots moving in from the channel are quickly filling with murk

I’m thinking Aylesbury through to Norfolk look like the best places from about 15:00 onwards

[sparky1972]

50 minutes ago, TJS1998Tom said:

Of course Lincolnshire is in a severe warning when I'm not there. Should be interesting to see how it pans out on radar at least 

i would not worry, it really looks like we will miss out, damp, low cloud, patchy drizzle/light rain and feeling cooler and fresher so far this morning, does not feel thundery at all.

[Nick F]

THUNDERSTORM WATCH - SATURDAY 03 JULY 2021

Issued 2021-07-03 07:06:13
Valid: 03/07/2021 0600 - 04/07/2021 0600

Forecast Details

A large elongated upper low and surface low to the west of the British Isles will drive a cyclonic SWly flow across the UK on Saturday. A moist airmass, characterised by high PWAT (Preciptable Water) values of up to 32mm, will become unstable to surface heating aided by steepening of lapse rates from cooling aloft as the upper low encroaches to the west. This will support the development of scattered heavy showers and thunderstorms – more particularly across England, Wales and southern Ireland.

It will be a generally cloudy start across England, Wales and Ireland thanks to an occluded front moving N and NE bringing outbreaks of rain NE across many areas. Behind this early rain, some sunny spells are likely to develop from the SW, allowing surface heating of the moist airmass  - which is forecast to yield in the region of 500-1000 j/kg CAPE across England, Wales and S Ireland – where greatest moisture will reside today. Scattered heavy showers and thunderstorms will develop as a result. Thunderstorms can’t be ruled out almost anywhere today, but areas most likely to see them look to be SW/CS England & S Wales northeastwards across Midlands, northern Home Counties, E Anglia, Lincs and N England.

Winds through the troposphere will be unidirectional, so vertical wind shear will be fairly weak and thus storms will be pulse-type and unlikely to produce organised severe weather. However, isolated severe events from stronger storms that develop can’t be ruled out, as fairly large amounts of CAPE locally could produce isolated large hail of 1-2cm, while fairly high PWAT will mean storms may produce locally intense downpours leading to flash-flooding. Localised strong convective wind gusts are also possible. Storms may produce frequent C-G lightning at times too.

Issued by: Nick Finnis

 

Severe Convective Weather & Storms Forecast - Netweather.tv

WWW.NETWEATHER.TV

 

[Flash bang flash bang etc]

Prediction:

[Harry]

Bit disappointing I’ll be missing out on today’s action, but wishing good luck to all those in the firing line. Look forward to seeing the pics and vids later - stay safe!

[Liam Burge]

1 minute ago, Harry said:

Bit disappointing I’ll be missing out on today’s action, but wishing good luck to all those in the firing line. Look forward to seeing the pics and vids later - stay safe!

If I get anything here I'll definitely be recording it.

 

[Methuselah]

Let's hope the PWATS get it right, for once?

[ChezWeather]

First time I've been in the thread since mid May, what a boring June that was! 

Looks like I'm in a reasonably good location today, would have considered chasing into Lincolnshire, but more pressing matters are taking place at 8pm

[hurricane-anna]

Prediction for tonight.. an amazing storm kicks off around 7.45, gets  closer and cuts out the sky box at work (bar supervisor) just in time for sterling to score the winning goal for england, storm passes and the match is all over, and the major party will commence till closing time... then I get a soaking on my midnight walk home

[BrickFielder]

Low level wind convergence looks key to where storms might initiate today and although there are some general agreements the detail is still different on different models. Comparing 9am wind patterns and forecast wind patterns on the models for 9am then I think I might give a nod to the Netweather SR model.

 

Based on a mix of models my best estimate is that the brown willy effect convergence zone along the Cornwall and Devon spine will be shifted somewhat northwards. More Dunkery Beacon effect across Exmoor than Dartmoor with North coast areas like Boscastle being of concern. Steering winds at mid levels will take this back building convection up into parts of the Midlands. This could result in some areas along the steering route seeing repeated heavy downpours rather than storms with a risk of localized flooding.

All models suggest some wind convergence across parts of the Midlands and providing cloud clears then storms may spring up. Surface winds are very light here with slightly  cooler air aloft suggesting some significant Cape/instability giving the possibility of High topped storms. Winds look lights so no strong updraft downdraft separation so convection could be pulse like and a bit messy. Surface winds are so low that outflow boundary and rear downdraft wind effects could create a occasional right turning storm. I would favour Stoke to Manchester and Northampton to Leicester areas mid afternoon based on a model blend.

As upper level air moves more eastwards then later in the afternoon storm focus moves eastwards to East anglia where Upper level winds are a little more pronounced meaning you might get some updraft and downdraft separation. Places around the wash, cambridge and lincolnshire could catch an isolated more severe storm perhaps even up to hull. The Instability window here is short so it is hard to tell.

Slack low pressure systems are notoriously hard for weather forecast models to get right and best guesses are bound to have inaccuracies so it'd better to watch the Netweather radar from this point.