Convective / Storm Discussion Thread - 31st May 2017 onwards

[Dangerous55019]

Convective Sky Watch. 

The sun is now trying to break through this mid level crud... Still lots of accas about. 

[Rob Walker]

So some models still lowering the likelihood of a chance of storms down central south.... meanwhile for only the second time since I can remember XC weather forecast goes the other way forecasting locally risk of thunderstorms in the afternoon here.

New Picture (7).bmp

[Bolt from the Blue]

Big bit of ac cas 

[Weather-history]

Well this Met Office forecast is wrong for my region already.

Today will start bright or sunny for many. Thunderstorms are likely into this afternoon however, mainly in the south and east, but it will feel warm in any sunshine in-between the downpours. Maximum temperature 26 °C.

A large part of the region is currently having showery rain.

[Norfolk Sheep]

Smiley Carol saying occasional showers in the south/intense storms in the Midlands northwards. As per usual 

[Nick F]

Today's Day 1 convective forecast revised from yesterday's day 2 for today in light of storms failing to materialise across the SE ... basically forcing from a subtle shortwave from the southwest delayed though now approaching East English Channel and triggering storms here, can't rule out some developing inland this morning and perhaps this afternoon across SE. Main emphasis for storms likely to be north of London across Midlands, parts of N and E England as convergence ahead of cold front and cold front itself trigger storms, which maybe surface-based.

Storm & Convective Forecast

Issued 2017-07-06 06:44:30
Valid: 06/07/2017 06z to 07/07/2017 06z

DAY 1 CONVECTIVE / STORM FORECAST - THURSDAY 6TH JULY 2017

Synopsis

A broad and increasingly cyclonic SWly flow aloft covers the UK on Thursday, an area of low pressure over NW France at the start of the forecast period will drift NE across SE England during the afternoon, a plume of warm and humid air continues to advance NE across S and E England ahead of this low. A cold front on the NW edge of the plume across Ireland this morning, as cooler Atlantic air pushes in here, will move east across central UK today.

… SE ENGLAND …

Despite most model guidance developing elevated storms across SE England before/by the start of this forecast period (6am) … these have so far failed to materialise. Current thinking is lack of forcing is there to trigger storms for now … however, WV imagery shows a subtle shortwave approaching the eastern English Channel, which is triggering isolated storms across far north of France and a few heavy thundery showers across Kent and Sussex recently. There could be further heavy elevated heavy showers moving NE from the E Channel and perhaps an isolated thunderstorm or two across the far SE this morning as the shortwave glances here. Isolated instances of flash-flooding are a possibility.

This afternoon, there is some uncertainty whether the cap in place, indicated by warm nose at 850mb by 00z Herstmonceux sounding, will be eroded by falling heights and increasing convergence as low moves NE. If the cap does break, any storm that develops will tap into a ‘reservoir’ of around 1000-1500 j/kg CAPE (GFS indicates more, but often overdoes this) and have an environment of increasing deep layer shear reaching 30-40 knts … so storms may organise updrafts which will be strong enough to produce isolated large hail (1-2 inches diameter), torrential rain leading to flash-flooding, strong wind gusts and frequent cloud-to-ground lightning. However, storms that do develop will be isolated, so a MARGINAL risk of severe weather cover London and counties to the south, however a SLIGHT risk cover northern Home Counties ... see below.

… N and E WALES, MIDLANDS, N and E ENGLAND …

Cold front and upper trough behind it moving in from the west and surface heating will induce lift of an increasing warm and moist airmass with CAPE values of 500-1000 j/kg. The atmosphere here will be less capped than further south, so storms that develop here will more likely be surface-based. Vertical wind shear will be weaker across much of N England and N/E Wales (less than 30knts) but stronger (>30knts) towards Lincs and E Anglia. Therefore greatest risk of severe weather … e.g. large hail (1-2 inches diameter), strong wind gusts and even an isolated tornado … will be towards E England – so have issued a SLIGHT risk for E England. Any storms across the above areas may produce large rainfall totals in a short space of time (20-30mm / hour) leading to localised flooding, marginally large hail, gusty winds and frequent cloud-to-ground lightning – so a broad MARGINAL risk of severe weather covers areas above not covered by a SLIGHT risk.

[ChezWeather]

All eyes on Wales in the early afternoon, dont lose hope over the models, anything can happen on days like this

[LightningLover]

[Summer Sun]

From light rain to heavy rain in a matter of minutes in Darlington

[East_England_Stormchaser91]

Just now, LightningLover said:

Stunning picture. Some towering accas here now, the atmosphere is certainly looking very unstable indeed. 

[RichmondWeather]

Why oh why, everything is there, yet the cells still make their way up the english channel, rather than going straight up.

[Rob Walker]

11 minutes ago, Rob Walker said:

So some models still lowering the likelihood of a chance of storms down central south.... meanwhile for only the second time since I can remember XC weather forecast goes the other way forecasting locally risk of thunderstorms in the afternoon here.

New Picture (7).bmp

Hmmm upload didn't seem to work again.... 

[Mapantz]

The Metoffice only uploaded this a few hours ago..

[James1979]

13 hours ago, Mapantz said:

Your time will come on Thursday evening.

 

 

Hmmm, not so sure buddy, I think it will go the usual way for me, I'm starting to think I have a force field around me deflecting the majority of storms away no matter where I am - even in storm hot spots in the med on holiday I've never seen one yet in 30 years! Ah well, more to life I guess.

[wimblettben]

4 minutes ago, Rob Walker said:

Hmmm upload didn't seem to work again.... 

So this would mean that we could stand a chance of getting something later on now then.

There are some pretty unstable looking mid level clouds West of here at the moment moving Eastwards so wouldn't be surprised as they look like they are towering more compared to yesterday evening. 

[sparky1972]

morning all, well the hope for storms here starts now, but the omens are not good, clouds all ready starting to fill in which wont help the heat build, temp currently 18.4c with hummidity at 82%

[Rob Walker]

Just now, wimblettben said:

So this would mean that we could stand a chance of getting something later on now then.

There are some pretty unstable looking mid level clouds West of here at the moment moving Eastwards so wouldn't be surprised as they look like they are towering more compared to yesterday evening. 

Well there's a chance I think, just less likely as the forcing from the shortwave looks to have happened east up the channel; it'll be better to just enjoy the day and see what develops rather than hanging on to forecasts as if they might actually materialise (though one things for sure; all forecasts have upped the temperature for here today).
Right now there are some clouds that have literally appeared out of nowhere not far to my south west so, going by visuals and feel of the air alone it certainly looks primed here at the moment. 

[Summer Sun]

Not going to plan in the south compared with the beebs forecast last night 

 

[<<Ryan>>]

View out to sea from camber 

[toggerob]

Manchester Airport METAR going for storms between 12 and 5 this afternoon, time to crash back to bed for a hour or two more sleep.

[seabreeze86]

Lightning just to my North good start to the day although is doesn't feel remotely warm or humid

[Cakie]

In Darlington. Steady rain and rumbles in the distance 

[Pursuer of Storms]

Very turbulent-looking skies over MK just over the past hour. Loads of convection around already. 

Edited July 6, 2017 by Pursuer of Storms

[Weather-history]

5 minutes ago, Summer Sun said:

Not going to plan in the south compared with the beebs forecast last night 

 

 

Not going to plan in the north neither because where is the rain over parts of northern England now on that screenshot? 

[NorthYorksWeather]

Nice thunderstorm along coastal areas just north of Middlesborough. Jammy gits!