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Convective/Storm Discussion Thread - 1st June onwards


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Hail from the storm in York. Wouldn't want that falling on your head!

It was worth all the effort ?

Explosive convection to my west in Norwich. I can see it growing, its immense! Not seen anything like it before except on Storm Chasers on the TV

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16 minutes ago, Tom dewey likes thunder said:

Can you see the thunderStroms on  edge of Cancale in France as you are in Jersey

I caught a glimpse of some convection a few hours ago through a lot of general cloud. 

I've been contemplating going out to take a look when the little one's asleep but it's hard to see anything where I am.  Too many trees, buildings, and a lack of hills, just like home

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Can clearly see the storms near Cherbourg from Poole they are low on the horizon and pink with haze. A large dome of updraught just pushed up above the flat anvil, looked impressive. 

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On ‎01‎/‎07‎/‎2018 at 16:44, lassie23 said:

Had all my action in April, looks like a long summer ahead with no?️

Same here. Summer's passing by and I haven't even seen a single cloud for a week and a half now - I'm not even joking.

Edited by Windblade
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Day 2 Convective Outlook

VALID 06:00 UTC Wed 04 Jul 2018 - 05:59 UTC Thu 05 Jul 2018

ISSUED 20:07 UTC Tue 03 Jul 2018

ISSUED BY: Dan

Elongated upper low will drift across the British Isles on Wednesday, gradually merging with the larger-scale Atlantic upper trough. The focus initially will be on pockets of elevated convection over S and SW England during the morning hours, although with weak instability any lightning activity should be fairly isolated. By the afternoon, strong surface heating and low-level convergence (due to the slack surface flow) will shift the focus to surface-based developments - primarily over S + E Ireland, Scotland into N England, and S / SW England into S Wales and the S Midlands. A few isolated showers may develop, the convection perhaps deep enough locally for a few lightning strikes - though the marginal instability, weak shear and sparse coverage precludes the issuance of a SLGT. Isolated showers may continue to develop during the evening hours, particularly near M4 corridor / S Wales, though most will generally decay overnight as nocturnal cooling commences. Main threats will be locally high rainfall totals, given slow movement of showers and very dry ground - especially so on roads where dust deposition on the road surfaces over the past few weeks may make conditions rather slippery.

http://www.convectiveweather.co.uk/forecast.php?date=2018-07-04

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7 hours ago, R Alto said:

Can clearly see the storms near Cherbourg from Poole they are low on the horizon and pink with haze. A large dome of updraught just pushed up above the flat anvil, looked impressive. 

I got a glimpse from the leisure centre in st hellier.  I reckon the best of it was obscured by a tree...

 

 

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51 minutes ago, Another Kent clipper said:

I got a glimpse from the leisure centre in st hellier.  I reckon the best of it was obscured by a tree...

 

 

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Thanks Clipper, very nice, deep blue sky and love the oddly stable looking alt c's in the first pic, an interesting variation for a storm environment.

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Went outside at 3pm to enjoy the first raindrops for 4 weeks. They were fat heavy ones, lasted about 2 minutes and came from a predominantly sunny sky. It didnt even wet the floor as it just evporated on contact with the ground and other surfaces.

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Actually saw some clouds this evening - had forgotton what they look like. Just cumulus, but even so they blocked out the oppresive heat from the sun for a few seconds. This stifling heat is too much. ?

Edited by Windblade
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28 minutes ago, TheToastPeople said:

Whats going on?? I see blobs on the radar

From Weedon,  Daventry I can see the towers over St Albans and nearer Oxford, spruced they aren't electrified as they are very high.

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Quite a lot of convective cloud bubbling up around here in west London, with dark bases, not overhead but nice to see the cauliflower clouds, which look like they are bringing some locally heavy downpours across western parts of London - though looks like they are already fading.

Similar area of Sern England at risk of a few showers, perhaps thundery, tomorrow - breeze convergence boundary providing the lift. Could be some showers forming along convergence along Pennines and Welsh Marches too?

 

 

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Edited by Nick F
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Day 2 Convective Outlook

VALID 06:00 UTC Thu 05 Jul 2018 - 05:59 UTC Fri 06 Jul 2018

ISSUED 19:50 UTC Wed 04 Jul 2018

ISSUED BY: Dan

The weakening upper trough over southern Britain will gradually clear eastwards to the nearby Continent on Thursday, as upper ridging builds more widely from the Atlantic. In general, rising heights will serve to inhibit deep convection - however, diurnal heating of residual surface moisture with dewpoints approaching 16-19C during the afternoon will yield up to (and locally in excess of) 1,000 J/kg CAPE, and combined with breeze convergence should aid in deep convection with the potential for a few isolated to well-scattered showers or thunderstorms in the afternoon and evening hours.

Have issued a low-end SLGT where there is best multi-model consensus, though some uncertainty over how much lightning there will actually be. Shear is rather weak, so pulse-type convection is expected, which will be fairly slow-moving given slack flow - leading to a risk of local surface water issues, especially given very dry ground present making roads particularly slippery following dust deposition on the road surfaces over the past few weeks. Such convergence-type setups can produce a few funnel clouds - though cloud bases will likely be quite high in this instance.
 
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Storm & Convective Forecast

stormmap_050718.thumb.png.034831e2e89c5b3f245fe258bf7a078e.png

Issued 2018-07-05 08:19:01
Valid: 05/07/2018 00z to 06/07/2018 00z

THUNDERSTORM OUTLOOK - THURS 5TH JULY 2018

Synopsis

A weak and diffuse upper trough will edge slowly east away from the UK on Thursday, with an upper ridge building in from the west. At the surface, a weakening cold front will edge SE across northern Britain before fizzling out by 00z Friday. Ahead of the front, a very warm and humid airmass will be in place across central and southern areas, with a risk of showers and isolated thunderstorms developing where breeze convergence boundaries develop, more particularly towards SE England.

... S/SE ENGLAND, E WALES, N ENGLAND  ...

Models depict an E-W breeze convergence zone developing inland across southern most counties of England through the day and also a N-S orientated convergence zones across E Wales and another straddling the Pennines. These convergence boundaries will provide the focus for lift of surface moisture pooling along where the opposing breezes meet and support development of showers and isolated thunderstorms through the afternoon and early evening.

Thunderstorms most likely across SE England, where lapse rates will be steeper and heights weaker than further north and west, with heating of surface moisture pooling along convergence here contributing to 400-700 j/kg CAPE, which will be sufficient for lightning generation, small hail and locally slow-moving downpours leading to localised surface water flooding - exacerbated by dry ground allowing little absorbtion. Weak vertical shear will mean short-lived pulse-type cells and low risk of severe weather.

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Yellow warning Thunderstorm

  • London & South East England
  • South West England

Between 12:00 Thu 5th and 19:00 Thu 5th

While some parts will see little rain, afternoon thunderstorms are likely to bring torrential rain, hail and lightning to a few places.

What to expect

  • 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 or hail
  • There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost
  • Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services
  • There is a small chance of fast flowing or deep floodwater causing danger to life

Further details

Heavy showers and thunderstorms are likely to break out this afternoon before fading away by early evening. 20-30 mm of rain in an hour is possible in a few places, leading to surface water flooding, whilst there is a chance of one or two impacts from lightning and hail.

https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-07-05

Edited by Summer Sun
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