Convective/Storm Discussion Thread - 1st August onwards

[Cheshire Freeze]

Just now, karyo said:

Gusty wind all of a sudden!

Yep, had the same here

[Frost HoIIow]

Well where did this thunderstorm come from? was it even forecast? I was sat here wondering what the rumbling was all about, at first I thought it was an earth tremor

[karyo]

Just now, CreweCold said:

Yep, had the same here

Those storms are still developing!

[Rachel O'Pray]

Very loud grumbling and prolonged thunder in Manchester 

[TJS1998Tom]

1 minute ago, karyo said:

Those storms are still developing!

Hopefully it pushes East for when we get heavy rain later

[Chris.R]

I've been watching tonight on gfs for a while, but as often happens meto forecast nothing. 

[TJS1998Tom]

Just now, Chris.R said:

I've been watching tonight on gfs for a while, but as often happens meto forecast nothing. 

This website here shows a fair bit of Cape that the GFS doesnt pick up https://www.windy.com/?cape,51.768,-2.549,6,m:e6AafZZ

[toggerob]

Certainly can't complain about not getting anything decent here for this year after that blighter of a storm, it wasn't quite a storm in the sense that it was more thundery rain. But quite a few local strikes that got the neighbours waking up and wondering what was going on. Managed to capture one lightning-flash on the camera but will have to edit-through in the morning as it was hit and miss where to look here.

[TJS1998Tom]

Had a flash of lightning a few mins ago which was picked up near Gainsborough

[NorthYorksWeather]

Was woken by deep rumbles around 1am as embedded thunder and lightning passed to my SE in the rain band.

First visible night storm this year albeit around 5 flashes it was a nice surprise to wake to.

[NL]

Interesting comments from ESTOFEX for the British Isles today. http://estofex.org/

British Isles

A highly dynamic situation evolves late in the period due to an intense trough moving into the British Isles. Its tropopause fault will cause lift and steep lapse rates will evolve. Low-level moisture will decrease from the west, however, warm sea surface will limit the moisture decrease somewhat. Currently, models do not indicate the development of a well-defined low-level convergence line that could support a convective line capable of producing severe wind gusts and tornadoes. Instead, only isolated showers and thunderstorms are expected, capable of producing gusty to locally severe wind gusts and also a tornado is not ruled out. The situation must be monitored in the next model runs as severe potential can increase if linear organization of storms occurs.

[Dangerous55019]

Morning all, I hope that everyone enjoyed last nights unexpected storm.

I've got to be honest, I've been keeping an eye on the Cape and LI charts, and yesterday was nothing to get excited over, or so I thought. 

It was pretty grey with gusty winds here yesterday evening, and I'll be honest, to me it felt more like an early autumn storm was starting to hit! So last nights storm came totally out of nowhere!

Just goes to show what can happen when there is no cap in place. 

Anyway... Here's hoping that we all get some more unexpected storms out of nowhere before the season is over. 

[Chris.R]

2 minutes ago, Dangerous55019 said:

Morning all, I hope that everyone enjoyed last nights unexpected storm.

I've got to be honest, I've been keeping an eye on the Cape and LI charts, and yesterday was nothing to get excited over, or so I thought. 

It was pretty grey with gusty winds here yesterday evening, and I'll be honest, to me it felt more like an early autumn storm was starting to hit! So last nights storm came totally out of nowhere!

Just goes to show what can happen when there is no cap in place. 

Anyway... Here's hoping that we all get some more unexpected storms out of nowhere before the season is over. 

 Morning :-) I was actually expecting something to happen as GFS has been showing last night as a period of interest for a few days. For my location it was  showing an LI of -4 but not as much CAPE as I was expecting with that LI. Tonight has also looked interesting for a while however the wind vectors are more westerly so I will be relying on something to develop  over the sea or Anglesey. You should be alright though as you've got the Clwydian range as a breeding ground. Quite a pronounced 500 mb cold pool comes over in the early morning and we are getting to that time of year now when the sea is warm enough to sustain convection  given steep enough lapse rates. 

[Nick F]

Storm & Convective Forecast

Issued 2017-08-17 08:16:18
Valid: Thurs 17th Aug 6AM to Fri 18th Aug 6AM

Day 1 Storm / Convective Forecast

Synopsis

Upper trough over the Atlantic will approach western UK today, before the trough axis slides in across northern and western Britain overnight. A strong cyclonic SWly flow aloft with 100 mph+ jet stream across S England will lie atop a moist and unstable SWly flow at the surface. 3 areas of convective/storm focus potential likely: 1. Sern UK this morning/early afternoon + far SE tonight; 2: W Scotland , W Ireland and N Ireland today; 3. Scotland, NW England and W Ireland today and tonight.

1 ... S ENGLAND, E WALES, MIDLANDS and E ANGLIA …

In wake of morning rain clearing the east coast, sunny spells developing will generate modest instability of up to 300-600 j/kg across the above areas – to coincide with mid-upper dry air intrusion with steeper lapse rates pushing in from the west on northern edge of jet across far S of England. As a result, convection may attain enough depth for a few thunderstorms amongst a swathe of showers developing from SW England/E Wales NEwards across Midlands, central S England towards Nern Home Counties and E Anglia this morning and early afternoon … before models indicate instability subsiding eastward through the afternoon. With 30-40 knts of DL shear … some organisation into clusters of shower/weak storms is possible – capable of producing localised flooding. Also hail and gusty winds may accompany showers/storms. No severe weather expected.

There is a risk (albeit below 30% risk) of some isolated lightning embedded in heavy perhaps convective rainfall clipping far SE of England (Sussex & Kent) tonight, as a frontal wave moves NE through the English Channel.

2 … SCOTLAND, W IRELAND and N. IRELAND …

Lapse rates will steepen through the day with approach of upper trough over the Atlantic to support heavy showers which may become weakly electrified with the addition of surface heating overland. Showers/storms maybe accompanied by hail and gusty winds, but no severe weather expected.

3 … W SCOTLAND, NW ENGLAND, W WALES and W IRELAND tonight …

Heavy showers with some thunderstorms amongst them look to continue overnight across coastal areas and moving inland as increasingly cold air spreads in aloft with arrival of upper trough from the W atop seasonally warm SSTs – creating instability over the sea. Fairly strong flow aloft may organise showers/storms into linear clusters capable of brief intense rainfall leading to localised flooding along with strong wind gusts and hail may accompany stronger convection.

Issued by: Nick Finnis

Edited August 17, 2017 by Nick F

[Carl46Wrexham]

 

Well...well.

 

Talk about unexpected. Many, many reports around my local area (several miles apart) of the thunder "shook my house".."sounded like a plane had crashed".."like a bomb had gone off"...being unusually loud. When I heard the first boom, I assumed the strike had been within a mile of my location. Imagine my surprise when I discovered it was over 5 miles away!

This occurred a few more times..relatively distant strikes (4-6 miles away) but explosive booming thunder.

Positive strikes?

 

[Chris.R]

9 minutes ago, Carl46Wrexham said:

 

Well...well.

 

Talk about unexpected. Many, many reports around my local area (several miles apart) of the thunder "shook my house".."sounded like a plane had crashed".."like a bomb had gone off"...being unusually loud. When I heard the first boom, I assumed the strike had been within a mile of my location. Imagine my surprise when I discovered it was over 5 miles away!

This occurred a few more times..relatively distant strikes (4-6 miles away) but explosive booming thunder.

Positive strikes?

 

Almost certainly. I remember thinking that the sferics around you sounded very powerful on the radio. Annoyingly all intracloud around here. 

[Nick F]

13 minutes ago, Carl46Wrexham said:

 

Well...well.

 

Talk about unexpected. Many, many reports around my local area (several miles apart) of the thunder "shook my house".."sounded like a plane had crashed".."like a bomb had gone off"...being unusually loud. When I heard the first boom, I assumed the strike had been within a mile of my location. Imagine my surprise when I discovered it was over 5 miles away!

This occurred a few more times..relatively distant strikes (4-6 miles away) but explosive booming thunder.

Positive strikes?

 

Looks like it was quite a lively night across parts of west Wales but especially N England.

Didn't expect thunder to be so prolific across N England! Was quite an active (split) cold front ...

Here was my storm forecast for yesterday:

Quote

Slow-moving upper low centred to the SW of Iceland will drive a deeply cyclonic SWly flow across NW Europe. A deep surface low to the west of Scotland will track NE towards the Faroe Isles over the next 12-24hrs, associated frontal system pushing east ahead of the low will spread outbreaks of rain east across the UK this evening and overnight, the cold front is indicated to modestly destabilise warm/moist conveyor just ahead  of it, bringing heavy convective rainfall with isolated thunder across the west this evening/tonight.

DAY 1 DISCUSSION ... 12PM WEDS 16TH AUG UNTIL 6AM THURS 16TH AUG

... IRELAND, N.IRELAND, WALES and N ENGLAND  ...

Cold front will create forced ascent of warm moist conveyor just ahead of it and will generate sufficient lift for convection, perhaps deep enough for isolated lightning across the above areas this evening and overnight. Given fairly strong deep-layer shear, broken line segments with isolated strong convective gust risk are possible - along with localised flooding. However, risk of severe is to low to warrant a categorical severe risk. 

 

[Weather-history]

Woken by loud thunderclap at about 12.20am. Not sure why the thunder was so loud and seemed to be drawn out.

https://mobile.twitter.com/AlanRenza/status/897978616579010564/video/1

[Windblade]

2 hours ago, Nick F said:

There is a risk (albeit below 30% risk) of some isolated lightning embedded in heavy perhaps convective rainfall clipping far SE of England (Sussex & Kent) tonight, as a frontal wave moves NE through the English Channel.

I'll take that bet and hope for the best! 

[LightningLover]

2 minutes ago, Windblade said:

I'll take that bet and hope for the best! 

Lol, here's hoping!

[Nick F]

Lincolnshire the thunderstorm hot spot, as usual!

[Jan]

A friend of mine has just told me her sister saw a possible tornado in Liverpool at about 3.30am. Not heard anything to confirm her story

[Chris.R]

3 minutes ago, Jan said:

A friend of mine has just told me her sister saw a possible tornado in Liverpool at about 3.30am. Not heard anything to confirm her story

 Wouldn't surprise me, there was a lot of turbulence with that cold front last night. I noticed what seemed to be quite a distinct outflow boundary/gust front as  The electrified cell passed off the coast at about 00:30. 

[Mark.C]

3 hours ago, Weather-history said:

Woken by loud thunderclap at about 12.20am. Not sure why the thunder was so loud and seemed to be drawn out.

https://mobile.twitter.com/AlanRenza/status/897978616579010564/video/1

That's crazy loud, did you film that?

[Chris.R]

3 hours ago, Weather-history said:

Woken by loud thunderclap at about 12.20am. Not sure why the thunder was so loud and seemed to be drawn out.

https://mobile.twitter.com/AlanRenza/status/897978616579010564/video/1

 Definitely a +CG, And less than a mile as well. Had a few of them around here in the last few years.  Can be a sign of a decaying cell. I've heard it hypothesised that pollution from large cities can increase their probability. 

Edited August 17, 2017 by Chris.R