Uk Convective General Discussion & Forecasts - April 2012 Part 4

[Darren Bown]

Asked this question this morning to the metoffice, 'what are the chances of storms in Manchester today? I hear there is a chance of storms down south?' and the reply was 'there are no warnings in your area today and there is no forecast for the winds to be storm force' laughed a bit at this as they've missed the point a little haha. Expecting the weather to be quite 'lively' later today!

[Weather Wizard]

UKASF have also just produced an updated forecast (rare to produce 2) with the SE in a High risk area

http://ukasf.co.uk/storm-forecasts/160

Edited April 25, 2012 by Weather wizard

[Robbie Garrett]

Sorry Azores it is "The Low Level Jet"

It helps lift the Parcels to create Convection and lots of it.

It happens almost daily in the USA usually from 5-6pm and helps substantailly in development of Tornadoes over there or it can create an Overnight MCS Affecting the EML (Elevated Mixed Layer)

It is a rare beast in the Uk but can happen on odd occasions but more prevalent in France and Continental Air Masses

UKASF have also just produced an updated forecast (rare to produce 2) with the SE in a High risk area

http://ukasf.co.uk/storm-forecasts/160

Interesting, but is that severe warning really warranted? I understand conditions look good, but in the UK can we really get something supercelluar with Tornadoes?

Will be interesting this afternoon, that's for sure. Possible MCS or mostly single cell?

[Andy Bown]

Robbie there was a supercell over Kent/Sussex in an evening I think a few years ago and another in the Essex area on a Saturday morning.

Interesting to see how the rain has been developing and heading North, there were 2 very heavy bursts that went to the E and W of here while we had

a 'drier' slot and now while it's 'drier' either side of the earlier 'drier' slot it's pouring in between!

[Nick F]

Storm & Convective Forecast - Issued 25/04/2012 AT 10:00

Valid: 25/04/2012 10:00 - 26/04/2011 06:00

Headline: ... THERE IS A SLIGHT OF RISK SEVERE THUNDERSTORMS FORECAST...

High amplitude upper trough over western Europe with a slow-moving deep surface low off SW England today, will pull a frontal system N and NE across the UK today - followed by an unstable rPm airmass across England and Wales with heavy showers and thunderstorms developing.

... SERN/CENTRAL ENGLAND and S WALES ...

Unstable returning Polar maritime airmass spreading in across southern Britain through the day, characterised by steep lapse rates and a moist boundary layer, will be favourable for the development of scattered thunderstorms. Storms that develop will benefit from some reasonable deep layer shear (30-40 knts) ... thanks to proximity of strong SW'erly jet and winds backing to SE'erly towards the surface ... so cell organisation is likely - with line segments or even supercells possible. Also, fairly strong low-level shear (20-30 knts) will be present across southern England ahead of low near SW England, enhanced by backing winds ahead one or two shortwave troughs moving NE, so there is the potential for a tornado to develop with stronger updrafts, Therefore have issued a slight risk for S England and SE Wales. Showers/storms may also be accompanied by hail to marble size, wind gusts to 60mph and torrential downpours bringing a risk of localised flooding. Scattered storms may continue through the night across England and Wales, though tornado risk diminishing.

[chionomaniac]

If the conditions are right for the risk of supercells and tornados, Robbie then it doesn't matter where in the world you are. A slight risk in the USA does not guarantee tornados just that the ingredients are there that make then more likely

[Coast]

Interesting, but is that severe warning really warranted?

Hmmmm, open to discussion of course but there is a lot of low level shear expected:

[Robbie Garrett]

Robbie there was a supercell over Kent/Sussex in an evening I think a few years ago and another in the Essex area on a Saturday morning.

Interesting to see how the rain has been developing and heading North, there were 2 very heavy bursts that went to the E and W of here while we had

a 'drier' slot and now while it's 'drier' either side of the earlier 'drier' slot it's pouring in between!

If the conditions are right for the risk of supercells and tornados, Robbie then it doesn't matter where in the world you are. A slight risk in the USA does not guarantee tornados just that the ingredients are there that make then more likely

Hello,

I knew there was, but I take it even if conditions where perfect they are not as severe as the ones in the US. Would be very interesting to get some sort of Supercell today if that's the case. Never seen or witnessed one here in London, and very much doubt it's possible to get one in this neck of the woods, maybe someone could correct me they seem to be coast huggers right??

Activity starting to perk up.

[Coast]

[toggerob]

Bins falling over had me rushing to the window this morning as deceptively I was thinking it was thunder aloft, needless to say I was slightly disappointed but some of the gusts coming from these fronts are pulling their weight despite only being 31mph max so far.

I'm not surprised about the threat of Tornadoes across the UK today and into tomorrow..the technical term escapes my memory, but it's akin to watching water drain down the sinkhole and smaller 'eddies' appear around the force of coriolis. The same effect happens with these types of convective lows, especially as TCu/CB heights enter the upper shear above 500hpa (FL180.)

[bobbydog]

isle of wight/ southampton area looks to be in the firing line soon...

[staplehurst]

but in the UK can we really get something supercelluar with Tornadoes?

Robbie there was a supercell over Kent/Sussex in an evening I think a few years ago

Yeah, 14th July 2010 during the late afternoon/evening along the coast, this photo taken by someone on Camber beach not far from Dungeness:

[gottolovethisweather]

Hello,

I knew there was, but I take it even if conditions where perfect they are not as severe as the ones in the US. Would be very interesting to get some sort of Supercell today if that's the case. Never seen or witnessed one here in London, and very much doubt it's possible to get one in this neck of the woods, maybe someone could correct me they seem to be coast huggers right??

Activity starting to perk up.

That is a stunning video capture there, looks more like something from away from the UK for sure.

[Paul Sherman]

Robbie

Recent Supercell Storms have occured Inland quite easily.

London Storm on 7th December a few years back that spawned the Kensal Rise Tornado was verified by Doppler Radar, SE Essex Supercell 15th November 2009 spawned an EF2 Tornado near Benfleet, Rye Supercell from Mid July a few years back, also Birmingham Tornado from 2005 with Wedge Tornado was a Supercell I believe.

Some of the Storms from many decades ago would probably fall into this category as well, have numerous written articles including a Long Track Tornado that initiated near NW London and tracked towards the North Norfolk Coast in the 1960's.

Never discount it if the conditions are favourable.......................But like the USA It is only a Risk as Chino says the conditions are favourable.

A few Weeks back whilst in Kansas, Oklahoma City was in a PDS Tornado Watch Box with High Risk of Long Tracked Strong Tornadoes, end result they did not get a drop of rain!

[Lynxus]

Am I right in thinking that we are more interested in whats behind this red line..

I assume once this front passes over , This is where the unstable air and convection is due to be... ( Seems to make sense to me anyway )

-G

Behind the cold front im thinking the major shiznit will hit..

Edited April 25, 2012 by Lynxus

[Kain]

Aww seems like the risk is dropping for the west mids! As someone said yesterday Meh...

[syncmaster]

Rains arrived here in north lincs, moderate easterly and 6c..

[Paul Sherman]

Keep a very close eye on developments SW Of Portsmouth in the next hour or so.

Very interesting radar signature, possible bow echo going to make landfall, could be something embedded in that if it holds together

[Kookylou]

Have had torrential rain all morning up until 10 minutes ago and now bright sunshine...... weather bloke on BBC last night emphasised vicious storms. Damn - got an exam on Monday and need to get my head down!!

[legritter]

sun as just come out ,lasted about 5 mins .my wife just commented how muggy its got all of a sudden .glass in summer house gone misty ,looking at radar it could become very lively down here mid afternoon onwards ,best of luck you members who have so far been starved of storms ,regards legritter .

[Lynxus]

Looking at the radar, As SOON as that ppn hits land its intensity has increased 10 fold.

Wow. Next hour is going to be very very interesting

[Robbie Garrett]

Robbie

Recent Supercell Storms have occured Inland quite easily.

London Storm on 7th December a few years back that spawned the Kensal Rise Tornado was verified by Doppler Radar, SE Essex Supercell 15th November 2009 spawned an EF2 Tornado near Benfleet, Rye Supercell from Mid July a few years back, also Birmingham Tornado from 2005 with Wedge Tornado was a Supercell I believe.

Some of the Storms from many decades ago would probably fall into this category as well, have numerous written articles including a Long Track Tornado that initiated near NW London and tracked towards the North Norfolk Coast in the 1960's.

Never discount it if the conditions are favourable.......................But like the USA It is only a Risk as Chino says the conditions are favourable.

A few Weeks back whilst in Kansas, Oklahoma City was in a PDS Tornado Watch Box with High Risk of Long Tracked Strong Tornadoes, end result they did not get a drop of rain!

Oh I wont discount it, just it seems very unlikely that we'd get some very very potent in the UK like you would in the USA. But then again, you know a lot more about these things that I do.

7th December and a Supercell?? yikes!! I remember that being on the news.

So form your experience what you think for today?? Some very powerful single cells (maybe nearing supercelluar) and maybe a small MCS?

By any chance, is this correct? This is for London.

Edited April 25, 2012 by Robbie Garrett

[Ian Ballinger]

Aww seems like the risk is dropping for the west mids! As someone said yesterday Meh...

You should know by now, that whatever is forecast for us, won't happen

[Paul Sherman]

Gotta favour Line Segments over Supercells but if something can get organised later and remain on it's own with no interactions with other Storms then Supercells remain a possibility.

So would favour Multi Cell Clusters the most today.

[sunny scunny]

The rain just won't get going here.A pathetic 0.2mm so far lol.