25th into 26th Aug 2011 - Storm/convective Forecast Discussion And Reports

[Harry]

For what it's worth, this is what I reckon for today....I went to do one yesterday but got distracted and never posted it - was quite pleased with how accurate it was

Will have to wait and see as to how this pans out today

(this for daylight hours up until around 7pm)

[London/SE] Here we go again. Another day with the now dreaded word 'thunder' in the forecast. Doesn't look great for home grown storms - simply not enough moisture in the skew-T. For sure, there will be some but very few, I think: There is CAPE/LI, and instability - it's not off the charts so can be believed. I imagine hail is quite possible, but strobe lightning - perhaps not. The interest is overnight tonight. Low pressure in the Bay of Biscay and shunts an active system towards the SE - all models agree on this. This is likely to produce excessive rainfall, and with it - potential for thunder. Back to the 1980's - middle of the night storms? Maybe. IoW area looking at rainfall of 4 inches:

Based on the models at the moment, the far eastern flank of this system will probably be accompanied by torrential rain and thunderstorms.

As per the other night, I suspect we'll be at risk of something heavy but sferics quite limited....as ever, I hope to be proved spectacularly wrong

Defo worth keeping an eye on though...

EDIT - Just seen the FAX chart...how complex is that!!! If we can drag in some muggy air as it approaches then who knows....

Edited August 25, 2011 by Harry

[VillagePlank]

For what it's worth, this is what I reckon for today....I went to do one yesterday but got distracted and never posted it - was quite pleased with how accurate it was

Will have to wait and see as to how this pans out today

(this for daylight hours up until around 7pm)

Based on the models at the moment, the far eastern flank of this system will probably be accompanied by torrential rain and thunderstorms.

As per the other night, I suspect we'll be at risk of something heavy but sferics quite limited....as ever, I hope to be proved spectacularly wrong

Defo worth keeping an eye on though...

EDIT - Just seen the FAX chart...how complex is that!!! If we can drag in some muggy air as it approaches then who knows....

The 6z is the key output today, along with Herstmonceaux ascent at 12z to verify model output.

EDIT - Just seen the FAX chart...how complex is that!!! If we can drag in some muggy air as it approaches then who knows....

Yes - it looks like every possible airmass colliding over the SE tonight - and with that an awful lot of advection and lift If we can get some surface heating going during the day ....

Edited August 25, 2011 by Sparticle

[EML Network]

IMO that this side of midnight you stand a better chance of seeing a TS the further West you are, Ireland, Wales, and SW England being favored spots, then as we go through the course of tomorrow the whole thing shifts East, and so SC, SE, and Midlnds look favored, and perhaps NE too , and although a bit off subject, N.Sotland could be in for a very windy Sunday morning !! (one to keep an eye out for)

[VillagePlank]

Here's the MetO output.

LP kicks off in Bay of Biscay:

This moves over NW France, and lands up over the SE starting early hours tomorrow, occluding over our heads - ie shed loads of mixing (and all that brings)

I am surprised about the lack of flood warnings. This systems looks to track up the channel, clipping the SE - but the active part of the storm looks to be it's northerly extent. LP tracking, as always, the key to this - even a slightly more easterly track and it's a no show.

Edited August 25, 2011 by Sparticle

[Coast]

I've changed the topic title to cover things later on into the night and tomorrow.

I'm not seeing a lot of CAPE for tomorrow for the SE......

Everything seems to be to the West on our bit of land again

More ruddy rain though, as if we aren't getting enough currently!

[VillagePlank]

I'm not seeing a lot of CAPE for tomorrow for the SE......

Helpful, but not required for imports.

[Coast]

SkyWarn:

SKYWARN UK SEVERE WEATHER WATCH #048

ISSUED: 1300UTC WEDNESDAY 24TH AUGUST 2011 (GJ/SM)

SKYWARN UK HAS ISSUED A SEVERE WEATHER WATCH FOR THE FOLLOWING REGIONS:

WEST MIDLANDS

EAST MIDLANDS

NORTHEAST ENGLAND

IN EFFECT FROM 0000UTC UNTIL 1400UTC THURSDAY 25TH

APPROCAHING UPPER TROUGH REACTIVATES COLD FRONT OVERNIGHT, WITH STRONG JET ALOFT ENHACNIG PRECIPITATION

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

HEAVY RAIN...FLOODING

DISCUSSION:

THERE IS STRONG MODEL AGREEMENT ON PRECIPIATION ACCUMUALTIONS OF UP TO 40MM WITHIN A SHORT PERIOD FOR SPOT LOCATIONS WITHIN THE WATCH AREA. LOCATIONS ARE SOMEWHAT DEPENDENT ON THE SPEED OF THE COLD FRONT WHICH STALLS OVER CENTRAL UK DURING THE DAY. AREAS OF HEAVIEST PRECIPITATION APPEAR TO BE ALONG AND WITHIN 50 MILES OF AN AXIS FROM BIRMINGHAM TO LINCOLN BY LUNCHTIME THURSDAY. WITH SOME AREAS POTENTIALLY RECEIVING SATURATING AMOUNTS DURING WEDNESDAY, THERE EXISTS A POSSIBILITY OF FLASH FLOODING AND EXCESS SURFACE RUN-OFF. THIS WATCH MAY BE UPDATED OR UPGRADED.

Helpful, but not required for imports.

But then everything portent has moved out to our South East over the continent?

Direction/Flow seems to be OK, but by then the potential has all gone East

Imports have struggled recently (well for a long while actually!) and I'm currently nervous of anything getting this far,

What a mess!!!!

[VillagePlank]

Yes, that's true. And worse - this is associated with the track of a LP, rather than nominally convective based systems - so it's even more uncertainty. 1/3rd degree more Easterly and it's curtains again.

Here's the little fella:

... and here's the reason ...

Anyone else thinking of a sting jet? http://en.wikipedia.org/wiki/Sting_jet

(It's not explosively deepening, so, really, with ramping mopped away - no chance!)

Edited August 25, 2011 by Sparticle

[Coast]

I've run a few variables for Tstorms on our own NMM models in Extra and through the day, into the night and as far out as I can currently go, the indices just don't do it for the Eastern side of the country! Here are two typical ones for the TT index:

[VillagePlank]

I've run a few variables for Tstorms on our own NMM models in Extra and through the day, into the night and as far out as I can currently go, the indices just don't do it for the Eastern side of the country! Here are two typical ones for the TT index:

Yes - but it's moist (T_d=14C) and lift is provided by the environment (occluding fronts)

KI, and TT will in effect show nothing because there is CIN about - the clouds will have already been 'made' - convection happens across France, not here.

Still, as in forecasting snow, anything that just isn't right does mean a no-show.

Edited August 25, 2011 by Sparticle

[cobbettp]

just had a very heavy downpoar here, eased of now didnt hear any thunder.

[Purplepixii]

Hmmm I woke up to very heavy rain just after 9am this morning but it's now just drizzling. Low risk for TS in my area but I guess you never know so fingers crossed for some weather fun!

[Coast]

Still, as in forecasting snow, anything that just isn't right does mean a no-show.

I'm afraid I'm with you there! Looks like any storm for the SE overnight into Friday, still tracks too far East for my liking and a Kent Clipper may be all we can get excited about?

[VillagePlank]

Here's the MetO's own output (Invent) :

Perhaps it's "localised" and doesn't require a flooding warning on already saturated Hampshire soil ....

Looks like any storm for the SE, still tracks too far East for my liking and a Kent Clipper may be all we can get excited about?

Yes - excessive rain is the forecast, methinks - with the odd embedded thunderstorm. Even my ramping has to die away sometime .... Still, 6z+Hersmonceauz ascent to look at before the lid closes. I note on your animation that it appears that the east of the LP is most active - a track more northerly would be good - clutching at straws and all that.

I've got my bum in the air with my hands on the floor to slow the Earth's rotation, by friction, for that slight bit of northerly track.

Edited August 25, 2011 by Sparticle

[Skyscape]

Starting to rain here!

[Coast]

I note on your animation that it appears that the east of the LP is most active - a track more northerly would be good - clutching at straws and all that.

Could actually do with the centre of the low shifting West a bit, anybody got a tow rope?

[Harry]

This is down to a matter of 30-50 miles which, given the feature is only just developing, is NOTHING!

It will be one of two scenarios!

1. What was forecast for Monday night actually happens tonight!

2. The worst stays further East over the continent with merely moderate/heavy rain for a time.

I am deeply encouraged by the fact that the MetO haven't issued a warning! I think given the 'knife-edge' models at the moment they're hanging onto their breaches

Edited August 25, 2011 by Harry

[Lynxus]

Now you see,

I think everyones having a laugh on my behalf now.

I keep seeing these storm warning and rain warnings and yet to actually see any...

My garden is like a desert and the only rain we have had this summer is small short showers .

Bring it on!

However i fear nothing will actually happen.,

[VillagePlank]

This is down to a matter of 30-50 miles which, given the feature is only just developing, is NOTHING!

It will be one of two scenarios!

1. What was forecast for Monday night actually happens tonight!

2. The worst stays further East over the continent with merely moderate/heavy rain for a time.

I am deeply encouraged by the fact that the MetO haven't issued a warning! I think given the 'knife-edge' models at the moment they're hanging onto their breaches

Perhaps the MetO warnings for Monday were actually meant for today ... lol -> no chance.

[Coast]

Actually, I've looked out a bit further on the forecast soundings and a very small glimmer of light appears above Eastbourne later tomorrow:

Like others, I am most definitely

[Nick F]

I'm afraid I'm with you there! Looks like any storm for the SE overnight into Friday, still tracks too far East for my liking and a Kent Clipper may be all we can get excited about?

Most models have an area of very heavy rain moving NNE and clipping Kent and coastal E Anglia Friday morning, as a wave over NW France tonight deepens NEwards into a low across the S North Sea by 12z tomorrow. Unfortunately it looks like SE England will be the 'wrong' or cool side of the frontal boundary - so just heavy rain likely from the wrap around occlusion, bit like the MetO event for the SE that never was the other night.

Today, another wave along the cold front is currently pushing NE across SE England hot on the heels of the earlier wave now exiting across NE England, could be some embedded convection that may produce the odd rumble before the CF clears this afternoon. Otherwise, plenty of heavy showers and a few t-storms across Ireland and the Celtic sea looking like spreading NE across northern and western areas today.

Tomorrow, GFS builds a fair bit of CAPE across England and Wales (away from the far east) once the early cloud and rain clears the east and also CAPE across E Eire and W Scotland, so scattered storms look likely in these areas as lapse rates steepen beneath the cooling air of the upper trough above us and the sun comes out.

[Coast]

Hmmm, maybe we need to go for later tomorrow?

[Harry]

Actually, I've looked out a bit further on the forecast soundings and a very small glimmer of light appears above Eastbourne later tomorrow:

Like others, I am most definitely

If some convection did initiate around Eastbourne tomorrow, then shear is looking good for perhaps something verging on severe.

[Mike Storm]

Very Heavy Rain here at mo......

[Harry]

Tonight for the SE from the MetO

After a dry start to the evening further rain will spread to most places by midnight. That will leave a wet night with some heavy and possibly thundery rain. Minimum temperature 12 °C

Intriguingly, looking at the radar it should be raining moderate to heavy here....hardly a thing! Nice updraughts maybe?