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Storm & Convective Discussion 12z 21/7/14 ------>


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Level 2 from Estofex as posted by Cheese above. There are already thunderstorms over the western Channel and around the Bristol Channel, these should develop as they move NE. Today is looking like it could throw up some pretty juicy thunderstorms. The Bristol Channel, Midlands and then Lincolnshire/EA look best placed currently. 

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TORNADO WATCH 2014/008 

A TORRO TORNADO WATCH has been issued at 22:45GMT on Saturday 9th August 2014 

Valid from/until: 03:00- 17:00GMT on Sunday 10th August 2014 for the following regions 

Parts of (see map) 

Much of southern, central, and eastern England, and parts of N England 

Wales 

Channel Islands 

THREATS 

Tornadoes; wind gusts to 60mph; CG lightning; hail 

DISCUSSION 

Deepening Atlantic storm with tropical airmass within its warm sector will cross the watch area during Sunday. Although the exact track is still somewhat uncertain, there are indications from several models that a dual-centred system will evolve. The first centre should move into Wales later tonight, with the main centre crossing SW England and heading NE to Lincs by afternoon, whilst the first centre tends to fill or is consumed by the second. 

Strong lifting from a sharpening upper trough should steepen lapse rates enough for embedded convection to develop close to and to the south of both centres of low pressure, with wind shear favourable for severe weather, especially to the south and east of the second, deeper, low pressure area. 

A mass of heavy rain is already moving in, and through the latter part of the night, embedded convection may affect parts of Wales and SW England, as the low pressure centre(s) move in. During Sunday morning, as the sharpening upper trough digs into the moist sector, it is possible that a squall line may develop across southern England/E Anglia. Additionally, ahead of the low pressure area moving from SW England to Lincs, convection may develop in the moist sector. 

In each of these areas, low-level and deep layer wind shear appears sufficient for severe thunderstorms with strong winds and perhaps a tornado or two. The main caveat with this watch is that the maritime nature of the airmass would typically suggest fairly meagre lapse rates - however, global and mesoscale models indication fairly decent instability associated with this system (~1000J/Kg CAPE). If instability and shear can combine favourably, a strong tornado is possible. 

The area from SW England to Lincs, and points south-east of there appear to have a higher risk of severe weather than elsewhere in the watch area. Please note this forecast has been issued early due to the fact the situation will not be monitored by TORRO overnight. 

Forecaster: RPK 

 

www.torro.org.uk

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Set alarm for 5am and checked lightning maps and was happy to see there was something coming shame it has died out now though:(

 

Yes it seems as soon as it made landfall the sferic activity died off :(

 

Still very early days yet though with lots of potential today.

Edited by Supacell
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 I think the risk of  a severe convective event are moderate today. There are a number of areas which are already interesting.  We can already see some sort of line convection along the unocluded cold front  and towards the tip of the bent back occlusion. Prime risk is still heavy rain and localized flooding.

post-2809-0-63809400-1407657278_thumb.pn

 

Not quite sure where the triple point is , but the estofex forecaster seems keen on it.

 

The area which catches my attention is a follows.

post-2809-0-78596800-1407657410_thumb.pnpost-2809-0-94792500-1407657415_thumb.pn

Its is the post cold front slight vorticity maximum moving from approximately the M4 area through to east Anglia between 11am to 3pm. It shows up clearer on the 300humidity charts.

post-2809-0-35951200-1407657536_thumb.pnpost-2809-0-86233100-1407657555_thumb.pn

post-2809-0-49341800-1407657567_thumb.pnpost-2809-0-61453700-1407657572_thumb.pn

 

It looks to me like an isolated supercell could develop somewhere around oxford or Reading and trundle through to east Anglia.  Bearing in mind that this is based on the NMM model only and most likely the area could move northwards or southwards and timing could be different. This could give a moderate risk of a tornado for east Anglia. Possibilities for hail look quite high as well.

 

post-2809-0-25396800-1407657791_thumb.pnpost-2809-0-75376900-1407657797_thumb.pnpost-2809-0-08819100-1407657803_thumb.pn

 

Further storms likely across Ireland and moving in through wales late afternoon.

 

As ever now casting is better of done with radar and satellite and just maybe the modelling is on to something.

 

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Squall line blasting through here in south London, just the one rumble of thunder so far .... interesting mass of storms further south across Sussex

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Just had some t`n`l up the road from you in Greenhithe just now.

To be honest, I really didn't know thunder could travel that far? The neareast recent strike has been Maidstone.I swear in the past there have been strikes much closer (as seen from the lightning map) and I haven't heard a thing.

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Well I haven't had much chance to catch up on the weather other than the news forecasts. Yesterday afternoon we had some heavy downpours and I was expecting it to get going through the night into this morning. Woken up to bright sky's with sun in between.

Can anyone tell me if that is it now and it has missed us all together or if things are just delayed?

Would love to catch some T&L in the mix of it all.

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Squall line has now passed over me - had some torrential rain for a while and a bit gusty with a couple of rumbles and one lightning flash with immediate thunder. Can now see a patch of blue sky to the West.

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Was thinking of heading up to reading / Oxford /A404 area in a bit and seeing if I can chase something good from there eastwards.Does that seem sensible from what the models are suggesting?

yes, not a bad area....I'm just off out on a chase 30 miles or so further west, north of swindon on the A420 towards Oxford

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