Uk Convective General Discussion & Forecasts - May 2012 Part 2

[Cloud 10]

The 12z gfs appears to have blown a fuse!

[dave48]

Juicy feel here in Southend at the mo, dep point at 16 degrees, temp at 23! Hopefully catch something in the next week or two.

[Robbie Garrett]

nice photos , an overshooting top too, what height was you at robbie?

Cheers, FL360 - 36,000ft

[Mapantz]

BBC graphics showing random showers tomorrow and Thursday. That's jinxed it then

They didn't show much at all for tomorrow or Thursday. In fact, it's that isolated, i'd rather stick to the warm and sunny conditions.

[Aaron]

The recent BBC forecast showed one shower in northern England around the Peak District.. and nothing else.!!!

Edited May 22, 2012 by Aaron

[Supacell]

Lets take today for example:

All that CAPE and not a shower in sight. I am not thinking tomorrow or Thursday will deliver widespread thunderstorms - although I would be inclined to think there is a better chance over the next 2 days. If a storm can develop through the cap and engage with that kind of CAPE in the "loaded gun" scenario then they would have the potential to produce short lived but electrically active storms.

Pennines may be a hot spot tomorrow late afternoon (if anywhere).

[Backtrack]

http://www.sat24.com/

Supercell just North of Brussels?!

[Hathers]

My local newspaper are reporting a chance of Thunderstorms tomorrow afternoon/evening. Is this likely? Is the air above us unstable enough to produce something. Not so sure.

[stormchaser1]

Evening everyone, {not been here for a while been busy} but im back!

Possible storms thursday and friday

[Backtrack]

My local newspaper are reporting a chance of Thunderstorms tomorrow afternoon/evening. Is this likely? Is the air above us unstable enough to produce something. Not so sure.

There is certainly enough energy in the atmosphere to create storms. That combined with high temperatures and a relaxed dewpoint will energize showers, although there is a lack of activity, and I would be surprised to see anyone reporting a thunderstorm tomorrow or Thursday.

[A.J]

http://www.sat24.com/

Supercell just North of Brussels?!

At a guess, I'd say a Nuclear detonation....lol

Certainly a beefy storm, almost perfect symmetry in shape and nice over-shooting top on visi-sat....Drifting WNW on infra-red

[Backtrack]

At a guess, I'd say a Nuclear detonation....lol

Certainly a beefy storm, almost perfect symmetry in shape and nice over-shooting top on visi-sat....Drifting WNW on infra-red

:lol: yeah I had to look twice!

Certainly WOULD like to be in that! Looks immense doesn't it!

[Aaron]

That storm over Belgium/Netherlands looks immense.. they have exactly the same climate as we do, virtually the same in every single way.. so why can't we get something that large? Well, I guess being an island doesn't help!

Edited May 22, 2012 by Aaron

[Hodgheg]

After being on here and taking such close interest in the weather for a while now, ive seen this kind of set up before and got a bit too excited when really all that happend we're a few isolated storms. Untill we get a real spanish plume event or something im not holding my breath

[Supacell]

Latest BBC forecast with Matt Taylor mentioning isolated but intense thunderstorms tomorrow evening. His graphic shows them down the spine of the country - pretty much as the GFS but about 3-4 hours later.

[Nick F]

Despite the pretty CAPE charts from GFS, rather uncertain whether convection can develop Weds - even along a sea breeze convergence zone inidicated for central spine of England - upper ridge present will hamper conevction by subsidence. Pennines probably most likely to squeeze something out, it can, could be rather potent.

Storm & Convective Forecast - Issued 23/05/2012 00:10

Valid: 23/05/2012 06:00 - 24/05/2012 06:00

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

Synopsis

UK lies under an upper ridge of high pressure on Wednesday, with weak surface troughing developing inland across England as a result of solar heating and sea breeze convergence.

... N ENGLAND, MIDLANDS and CENTRAL S ENGLAND...

Despite the presence of an upper ridge across the UK, sea breeze convergence towards the central spine of England, helped by lift of high ground, may force upwards increasingly moist airmass at surface to perhaps produce isolated heavy showers or even thunderstorms Weds afternoon. GFS builds several 100 j/kg CAPE by Weds afternoon, though feel it maybe over-doing dew points by a few degrees and thus CAPE projections. Nonetheless, DPs of 16C seem achievable, though its a big 'IF' whether uplift of this moist air along likely wind convergence zone can overcome the general subsidence of air under the ridge.

Current thinking is that, in addition to the wind convergence, uplift of higher ground, along with sufficient surface trigger temps, will be required to break out any convection - this would most likely occur over the Pennines of northern England. Though a few isolated showers or storms cannot be ruled out across the Midlands and central southern England either ... where higher ground works together with wind convergence to force pockets of convection. Should heavy showers/storms develop, they are likely to be slow-moving ... bringing the risk of localised flooding.

[Coast]

Morning storm fiends!

Here's a quick round up of some dedicated storm sites and what they think we have for today:

Storm Forecast

Valid: Wed 23 May 2012 06:00 to Thu 24 May 2012 06:00 UTC

Issued: Wed 23 May 2012 06:32

Forecaster: PUCIK

A level 1 was issued for BENELUX, Western Germany and Eastern France mainly for marginally large hail, brief downburst and to the lesser degree for excessive precipitation.

A level 1 was issued for Northern Italy mainly for marginally large hail or brief downbursts.

SYNOPSIS

A blocking pattern is currently in progression over Europe, with a significant amplifying ridge stretching from Iberia towards Northern Scandinavia and a weakening mid-level low over Southeastern Europe. Closer to the surface, a large high presssure system builds over Northern Europe, while a widespread, but shallow low dominates southeastern part of the continent. Between these two features, a relatively warm airmass in the weak easterly flow is observed over most of Central and Western Europe. As cooler mid-level temperatures spread towards southwest thanks tot he mid-level ridge, high lapse rates result in a widespread built up of a latent instability during the day. Mostly disorganised convection, forming in the environment of weak to moderate instability and weak vertical wind shear can be expected in the large extents of Europe.

DISCUSSION

... Western Germany, Eastern France, BENELUX ...

Models are in relatively good agreement on the moderate latent instability release during the day, with MLCAPE values likely in the range of 1000-2000 J/kg. This is supported by the 00 UTC sounding measurements from the region, which already show 500-1000 J/kg of MUCAPE. Convection will likely be driven diurnally, thanks to the local initiating factors without any significant synoptic scale support. Only a slight advection of higher PV values is simulated by GFS towards the afternoon. In the environment of a weak wind shear, mostly disorganised convection is anticipated. Nevertheless, especially if CAPE values will approach 2000 J/kg, strong pulse updrafts might produce marginally large hail and brief downbursts. Due to the slow movement of DMC, locally excessive precipitation is not ruled out either.

Storm Forecast Slight

Forecaster: Dan

Last Updated: 2012-05-22 22:39:00

Valid: 2012-05-23 00:00:00 - 2012-05-23 23:59:00

Areas Affected:

SLGT: High ground of Scotland, N England

Synopsis:

Shortwave trough beneath upper ridge may allow isolated convection to occur in response to daytime heating and orographic forcing.

Discussion:

As LSTs rise sharply, >800J/kg CAPE is likely to build up. However, with a distinct lack of forcing, primary focus then turns to either convergence from seabreezes, or orographic forcing, or ideally a combination of both. This seems most prevalent over the Pennines where seabreezes and topography will play a key part in providing forced ascent and the potential for a few isolated showers/thunderstorms to form, but this risk is considered quite low (10-20%). Initiation time is likely to be quite late in the day.

Forecast soundings indicate a qute dry profile, so it is questionable as to how much precipitation such showers could produce. Nevertheless, PWAT >32mm locally combined with very light steering winds means locally a quasi-stationary cell could produce a significant amount of rain over a relatively small area - one to watch, perhaps.

Very week shear not only limits severe potential, but also suggests such showers (or storms) will become poorly organised, but given dry air aloft there could be some hail if any stronger cores can develop.

Several models also indicate high ground of W Essex and London may also have the potential for an isol shower, but given lack of significant topographic forcing and/or convergence, for now we ignore this idea. It is also possible that a few showers may form over East Anglia (Norfolk and Cambridgeshire in particular) during the morning hours from mid-level instability, but most models seem to have backed from this idea in recent runs.

Nothing from TORRO (Paul Knightly is storm chasing in the States isn't he?) or SkyWarn as of yet, 21st OWS have:

Looking like a nice area somewhere down the middle of the UK might see some isolated action, I'll grab a load of charts so we can see where we think it might be.

[Coast]

Well if it's going to happen, it may be down that central spine of England:

With still some emphasis on East Anglia later in the day?

Convergence right through London and the home counties:

Could be interesting to grab those favourite radar and lightning detector sites as the afternoon wears on!

Dew-points will be high through the day:

[VillagePlank]

Crikey!

[Coast]

Crikey!

Blimey BW, where's that for???!!!! (can't work out the coordinates)

[VillagePlank]

London, Heathrow. Waiting for 6z in case it's in error! Only downside is the K-Index which doesn't look so good, and the trigger has to be surface heating so early clouding over will spoil the party.

Edited May 23, 2012 by Boar Wrinklestorm

[Coast]

London, Heathrow. Waiting for 6z in case it's in error! Only downside is the K-Index which doesn't look so good, and the trigger has to be surface heating so early clouding over will spoil the party.

It starts to get going after lunch according to forecasts, a nice little patch around London too!

[VillagePlank]

The interesting thing is that CAPE and LI are favourable well into the night hours; haven't seen that very often. We just need it to get hot. Damn hot. Convection initiates at approx 26C - a little CIN would be nice on a day like today. Met Office going for max, today, of 25C, in Rochester. Presumably, then, one needs to be very lucky to catch a storm, today. It's rather like having all the ingredients to bake a cookie, but not owning an oven.

Edited May 23, 2012 by Boar Wrinklestorm

[Coast]

The interesting thing is that CAPE and LI are favourable well into the night hours; haven't seen that very often. We just need it to get hot. Damn hot. Convection initiates at approx 26C - a little CIN would be nice on a day like today.

I've got the local projection for me and indeed CAPE increases as the afternoon turns into evening:

Not wonderful and certainly better further inland (Heathrow as you say) but still a nice sign:

[Robbie Garrett]

Coast, that looks like Heathrow to me A friend was telling me early this is quite a convergence line along the south coast.