El Gordo! - Spanish Plume Thunderstorm Discussion 2

[Nick F]

Convective / Storm forecast - Issued 27/06/2011 07:00

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

Synopsis

Amplified long-wave upper trough extends south across the E Atlantic from Iceland to the west of the UK with a strong SW flow aloft on the forward side - characterised by a 100 knot+ SWerly jet across N and W UK. Warm air advection continues to take place nearer the surface from the south characterised by high wet bulb potential temperatures, this plume of warm moist air destabilising across Biscay as a thundery trough drifts NE towards the UK on Monday. By 00z Tues, thundery trough lies across SE England with cold front lying from Scarborough SW to Exeter.

... ENGLAND and WALES …

Warm moist airmass across England and Wales, with dew points ranging from 16-20C currently will become increasingly unstable during Monday, as an elevated mixed layer plume with high theta-w values orginating over Iberia expands northwards over Sern UK markedly steepening lapse rates (30-32C between 850-500mb). The elevated plume is already undergoing destabilisation across the Bay of Biscay this morning - with sferics detected here ahead of thundery trough moving NE out of Iberia. Large amounts of CAPE (up to 2500 j/kg) are indicated by GFS this afternoon across southern and eastern England, but given the model tends to over-estimate moisture, 500-1000 j/kg CAPE seems more reasonable. Elevated plume is likely to destabilise across England and Wales this afternoon from the SW, with a few scattered mainly elevated thunderstorms possible this afternoon developing from the SW, though far SE will likely stay dry until evening. Surface reservoir of moisture/CAPE unlikely to be tapped into initially. Storms then look likely to increase in coverage from the SW during the evening and overnight - especially across central S/SE England and E Anglia. Given increasingly strong flow aloft from the west this evening as jet advances from the W and with deep layer shear increasing to 40-50 knots across SEern UK, organistation of storms is likely - with mulitcell line segments or perhaps one or two supercells possible across S and E England with a risk of large hail, damaging wind gusts, frequent lightning and flash flooding. If storms can root into the boundary layer, increasing low-level shear suggests an enhanced risk of a tornado with any supercells during the early evening. Hence have issued a MODERATE risk of severe storms for this area.

Late evening onwards through the overnight period, storms are likely to grow upscale and merge into an MCS, though storm bases may tend to become elevated in nature with any tornado risk subsiding, but the risk of large hail, damaging wind gusts, frequent lightning and flash flooding still remain though storms probably returning to SLIGHT risk criteria early hours of Tuesday. Storms will clear most of Ern England Tuesday morning.

Issued by: Nick F - Forecaster for Netweather

http://www.netweather.tv/index.cgi?action=convective;sess=

[weatherobsuk]

Thanks for the charts Coast, haven't had much time to catch up with what every other model was forecasting yet in trying to get my head around this MCS shift. But it seems that's not much of a issue now anyway. 45mins i'm out the door and hitting the road incase anyone wonders where my posts have gone, hope to be back with at least 1 cloud pic

[Alex95]

21°C with an almost clear sky, though it has that continental haze. Hopefully something will kick off here this afternoon as I expect temperatures to rise to around 27°C. I think the Met Office's 22°C will be way off the mark as they thought it would be cloudy.

Loads of thunderstorms clipping Brittany at the moment, could get tasty on the South Coast later on!

[I remember Atlantic 252]

already seen altocumulus castellatus, sign of change normally due in evening, definitely hottest night of year (again during wimbledon) 17.3°C minimum

[Guest]

Thanks for the forecast Nick, going to print it off for reference today

[tomp456]

many of the posts keep mentioning east sussex and not west to get storms later on.

meh.

[Coast]

Thanks for the charts Coast,

Sorry they are so big until the forum software kicks in! I'm really undecided about today. Going to play it by ear and maybe just head up to Beachy Head after work. Going to be a classic day somewhere today in the UK!!

[Guenhwyvar]

many of the posts keep mentioning east sussex and not west to get storms later on.

meh.

Says we have a 0% chance today,yet we are on the south coast

[loopydreamer]

hmmmm! could be a hit or miss in the medway area but i will be heading up the lines later ^_^

[Coast]

Says we have a 0% chance today,yet we are on the south coast

Don't worry too much. This will be all about the radar, detectors, webcams and something going bang overhead later!!!!

[WillinGlossop]

830 am its 26c....... pretty heavy oppressive outside..... feels like it should go with a bang..... a warm breeze out there too.....

[Biggin]

830 am its 26c....... pretty heavy oppressive outside..... feels like it should go with a bang..... a warm breeze out there too.....

My local ws http://home2.btconne...ley_Weather.htm has 27.4c Can that be right??

EDIT prolly not Biggin Hill airport has 25c as does London City airport.

Edited June 27, 2011 by Biggin

[sunny scunny]

830 am its 26c....... pretty heavy oppressive outside..... feels like it should go with a bang..... a warm breeze out there too.....

Unbelievable temp considering it's not 9am yet :o 24c here and should reach 30c later, and it's been a long time since that last happened.Not expecting much action later today or tonight up here though.

[WillinGlossop]

My local ws http://home2.btconne...ley_Weather.htm has 27.4c Can that be right??

It could well be its hot out there..... and rising fast...... I wouldnt rule out a few places recording 33-34c today

before the rain/thunder arrives..... sticky is todays choice word.....

[tomp456]

Says we have a 0% chance today,yet we are on the south coast

whats your location? i wouldnt pay any attention to will it thunder...

[Hammer]

My local ws http://home2.btconnect.com/brettoliver/Kenley_Weather.htm has 27.4c Can that be right??

What is at the end of that time lapse video at that site, cloud formation?

[WillinGlossop]

http://www.wunderground.com/wundermap/

look at current temps on here, 26-27c already in numerous areas...... including here.....wowza.....scorchio

[D-J-V]

Locked & Loaded........

BBC just referred to the storms later today as 'Humdingers' lets go get sooooooome!

Never know might even earn ourselves a steak by the end of todaaaaay!

[P-M]

Can anyone confirm this http://www.ukweatherworld.co.uk/forum/forums/thread-view.asp?tid=43645&posts=5 last post. Seems to place northeast england in a tornado and storm risk. Is this just because it's up until 9pm tonight and then the action starts further south? The forecasts are confusing, at first I didn't think the north stood a chance!

[Guest]

Some confusion over the strange forecasts Tony G is offering on UKWW, no mention of the south at all. Either he's posted the wrong chart, or got too much sun yesterday IMO. :huh:

[Nick F]

Euros (00Z ECM UKMO and NAE) seem to have more precipitation than GFS over E Anglia and the SE tonight and early tomorrow. 00z ECM shows a possible MCS across this area at 0600 Tuesday:

Would think the Euros seem to have a better handle on spatial extent of storms later than GFS which just indicates a clipper for the far southeast corner.

[Paul Sherman]

Locked & Loaded........

BBC just referred to the storms later today as 'Humdingers' lets go get sooooooome!

Never know might even earn ourselves a steak by the end of todaaaaay!

Lol @ Dave - It would be Ironic that my 50th Tornado would be in the Uk - Here's Hoping - See you later

Great Forecast by Nick there, and this is why I have been ramping today up for the last 4-5 days, this is a pretty rare Set-Up for the Uk and the possibility of a Supercell or two is very real for today!

Paul S

[VillagePlank]

Forecast comparison to observed, T, and Td, 9z

Observed: T=26, Td=17.9, GFS(00z): T=21, Td=18.3

For comparison the four temperatures around the SE are averaged. Looks like GFS' normal propensity to over-cook moisture content is showing (but 0.4C isn't outrageously out) - but the temperature is wildly out at 5C already!

(Weather station is Davis Vantage Pro 2, is sited correctly, and correlates well with official published figures, locally, from MetO - est err +/-0.2C)

Next comparison 12z observed to GFS 06z

Edited June 27, 2011 by Sparticle

[Biggin]

What is at the end of that time lapse video at that site, cloud formation?

Could it be sun on lens??

[Norfolk Sheep]

Locked & Loaded........

BBC just referred to the storms later today as 'Humdingers' lets go get sooooooome!

Never know might even earn ourselves a steak by the end of todaaaaay!

If that was Carol Kirkwood, the last time she said that absolutely nothing happened