7th Aug 2011 - Storm/convective Forecast Discussion And Report

[Staffordshire]

I think the SW may be the sweet spot tommorow, personally not holding out any hope because of the shear amoun of times I've been let down. However I think some people could get some fairly heavy showers.

[MP-R]

I think the SW may be the sweet spot tommorow, personally not holding out any hope because of the shear amoun of times I've been let down. However I think some people could get some fairly heavy showers.

The southwest becomes more favourable in this sort of setup the later in the summer you get, especially in September/early October as the sea has warmed up a bit.

I'm hoping for something as the last thunder'storm' as opposed to shower was May 6th - when I was in the parched southeast.

[A.J]

Just a quick re-post of my thoughts for the midlands convective forecast for tomorrow.....

In reply to an earlier post...

"The FAX goes with the NMM and shows a trough moving into the SW tomorrow focusing showery activity in that area, the FAX though does show an Occlusion straddling through the midlands, meaning plenty of cloud cover, I reckon it's this occlusion that's making the NMM & GFS shy away from marked convection in our area as if cloudy, it will inhibit convection...Apart from that, as you say, the parameters are pretty good, plenty of convective energy & lift, a cold pool of air pushing in from the west steepening lapse rates...Still, will be watching the skies/radar with interest tomorrow afternoon"

[Nick F]

Convective / Storm forecast - Issued 06/08/2011 23:00

Valid: 07/08/2011 06:00 - 08/08/2011 06:00

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

Synopsis

Upper low extends across E Atlantic and the British Isles with a shortwave trough and attendant surface low to the west of Ireland Saturday evening moving east overnight into Sunday morning, to be centred south of Ireland at 12z and as an open wave across southern England by 00z Monday. Meanwhile, low near NE England Sat evening will deepen and move slowly north over the N Sea, with associated slow-moving occlusion bringing persistent heavy rain to parts of Scotland

... ENGLAND, WALES and IRELAND...

Short-wave trough over the Atlantic moving east towards the SW approaches by Sunday afternoon will steepen lapse rates across Sern UK and Ireland as colder air is introduced aloft. Ascent ahead of this approaching upper trough and attendant surface low from the west will likely lead to scattered heavy showers and thunderstorms moving in from west across Ireland then Wales and SW England intially by early afternoon, then becoming more widespread further E across central, southern and eastern England by evening.

Although vertical shear will be fairly weak where greatest instability is likely, fairly strong mid-upper SWerly flow across Sern UK suggests possible organisation of storms into clusters or line segments with a threat of gusty winds, hail, torrential rain and cg lightning. Also, where surface winds back ahead of approaching surface low from the W, sufficient low-level shear may combine with the low LCLs and low-level instability to produce an isolated weak tornado - more especially across S England. Though for now, do not expect an organised risk of severe weather - given weak vertical shear, and lack of any particularly warm and moist air in place. With the steep lapse rates aloft, storms may continue into the night for a time across southern counties.

Issued by: Nick F - Forecaster for Netweather

[Chris K]

Looks like it will be an interesting day but one of those days of watching the radar to see where things develop. Good luck for tomorrow Im hoping to finally catch something...

[Wilxy]

Looks like it will be an interesting day but one of those days of watching the radar to see where things develop. Good luck for tomorrow Im hoping to finally catch something...

Did you see the lightning at about 10:45pm.

[DeepSnow]

Looks good for us in south wales and the south west, hope that we actually get something tomorrow!

[Chris K]

Did you see the lightning at about 10:45pm.

I was in the pub and didnt unfortunately. We had a torrential downpour, and another has just started now, but so far I havent heard any thunder or seen lightning.

[Wilxy]

I was in the pub and didnt unfortunately. We had a torrential downpour, and another has just started now, but so far I havent heard any thunder or seen lightning.

I was driving and saw a few flashes of lightning then heard some thunder but it soon died off.

[Chris K]

There seems to be showers intensifying in the Bristol Channel right now. Its actually looking promising from quite early in the day tomorrow. I dont want to jinx it tho..haha.

[MP-R]

Think I just heard some very distant thunder somewhere to my northwest. Had a very brief heavy downpour, must have clipped one of the Bristol Channel ones. I remain sat here with the window open listening.

[Nick F]

Think I just heard some very distant thunder somewhere to my northwest. Had a very brief heavy downpour, must have clipped one of the Bristol Channel ones. I remain sat here with the window open listening.

Recent sferic plot on Atd over Bristol Channel/S Wales coast - so certainly a storm not far away.

[Chris K]

Theres a small cluster thats merged together scooting along the South Wales coast, intensifying heading in a line towards Cardiff then could hit Bristol. It might just miss me as im about 10 miles north of Bristol but if it keeps merging/growing could be a heavy downpour!

[SimonP]

UKASF have gone with a moderate risk for much of southern England and Eire for Sunday (map of areas affected at http://www.ukasf.co....rm-forecasts/64):

Areas Affected:

Southern Britain and southern Ireland.

Synopsis:

A complex, multi-centred area of low pressure will be present across much of Britain allowing for large scale ascent and unsettled conditions. An occluded front across northern Britain will be the focal point for a large area of heavy rain which may produce some localised flooding, but no lighting / deep convection is expected with this. However, the warmer, more unstable air further south will have the potential to produce thunderstorms.

Discussion:

Low pressure as stated in the synoptic discussion will allow for unsettled conditons and suffient SBCAPE values of 500-700j/kg are possible in the moderate zone during the afternoon. ELTs in the range of -40C indicate suffiently deep enough convection for plenty of lightning and also, the risk of moderate hail. Both LLS and DLS values are relatively weak, so sustained updrafts won't be likely, meaning storms will be of the pulse variety, but could produce some brief gusty winds. Funnels are also unlikely except for near topographcially (Wicklow Mountains) or coastline enhanced (south coast of England) boundaries.

[Raidan]

The rain passing over my part of Bristol is not electrical,Had a downpour about a hour ago and that was it,lights flickered a few times which made me think something was near but nothing came of it.

[Raidan]

Just to add im getting frequent short showers only lasting seconds.

[ZONE 51]

A day of Thunderstorms and hail with flooding possible

see Netweather storm forecast for details about the storms

-

an earlier radar image showing the heavy rains or torrential rains over Northern areas with heavy downpours in other areas showing up especially in the SW. radar is for 5.30am.

-surface temperatures-1500hrs NAE 000z

GFS 00z latest run.

-upper temps at 500hpa - 1200hrs

-upper temps at 500hpa - 1800hrs

-CAPE 1500hrs

CAPE 1800hrs

-Lifted index 1200hrs

Lifted index 1800hrs

-

A very high risk of Thunderstorms today and this evening-lasting into late evening and maybe rumbling on into early hours.(in the storm risk areas)

[NO LONGER POSTING]

wow! The day I pick to go out and we could get T-storms..And knowing my luck it will left trouser leg down!!! I know it -.- Oh well would be good to see something XD

[Stuart]

Good Luck all for today i Missed out on sat Afternoon there all die out before it get in to the area

[NO LONGER POSTING]

Some info I found for my area on storm risk 0.o

SurfaceUpper AirDayTimeTempSpeedDirCAPELIRainCloudSpeedDir

Sun0:0011 °c8 mph0 j/kg40 %32 mphSun3:0011 °c8 mph0 j/kg40 %32 mphSun6:0015 °c11 mph93 j/kg0V Light19 %22 mphSun9:0018 °c12 mph432 j/kg-2V Light42 %24 mphSun12:0019 °c13 mph524 j/kg-3V Light44 %25 mphSun15:0019 °c10 mph514 j/kg-3V Light18 %26 mphSun18:0016 °c7 mph73 j/kg0V Light2 %26 mphSun21:0016 °c5 mph0 j/kg2V Light15 %18 mph

[NO LONGER POSTING]

http://www.metcheck.com/V40/UK/FREE/stormwatch.asp

Dosnt look that good 0.o

[SteveB]

Well had some very heavy showers overnight & this morning, already had 11mm from them, I have not heard or seen any thunder & lightning but it looks like there has been some already.

[MP-R]

Well the ol' man who insisted on staying up until 2am playing on the Wii said this morning there was a monumental downpour overnight around that time with high winds and loud thunder! Typically, I was fast asleep in bed.

Already had another very heavy downpour this morning and looks like more to come with some sferics popping up already. Just short of 15mm in the guage at the moment.

[Coast]

UKASF have gone with a moderate risk for much of southern England and Eire for Sunday

ESTOFEX and TORRO have nothing so far for today, but I susopect that may change during the morning to something like the NW and UKASF ones. SkyWarn have a severe warning mostly for the rain in Scotland:

SKYWARN UK SEVERE WEATHER WARNING #040

ISSUED: 1000UTC SATURDAY 6TH AUGUST 2011

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

CENTRAL SCOTLAND

EASTERN SCOTLAND

NORTHERN ENGLAND

IN EFFECT UNTIL 1200UTC SUNDAY 7TH AUGUST

DEVELOPING SURFACE CYCLOGENESIS UP THE EASTERN SIDE OF THE UK STALLING A FOCUS OF CONVECTIVE RAINFALL

SEVERE WEATHER IS EXPECTED IMMINENTLY, OR OCCURRING, SOMEWHERE WITHIN THE REGIONS INDICATED. THREATS WITHIN THIS WARNING INCLUDE, BUT ARE NOT LIMITED TO: HEAVY RAIN...PERSISTENT RAIN...FLOODING...STRONG GUSTS

DISCUSSION:

THERE IS STRONG MODEL CONFIDENCE OF A SEVERE RAINFALL THREAT TO THE WARNING AREA. DURING THE LATE AFTERNOON AND EVENING, STORMS ALREADY EVIDENT WILL CLUSTER INTO A DYNAMIC RAINMASS WHICH BECOMES STALLED OVER THE SOUTHERN UPLANDS AND AREAS WITHIN 50 MILES OF THERE. RAIN IS EXPECTED TO BE HEAVIEST OVERNIGHT AROUND EASTERN PORTIONS, BUT NONETHELESS ACCUMULATIONS ABOVE 40MM ARE EXPECTED FOR THE AREAS CONCERNED WITHIN THE PERIOD, WITH UP TO 100MM POSSIBLE OVER HIGH GROUND. FURTHER RAINFALL IS EXPECTED TO LAST WELL INTO SUNDAY MORNING. THERE EXISTS A DEFINITE THREAT OF FLOODING IN STEEP CATCHMENTS, AND SURFACE FLOODING ELSEWHERE. PLEASE MONITOR WEATHER AND TRAVEL INFORMATION REGULARLY.

Here's the Scottish and South West threats on the 21st OWS map for 12Z:

Their MetO interpretation shows all the other areas of the UK under threat for thunder, but the rain is defintely in Scotland:

Aviation weather shows the SW, Channel and Scotland areas and more on the way in the Atlantic:

KO and Soaring indices with areas of convection over RoI and coming up the Channel approaches at lunchtime:

CAPE doesn't really get going until later in the day

Some areas of Scotland will continue to be pounded by rain

GFS has more CAPE along The Channel:

Shear in Devon, Dorset and surrounding:

Some convergence in that area too:

Look at the lift in the SW and Scotland:

and the convective rain in the SW too:

Lapse rates higher than yesterday

The spout potential:

Blimey, there's a lot going on today in the air! Big rain for Scotland and a few possibilities for storms in Southern Ireland and the South West of England, moving East perhaps overnight?

[Lynxus]

WOW,

Its actually looking good for here for ONCE this year..

I do however fear it will drift north of here..

Anyway...

Lookin good!

Theres some beefy showers already affecting the west of here..