Convective Outlook

[BlueHedgehog074]

Greetings,

I was wondering whether anyone in the Midlands reported any hail or lightning? because it was absolutely throwing it down with rain on my way to my music lesson about two and a half hours ago.

I do kind of feel sorry for the people who have been caught out in this, but I would admit that I did find the heavy torrential downpours quite amazing to watch and I wasn't quite expecting the big shower from the South to keep most of its intensity, as it reached here.

There were some very interesting dangling looking nimbostratus-like cloud from the earlier downpour, too, which is a bit odd because I did not think nimbostratus clouds produced thunder, or sudden squally downpours like this.

Edit: Although I suppose there were a mixture of cloud layers from this?

Edited March 25, 2010 by Rainbow Snow

[Paul Sherman]

Hi Weather09

Yeah have nailed the time from another poster on Ukww and it is about 15 minutes before your Images above.

Seems something very Interesting went over at 1755pm

[gpspete]

just had a phone call from my partner she thinks a tornado has just gone through Thame Oxfordshire removing some roofing on an indusrial estate lots of debri in roads lots of thunder & lightning shall go on a reccy in an hour

Had a drive around Thame some very minor roof damage on trading estate lots of rubbish blown around nothing of much note except that only that area was worst effected the rest of Thame had the odd small branch and abit of rubbish blown around even a couple wheelie bins blown over quite a bit of standing water around,

I suspect just a bit of squally wind shear

but who knows I only looked at night and didnt speak to any eye witnesses but my girlfriend is convinced of the possibilty from what she saw and heard but it was hard to see what was going on as extremely heavy rain and hail at time

just been looking at my lightning detector some activity of sw brittany looked at latest sat pics some nice lumpy cloud in same area plus some out in sw aproaches so keep a weather eye open today

[Coast]

Well after a big bang start to this years storm season yesterday (typical, it really kicked of at home in Eastbourne while I was at work!!) ESTOFEX have something more showing for today and it's a very in-depth and interesting one!:

Storm Forecast

Valid: Fri 26 Mar 2010 06:00 to Sat 27 Mar 2010 06:00 UTC

Issued: Thu 25 Mar 2010 20:22

Forecaster: TUSCHY

SYNOPSIS

An omega-like pattern is anchored over Europe with two major troughs (first one is placed over the Bay of Biscay, drifting northeastwards during the forecast and a second one over west Russia with a marginal eastward movement) and a stout low/mid-level ridge in-between. Zooming into the western trough, a complex nature of various waves with different amplitude circle that feature, causing a tricky mid-/high-level streamline pattern.

i) First short-wave exits the S/E North Sea (06Z-12Z) to the north while weakening over Norway (15Z onwards)

ii) A second one over SW-France (06Z) with an ENE-ward motion, affecting E-France (12Z) and SW-Germany (18Z)

iii) The most dynamic wave, moving over S-France and N-Italy to the east during the outlook period

iv) The upper trough axis, entering the W-English Channel/N-Bay of Biscay area during the evening hours with slow eastward movement.

At lower levels, a cold front/convergence zone ranges from SE-France to SW-Germany during the morning hours, which already reveals impressive LL convergence signals. This slow moving cold front intensifies thereafter due to numerous reasons:

i) augmented convergence due to the rough orography over Switzerland (SE-France/Switzerland)

ii)the dynamic / kinematic reasoning due to the NE-ward traveling short waves (SE-France/SW Germany)

iii)falling surface pressure over SE Germany due to diabatic heating but also due to adiabatic warming as strong foehn winds continue

This surface low lifts out to the north beneath a favorable jet coupling and good high-level divergence.

It is a bit hard to determine the structure of this cold front, but many signs hint on an ana-type cold front. This type of front is characterized by a broad stratiform postfrontal rain shield and a narrow zone with enhanced convection along its leading egde. In addition, due to continued geostrophic adjustement, as front strengthens, the thermal circulation ought to play an increasingly important role for potential initiation over parts of Germany later-on.

DISCUSSION

The model bias is insignificant with NOGAPS, GME, GEM, EZMWF and GFS all print the sub-990hPa depression SW of UK and a developing 1005hPa surface depression over SW-Germany beneath impressive upper divergence. Minor discrepancies in strength and placement of this depression are visible, but nothing too significant. This similarity is also present over NE-Germany during the night hours with the northward moving depression. Major discrepancies exist in the BL air mass quality with EZMWF running below the GFS output, so CAPE fields still reveal differences. For now, we stick with a medium between EZMWF and GFS, as surface dewpoint reality is found somewhere in between both outputs. Run to run consistency of the model outputs is good.

... France, Ireland and parts of UK ...

In the postfrontal air mass, daytime driven showers and thunderstorms occur over central France and westwards, as diabatic heating, a well mixed BL and steep mid-level lapse rates result in 200-500 J/kg SBCAPE. Shear is weak at best, so the main risk will be marginal to isolated large hail due to a low WBZ level. The activity wanes after sunset. The same will be the case over parts of Ireland and SW-UK.

The next convective flare-up occurs over NW-France at midnight onwards, as the upper trough axis draws near from the west. This feature is of special interest, as the occluded depression beneath the upper trough results in an increase of the BL moisture in a strongly sheared environment (0-1km speed shear 15-20m/s and direcitonal shear 150-250 m^2/s^2). Despite a severe wind gust risk with 850hPa winds increasing to 25m/s, the tornado risk will not be negligible. A level 1 mainly for severe wind gusts was issued as the final tornado risk has to be evaluated in upcoming model runs, but at least an isolated tornado event can't be ruled out.

Nothing from UKASF as they are on maintenance shutdown, also nothing yet from TORRO although they did come in with a late one yesterday afternoon just before it kicked off down here.

Charts and models for today:

Look at this one and consider the direction it might head in:

So what do we think today then peeps? A reapeat of late yesterday afternoon??

[Harry]

That radar grab throws something interesting I think.

Just to the East of Ockenden (circled yellow) there is an area of very heavy precipitation, right next to an area of very light precipitation, which would suggest a very strong downdraught adjacent to a very strong updraft, and potentially a funnel.

Thoughts?

[Paul Sherman]

Brother in Law has confirmed that he is trying today to get the CCTV Footage of the Builders Yard that sustained damage from 1745-1815 from yesterday so should be good to see what happened if he can get this data.

On another note if we were not surrounded by water then Southern Ireland would be my pick for today. Think they could get some lively Storms later this afternoon. Wales also looks quite good for something as well.

Paul S

[snow raven]

That radar grab throws something interesting I think.

Just to the East of Ockenden (circled yellow) there is an area of very heavy precipitation, right next to an area of very light precipitation, which would suggest a very strong downdraught adjacent to a very strong updraft, and potentially a funnel.

Thoughts?

I'm not too hot with Essex locations, but is Ockenden anywhere near Thurrock? I reported yesterday on this thread I could see a storm in that direction, and I have to admit, the sky looked positively evil. There was also loads of scud cloud (I think thats what its called) and I did wonder if there would be any reports of possible tornados.

[Coast]

I'm not too hot with Essex locations, but is Ockenden anywhere near Thurrock?

Close enough SR!

[Nick F]

Have released a storm forecast for today: http://www.netweather.tv/index.cgi?action=convective;sess=

More widespread risk of catching a heavy shower - with risk of hail and thunder, more tending to form overland today with more in the way of sunshine than yesterday.

[Thundery wintry showers]

As long as that "pesky" low pressure doesn't hang around in the western North Sea next week it could well be a very productive period for convection coming up- today looks like many places have a chance of seeing major convection (especially towards the SW) and to a lesser extent tomorrow as well. Then, as long as that low moves out into the North Sea, following a spell of dull wet weather and possible rain to snow event, a northerly regime with sunshine and wintry showers is suggested for next week, and those regimes can be pretty dramatic at this time of year.

[snow raven]

Close enough SR!

Thanks Coast. I only know where Thurrock is thanks to Lakeside Shopping Centre

[Harry]

Not sure if GFS has recently updated, but I can't see much CAPE to get excited about to be honest, nor substantial storm risk. Decent levels across NW France, which unless we are relying on imports like yesterday, should be our only hope. Unless you live in the SW which still has some CAPE available for some action.

I'd say based on current GFS models, my best bet to see any action will be tomorrow, with an area of CAPE lining up along with M4 corridor, stretching from the SW to the SE.

I've gone exceptionally rusty again knowledge wise over the winter period so will rely entirely on Nick F and co me thinks, because what I've written above seems well off the mark to what others have said

[The PIT]

Yup looking pretty quiet at the moment. Some shower activity in the west but nothing major on the radar.

[kold weather]

Might also have news of a Tornado in South Ockenden (Essex) at approx 6pm to 630pm this evening. Brother in Law phoned me to say he witnessed a Thunderstorm with Hail that has created some damage in the General RM15 Area more specifically (Arrowdale Road)

The damage includes some 20ft Empty Containers that have been moved 50ft across a yard and Eye witness reports of a Funnel Cloud.

If anyone has the radar grab from approx 630pm this would be great.

Paul S

NOOO!!!

I can't believe that, thats where I live in non uni times, unreal to have something like that in my hometown, thats the second huge weather event I missed back home now in 2 years!

Still I suppose the thunderstorm yesterday and cracking CG bolt helps ease the annoyance a little.

Anyway I'm too close to the coast today probably to get much in the way of storms given the shift in wind direction, hopefully see some good structure though and the line coming up into the SW could be quite potent as well.

[MP-R]

I'm surprised at the lack of shower activity around here at the moment, have seen plenty of dark clouds but nothing falling from them, just lots of low cloud drifting passed stopping the sun getting to work.

Hopefully, some bigger ones will kick off over hte next few hours, I can see some slightly larger ppn areas to the west of here on the radar at the moment.

[SteveB]

Cloudy dull weather here at the moment, had some light showers earlier, but nothing major.

[BlueHedgehog074]

Looks like I had a direct hit with that shower. Surprisingly, though, it didn't look that dark as it passed over here (except possibly at the start), although there was a bit of a downpour with some gusty winds. It almost looked like hail was going to fall along with the large rain at one point.

Seems to have grown into a more of a king-sized shower since I last looked at the radar about 40 minutes ago.

[Andy Bown]

I was recording some footage towards Thame around 5.20pm today, certainly was very squally with vicious hail , winds shook the car a bit http://www.youtube.com/watch?v=xaB-Uyo_4dQ

Why is the same flash of sheet lightning repeated several times at the beginning of your video?

[kamboocha_mushroom]

Just had a heavy downpour for 10 minutes or so, along with some hail. Well, at least a reminder of the summer weather to come :lol:

[Coast]

I'm surprised at the lack of shower activity around here at the moment, have seen plenty of dark clouds but nothing falling from them, just lots of low cloud drifting passed stopping the sun getting to work.

Plenty of heavy showers here in Mid Sussex!

[tcc]

Plenty of heavy showers here in Mid Sussex!

Really? I can see some darkish clouds to my south and south west, but it's mostly sunny here!!

[Harry]

Lots of Cu clouds building up around here, some with very dark bases!

Reliable blue sky and sunshine in between however :lol:

Spotted a rather potent looking downpour across Hants at the moment - all starting to kick off now it would appear!

Edited March 26, 2010 by Harry

[SteveB]

Looks like the cloud has killed of any convection here in Somerset.

Dull & cloudy.

[Coast]

Really? I can see some darkish clouds to my south and south west, but it's mostly sunny here!!

Was chucking it down but now the sun is out - which is a good thing I hope!

[staplehurst]

Thunderstorm in Yorkshire