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Is a late post but just thought I'd mention that Estofex have issued a Level 1 for the Southern half of the UK for tomorrow evening, mainly for Tornadoes and Severe wind gusts. As well as that we're under a general thunderstorm risk area.

Yep, a little belter if it comes off!

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I just hope it's light enough outside to see anything that happens.

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But if we also get some Tstorms.....

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No update on yesterdays forecast from TORRO, worth keeping an eye on their site as well as here today. Trust this stuff to come up when the kids are due back at school in the morning!!! :)

Looking further ahead, it could be quite quiet I'm afraid:

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Things look to get started late afternoon in the SW as the front moves through and a surface trough follows it.

All this talk of the intrusion of drier air and strong low level shear might bring the convective line we want!

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Going to keep an eye on this cold front as it sweeps through with Danny on its tail!

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Brick as just posted an in detail of the technical side of things..

Just hope for some sqaully hail shower's tonight as the cold front passes

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met office updated now for warning's for Devon and Wales

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Many of the charts has the middle part of next week seeing the start of a fairly warm, even hot spell across many areas of the UK, though as you may have guessed, predominately England and Wales. As we all know by now, this is a fair way off and subject to change, potentially significant change, however with most if not all models currently in agreement for a warmer/hotter spell, it looks promising IMO.

With the increasing temperatures, we can expect humidity to rise as well. The spell, while appearing at this stage to last a fair few days, will be governed by areas of HP moving around the British Isles, so while generally warm, it is likely the humidity will be up and down and therefore Convective potential quite erratic also.

GFS is pointing at rising CAPE levels later next week, at this stage favouring the West.

As I said however, this is all subject to change, hopefully not too much however - while we have left an appalling month for thunderstorms and for the N and W in particular, quite poor weather, this may perhaps offer some hope for September!!

Scottish/N Irish residents may not like it too much however - especially the 4th chart :mellow:

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another warning(amber) up date from meto.

going to be an interesting evening and the small hrs

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Tornado Watch issued from TORRO:

Severe Weather Forecast

Will be interesting to see what comes of this evening and into the night. Like Coast said, this note about there being a few small dry air intrusions makes me think that there's certainly a chance of a intense storm. But with little CAPE can't help but feel instability is too low to promote some serious convection. I'm not sure though, my limited knowledge doesn't help :mellow:

I like this bit

The intensity of the low-level flow, especially SE of S Wales to the Wash, means that a strong tornado is possible.

:D

weather 09 its not just Cape that is needed for storm's..if my knowledge is correct...

i think 3 factor's can produce a good storm ..instability with vertical shear and of course lift...

but im still studying like you...but i think a few factor's need to come together

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I like this bit

The intensity of the low-level flow, especially SE of S Wales to the Wash, means that a strong tornado is possible.

:mellow:

weather 09 its not just Cape that is needed for storm's..if my knowledge is correct...

This is my view on it - like Weather09, not a meteorology boffin by any stretch so feel free to ignore :D

We have at our disposal today/tonight the following:

Areas of CAPE for southern most regions

An airmass with a high content of moisture

A relatively warm airmass, with cold air aloft however (should be a nice convective gradient in that case)

Strong upper level and lower level winds

Shearing winds

Fronts and troughs providing some good lift, aiding Cb development, with the aforementioned helping organising this in places, perhaps providing some quite potent thundery downpours in places

To me, we seem to have many of the ingredients for some exciting weather. The two things we do not have, which would make things a lot more exciting, is decent CAPE/LI values (as per Weather09's post) and higher temperatures. What my 'instincts' are telling me (please feel free to correct me if I am wrong), is that absence of decent CAPE/LI values may be compensated by the presence of the fronts/troughs, and also the temperature gradient.

Thoughts/opinions?

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Guest North Sea Snow Convection

Brickfielders good analysis suggests a low risk. Isn't it the case that TORRO etc often get over excited with these forecasts?

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Harry I think that is a real good post you have made there...

I have my ideas on some of your thought's but I would prefer an expert to answer some of them

Severe weather and tornadoes can develop in an area of relatively low CAPE values

Other factor's can play a part

edit...Weather 09 please dont get me wrong im not at all having ago...just saying sometimes other factor's can produce Severe weather :mellow:

Edit...

exampleA

April 20, 2004 tornado outbreak over all

i hope thats the correct date :D

CAPE was weak

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This is my view on it - like Weather09, not a meteorology boffin by any stretch so feel free to ignore :D

We have at our disposal today/tonight the following:

Areas of CAPE for southern most regions

An airmass with a high content of moisture

A relatively warm airmass, with cold air aloft however (should be a nice convective gradient in that case)

Strong upper level and lower level winds

Shearing winds

Fronts and troughs providing some good lift, aiding Cb development, with the aforementioned helping organising this in places, perhaps providing some quite potent thundery downpours in places

To me, we seem to have many of the ingredients for some exciting weather. The two things we do not have, which would make things a lot more exciting, is decent CAPE/LI values (as per Weather09's post) and higher temperatures. What my 'instincts' are telling me (please feel free to correct me if I am wrong), is that absence of decent CAPE/LI values may be compensated by the presence of the fronts/troughs, and also the temperature gradient.

Thoughts/opinions?

yep, good post, have yourself a complementary reputation point H.....key ingredient is instability in the atmosphere, and with this ex-tropical low, with a mixture of dry & very moist air, there's plenty of that pushing across the country this afternoon & tonight

indeed SAT24 visibile & infra-red imagery is already showing some pretty deep convective clouds building on the rear flank of the frontal system approaching SW England and the Welsh coast

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Well even though I'm still learning, I'd like to think I've got some knowledge on storm development under my belt :D First and foremost, instability. I don't see much of this for this evening. Indeed there will be favourable forcing as Estofex have mentioned, but as they have also added, MLCAPE is at least, marginal and how much of this instability will materialise is difficult to predict. Of course, should any cells form then the conditions are there for them to turn severe (Low level shear being the more notable factor).

I think sometimes people misunderstand what I'm saying. I have a lot to learn about storm development and structure, but I don't have such simplistic view, as think CAPE is the only thing needed for storms.

Please don't view my post as suggesting your views/you are simplistic - that's not what I meant at all :(

I just read your post as saying, little CAPE, little instability, little chance :(

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Cheers for the rec's above :D

Just thought I'd mention the mass of rain is now starting to develop quite a pronounced hook over Ireland, with some heavier pulses of rain showing up across Rep of Ireland, CS England, and also appearing to be re-organising across the SW/S Wales.

Can't seem to find any sferics, however should (emphasis on SHOULD) any occur it is likely to be into the evening and overnight period (good really as it should mean more will see it/them :()

Also noticed the breeze is slowly but surely starting to build here too - it's a-coming people :(

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just a thought....there's an area of substantial CAPE, lift and steep lapse rates currently in the LP centre just off the welsh coast, I wonder if this area of potential will traverse eastwards with the LP centre?....could be very interesting tonight if it does!

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just a thought....there's an area of substantial CAPE, lift and steep lapse rates currently in the LP centre just off the welsh coast, I wonder if this area of potential will traverse eastwards with the LP centre?....could be very interesting tonight if it does!

Indeed - 06Z GFS seems to indicate an area of CAPE running up towards the SW around this time, and travel E throughout the course of this evening and overnight, before becoming more pronounced as it leaves the SE/EA coastline...will be interested to see what the 12Z view is on the CAPE, which should be updating around now.

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One of the main methods that Strong tornadoes are created is from low level speed shear. Mid level directional shear which can form super cells then tends to help sustain the tornado.

Notice that updraft strength can play a part in lifting any low level vorticity and for updrafts to be strong you would typically look for steep low level lapse rates which you tend to get with higher surface temperatures.

Since we have some low level directional wind shear as well then a number of other tornado genesis methods may come into play. These include vortex shedding around ground features, outflow boundary vortex creation, but what these tend to have in common is that tornadoes tend to be short lived and weak.Having said all that individual storms can create their own little micro environments.

Predicting severe storms is slightly different from looking at tornado possibilities and here the ingredients may come together. Drier air coming in aloft with shallow areas of moisture are good conditions for severe storm development. If this was June and this system was coming through earlier in the day then I think the risks would have been moderate of a severe storm developing. Cape or instability is the concern, although we should note the divergent air aloft which will act rather like blowing across a bottle top, sucking up air from below.

Satellite pictures suggest to me some storms are likely, however how long they last and whether they will be severe is debateable. Those looking at Torro should note the subtle differences in discussions, watches and warnings. The best bet is to ignore the models now for this evenings potential and concentrate on radar and satellite pictures.

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Cheers BF! As ever I learn more and more from your posts :D

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The rainfall really seems to be beefing up now across CS England, and moving towards the SE/EA - I should have thought coinciding with rush hour traffic around London, an amber will be posted pretty toutes-suites by the MetO!!! Rain starting to sprinkle at the moment and the breeze getting that bit stronger too - with some very dark dense clouds moving in - rather warm too :D

Some slightly more convective downpours getting going across the SW it seems too! :(

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I wouldnt take the Cape charts too literally. Quite often it predicts a little cape then on the next run it suggests a wide area of good Cape. Anyway thats not is only needed for a storm.

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The rainfall really seems to be beefing up now across CS England, and moving towards the SE/EA - I should have thought coinciding with rush hour traffic around London, an amber will be posted pretty toutes-suites by the MetO!!! Rain starting to sprinkle at the moment and the breeze getting that bit stronger too - with some very dark dense clouds moving in - rather warm too :D

Some slightly more convective downpours getting going across the SW it seems too! :(

We had a nice little convective downpour when I arrived at work this morning (8.10am), a few heavy showers during the day has given 4.7mm of rain already! That is also the most rain to fall in a day since 7th August! Shows how dry we've been down here, I bet the grass is loving it! Looking forward to tonight :(

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One of the main methods that Strong tornadoes are created is from low level speed shear. Mid level directional shear which can form super cells then tends to help sustain the tornado.

Notice that updraft strength can play a part in lifting any low level vorticity and for updrafts to be strong you would typically look for steep low level lapse rates which you tend to get with higher surface temperatures.

Since we have some low level directional wind shear as well then a number of other tornado genesis methods may come into play. These include vortex shedding around ground features, outflow boundary vortex creation, but what these tend to have in common is that tornadoes tend to be short lived and weak.Having said all that individual storms can create their own little micro environments.

Predicting severe storms is slightly different from looking at tornado possibilities and here the ingredients may come together. Drier air coming in aloft with shallow areas of moisture are good conditions for severe storm development. If this was June and this system was coming through earlier in the day then I think the risks would have been moderate of a severe storm developing. Cape or instability is the concern, although we should note the divergent air aloft which will act rather like blowing across a bottle top, sucking up air from below.

Satellite pictures suggest to me some storms are likely, however how long they last and whether they will be severe is debateable. Those looking at Torro should note the subtle differences in discussions, watches and warnings. The best bet is to ignore the models now for this evenings potential and concentrate on radar and satellite pictures.

excellent post..many thanks very informative

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I wouldnt take the Cape charts too literally. Quite often it predicts a little cape then on the next run it suggests a wide area of good Cape. Anyway thats not is only needed for a storm.

with Cape also there is a value you can add on or take away...500 I think..not sure though

of how much....so add 500 or take away 500...not sure cant remember how much

chucking it down here...on the edge of torrentail

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with Cape also there is a value you can add on or take away...500 I think..not sure though

of how much....so add 500 or take away 500...not sure cant remember how much

chucking it down here...on the edge of torrentail

light to moderate rain here, 2mm so far, looks like its all over for the midlands at the moment.

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light to moderate rain here, 2mm so far, looks like its all over for the midlands at the moment.

I cant see why it would be al over for the Midlands. Unfortunately it looks like we wont get much rain but any storm risk comes later and the risk id for the Midlands, Wales and the rest of the south. :)

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