Convective Outlook

[Coast]

So maybe some activity on Sunday 25th, but use this thread to discuss any UK convective potential and current thunderstorms/hail/tornadoes etc.

[BlueHedgehog074]

The video dogs32 posted in the other thread:

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Edit: http://www.youtube.com/watch?v=4UwwrzAu70Q&feature=player_embedded

That's quite a cloud base, I must say.

Really do have my fingers crossed for the chance of any storms in a few days time. But out of all the the possible convection possibilities on the models and maps, which convection signs on the models and maps would you say was the most important for thunderstorm development?

[dogs32]

The video dogs32 posted in the other thread:

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That's quite a cloud base, I must say.

Really do have my fingers crossed for the chance of any storms in a few days time. But out of all the the possible convection possibilities on the models and maps, which convection signs on the models and maps would you say was the most important for thunderstorm development?

I think that was around Heulva Southern Spain...lots of video's of it on youtube..

Sunday could be my day for a Thunderstorm(first of the year) :drinks:well I can hope

[Stuart]

yep i hope i see some here to pat or i will go and

[dogs32]

yep i hope i see some here to pat or i will go and

lol...Stuart...Realy its still very early in the Season for the UK...but we do get some suprises from time to time.

Hopefullly this week.

but to be honest I dont hold alot of faith on this event

[Stuart]

metoffice not saying anything about it yet

so dont look like it happing but still time

[Harry]

It is normally around this time and into May that I start to get a little excited for the impending UK storm season

Past years have shown (in my observations at least) that the second week of May onwards is when you can really start to get some decent storms, in particular the imports. Prior to then, like last year for example, plumes do occur and you can get some relatively decent thunderstorms moving N from France (two days running last year) but they then tend to weaken quite quickly after travelling across the cold Channel. Unless you live in Kent/Essex you tend not to see too much. Best hopes for the imports is if they are coming in from a SE'rly direction - minimal channel to pass, better chance of maintaining umpf!

Years when I've had SATs, GCSEs and A Level/IB exams, there has always been at least one big night time storm and several day time storms too. As today is Apr 22nd, I'd say give it another 3 weeks to a month and we might be in business

[Stormyking]

Hi Rainbow Snow,

Still plenty of time for changes to the set-up regarding Sunday's thunderstorm potential, but hopefully it'll turn out to be a decent day for convective activity. Regarding most important indications for thunderstorm development, the charts provided by GFS that show surface-based or mixed-level CAPE (Convective Available Potential Energy) will give you a quick indication of what day has thunderstorm potential.

Contributors to CAPE are low-level warmth and moisture (which are indicated by dewpoint and humidity charts) under cold air aloft (indicated by 500mb temperature and 850-500mb lapse rate charts). Mid-level dry air intrusion (indicated by relative humidity and dewpoint depression charts) will enhance hail potential and downdraught strength within a thunderstorm as negatively buoyant air aloft sinks, resulting in strong convective downdraughts.

As we get closer to the time, provided there is sufficient instability you would want to look for a forcing mechanism, such as a small-scale trough (shown on Met Office FAX charts). Other forcing mechanisms could be frontal forcing where showers, storms form along a cold front, or through surface heating.

Sunday doesn't look to produce any severe convective weather. When wanting to see whether thunderstorms have the potential to become severe, you would want to look at the shear charts, both deep-layer and at low-levels - this will give a good indication of whether storms will become organised or turn with height, enhancing the potential for tornadoes.

Hope this helps.

Hi what are shear charts adn what do they mean?

Sorry jsut trying to learn more hehe. Anyway Sunday does look interesting for some convection and maybe a storm or 2 in places so lets hope it stays

[Stormyking]

Shear can fall into two types: Directional shear and Speed shear. Directional shear is a change in wind direction with height, i.e the higher up into the atmosphere you go, the more the wind changes direction. For example, surface winds may flow from a south west direction, whereas higher up they are backed to a southerly or south easterly direction. Speed shear is a change in wind speed with height, i.e wind speed increases the higher up you go.

Strong speed shear can tilt a thunderstorm's updraught, seperating it from its downdraught, thus sustaining the upward ascent of warm, moist air into the thunderstorm without being cut-off by its downdraught. This results in a more long-lived thunderstorm. Both deep layer and low-level shear can enhance the tornado potential by causing a thunderstorm's updraft to rotate.

The GFS measures shear in metres per second, indicating its strength. When GFS forecasts days of strong deep-layer or low-level shear, also check to see there is sufficient instability. Usually several 100j/kg CAPE is enough for tornadic activity given sufficient low-level shear.

Here is a very useful site on thunderstorm development and structure: http://www.theweathe...re/ingredients/

Hope this helps.

Thankyou for that, that was very helpful and the site helps alot too.

[Jane Louise]

Hi Storm lovers , take a look at this On the left click the Paremeter and choose Modellwetter tick the panel underneath and then scroll down to Sunday 15 UTC ... It's looking good so far But I expect it will be downgraded lol.

http://www.wetter3.de/preview.html

[Coast]

Still a way to go, but a nice sunny day on Sunday might just let this lot kick off:

[Stuart]

Seem been still downgreading for me but we dont get 1st storm tell may here

[Coast]

Still a way to go, but a nice sunny day on Sunday might just let this lot kick off:

Might be a Midlands thing:

[Jane Louise]

How on earth do you interpret those lightning charts Coast lol?I tried learning but I still don't understand them lol

[Coast]

How on earth do you interpret those lightning charts Coast lol?I tried learning but I still don't understand them lol

Still learning myself Jane Louise!!

Sit yourself down in a quiet spot, with a nice drink and a biscuit and read through this lot (if you haven't already seen them all):

http://forum.netweather.tv/topic/16002-a-simple-guide-to-understanding-skew-t-diagrams/

http://www.atmos.millersville.edu/~lead/SkewT_HowTo.html

https://www.e-education.psu.edu/meteo361/cape_primer.html

Then roll yourself off a copy of today's Skew-T charts/soundings (with explanations) from here:

http://www.skystef.be/sounding.htm

and see how they compare with your own thoughts/understanding.

Nothing going on for me this morning according to the Herstmonceux reading taken last night:

There's no magic answer to this stuff other than keep observing , reading and learning the guides + seeing the outcome. I'm no expert at all, but I know where to go for the info!

[Jane Louise]

Still learning myself Jane Louise!!

Sit yourself down in a quiet spot, with a nice drink and a biscuit and read through this lot (if you haven't already seen them all):

http://forum.netweat...kew-t-diagrams/

http://www.atmos.mil...kewT_HowTo.html

https://www.e-educat...ape_primer.html

Then roll yourself off a copy of today's Skew-T charts/soundings (with explanations) from here:

http://www.skystef.be/sounding.htm

and see how they compare with your own thoughts/understanding.

Nothing going on for me this morning according to the Herstmonceux reading taken last night:

There's no magic answer to this stuff other than keep observing , reading and learning the guides + seeing the outcome. I'm no expert at all, but I know where to go for the info!

Thank you Coast

I will start learning soon

[Harry]

Potential improved again for the SE - region of 800-1000 J/Kg of CAPE with relatively decent LI values.

Not expecting a great deal here action wise, but could provide some nice cloud scapes for photography practice

[Nick F]

Potential improved again for the SE - region of 800-1000 J/Kg of CAPE with relatively decent LI values.

Not expecting a great deal here action wise, but could provide some nice cloud scapes for photography practice

Probably stay dry in the far SE corner, given the S or SW flow - with any storms tending to track NE to the N of Kent and Sussex, unless there's sufficiently strong forcing along the cold front - though front looks weakest on southern most extent with high pressure close to the south.

[BlueHedgehog074]

Hi Rainbow Snow,

Still plenty of time for changes to the set-up regarding Sunday's thunderstorm potential, but hopefully it'll turn out to be a decent day for convective activity. Regarding most important indications for thunderstorm development, the charts provided by GFS that show surface-based or mixed-level CAPE (Convective Available Potential Energy) will give you a quick indication of what day has thunderstorm potential.

Contributors to CAPE are low-level warmth and moisture (which are indicated by dewpoint and humidity charts) under cold air aloft (indicated by 500mb temperature and 850-500mb lapse rate charts). Mid-level dry air intrusion (indicated by relative humidity and dewpoint depression charts) will enhance hail potential and downdraught strength within a thunderstorm as negatively buoyant air aloft sinks, resulting in strong convective downdraughts.

As we get closer to the time, provided there is sufficient instability you would want to look for a forcing mechanism, such as a small-scale trough (shown on Met Office FAX charts). Other forcing mechanisms could be frontal forcing where showers, storms form along a cold front, or through surface heating.

Sunday doesn't look to produce any severe convective weather. When wanting to see whether thunderstorms have the potential to become severe, you would want to look at the shear charts, both deep-layer and at low-levels - this will give a good indication of whether storms will become organised or turn with height, enhancing the potential for tornadoes.

Hope this helps.

Thank you. Wow, there is much more to condsider than I imagined and the development of hail was particularly interesting, too, so thank you.

Will be useful for trying to predict any possible thunderstorm activity. Although I have not looked at the charts yet, I see that the 10 day NetWeather forcast has upped the storm risk to 51% for here on Sunday.

[Supacell]

Well i am back and ready for the 2010 storm season, will be chasing around the UK again as usual - but from a different base now as I have moved from Derbyshire to Yorkshire.

Nice to see chances so early on on the season this coming Sunday. I will be watching the charts and forecasts closely over the coming couple of days and i'm hoping to get my first chase. Decent CAPE and LI values over a good part of the country.

[Costa Del Fal]

Looking good for us on Sunday with some good Cape etc.

If there was one place i think has the best chance of storm, it will be somewhere near Manchester.

[Stuart]

Look better for me on this run more caps and Li

[Costa Del Fal]

Look better for me on this run more caps and Li

Doesnt necessarily mean you will get a storm though. Just more favourable. GFS is keen to have precipitation around here on Sunday so a good chance hopefully.

GFS is keen to give The Midlands, parts of S & N England and Ireland the best chances.

[Lynxus]

Awesome!

Cant wait for tomorrow ( Beer garden )

Cant wait for sunday STORMS!

Fingers crossed!

[Nick F]

Potential for storms on Sunday looks mostly to be in post cold front environment with steeper lapse rates, cold front itself looks mainly dynamic rather than convective rainfall atm - though that's not to say it might yield convective elements along it. Can't see any severe potential, wind shear should be rather weak, perhaps some small hail and gusty winds accompanying showers/storms.