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Convective / Storm Discussion - 21st April 2014 onwards


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Posted
  • Location: King’s Lynn, Norfolk.
  • Weather Preferences: Hot and Thundery, Cold and Snowy
  • Location: King’s Lynn, Norfolk.

Thursday looking like kind of a knife edge for the Midlands/E Midlands, another 50 miles shift South, then we're out of the game! 50 miles North, we're well within the boundary for some potentially impressive storms. 

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

Looking at the charts there does look to be some CAPE around, perhaps more so inland in areas bordering the Pennines. Nothing spectacular but enough to bring about a risk of thunderstorms.

 

Posted Imageukcapeli.png

 

When you then add to that the numerous convergence zones you then increase the risk, with areas along these zones being at the greatest risk (these zones are subject to some revision so I wouldn't take at face value).

 

Posted Imageukwind.png

 

There is very little shear so organised storms or severe weather would seem unlikely but showers and storms may continue to erupt in similar areas through the day and be slow moving and so localised flooding a possibility.

 

EDIT: WRF has the higher CAPE extending slightly further west than GFS with around 300-500j/kg by late afternoon.

Ties in with the MO forecasts for thundery showers further north tomorrow.
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Posted
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67
  • Weather Preferences: Winter - snow, Irish sea convection. Summer - thunderstorms, hot sunny days
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67

A bit early in the day for the Met office to be issuing warnings isn't it? Let's have a look. 

By the way who's ever idea it was to include push notifications in their iPhone app is a genius. So useful that.

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Posted
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67
  • Weather Preferences: Winter - snow, Irish sea convection. Summer - thunderstorms, hot sunny days
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67

Oh it's just for fog, nothing convection  related.

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Posted
  • Location: Leeds
  • Weather Preferences: snow, heat, thunderstorms
  • Location: Leeds

GFS shows decent cape values for this part of the world, while EURO4 shows heavy showers developing in the afternoon/evening. Looks good to me.

Edited by cheese
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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

The emphasis on showers and thunderstorms shifts north today, cloudy all day for many in the south, with a weak front pushing in to the south west later.

post-15177-0-46974100-1398847118_thumb.p

post-15177-0-09668000-1398847073_thumb.ppost-15177-0-38650600-1398847082_thumb.p

post-15177-0-03454800-1398847098_thumb.gpost-15177-0-89356400-1398847106_thumb.g

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Posted
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67
  • Weather Preferences: Winter - snow, Irish sea convection. Summer - thunderstorms, hot sunny days
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67

Nothing of interest really today:

 

Tomorrow though...

 

 

 

Posted Image

Posted Image

 

Posted Image

 

 

Posted Image

 

Looks like Corwnwall Devon is the breeding ground and then pushed Eastwards..

Posted Image

 

Hmmmmm 

 

Posted Image

 

Thats a nice chart!!

You forgot to say in southern England! Here the opposite is true, looks great today but crap tomorrow.

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Posted
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67
  • Weather Preferences: Winter - snow, Irish sea convection. Summer - thunderstorms, hot sunny days
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67

Sun is out strong now, temperature 14.9 °C

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Posted
  • Location: Dorset
  • Weather Preferences: warehamwx.co.uk
  • Location: Dorset

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1398898800

Yellow warning out for tomorrow.

Nice not to be in it :rolleyes: mind you, I don't get anything thundery when I'm bang in the zone haha

That's the nature of showers unfortunately!

Edited by Mapantz
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Posted
  • Location: East Devon
  • Location: East Devon

I saw it from Beaminster when picking the kids up from school. It was off to the west so in your general direction.

 

Interesting and that's quite far from here, nice to have a report from another angle

Nice catch ET not easy to observe as you said only lasting a few minutes. Looking well defined on the 2nd photo. Should send a report to ESTOFEX,TORRO.

 

 

 

 

A bit of a late reply but thanks guys :) I had noticed a lowering to keep half an eye on, then a couple minutes later it had formed the suspicious shape in the photos. I wasn't completely sure as it was quite far away (these photos are at x3 zoom) and I could not confirm rotation though it looked as if it could have been rotating and looked a bit too 'smooth' to be ordinary scud

I've now seen this thread on UKWW, at first I thought it was the same funnel I saw from a different direction, but this was 2 hours later at 17:30 after I had set off for uni, and puts my pics to shame.. it seems like there may have been multiple funnels and from different showers in this general area yesterday.. Maybe I should have driven to near Tiverton instead of back to uni!

http://www.ukweatherworld.co.uk/forum/index.php?/topic/103148-huge-funnel-cloud/

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Posted
  • Location: South Gloucestershire BS35
  • Weather Preferences: Severe weather enthusiast
  • Location: South Gloucestershire BS35

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1398898800Yellow warning out for tomorrow.Nice not to be in it :rolleyes: mind you, I don't get anything thundery when I'm bang in the zone hahaThat's the nature of showers unfortunately!

 

True but they did quite well earlier this week with their warnings I thought :)

 

Here's hoping....just inside the zone but feel my area may be breeding the showers rather than actually being in any.

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire

Perhaps a daft question, but can someone explain what to look for with regards to the amount of shear to help me improve my learning on how to forecast where storms may develop?

I do have access to charts that show LLS(low level shear 0-1km and also DLS(Deep level shear 0-6km). Which is used more commonly in terms of forecasting organised storms? Or is it both?

 

Well, there's no quantitative value for what level of shear causes more prolonged thunderstorms. But I tend to look at the deep level shear, as thunderstorms are a damn tall things! For those that don't know, wind shear is simply the change in wind speed or direction with height.

 

But why is shear important when it comes to thunderstorms? It's useful to discuss the structure of a normal thunderstorm in a non-sheared environment. In the early stages, the updraft (which "feeds" the storm) is dominant, intensifying the thunderstorm. Once the thunderstorm reaches its mature stage, rain begins to fall and enhances a downdraft. In a non-sheared environment, the downdraft works against the updraft, thus cutting off the fuel source for the thunderstorm, and dying away fairly quickly.

 

Now, if we add a bit of wind shear, we can get much more prolonged storms. This is because the change in wind speed/direction with height causes the storm to tilt, and this tilting separates the updraft and downdraft, meaning the fuel source is sustained for longer. The image attached shows it quite nicely. The rain shaft is normally associated with the downdraft. This is all in fairly basic terms and I may have made a mistake, so if I have, someone shout up :D

 

Posted Image

Edited by Nick L
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Posted
  • Location: Weston-S-Mare North Somerset
  • Weather Preferences: Hot sunny , cold and snowy, thunderstorms
  • Location: Weston-S-Mare North Somerset

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=map&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1398898800Yellow warning out for tomorrow.Nice not to be in it :rolleyes: mind you, I don't get anything thundery when I'm bang in the zone hahaThat's the nature of showers unfortunately!

They might as well remove my area from that warning, unlikely to see anything here other than the odd light shower...... toy's are well and truly thrown out of pram :sorry:

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Posted
  • Location: Bedworth , Warwickshire , 52.475°N 1.477°W
  • Weather Preferences: Dull And Uninteresting Weather
  • Location: Bedworth , Warwickshire , 52.475°N 1.477°W

even though the county I am in is the the warning zone (Warwickshire)

 

not sure if my actual actual area (Bedworth) is

 

will wait and see but hopefully they'll be further south

 

perhaps the storms will be like the economic recovery and limited to down south

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Posted
  • Location: South Gloucestershire BS35
  • Weather Preferences: Severe weather enthusiast
  • Location: South Gloucestershire BS35

Well, there's no quantitative value for what level of shear causes more prolonged thunderstorms. But I tend to look at the deep level shear, as thunderstorms are a damn tall things! For those that don't know, wind shear is simply the change in wind speed or direction with height.

 

But why is shear important when it comes to thunderstorms? It's useful to discuss the structure of a normal thunderstorm in a non-sheared environment. In the early stages, the updraft (which "feeds" the storm) is dominant, intensifying the thunderstorm. Once the thunderstorm reaches its mature stage, rain begins to fall and enhances a downdraft. In a non-sheared environment, the downdraft works against the updraft, thus cutting off the fuel source for the thunderstorm, and dying away fairly quickly.

 

Now, if we add a bit of wind shear, we can get much more prolonged storms. This is because the change in wind speed/direction with height causes the storm to tilt, and this tilting separates the updraft and downdraft, meaning the fuel source is sustained for longer. The image attached shows it quite nicely. The rain shaft is normally associated with the downdraft. This is all in fairly basic terms and I may have made a mistake, so if I have, someone shout up :D

 

 

 

Brilliant! Thank you :)

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire

Brilliant! Thank you :)

 

No worries! When I said "there's no quantitative value", I mean there's no definitive threshold. Just that the higher the wind shear, the higher probability you will get prolonged storms. No shear causes the "pop up" storms that only last an hour or two.

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Posted
  • Location: Belper, Derbyshire
  • Weather Preferences: Thunderstorms
  • Location: Belper, Derbyshire

Some sunny spells here now and BBC has the lightning symbol right over the top of Derby for this afternoon. I was thinking Derby is probably just a little far south today but if GFS is slightly out then I could be in luck staying at home.

 

Tomorrow I am hoping to go chasing and am not limited by time or work.

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Posted
  • Location: Llanwnnen, Lampeter, Ceredigion, 126m asl (exotic holidays in Rugby/ Coventry)
  • Location: Llanwnnen, Lampeter, Ceredigion, 126m asl (exotic holidays in Rugby/ Coventry)

Ireland the only place with thunder so far this afternoon.

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Posted
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast
  • Weather Preferences: Severe Storms and Snow
  • Location: Home near Sellindge, 80m/250feet, 5miles from Coast

Thunderstorm risk tomorrow?  That'l be the third time that's been forecasted then lol

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland

Well, there's no quantitative value for what level of shear causes more prolonged thunderstorms. But I tend to look at the deep level shear, as thunderstorms are a damn tall things! For those that don't know, wind shear is simply the change in wind speed or direction with height.

 

But why is shear important when it comes to thunderstorms? It's useful to discuss the structure of a normal thunderstorm in a non-sheared environment. In the early stages, the updraft (which "feeds" the storm) is dominant, intensifying the thunderstorm. Once the thunderstorm reaches its mature stage, rain begins to fall and enhances a downdraft. In a non-sheared environment, the downdraft works against the updraft, thus cutting off the fuel source for the thunderstorm, and dying away fairly quickly.

 

Now, if we add a bit of wind shear, we can get much more prolonged storms. This is because the change in wind speed/direction with height causes the storm to tilt, and this tilting separates the updraft and downdraft, meaning the fuel source is sustained for longer. The image attached shows it quite nicely. The rain shaft is normally associated with the downdraft. This is all in fairly basic terms and I may have made a mistake, so if I have, someone shout up :D

 

Posted Image

excellent post Nick....might be worth copying this post into the learning forums as well? :good:

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Posted
  • Location: Cheddington, Buckinghamshire
  • Weather Preferences: Winter: Cold & Snowy, Summer: Just not hot
  • Location: Cheddington, Buckinghamshire

excellent post Nick....might be worth copying this post into the learning forums as well? :good:

 

Thanks, seeing as no obvious mistakes have been pointed out, I'll paste it across :D

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