Convective / Storm Discussion - 4th October onwards 2013

[Nick F]

Storm & Convective Forecast

 

Issued 2013-10-20 08:04:21

Valid: 20/10/2013 0600Z to 21/10/2013 0600z

 

THERE IS A RISK OF THUNDERSTORMS FORECAST

 

Synopsis
Cylconic southwesterly upper flow will contain two or more shortwave troughs moving NE today, atop of mild and moist and southerly flow at the surface ahead of low pressure close to Ireland, providing another day with deep convection across much of Ireland, England and Wales.

... IRELAND, ENGLAND, WALES, S SCOTLAND  ...

Midnight Herstmonceux (E Sussex) and Camborne (Cornwall) radiosonde ascents indicate an unstable moist airmass in place across Sern Britain this morning with cloud tops likely to reach 25-30,000 ft and 200-300 j/kg CAPE sampled - indicating deep convection likely. One shortwave trough lying between SW Scotland and SE England and moving NE is currently bringing a line of thunderstorms across SE England. Further heavy showers and thunderstorms will likely move northeast across England, Wales and Ireland/N Ireland through the day as the airmass remains unstable. Further shortwave troughs are expected to move NE, providing additional lift and allowing showers/storms to organise into lines bringing a risk of strong winds gusts and large rainfall totals within a short space of time - bringing a risk of localised flooding.

Additionally, 30-40 knts of deep layer shear, low Lifted Condensation Levels (LCLs) and sufficient low-level veering winds across southern Britain may allow one or two storms to exhibit rotating updrafts or mesocylones - which could bring the small risk of tornadoes or waterspouts - particularly towards windward southern and western coastal areas. Therefore have issued a SLIGHT risk for southern portions of England and Wales.
 

Issued by: Nick Finnis

Edited October 20, 2013 by Nick F

[Guest William Grimsley]

 

Storm & Convective Forecast

convmap_201013.png

 

Issued 2013-10-20 08:04:21

Valid: 20/10/2013 0600Z to 21/10/2013 0600z

 

THERE IS A RISK OF THUNDERSTORMS FORECAST

 

Synopsis

Cylconic southwesterly upper flow will contain two or more shortwave troughs moving NE today, atop of mild and moist and southerly flow at the surface ahead of low pressure close to Ireland, providing another day with deep convection across much of Ireland, England and Wales.

... IRELAND, ENGLAND and WALES ...

Midnight Herstmonceux (E Sussex) and Camborne (Cornwall) radiosonde ascents indicate an unstable moist airmass in place across Sern Britain this morning with cloud tops to 25-30,000 ft and 200-300 j/kg CAPE sampled - indicating deep convection likely. One shortwave trough lying between SW Scotland and SE England and moving NE is currently bringing a line of thunderstorms across SE England. Further heavy showers and thunderstorms will likely move northeast across England, Wales and Ireland/N Ireland through the day as the airmass remains unstable. Further shortwave troughs are expected to move NE, providing additional lift and allowing showers/storms to organise into lines bringing a risk of strong winds gusts and large rainfall totals within a short space of time - bringing a risk of localised flooding.

Additionally, 30-40 knts of deep layer shear, low Lifted Condensation Levels (LCLs) and sufficient low-level veering winds across southern Britain may allow one or two storms to exhibit rotating updrafts or mesocylones - which could bring the small risk of tornadoes or waterspouts - particularly towards windward southern and western coastal areas. Therefore have issued a SLIGHT risk for southern portions of England and Wales.

 

Issued by: Nick Finnis

 

Looking good. I've never seen slight used in this forecast, before. Only thunderstorms.

[johnholmes]

Looking good. I've never seen slight used in this forecast, before. Only thunderstorms.

 

Please do not copy a complete text William especially when that text sits just above your post, it clutrters up the thread-thanks

 

regarding the forecast from Nick, this is the one to watch always in my view above any of the others

[poseidon]

Just had a bout of torrential rain go over with very dark sky - looked like the bright echo area on the rain radar. However, seems that this group of cells has finished it's thunder for the day.

[Supacell]

Very true JH. I await Nicks forecast on any convective days.

Well, a slight severe risk just touching Derby. I think radar watching, a car full of petrol and a charged camcorder will be the order of the day today. A lot of sferics around in the western channel currently.

Edited October 20, 2013 by Supacell

[MP-R]

Nope went home this weekend unfortunately, thought it might coincide with increased thunder chance here too but not the case.  Oh well there will probably be a storm at home in Devon this week while I'm back in Egham.

The heaviest pixel on the radar passed right over my student house lol.

 

Fair enough, well normally you'd be right haha. Though that clump of activity to the SW of the UK has more your name on it than here so if it can keep its intensity, fingers crossed! 

[Bluebreezer54]

Some rather menacing skies looking west towards Heathrow from my Office, can hear thunder too.

 

IMG00188-20131020-0759.jpgIMG00189-20131020-0759.jpg

Nice captures of the Singapore Airlines Airbus A380 there Nick. The dark stuff in the background is what passed over here delivering about 10 minutes of torrential rain, strong gusty winds and a couple of very close lightning strikes. Apparently lightning damaged railway signalling equipment in the Watford area, delaying train services.

 

There are as yet unconfirmed reports of a tornado on Hayling Island at about 7.30am  this morning, some photo's of damage now emerging.

 

https://twitter.com/ianhoult/status/391847153892859904/photo/1

[dave48]

Torrential rain and pea sized hail observed here over the last hour. No thunder yet though.

 

Have been caught in this streamer but skies clearing now.

Edited October 20, 2013 by dave48

[Mapantz]

Unfortunately, i've missed all the action again. How? I don't know! That aside, there's been a tornado in Hayling Island, reports of damage to 100 homes. I can't copy and paste the link, sorry.

 

Beach huts damaged, cars damaged, trees down .. and that horrible term was used 'mini' tornado,  i'll be on the lookout for mini-hurricanes next! 

Edited October 20, 2013 by Mapantz

[Wivenswold]

A few rumbles here from the cell that clipped the Tendring Coastline. 2nd storm in October, so can't complain.

[tinybill]

all eyes  on what coming  up the  channel ,its  near jersey  at the  moment  acc  to the  rain alarm

[Jax]

http://www.portsmouth.co.uk/news/local/mini-tornado-causes-damage-on-hayling-island-1-5605874

 

 

EXTENSIVE damage has been caused to a number of houses in Hayling Island after what is being a ‘mini-tornado.’

This morning, nearly 100 houses have had their roofs damaged after high winds and rain hit the island.

Several cars have also been damaged from fallen trees and broken fences.

Hampshire Constabulary were called to the incident that happened on Fishery Lane, Blackthorn Road and Ilex Walk,

A spokesman for the police said: ‘We received a call at 7.45am of a fallen tree in Fishery Lane.

‘Other calls came in shortly aftewards of broken fences, damaged cars and damaged roofs to around 100 houses.

‘Beach huts on the seafront are also damaged.

‘Reports are saying it was a mini-tornado.

‘Police officers and on the scene and working with the council to clear the damage.’

 

[Jax]

Now on the beeb

 

 

http://www.bbc.co.uk/news/uk-england-24601190

[VillagePlank]

A ' mini tornado' once again. Did it come in a box nicely wrapped for Christmas?

Edited October 20, 2013 by Sparkicle

[Mapantz]

That mass in the South West looks to be heading this way, hopefully it'll hold it's own and produce more sferics as it makes it's way here. I've switched on my lightning detector, so it's just a matter of waiting now.  

[ardsar]

There is a small cell just to the right of St Austell Looks to be tracking NE towards Liskeard area. 

[TropicThunder]

Unfortunately, i've missed all the action again. How? I don't know! That aside, there's been a tornado in Hayling Island, reports of damage to 100 homes. I can't copy and paste the link, sorry.

 

Beach huts damaged, cars damaged, trees down .. and that horrible term was used 'mini' tornado,  i'll be on the lookout for mini-hurricanes next! 

 

You're not alone, sod all here as usual. All the action this morning seemed to kick off to the east of here, hence the tornado reports in Hayling Island.

 

Like the look of what's coming up the Channel though. 

[Tom Jarvis]

I have looked for a lingering detector app for my I phone but have been unable to find one can I have some help??

[Carl]

Can anyone help me understand this...?

 

This afternoon, Netweather suggests there will be Cape of 1249 j/kg and an LI of -4 yet there is 0% chance of a storm.

 

I'd always understood that the higher the cape value and the more negative the LI value, the greater risk of a storm.

 

Is this correct?

 

If so, is the issue here that there needs to be a trigger but that one is unavailable? We currently have a band of rain approaching the area so i'd have thought that would serve as such.

 

What am i not understanding here?

[Casper]

Had a rumble of thunder here in Swindon about 30 mins ago, yesterday I was in Western Super Mare and had thunder there too. Two days in a row for me in October, I honestly can't remember the last time this happened.

Down in the Channel is looking good for the SW, fingers crossed.

[Tom Jarvis]

Ps licking the hook on that cell heading for Poole looks like there may be a water spout there

[Sprites]

Not sure the convection will be heading as far inland today, the South coast and S.W. doing best.

[VillagePlank]

 

 

Can anyone help me understand this...?

 

This afternoon, Netweather suggests there will be Cape of 1249 j/kg and an LI of -4 yet there is 0% chance of a storm.

 

I'd always understood that the higher the cape value and the more negative the LI value, the greater risk of a storm.

 

Is this correct?

 

If so, is the issue here that there needs to be a trigger but that one is unavailable? We currently have a band of rain approaching the area so i'd have thought that would serve as such.

 

What am i not understanding here?

CAPE is Convective Active Potential Energy - it has to realised. This can be from a trigger as you say, but that trigger may well be capped with CIN which is Convective Inhibition. So for, instance, in your area we can see CAPE degrading and CIN increasing during the afternoon. Some quite substantial lifting mechanism is needed to overcome this, so you're looking at strong surface heating - you'll get some, and it'll feel pleasant, but it won't be enough - and maybe shear, and shear is not prominent in your area. Of course, this is a back of postage stamp explanation .....

 

The NetWeather forecast looks good to me.

Edited October 20, 2013 by Sparkicle

[Costa Del Fal]

Lovely little thunderstorm about 30 mins ago with some really torrential rain and hail. that's about the 3rd or 4th lightning cell now.

[Carl]

 

 

 

 

What am i not understanding here?

CAPE is Convective Active Potential Energy - it has to realised. This can be from a trigger as you say, but that trigger may well be capped with CIN which is Convective Inhibition. So for, instance, in your area we can see CAPE degrading and CIN increasing during the afternoon. Some quite substantial lifting mechanism is needed to overcome this, so you're looking at strong surface heating - you'll get some, and it'll feel pleasant, but it won't be enough - and maybe shear, and shear is not prominent in your area. Of course, this is a back of postage stamp explanation .....

 

The NetWeather forecast looks good to me.

 

Thanks for that, helps me get my head around the situation a bit.