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Convective / Storm Discussion - 1st May 2014 onwards


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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

Just been looking at tomorrow midday and see that there are some high lapse rates for the east, cape of 400 and li of -2. The highest potential out off the east coast. This was more inland on the previous run. Total totals are very high in the area of interest however the shear isn't as high as it would have been for today but I'm sure it is enough to sustain any storms that may develop.

 

Scotland which also has potential has wind convergences which I believe is another trigger for storms to develop. I don't think cloud cover is going to be quite as much of a factor tomorrow as it was today from what I'm seeing but I think there will be some around.

 

Let's see what tomorrows run shows, anyone else want to add or correct me please feel free to do so :)

 

Edit: Ooh nice, I hope someone see's something today :)

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Edited by Greenday
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Posted
  • Location: Dunmow, Essex (72m asl)
  • Weather Preferences: Anything apart from grey days
  • Location: Dunmow, Essex (72m asl)

You can have favourable CAPE and LI, but without a "trigger" then nothing will happen. A trigger in this case would be surface heating in order to enable air parcels to ascend (i.e. convection). But seeing as it's cloudy, this surface heating isn't really happening. The atmosphere is unstable, but we need something to kick-start that instability so-to-speak. Other forms of triggers can be convergence zones (where opposing winds meet or converge, forcing air upwards) or a frontal boundary to provide that lift. Even sea breezes can act as a sufficient boundary. In short, favourable CAPE and/or LI values don't automatically mean thunderstorms are going to occur. Over the weekend (have an exam tomorrow...) I'll add a more extended and full explanation in the learners area.

Ah yes, I got it into my head that GFS cape/LI calculations would include some impact of cloud cover which presumably they don't.Definition of CAPE:A measure of the amount of energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft; thus, higher values indicate greater potential for severe weather.Emphasis on POTENTIAL vertical speed.LI is defined as:A rising parcel's temperature when it reaches the 500 millibars level (at about 5,500m or 18,000 feet asl), subtracted from the actual temperature of the environmental air at 500 millibars. If the Lifted Iindex is a large negative number, then the parcel will be much warmer than its surroundings, and will continue to rise.So a "trigger" helps to realise the maximum potential vertical speed of a parcel and today's lack of both surface convergence and significant dynamic lift from the cold front meant that we had to fall back on surface heating as the trigger. Think I need to look at the equation for cape to understand it a bit better.Thanks for taking the time to explain Nick.
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Posted
  • Location: BRISTOL
  • Location: BRISTOL

Quite windy here this morning gusting at times no rain yet and bbc have not mentioned thunder the last two days so not sure what to expect today.

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

After yesterday's disappointment, which I half expected, I am not going to go into detail today. However, although GFS is showing less CAPE than for yesterday the WRF are more on-board today and the fact that we may actually get some sunshine means that CAPE is more likely to be realised. Any chances are earlier on in the day with a ridge killing off any showers from the west, restricting chances to the far east of the country by the afternoon.

 

Once more, where storms develop, they could become organised and bring with them the risk of reasonable sized hail, gusty winds and tornadoes. Rather than post multiple charts I will just post my thoughts on today's risk area.

 

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The yellow area is for general heavy showers and the slight risk of a weak thunderstorm up to around 12-2pm before showers start dying out from the west. The red area is where any stronger storms are likely up to around 3-5pm with Norfolk, Suffolk and Lincolnshire at the highest risk of all. 

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Posted
  • Location: Saddleworth, Oldham , 175m asl
  • Weather Preferences: warm and sunny, thunderstorms, frost, fog, snow, windstorms
  • Location: Saddleworth, Oldham , 175m asl

A rumble of thunder earlier in absolutely torrential rain! Looking at the radar there was a couple of strikes around Stockport/ Marple area which sounds about right.

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
THERE IS A RISK OF THUNDERSTORMS FORECAST

 

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Synopsis
A large low pressure system/area of low geopotential heights covers the NE Atlantic and N Sea, with a broad belt of upper westerlies covering northern Europe, with a 100knt+ westerly jet lying across southern Britain. A wave in this jet stream will move quickly east across central and northern Britain today, bringing a risk of heavy showers and thunderstorms here today.

... N IRELAND, SCOTLAND, N ENGLAND, N WALES, MIDLANDS, LINCS, E ANGLIA ...

Well modified polar maritime airmass, to the north of the jet stream over southern Britain, will be readily unstable this morning bringing heavy showers west to east accompanied by hail and isolated lightning. Probabilities of thundestorms increasing through the day across the above areas as surface temperatures rise in response to sunny spells and approaching wave increases forced ascent of moist maritime airmass. Close proximity of jet stream over N Wales, N England through to E Anglia will see strongest vertical shear here, with any storms forming here likely organising into fast-moving multicell or bowing line segments capable of producing hail up to 1 to 2cm in diameter along with squally strong wind gusts and torrential rainfall leading to localised flooding. Increasing low-level shear indicated with approach of wave suggests the odd isolated short-lived tornado can't be ruled out too.
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Posted
  • Location: Morley, Leeds West Yorkshire
  • Weather Preferences: Snow and thunderstorms
  • Location: Morley, Leeds West Yorkshire

Heavy showers have been passing through all morning with the sun popping up as well. Lets hope all the ingredients are here today. 

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Posted
  • Location: Newton-le-Willows, Warrington, Merseyside
  • Location: Newton-le-Willows, Warrington, Merseyside

It's darker than the middle of winter today. Truly horrible weather. Wouldn't mind if we have thunderstorms!

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

Bright sunshine but breezy here this morning with just some cumulus floating around. From Nick's forecast and the charts I have seen I look to be in a decent spot today with being just north of the upper jet stream and within the risk area. 

 

I may head slightly east more towards Nottinghamshire/Lincolnshire shortly anyhow as I would think anything that does develop would have more chance of being thundery further east.

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

Ah yes, I got it into my head that GFS cape/LI calculations would include some impact of cloud cover which presumably they don't.Definition of CAPE:A measure of the amount of energy available for convection. CAPE is directly related to the maximum potential vertical speed within an updraft; thus, higher values indicate greater potential for severe weather.Emphasis on POTENTIAL vertical speed.LI is defined as:A rising parcel's temperature when it reaches the 500 millibars level (at about 5,500m or 18,000 feet asl), subtracted from the actual temperature of the environmental air at 500 millibars. If the Lifted Iindex is a large negative number, then the parcel will be much warmer than its surroundings, and will continue to rise.So a "trigger" helps to realise the maximum potential vertical speed of a parcel and today's lack of both surface convergence and significant dynamic lift from the cold front meant that we had to fall back on surface heating as the trigger. Think I need to look at the equation for cape to understand it a bit better.Thanks for taking the time to explain Nick.

 

No worries, once I've got my horrendous exam out of the way this afternoon and completed drowning my sorrows this evening, I'll put a more comprehensive explanation into the learners area, and how each trigger can act as such :)

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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

No chance, estofex forecasted it :p

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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

Too much cloud cover. 3 recorded strikes so far. All way out to sea.

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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

I'm no expert by any stretch but there is a lot of large cumulus building here, some big-ish tops that seem like they're trying to rise. Only getting a few mins of sun here and there though.

Anyone seen anything interesting?

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Posted
  • Location: Solihull, WestMidlands, 121m asl -20 :-)
  • Weather Preferences: Cold and Snow -20 would be nice :)
  • Location: Solihull, WestMidlands, 121m asl -20 :-)

I'm no expert by any stretch but there is a lot of large cumulus building here, some big-ish tops that seem like they're trying to rise. Only getting a few mins of sun here and there though.Anyone seen anything interesting?

Welcome :) Put your location in your avatar, we have no idea where these pictures are from, if you don't mind :wink:

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

A few sferics around the Wash.

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Posted
  • Location: Morley, Leeds West Yorkshire
  • Weather Preferences: Snow and thunderstorms
  • Location: Morley, Leeds West Yorkshire

A few sferics around the Wash.

Not looking too good
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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

Welcome :) Put your location in your avatar, we have no idea where these pictures are from, if you don't mind :wink:

Sorry :)Done.
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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

Getting darker, but I don't hold high hopes. Temps have taken a small tumble.

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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

Storms have hit norwich and especially Yarmouth CG strikes seen. First heading towards acle on a47. Still working will post more later.

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

Storms have hit norwich and especially Yarmouth CG strikes seen. First heading towards acle on a47. Still working will post more later.

 

Yes it's looking quite good around the east and north of Norfolk, pity I didn't take the plunge and travel there. Then again, Norwich and Great Yarmouth probably a little too far. Tomorrow looking possible again for East Anglia, although we are back to cloud scuppering possibilities by then.

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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

Caught this bad boy moving just to my south. I'm just north of the city.

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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

I can see rising columns to my north and south. The most frustrating thing is my view to the west is completely blocked.

I need to get to higher ground, which in Norfolk is a problem.

To the north:

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To the south:

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Posted
  • Location: Chesterfield, Derbyshire, 110m
  • Location: Chesterfield, Derbyshire, 110m

I can see rising columns to my north and south. The most frustrating thing is my view to the west is completely blocked.I need to get to higher ground, which in Norfolk is a problem. 

 

A few showers near to you on the radar, one putting out some strikes. :) 

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Posted
  • Location: Norwich, Norfolk, UK
  • Weather Preferences: Anything interesting - mostly storms or snow
  • Location: Norwich, Norfolk, UK

A few showers near to you on the radar, one putting out some strikes. :)

That blob of rain on the left of that shot looks ominous. Got a small white core. I got to pop out to the shop and it looks 50/50 as to whether it'll pass right over my head.
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