Convective Weather Discussion UK

[Coast]

KO Index = blue lines with values. (S = >+6 = stable, L = < -6 = unstable).

Vertical motion forced by dynamical forcing at 500 hPa = zones in color (hPa/hour).

Critical values KO.

> 6: no potential risk thunderstorms.

2-6: small potential risk for thunderstorms.

< 2: potential risk for thunderstorms.

Vertical motion: large negative values = strong ascent

Combination of both:

Stable KO region + negative motion = frontal zone. If the negative motion is positioned on a strong gradient in the KO indices between a stable and unstable zone: front is potentially unstable with risk for severe embedded thunderstorms

Unstable KO region + negative motion = active upper trough with risk severe thunderstorms

Unstable KO region without negative motion = air mass instability which may produce thunderstorms due to diurnal heating (mainly in the afternoon)

Convective clouds = grey lines with values in %.

Soaring-Index = values in color (in deg Kelvin)

Some critical values for the Soaring Index.

15-20: isolated showers, 20% risk for thunderstorms

20-25: occasionally showers, 20-40% risk for thunderstorms

25-30: frequent showers, 40-60% risk for thunderstorms.

30-35: 60-80% risk for thunderstorms.

>35 : >80% risk for thunderstorms.

Storm-relative Helicitity (SRH) in m²/s² = colors

Bunkers Storm Motion in knots = wind barbs

SRH is a measure of rotation potential. Some critical values SRH:

If showers form:

150-300: supercell development possible with large CAPE, risk for weak tornadoes (F0, F1)

300-450: supercell development possible with small CAPE, risk for strong tornadoes (F2, F3)

>450 : large risk for supercell development, risk for violent tornadoes (F4, F5)

Bunkers Storm Motion barbs determines the movement of supercells.

Barbs indicate direction and speed. Wind speed is indicated in knots. Wind barbs always point in the direction the wind is blowing "from". A short barb means 5 knots, a long barb means 10 knots.

[Guest]

First shower cloud gone up to the nw very rapid development no sign of anything at all not long back.

Yep just going to mention towers going up west of here with a hearty shower cloud to the NW. It's started

[dave48]

First storm of the day gone up over the pennines with sferics from UKMO ATD.

[Coast]

TORRO CONVECTIVE DISCUSSION 2010/003:

A TORRO CONVECTIVE DISCUSSION has been issued at 12:00 GMT on Saturday 23rd April 2011

Valid from/until: 12:00 – 21:00GMT on Saturday 23rd April 2011 for the following regions of the United Kingdom & Eire:

NE England Yorks Lincs Midlands Mid & N Wales NW E Anglia

THREATS

Hail to 1.5cm diameter; heavy rain; gusty winds; funnel cloud/weak tornadoes; CG lightning

SYNOPSIS

Strong heating of a relatively moist and unstable boundary layer, coupled with low-level convergence INVOF sea breeze convergence zones, and differential heating over elevated terrain will allow scattered showers and thunderstorms to develop across the area this afternoon. Northern parts will initially be most at risk, as weak lift associated with approaching upper trough moves in. Recent sferics near Barnsley confirm this.

Shear is generally weak but ~25 knots of 0-6km shear across the northern part of the area suggests that organised multicells are possible bringing the chance of gusty winds and hail. In addition, steep low-level lapse rates along with low-level convergence zones suggest that a few funnel cloud or possibly even brief, weak non-mesocyclone tornadoes are possible - this risk is more general.

Locally heavy rainfall of 25-35mm in a short space of time is also possible.

Activity should tend to develop further southwards this afternoon, but the lack of shear will tend to preclude much organisation. However, a cluster of showers/storms may move SE from mid-Wales, with the chance of gusty winds. The discussion area may need to be extended south-eastwards later on.

[A.J]

A couple of big Cu Congestus have gone up around 15-20 miles to my SE, heading SE, look quite promising above the heat haze, nothing heading my way though

[Mesoscale]

I must live in the Hertfordshire Desert!

I didn't get much snow last year when the rest of the SE got burried and I haven't had a proper thunderstorm in about 2 years now. We are turning into texas down here... next there will be wildfires. WILDFIRES I TELL YOU!

Same trend as last year, the midlands will get it all. oh well maybee I should go outside and enjoy the sun with some Kopparburg. and pray to mother nature.

[A.J]

I must live in the Hertfordshire Desert!

I didn't get much snow last year when the rest of the SE got burried and I haven't had a proper thunderstorm in about 2 years now. We are turning into texas down here... next there will be wildfires. WILDFIRES I TELL YOU!

Same trend as last year, the midlands will get it all. oh well maybee I should go outside and enjoy the sun with some Kopparburg. and pray to mother nature.

If you think that the midlands got it all last year, then me thinks you've already had too much Kopparburg today!

[Static Prevails]

Okay, I haven't done this for a while, so I'm overdue to ask somebody now (:winky:)- what are my chances for today? Just wanting the opinion of someone who has more knowledge than me.

Edited April 23, 2011 by IAmJohnnyDisco

[dave48]

Okay, I haven't done this for a while, so I'm overdue to ask somebody now (:winky:)- what are my chances for today? Just wanting the opinion of someone who has more knowledge than me.

Good, there is a thunderstorm 20 miles north of you!

[Coast]

Current observations:

Temp

Dew point

[Static Prevails]

Good, there is a thunderstorm 20 miles north of you!

Nice! I have to use Rain Today, so I'm a little behind!

[Kain]

Okay, I haven't done this for a while, so I'm overdue to ask somebody now (:winky:)- what are my chances for today? Just wanting the opinion of someone who has more knowledge than me.

Its pretty good, both ESTOFEX and Torro has put you smack bang in the watch area (along with me) So now its just a case of waiting and see what happens. We have a pretty good chance so the rest is up to Thor

[Evening thunder]

A couple of cumulus congestus towers growing quite quick in the distance through the haze. Interesting..

Sea breeze not effecting temps yet, 22.8C with 15.1C dew point. Perhaps a sea breeze convergence zone may be on my side for once.

[Mesoscale]

If you think that the midlands got it all last year, then me thinks you've already had too much Kopparburg today!

Is there a Lightning archive anywhere? I would like to see the data from last year, it might be quite interesting.

[Lynxus]

Few Cu now bubbling up.

Still nice and hot here.

Im gonna wash the car and clean the BBQ and put some washing out.. This should insure! a thunderstorm.

[Static Prevails]

Its pretty good, both ESTOFEX and Torro has put you smack bang in the watch area (along with me) So now its just a case of waiting and see what happens. We have a pretty good chance so the rest is up to Thor

I just warned my mother not to put any washing out- she said nothing would hit us. If she has wet clothes, it's not my fault. :winky:

Edited April 23, 2011 by IAmJohnnyDisco

[A.J]

Is there a Lightning archive anywhere? I would like to see the data from last year, it might be quite interesting.

Judging by my hazy memory, I think eastern parts (east of the M1 Corridor,and to the north of London) did rather well in what was generally a pretty pants year for storms nationwide....

[dave48]

Is there a Lightning archive anywhere? I would like to see the data from last year, it might be quite interesting.

This would have everything you need.

http://www.metoffice.gov.uk/climate/uk/anomacts/

[PurpleButterfly]

Afternoon all and happy Easter

I'm just wondering what the chances are of seeing anything in my part of the country? Haven't had a good storm in a long time.....the last good one i can remember was back in 2007/08!!

:o

[Paul R]

Hot and sunny in Cardiff at the moment. Most clement. Hoping for a cheeky storm later. Had a downpour around 3pm yesterday - refreshing but disappointing due to distinct lack of thunder.

Edited April 23, 2011 by Paul R

[pinball wizard]

Current observations:

Somewhere like Wisbech could be in the sweet spot come 4pm

[Static Prevails]

Can anyone tell me which direction that Pennine storm is heading and whether it's likely to hit me? Rain Today isn't really helpful in that regard. :winky:

[johnholmes]

Okay, I haven't done this for a while, so I'm overdue to ask somebody now (:winky:)- what are my chances for today? Just wanting the opinion of someone who has more knowledge than me.

see post 76

[Coast]

Somewhere like Wisbech could be in the sweet spot come 4pm

I am thinking that East Anglia upwards would be the best place to be currently.

[camiscool]

Coast I think we have a chance. A few towers growing around here.