Uk Convective General Discussion & Forecasts - April 2012 Onwards

[Coast]

I guess if anything is going to happen it's mid afternoon onwards?

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)

http://www.skystef.be/forecast11.html

[johnholmes]

and of course this link which rarely seems to get a mention amongst the plethora of charts from other sites

http://www.netweather.tv/index.cgi?action=convective;sess=

in plain English as well!

[NO LONGER POSTING]

Don't think that cloud is going anywhere fast lol!

[Coast]

Yesterday in one gif:

(Click through to view)

[Nick F]

Looking at the 00z Herstomonceux ascent, not much needed to get cloud tops to around 22,000ft with an expected surface temp of 11C, just need to get some sunshine to break through the cloud shield across many areas:

[Kain]

Argh another day of radar and sky watching...man what we go through to get our storms huh. Today does look better than yesterday, but as Nick said we need some of this cloud layer to kindly move its backside to allow for some surface heating.

[Stuart]

just hopeing i will see some on friday and sat

[Kain]

Sun is peeing through now

[NO LONGER POSTING]

Humm cloud slowing breaking up..As it does so..More piles in lol!!

[Guest QuantumSnow]

Sun is peeing through now

Erm.. that's those special golden rays then?

[Kain]

Erm.. that's those special golden rays then?

Whoops lol, what a typo to make :o

[Guest QuantumSnow]

Whoops lol, what a typo to make

I'm suprised the filter let you have that one! I'm definately getting the umbrella out today now

[johnholmes]

Looking at the 00z Herstomonceux ascent, not much needed to get cloud tops to around 22,000ft with an expected surface temp of 11C, just need to get some sunshine to break through the cloud shield across many areas:

looking at the sat piccs and surface obs it suggests that only the SW and Channel Isles are currently getting much in the way of sun. With the circulation around the low, at most levels, its probably expecting too much for any substantial breaks in many places. As the low drifts north (roughly) then these breaks may slowly extend a little further NE?

A closer scrutiny of the METARS shows a hole in parts of the Midlands with both Coventry and Birmingham showing SCT low cloud, so breaks are possible on a wider scale perhaps than my initial post suggested. As Nick shows on the skew-t it needs 11C+ to give convection to sufficient height to produce heavy showers with the prob of thunder and hail.

Edited April 19, 2012 by johnholmes

[NO LONGER POSTING]

The low deffo needs to shift its @$$!!

[johnholmes]

The low deffo needs to shift its @$$!!

something it is only doing VERY slowly

[Eskimo]

Cloud breaking up here

[Eskimo]

Cloud burning quite quickly here actually, it was miserable just 15 minutes ago, now there's 50/50 cloud/sky

[NO LONGER POSTING]

wow yes the cloud is breaking up going with the sat24 over the midlands..Still low cloud here...Is it me or does that low have some embedded very high top clouds..

Like people have been saying..Today I think we need to wait and the action should go bang at around 3-7pm...

Edited April 19, 2012 by Surrey

[Kain]

Woot just had a rumble!!! First of 2012!

[sunny scunny]

Very frustrating here with a band of rain to the north and south, and my area is stuck in a dry slot which shows no sign of changing anytime soon.

[A.J]

Woot just had a rumble!!! First of 2012!

no thunder here but twas a pokey cell for sure giving a downpour here....sun is breaking through now, and with convective rainfall building up over Yorkshire currently, this should wrap around and affect our region this afternoon/evening....here's to a lively one!

[Nick F]

Sun just popped out briefly here in S London, hopefully the still overcast skies will thin and break early this afternoon.

[NO LONGER POSTING]

first shower here..Boy did it come down for a bit!

[Kookylou]

just cloudy here in Cardiff. No sun at all.

[SalopWatcher]

Big shower building over Shrewsbury and heading south on the Radar... cell popped up and we have been overcast all morning with no sun... Really heavy rain from it. Looking at the radar a few cells popped up west of here too. rain at the moment, but who knows later today.