Uk General Convective Discussion & Forecasts, 13th March 2013 onwards

[Hathers]

Friday 12th April 2013

http://www.estofex.org/

The vertically stacked vortex (most healthy in the lowest 3 km) won't see any serious strengthening as it crosses S-C UK during the daytime hours from W to E. At 21Z (11th April), BL moisture already features dewpoints up to 8°C over S-UK which continue to spread north beneath cold mid-levels. Diurnal driven showers and thunderstorms are forecast with a prolonged period of CI expected due to the proximity to the low and the presence of the nearly uncapped air mass. However, early departure of a weak vorticity lobe and gradually increasing NVA from the west may induce a decrease in thunderstorm activity during the afternoon hours and therefore during the maximized activity for diurnal driven convection. Marginal hail/sleet and gusty winds accompany stronger pulsating thunderstorms although an isolated funnel/short-lived tornado report can't be ruled out with improving LL CAPE, some weak background vorticity and low LCLs. The overall coverage of storms and expected severe probabilities remains too low for either a 50 % lightning area or a level 1 (although SE-UK might come close to a 50-% lightning verification with best parameters/timing for thunderstorm activity).

Edited April 11, 2013 by villaman

[Supacell]

Looking at the various charts on offer this morning I am thinking the map below is a fair depiction of what is likely to happen today.

There are already a number of heavy showers around and as the sun allows temperatures to rise into double figures this will allow around 500-700j/kg of CAPE to develop across a large portion of England. By 12noon I would expect we will already be seeing isolated storms amongst a mass of heavy showers and during the afternoon there is likely to be numerous showers and scattered storms. The best activity will transfer eastwards by the afternoon as ridging from the west takes away the shower risk here. For this reason I would go for anywhere east of a line from the IOW up to Manchester, with the greater lightning risk being Midlands south. Any of these showers could contain hail, with the risk of some getting up towards pea sized in any heavier storms.

Although there is a moderate risk anywhere within the blue box I have marked on some wind convergence zones showing on the NMM model. The northern convergence line may not interact with the highest CAPE values but still, there could be a concentration of heavy showers and one or two storms along this line, transfering eastwards as the afternoon progresses.

The southern convergence zone does cross the area of highest CAPE and in this area a brief organisation of storms could occur through the afternoon, running eastwards towards the northern Home Counties, and into the SE by evening. Therefore, if I was to pick a hotspot this afternoon, I would go for somewhere north of London - possibly Bedfordshire into Cambridgeshire and maybe the city itself.

Edited April 12, 2013 by Supacell

[Darren Bown]

Today certainly looks the best of the year so ar for convective activity. I'm hoping for some heavy showers here this afternoon. Was good to finally see some rain yesterday!

[VillagePlank]

[VillagePlank]

Looks favourable for thunderstorm development, today in the SE,

[Karl83]

Saw some rotation whilst @ Parkway Station yesterday eve, looked impressive. Did post some pics but post has gone so I will post a couple of them again.

EDIT: Saw a fair bit of lightning too.

Edited April 12, 2013 by Karl83

[Supacell]

 

Saw some rotation whilst @ Parkway Station yesterday eve, looked impressive. Did post some pics but post has gone so I will post a couple of them again.

I'm hoping the grey leaden skies that have been over me all yesterday and now this morning clear so we can see similar scenes up in this region today. Although I am thinking I may aim to head a little SE, maybe get the M1 down towards Leicestershire and then see where to go from there.

[Karl83]

I'm hoping the grey leaden skies that have been over me all yesterday and now this morning clear so we can see similar scenes up in this region today. Although I am thinking I may aim to head a little SE, maybe get the M1 down towards Leicestershire and then see where to go from there.

Yeah I 'd say so Supacell! Best of luck mate!

[lewisosd]

still a thin layer of grey cloud over Ipswich area. Hoping this cloud cover will go soon as to not inhibit convection

[Nick F]

Storm & Convective Forecast - Issued 12/04/2012 10:30

Forecast Summary Map

Valid: 12/04/2012 10:30 - 13/04/2012 06:00

Headline: ... THERE IS A RISK OF THUNDERSTORMS FORECAST ...

Synopsis

Upper trough over the UK and surface low across southern UK will move slowly east during Friday, with an unstable airmass in place across southern UK.

... S ENGLAND, SE WALES, MIDLANDS and E ANGLIA ...

An increasingly moist airmass, with dew points reaching 8C, will advect north across Sern UK beneath cold mid-levels of the upper trough. This will create steep lapse rates across this region, with 200-300 J/KG CAPE forecast to build as surface heating occurs in the strong April sunshine, which will drive heavy showers and, increasingly, scattered thunderstorms by the afternoon - as we approach max heating. Deep-layer shear will be rather weak, given winds are light and blowing in a similar direction at all levels, so no organised severe weather is anticipated. Any storms maybe accompanied by hail and slow-moving torrential downpours that may lead to localised flooding.

Increasing 500mb temps from the SW later today will mean risk of storms will quickly subside by early evening as lapse rates weaken.

Issued by: Nick F - Forecaster for Netweather

Edited April 12, 2013 by Nick F

[NorthNorfolkWeather]

still a thin layer of grey cloud over Ipswich area. Hoping this cloud cover will go soon as to not inhibit convection

Same sort of problem her in North Norfolk.  Just had a small shower pass through, hoping for some sun now to get things moving.

 

Nice to see dewpoints ABOVE Zero, most of March the DP's were below 0 sometimes as low as -8

Edited April 12, 2013 by NorthNorfolkWeather

[chrisbell-nottheweatherman]

Same sort of problem her in North Norfolk.  Just had a small shower pass through, hoping for some sun now to get things moving.

 

Nice to see dewpoints ABOVE Zero, most of March the DP's were below 0 sometimes as low as -8

Much the same here SSW of Norwich.

[Supacell]

 

NMM-6 generous in its CAPE prog across the Midlands this afternoon- also modeling a rash of showers/storms over the region by around 15z (4pm) as a result. Let's hope we see a clearance of the crud aloft sooner rather than later.

 

Its definitely getting brighter here within the last half hour after a cold, dreary morning with light rain. As you say, quite a bit of CAPE on NMM and I am now free up until about 6pm so hopefully will see something between now and then (although I may have to drive south a few miles to be in the best location).

Actually the latest NMM (6z) has my area under some of the highest CAPE and precip rates - maybe I should stay put

Edited April 12, 2013 by Supacell

[Captain Shortwave]

had about 10 minutes of torrential rain here this morning. Probably had more rain in that time than the last month put together. Bright but cloudy now. Heavy showers forecast so maybe could squeeze a thunderstorm today. Great Yarmouth was in the firing line most days last last summer.

Edited April 12, 2013 by Captain shortwave

[chrisbell-nottheweatherman]

Gone more showery here now - decent brief shower and clouds more structured now rather than just flat grey.

[NorthNorfolkWeather]

Gone more showery here now - decent brief shower and clouds more structured now rather than just flat grey.

Hopefully heading my way then, it looked better for about 10 minutes, then back to flat grey

[lewisosd]

cumulus congestus here. Couple of breif showers in between the sunshine. Looking at radar there are a lot of cells around. Hoope one or two of these intensify

[Cheshire Freeze]

Nice to see the risk to the S and E of here- carrying on nicely from last year I see.

[Costa Del Fal]

Nice to see the risk to the S and E of here- carrying on nicely from last year I see.

Yep, surprise surprise the London and surroundings look to be copping it again.

[Sprites]

Yep, surprise surprise the London and surroundings look to be copping it again.

youre not missing too much, nice cloud scapes at times, but very isolated thunder ...atm , just messy showers.

[Alex95]

Torrential downpours with hail here in Keswick, Cumbria this afternoon.

Edited April 12, 2013 by Alza

[Cheshire Freeze]

Yep, surprise surprise the London and surroundings look to be copping it again.

You can bet your bottom dollar every single time that the low brings us rain the first day then overnight the low is slap bang over us when during the daytime this would have been the best chance of storms. The 2nd day the low has pushed east and the east get the storm risk. Happens every time.

[Sprites]

Nice to see the risk to the S and E of here- carrying on nicely from last year I see.

well if youre going to feast on black pudding, constantly play bingo while walking whippets and wearing flat caps you don't deserve to get any storms lol

(joking)

[Cheshire Freeze]

It never used to be this bad for storms Only had 1 thunder day last year and even that was distant! I have needs!

[Sprites]

It never used to be this bad for storms Only had 1 thunder day last year and even that was distant! I have needs!

lol yes it is frustrating and we havent had many storms here for a while, its early as yet so i hope you get your storm fix this year CreweCold.