Storm & Convective Discussion April 2016 Onwards

[weather09]

Upper trough and deep cold mid-levels/steep lapse rates (sub -35C at 500mb) to the NE of the UK extending south and west over the country tomorrow- marginal CAPE developing in sunny skies during afternoon/early evening period so widespread low risk of scattered thundery showers/weak storms.

Gusty downdrafts and hail likely features given steep lapse rates and cold air aloft, and even brief wintriness to low-levels where freezing level is lowered locally within downdrafts. Few more risk days this week as cold air aloft hangs around. Not a very interesting outlook in all. Until we see proper ridge building over Europe instead of troughing and mid-Atlantic ridge, not going to see those really good storm opportunities arise.

For now, more focused on tomorrow's severe risk for the US central plains..

[Summer Sun]

TUE 26 APR 2016: A LOW chance of thunderstorms:

Upper trough sinks slowly southwestwards across British Isles on Tuesday, introducing unseasonably cold airmass of Arctic origin. Showers will be ongoing along exposed coastal counties at the beginning of this forecast period, and will only become more widespread inland as diurnal heating coupled with cold air aloft generates deep instability. CAPE is rather limited given dry surface air (hence very low dewpoints and high cloud bases away from windward coasts), around 200-300 J/kg at best, but very steep lapse rates will result in some sporadic / isolated lightning activity, with the potential for numerous events of small hail.

http://www.convectiveweather.co.uk/forecast.php?date=2016-04-26

[Allseasons-Si]

A nice convective day here with everything thrown in except the thunder,love this hail shaft i have just took

jellyfish in the sky

 

[Weather-history]

 

[Weather-history]

Some Scottish time-lapses yesterday

 

[Nick F]

Should be some good photogenic convective skies in the cold and clear arctic air today, have issued a convective /  storm forecast - as lapse rates have become rather steep today, so some thunder is possible in the showers.

Storm & Convective Forecast

Issued 2016-04-26 09:50:19

Valid: 26/04/2016 0600z to 27/04/2016 0600z

DAY 1 CONVECTIVE FORECAST - TUESDAY 26TH APRIL 2016

Synopsis

Highly amplified upper flow persists over the Atlantic and Europe with deep upper trough extending south from the arctic across northern Europe and an upper ridge extending north over the Atlantic and across Greenland. Surface low will remain slow-moving today to the east of the UK, centred near Denmark / Nern Germany, with a strong, unseasonably cold flow across the UK - unstable to surface heating leading to showers and scattered weak thunderstorms.

... ENGLAND, WALES and SCOTLAND ...

Upper trough extending down North Sea and eastern UK, with unseasonably cold mid-level  temperatures (below -35C at 500mb), will create very steep lapse rates between the surface and mid-levels. Heavy showers, wintry in the north, are already ongoing across coastal areas exposed to the northerly wind ... strong late April sunshine warming the ground will allow more widespread convection/showers develop inland too as the day wears on. GFS  indicates a few 100 j/kg CAPE, so some well scattered weak thunderstorms will develop amongst the showers almost anywhere across mainland UK, particularly inland where surface heating is maximised. Dry surface flow will mean showers/storms will be high-based, which combined with weak vertical shear and lack of warmth/moisture will mean there is no risk of severe weather. However, showers/storms will be accompanied by hail and gusty winds locally.

Forecast online on Netwx website: http://www.netweather.tv/index.cgi?action=convective;sess=

[weather09]

Nice clear air out there today- lofty cloud ceiling.  Hopefully get to see something late this afternoon or this evening.  

On another note, nice to see GFS's 06/18z outputs amplifying the ridge over Europe towards the end of those runs; upper trough stalling to the W.  00/12z modeling the opposite (troughing over mainland and ridge to the west). Perhaps due to data input discrepancies, but far out enough anyway for there to be high variability in outputs. But always nice to have something to look at especially given recent weather.  

[Harry]

Just chucked it down with snow in C London, followed by a nice clap of thunder

Good start to what promises to be a reasonably interesting day.

[Summer Sun]

8 minutes ago, Harry said:

Just chucked it down with snow in C London, followed by a nice clap of thunder

Good start to what promises to be a reasonably interesting day.

The beeb are saying its most likely light hail

 

[weather09]

Heavy snow shower here in C Birmingham too. Nice! No thunder, though.

[Karl83]

Just had a heavy Graupel? shower here.

[Arnie Pie]

1. Light sleet showers falling from high, here in South Birmingham...could be a very photogenic day

 

Edited April 26, 2016 by Arnie Pie

[Greeny]

Difficult to say whether graupel or hail is falling. No thunder and lightning although we've definitely been having sleet and graupel today.

[Evening thunder]

Just too far west here typically, a line of showers further west giving temporary dustings on Dartmoor, and all the convective showers just to the east. Here, just out of the more unstable zone, we have a gap of nothing.

[Harry]

1 hour ago, Summer Sun said:

The beeb are saying its most likely light hail

 

Snow certainly fell earlier (floating down), together with graupel (bouncing polystyrene like balls) and hail.

Another clap of thunder as I typed

Edited April 26, 2016 by Harry

[vladthemert]

Had some hail here 1.30pm.  Looked decent size too nearly half an inch they looked though could be clumped together.

[Richard Taylor]

Had sun/rain/sleet/hail/snow/thunder in Aberdeen so far. Safe to say a mixed day!!

[William Grimsley]

Very convective skies here today. I'm not sure what planet @Evening thunder's on. LOL. Anyway, looks like we may see some showers later on today possibly giving hail, sleet and/or snow.

Edited April 26, 2016 by William Grimsley

[Allseasons-Si]

Just got in from work to see this Mammatus just past me,heavy snow from that too

snowing here again as i type,a thunderstorm to my west,i can hear distant rumbles

 

 

Edited April 26, 2016 by Allseasons-si

[William Grimsley]

Looks like snow falling to my NNE now, it may just go east but not sure, shame I can't get in it.

[Allseasons-Si]

Crash of thunder here

[Evening thunder]

14 minutes ago, William Grimsley said:

Very convective skies here today. I'm not sure what planet @Evening thunder's on. LOL. Anyway, looks like we may see some showers later on today possibly giving hail, sleet and/or snow.

Lol, just in that there's been minimal showers here, while there are showers both to the west and east lookng at the radar with a gap between them.

[Raidan]

Strange weather here the sky is blue sun out but there is hail falling very odd

[Arnie Pie]

19 minutes ago, Allseasons-si said:

Just got in from work to see this Mammatus just past me,heavy snow from that too

snowing here again as i type,a thunderstorm to my west,i can hear distant rumbles

 

 

Great photos their Allseasons-si

[Spikecollie]

It looks like a lively day over there in the UK. Enjoy it!