Storm & Convective Discussion April 2016 Onwards

[LadyEv06]

We had heavy snow around 9.15pm alongside 2 very loud bangs of thunder and lightning that lit the whole room. Snow has left a thin covering. Can't remember the last time I heard thunder quite as loud as we had tonight 

[Summer Sun]

A low chance of thunderstorms today

Day 1 Convective Outlook

VALID 06:00 UTC Thu 28 Apr 2016 - 05:59 UTC Fri 29 Apr 2016

ISSUED 21:31 UTC Wed 27 Apr 2016

ISSUED BY: Dan

Broad upper low, and associated cold mid-levels, will sit over the British Isles on Thursday, digging farther south by Friday morning. Around the base of this trough, increasing baroclinicity will promote frontogenesis, ultimately forming a slowly-deepening close low, which is then forecast to slide SEwards across SW Scotland into N England. 

The frontal zone will pivot across England and Wales, with scope for convective elements to develop during the afternoon/evening across Wales / Midlands / E Anglia in particular close to and along the cold front given relatively steep mid-level lapse rates and increasing DLS with the arrival of a jet streak from the west. Instability is limited, but shear may be enough to compensate to produce some isolated lightning, hence the LOW finger across these areas. Furthermore, ahead and along this cold front, numerous showers are forecast to develop during the evening over the English Channel and affect adjacent coasts, again with a fairly low probability of lightning.

Perhaps the most likely area for lightning activity will be in the post-frontal airmass across SW Scotland then NW England (perhaps also Northern Ireland) on Thursday night, as a wrap-around occlusion close to the surface low centre drifts SEwards. This is still considered a LOW probability for now, but given very steep lapse rates and cold air aloft over relatively warm SSTs (and orographic forcing / frictional effects as showers move inland) then there is certainly scope for some sporadic lightning activity.

Small hail and gusty winds will be possible in the strongest cells.

http://www.convectiveweather.co.uk/forecast.php?date=2016-04-28

 

Edited April 28, 2016 by Summer Sun

[Weather-history]

Overnight time-lapse. Can actually see the snow/hail fall as shower develops

 

[Paul]

Amazing footage of lightning hitting a plane over London yesterday. (For those unsure, this is pretty common and safe).

 

[Spikecollie]

1 hour ago, Paul said:

Amazing footage of lightning hitting a plane over London yesterday. (For those unsure, this is pretty common and safe).

Crikey, how do some photographers manage to be in the right place at the right time? That's an incredible piece of footage. Common and safe, yes, but I wouldn't rank it among my "most want to repeat" of life's experiences!

[weather09]

Nice to see continued signal from GFS & ECMWF for amplified ridge building over Europe in medium-range (post-T144), as has been mentioned in MOD, though naturally discrepancies on how we'd get there. But, hopefully, we'll see increasing likelihood of good convective potential during first part of May.  

Short term, less cold air aloft and increased cloud cover today ahead of approaching frontal system, meaning lack of instability and lower risk of thunder on previous days.  Tomorrow, cold mid-level air (-35C or lower at 500mb) and steep lapse rates returns sinking south and east in post front environment. Marginal CAPE (few 100j/kg) building once again under sunny skies, though cloud debris associated with wrap-around occlusion over northern/north-east parts may hamper instability.  Other than small hail and gusty winds, dry surface air mass, low instability and weak shear prohibits anything significant/severe.

Edited April 28, 2016 by weather09

[Spikecollie]

Some activity going on in the west of the UK right now...

[Arnie Pie]

Dark to my North and West....Recent activity to the front of the cells approaching

Looks promising

Edited April 28, 2016 by Arnie Pie

[Arnie Pie]

Heavy gust front coming through with a crack of thunder

Edit yep 5mins of windy gusts + a single crack of thunder

Edited April 28, 2016 by Arnie Pie

[matty40s]

Just had thunder here, junction 19 Caththorpe is the nearest location I can give - certainly didn't expect this !!

 

I can now see and feel the squall front approaching...

Edited April 28, 2016 by matty40s

[carl1980]

Just had a great storm large Hail plenty of lightning 

[Dami]

I can see it on radar. my shoe it will be nothing time it reaches here.

[Chris.R]

Was watching sferics  coming closer but  wasn't expecting that. Wow!   Lightning frequency was low but was  right  overhead at one point. Torrential hail left a thick  covering. Still producing sferics, now  inaudible. Other sferics around now  as well from other cells.

[Allseasons-Si]

Hey up! what's happening here,there is a storm approaching

oh! and guess what,i have a little surpise to show you all from yestesday,can you guess what it is,put it this way,it's the first time i have seen one,i am going to upload the pics in a bit.

Edited April 28, 2016 by Allseasons-si

[Spikecollie]

Crikey! Parts of the UK are lighting up nicely. Late on, but enjoy your storms if you get them. Over here in France, next week onward looks good for some warmth (thankfully) and some thundery activity.

[IanR]

thunder here, saw a couple of forks of CC  you could hear the hail coming like a train  amazing, gusty wind with the storm,  now calm again,   third thunder day of 2016 

Edited April 28, 2016 by IanR

[shogan83]

Just like yesterday evening another little storm close by

[weather09]

Was a good call by Dan re. convection associated with the cold front, and post-front this evening.  Not surprised there's thunder, given the reasons he stated (sufficiently steep mid-levels, strong shear with mid-upper level jet, etc), though the lower the risk appears in advance the more it feels like it's not worth the detail, and the risk did, on the whole, look marginal. Nice example, though, of how CAPE progs don't always tell the whole story, where mid-level instability (steep lapse rates) and frontal forcing and support aloft can produce the goods. 

Environmental instability is expected to better tomorrow with colder mid-level air overspreading and better surface heating, however where one factor improves another diminishes- namely shear and forcing aloft (where greatest instability is modeled to be anyway).

 

Edited April 28, 2016 by weather09

[Allseasons-Si]

Ok,while i was traveling up to glasgow yesterday afternoon i cought this,a funnel,not touching the ground but it was a great sight to see,i was so chuffed

sorry about some of the pics being a bit smudgy,we was on the move.

 

 

Edited April 28, 2016 by Allseasons-si

[matty40s]

9 minutes ago, Allseasons-si said:

Ok,while i was traveling up to glasgow yesterday afternoon i cought this,a funnel,not touching the ground but it was a great sight to see,i was so chuffed

sorry about some of the pics beimg a bit smudgy,we was on the move.

 

 

close but no cigar.....

[Allseasons-Si]

And here is some cloudscape pics while we was on our travels too and drove through some intense hail cores with some graupel being the size of marbles,was another great day for photogenic snapping,again,some of the pics are a bit blury but still nice.

 

[Dami]

well i got the rain, shame no thunder from it now

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Fri 29 Apr 2016 - 05:59 UTC Sat 30 Apr 2016

ISSUED 20:00 UTC Thu 28 Apr 2016

ISSUED BY: Dan

On Friday, a surface low will slowly retreat eastwards from NE England to the North Sea, beneath a broad upper low with various embedded troughs rotating around the main parent low - one such trough will pivot and begin to sharpen and extend towards SW England during the day. The associated cold mid-levels combined with diurnal heating will serve as the main focus for convection.

Expected scattered showers to develop in response to diurnal heating, although a lack of any significant DLS will result in numerous small "pulse type" showers, some perhaps just deep enough to produce sporadic/isolated lightning. Main focus for lightning is in a W-E zone that begins over the north Midlands around noon, and sinks slowly southwards through Wales / Midlands / E Anglia through the afternoon, towards the West Country / Home Counties by evening. Parts of the West Country and the Midlands get close to SLGT category, but confidence is not high enough to upgrade here, especially given lack of any organisation - in fact, multiple consecutive runs of the EURO4, for example, are distinctly lacking in any noteworthy shower development across a good portion of the main interest areas, and hence have chosen to reject this model for now.

Showers that form furthest to the SE may benefit from stronger DLS, and thus automatically increasing their chances of producing lightning. Small hail/graupel is likely in the strongest cells.

http://www.convectiveweather.co.uk/forecast.php?date=2016-04-29

[Weather-history]

What a day's weather:

Frost, heavy snow, slight covering, sunshine, rain, torrential rain, sunshine, hail, thunder, lightning. That has been today's weather in Irlam

 

 

[Mesoscale]

Blitzortung showing lightning within 5 miles of me but I havent heard or seen anything?