Storm & Convective Discussion - 01/09/14 onwards

[Spikecollie]

Even this afternoon there were some great CBs over the hills here, backlit by the setting sun...magic. And I heard something like thunder in the distance last night too.

[Supacell]

An interesting looking radar signature in South Wales just NW of Cardiff. There are sferics and it is exhibiting a definite hook shape.

[DH764]

Had hail , snow and lightning , as in 3 flashes over Tees-Side at around 6pm tonight.

[Darren Bown]

Epic thunder snow and hail here NW of Cardiff.

[Raidan]

Could be in for some thundery weather, Yay!

[Darren Bown]

The Lightning core looked to be between Cardiff and Barry, intermittent lightning, but powerful blue strikes.

[Snowshine]

Estofex issued a level one storm warning for pretty much all of Southern England yesterday. Also, they predicted a >49% chance of thunderstorms in the North of England, East of Ireland and South of Scotland.

 

DISCUSSION A

 

... S-UK, Belgium, the Netherlands, far N-France, NW Germany and SW-Denmark ...

The focus for isolated better organized convection exists over the highlighted area during the evening and overnight hours. At least 2 more significant mid-level troughs are embedded in this brisk westerly flow with the strongest one entering the area of interest during the night. Local area models show enhanced backing ahead of those vorticity maxima with SRH-2 in the 150-300 m^2/s^2 range. Enhanced BL convergence with locally enhanced moisture and therefore elevated pobabilities for deeper updrafts in an environment of 30-40 m/s DLS show a risk of organized convection. Severe wind gusts and isolated large hail will be the main risk, but an isolated tornado event cant be ruled out with low LCLs and strong LL shear. LLCAPE (inland) remains in the 50 J/kg range with 100-150 J/kg offshore, so the main interest will be onshore moving convection, before encountering an increasingly hostile environment. Amount of forcing and speed of steering winds could take the convection well inland with WRF showing convection even affecting NW Germany during the night. We therefore expanded the level 1 far inland. Over NW Germany, the overall risk should decrease but an isolated large hail and/or severe wind gust event can't be ruled out.

DISCUSSION B

... Ireland, Scotland, CNTRL/N-UK and the North Sea ...

The broad atmospheric picture showes limited risk for organized DMC. Nevertheless, SSTs next to Ireland, west of UK/Scotland and in the English Channel range between 10-12 °C with lower values in the North Sea (10 - 7 °C from west to east). Placing temperatures of less than -40°C at 500 hPa and less than -20 °C at 700 hPa atop the warm SSTs, very steep lapse rates of 8-9 K/km can be expected. Very low WBZ levels with elongated but thin CAPE profiles in offshore forecast soundings show a good chance for scattered thunderstorms. Somewhat drier air is seen especially around 800 hPa, but this should be compensated by the otherwise favorable conditions. Therefore a broad high probability lightning area was issued despite general concerns of lightning activity with marine convection and current (22Z at 12th January) lull in activity over the N-Atlantic.

BL moisture profiles indicate slim moisture to work with, which also decreases rapidly onshore. We therefore kept the coasts in the high probability lightning areas with decreasing values well onshore.
Thunderstorms will bring gusty winds due to 20 m/s LL flow in a well mixed air mass. Unusually cold air mass will also increase the risk of numerous marginal hail reports.

Edited January 13, 2015 by Cumulonimbus123

[Costa Del Fal]

Could be a loud night here in Falmouth. Already had one thunderstorm with hail and sleet in so I have seen thundersleet! Hoping some snow occurs soon also as temps drop further!

[poseidon]

Torro convective discussion issued for the cold front overnight: http://www.torro.org.uk/site/forecast.php

[timeless]

whats the potential for thunder for hereford thursday? reason l ask is because currently the UKMO seems to suggest possibilities for today as well as the next couple of days. however from the looks of the GFS storm forecasts it looks like a very low probability. not to mention for today estofex seems to only cover Carmarthen and the tip of the south west..

 

or are there other factors that lm unaware of? bare in mind lm a relative newbie to all this and lve only really taken an interest in convective weather due to running sensitive computer equipment, it gives me an idea when l should disconnect it for pending thunderstorms.

[mike57]

A few rumbles of thunder and some small hail in Bolton this morning, was working so not sure how near it was as I didnt see any lightning due to being inside.

[Reubinator]

Something weird happened yesterday morning (Jan 19th) at around 7.30/8 am... here in Grimsby! I was in bed, and I swear I heard thunder twice outside... I immediately looked on the lightning detector but nothing! Asked other people if they heard it, no, not a thing. I don't know whether it was just a few isolated distant strikes that the detectors didn't pick up but it was really strange. There was first a distant rumble but definitely loud enough to catch my attention and think 'No way!' Then about 3 to 4 minutes after there a smaller rumble that I probably wouldn't have noticed if I hadn't been listening for it. But the second rumble convinced me that what I was hearing was thunder. Now I'm not sure what it was but it sure did sound like it, pretty strange to hear after the light snow we had last night (although it doesn't surprise me because we seem to get more and more thundery-type activity with snow these days in this country).

Edited January 20, 2015 by Reubinator

[Dale Hay]

Just noticed this from the local newspaper's website, posted earlier, however in the article it says "Thursday" (so I'm guessing 15th Jan).

(Oh and they use that dreaded term "mini tornado" too *rattles*)

-> Freak wind hits quiet cul-de-sac

[mike57]

Something weird happened yesterday morning (Jan 19th) at around 7.30/8 am... here in Grimsby! I was in bed, and I swear I heard thunder twice outside... I immediately looked on the lightning detector but nothing! Asked other people if they heard it, no, not a thing. I don't know whether it was just a few isolated distant strikes that the detectors didn't pick up but it was really strange. There was first a distant rumble but definitely loud enough to catch my attention and think 'No way!' Then about 3 to 4 minutes after there a smaller rumble that I probably wouldn't have noticed if I hadn't been listening for it. But the second rumble convinced me that what I was hearing was thunder. Now I'm not sure what it was but it sure did sound like it, pretty strange to hear after the light snow we had last night (although it doesn't surprise me because we seem to get more and more thundery-type activity with snow these days in this country).

We live near Bridlington, and have experienced thundersnow when the conditions are right, one ehing I have noticed that it doesnt always show up on the lightning detectors, anyone know why?

[Spikecollie]

There seem to be frequent lightning strikes in the Norfolk direction at the moment...

[Thunderbolt_]

Finally managed to record thundersnow!

 

[Daniel*]

Finally managed to record thundersnow!

 

Great footage, very atmospheric.

[Thunderbolt_]

Great footage, very atmospheric.

 

Thanks!

[Supacell]

Great footage Scott.

 

I have hopes that a few more people will hear the odd rumble of thunder today with several disturbances in the NW flow. Anything that does develop is developing in an environment of around 40-60knts of deep layer shear, although this tends to decrease from the north during the afternoon. The whole UK is in the 15% lightning risk area for today according to Estofex. NMM shows CAPE values of 200-400j/kg, higher along the Lancashire and Merseyside coastlines this morning. Overnight the CAPE values increase in the SW and then along the S coast also.

 

Snow is unlikely along the coasts where the highest CAPE is but inland there is the chance for more lucky folk to see the elusive thundersnow today. Get your recording equipment ready when you see those dark skies approaching

[dodge]

Finally managed to record thundersnow!

 

 

Nice capture, you're just down the road from me (Hathershaw) and I counted about 4 flashes of lightning last night.  Strangely didn't hear any thunder but probably because it was muffled and I was inside.

[Thunderbolt_]

Great footage Scott.

 

I have hopes that a few more people will hear the odd rumble of thunder today with several disturbances in the NW flow. Anything that does develop is developing in an environment of around 40-60knts of deep layer shear, although this tends to decrease from the north during the afternoon. The whole UK is in the 15% lightning risk area for today according to Estofex. NMM shows CAPE values of 200-400j/kg, higher along the Lancashire and Merseyside coastlines this morning. Overnight the CAPE values increase in the SW and then along the S coast also.

 

Snow is unlikely along the coasts where the highest CAPE is but inland there is the chance for more lucky folk to see the elusive thundersnow today. Get your recording equipment ready when you see those dark skies approaching

 

Nice capture, you're just down the road from me (Hathershaw) and I counted about 4 flashes of lightning last night.  Strangely didn't hear any thunder but probably because it was muffled and I was inside.

 

Thanks, guys!

[Stargazer]

Thundersnow! After a snow-free season so far we had a short sharp shower this afternoon with the lot Within a couple of minutes we managed hail, thunder, graupel and a few flakes of snow.  It even settled for a while but has mostly gone now.

[Nick F]

Risk of some heavy downpours with hail and thunder across Ireland, Wales and SW England later today, as an unstable airmass moves in behind the rain band moving east, perhaps downpours with thunder moving along south coast overnight.

 

First Netweather storm forecast of the year, though I know some have had thunder since the New Year:

 

http://www.netweather.tv/index.cgi?action=convective;sess=0c66f9a2744a49c1af2bbe268d408027

[Mapantz]

Risk of some heavy downpours with hail and thunder across Ireland, Wales and SW England later today, as an unstable airmass moves in behind the rain band moving east, perhaps downpours with thunder moving along south coast overnight.

 

First Netweather storm forecast of the year, though I know some have had thunder since the New Year:

 

http://www.netweather.tv/index.cgi?action=convective;sess=0c66f9a2744a49c1af2bbe268d408027

 

Nice one Nick F

 

It has been so long, i nearly forgot about this thread.

[Spikecollie]

Risk of some heavy downpours with hail and thunder across Ireland, Wales and SW England later today, as an unstable airmass moves in behind the rain band moving east, perhaps downpours with thunder moving along south coast overnight.

 

First Netweather storm forecast of the year, though I know some have had thunder since the New Year:

 

http://www.netweather.tv/index.cgi?action=convective;sess=0c66f9a2744a49c1af2bbe268d408027

Thunderstorms forecast for me in northern France tomorrow, another cloudspotters flight out of Paris!