Thunderstorm Potential - Weekend June 26-27th

[martinastro]

Just a quick heads up on the potential for convection/thunderstorm potential across portions of UK, Ireland,,and N. Ireland over the coming weekend with Sat, Sun, and possibly even Mon showing signs of warm-hot temps, humidity, moderate to high instability, decent lapse rates and convective precip release for scattered heavy showers and thunderstorms. The exact location and value of the CAPE keeps changing with each run however the trend has been visible for some time on GFS. Britain is currentlly showing the best instability. The expected activity is associated with a shallow low over the Atlantic to the W of Ireland along with a cold front, and post frontal troughing. There are early indications that next week could also be unsettled and perhaps thundery in nature. Will update with more info closer to the time.

[martinastro]

Sun's GFS CAPE and LI charts from Netweather.tv. This will change alot between now and then, however signs are there for a risk of severe thunderstorms over Britain.

[martinastro]

Still looking good this weekend....

[martinastro]

Convective outlook for Sat...



Storm Forecast Issued: 2010-06-25 13:27:00
Valid: 2010-06-26 00:00:00 - 2010-06-26 23:59:00

Regions Affected
NW England, W/N Midlands, E Wales and W Northern Ireland (C/S Scotland, N England, Midlands, Wales and Northern Ireland are included in the WATCH)

Synopsis

Low pressure "Ilse" approaches the United Kingdom from the North Atlantic on Saturday, whilst High pressure "Xerxes" remains firmly situated over the North Sea.

Ahead of an increasingly weak eastward-moving cold front, a convergence line is forecast to develop in a N-S direction from the Bristol Channel northwards to southern Scotland. Along this line, aided by local sea breeze effects, scattered showers and thunderstorms are expected to develop. There is a slight risk of a convergence-type funnel. Showers will persist in some areas until the end of this forecast period.

Across Northern Ireland/Ireland, scattered showers and thunderstorms are forecast to develop in the post-frontal airmass, moving northwards. These may persist into the night as they drift towards the Hebrides.

[Conor McDonald]

Looking great for sunday as said dam good cape and -LI's and quite high lapse rates. Also worth mentioning these stroms cloud run into evening hours with cape sticking around until evening and it looks like the showers/storms will be slowing moving too so there is the potential for flooding in areas. There also seems to be more sheer in the evening hours on sunday so that might be a good time for funnel/tornado development.

[martinastro]

Conor I intercepted a huge multicell moving S to N with a precip core the size of Lough Neagh, complete torrential precip falling with caused significant flooding on some of the roads. Cell was a beast with rotating inflow and low level black scud of large size getting sucked into the RFB. Very strong towers re-generating on it for a long time. Very fast moving also!. It produced c-g lightning further N.

[brianb]

Fearsome storm here approx. 1640 BST - only lasted 10-15 mins with lightning seen & thunder heard - strong wind associated with storm - rainfall approx. 10mm. Grey overcast cleared after the storm passed but seems to be reforming, it's still warm & very humid air :angry:

[martinastro]

Thanks for the report Brian!!, I was just about to ask you if you seen it but you beat me to it  , we chased it until outside Swatragh then let it go north, we knew by the back of it that it was a strong one. I thought you would have got some action from it. Rainfall was impressive!, here's the sferics chart

[martinastro]

Here's some of the flooding outside Swatragh from that storm

[Padraig OBrien]

Well done lads on the storm today nice one Martin our old friend, the flood on the bend

[Conor McDonald]

Just one from todays chase

[martinastro]

Class image Conor!.

Sun's outlook...

http://ukasf.co.uk/

Storm Forecast Issued: 2010-06-27 00:55:00
Valid: 2010-06-27 00:00:00 - 2010-06-27 23:59:00

Regions Affected
C, E + S Scotland and Northern Ireland (all of Scotland, Northern Ireland and eastern England are included in the WATCH)

Synopsis

A slack southerly airflow develops between Low pressure "Ilse" over the North Atlantic and High pressure "Xerxes" to the east of the United Kingdom

Scattered showers and thunderstorms will develop across Scotland and Northern Ireland in response to daytime heating and instability. Local torrential downpours are possible, and there is a threat of a weak funnel or tornado developing.

Isolated sharp showers or local thunderstorms may develop in a few places across eastern England later in the afternoon and into the evening. Such storms may produce locally very high rainfall totals, gradually drifting northeastwards during the evening, before fading as they cross the North Sea.

[martinastro]

Could be game over here today, strong cap has killed convective growth.

[Conor McDonald]

Things might change from now on in, as this is really only time when cape starts.

[paulster78]

Great shot Conor! Glad you guys caught some action over the w-end, i was away all w-end saw nothing interesting weatherwise.  Its been a very disappointing June for me anyway, looking forward to July for some more heat and strong convection.