Convective Outlook N UK - Thurs Feb 3rd

[martinastro]

Storm Forecast
Valid: Thu 03 Feb 2011 06:00 to Fri 04 Feb 2011 06:00 UTC
Issued: Wed 02 Feb 2011 20:52
Forecaster: GATZEN

DISCUSSION

Scotland, North Sea

A region of interest will be north-western Europe. A strong westerly flow will affect this area on Thursday. Late in the period, another, very strong mid-level jet streak is forecast to reach more than 60 m/s at 500 hPa over the northern British Isles. A frontal wave will be located to the east of this jet streak and will rapidly move eastward. Current scenario is that the moist low-level air mass will be not overlap with the deep lift near the jet streak axis, where quite cold mid-levels are forecast to lead to CAPE. So only a shallow line of convection may develop along the cold front and only sporadic lightning is forecast if any. Nevertheless, this strongly forced line may produce severe wind gusts and tornadoes given a bulk shear up to 20 m/s in the lowest kilometre. An upgrade to level 1 may be needed when sufficient instability will develop along the cold front. To the west of the cold front, severe synoptic winds are forecast with the sting jet of the low. Weak instability in the cold air mass will likely assist for some showers that may lead to a mixing of the high winds that will be about 45 m/s at 850 hPa to the ground.

[martinastro]

This from Paul Knightly via TORRO..

I'm very interested in the explosive cyclogenesis which is progged to occur west of Scotland tomorrow, with the storm passing close to the Faeroe Islands tomorrow night. The cold front looks to be marked by weak instability (a few 10s of Kg... of CAPE) and neutral to slightly negative 700 hPa LI values. Also, a 'wedge' of colder air looks to mark the front. This surging front combined with weak instability, and strong lift via low-level convergence and DVCA aloft brings a risk of embedded thunderstorms within the frontal precip.

With an intense low-level jet just ahead of the front, severe wind gusts will probably occur regardless of convection. However, these may be enhanced by convection across N Ireland and Scotland in the late afternoon/evening, with a risk for tornadoes too.

Overnight, very strong winds for northern Scotland (~100mph gusts) and the N Isles. The cold front becomes slow-moving, and orientated within the mean deep layer wind field overnight, through Ireland, Wales and northern England. Models suggest convective elements within this line are possible - minor waves may run along the front too. A risk of convective gusts and perhaps isolated tornadoes with this.

[brianb]

Don't know (or care much) about convection but there seems to be strong wind around somewhere ... the surf is really up with very large, very long waves crashing onto the northern coastline

[martinastro]

Tornado watch from TORRO issued for Scotland and N. Ireland. Lightning to the W and NW of Ireland associated with cold front which is highly convective...

http://www.torro.org.uk/site/forecast.php



TORRO TORNADO WATCH 2011/001

A TORNADO WATCH has been issued at 1400GMT on Thursday 3rd February 2011

Valid from/until: 1400-0100GMT on Thursday 3rd/Friday 4th February 2011, for the following regions of the United Kingdom & Eire:

Parts of (see map)

Eire

N Ireland

Scotland, including the Northern and Western Isles

THREATS

Tornadoes; hail to 10mm diameter; convective wind gusts to 90 knots; cloud-ground lightning; heavy rain

SYNOPSIS

Intense Atlantic depression will move north-east, to pass close to the Faeroe Island tonight. The associated cold front will sweep eastwards across the northern parts of Eire/N Ireland, and Scotland this afternoon/evening, and thence through the Northern Isles. Sferics have been detected west of Eire and Scotland, showing that there is strong lifting associated with this. Strong low-level wind shear is likely along the front, suggesting that gusts of 60-70mph, and perhaps 80mph will be possible. In addition, tornadoes are also possible.

Behind the front, heavy showers and a few thunderstorms are likely across Scotland, mainly in the west, and across the Western and Northern Isles. The intense pressure gradient is likely to allow gusts of 80-90mph even outside of convection, and up to 100mph possibly across the N Isles. A small risk of tornadoes too.

As the front moves southwards across Eire tonight it will become increasingly aligned with the deep layer wind field. Low-level convergence still looks strong along the front, and as minor waves run along the front, a risk exists of tornadoes and strong wind gusts. However, convection will likely be fairly shallow in nature.

Forecaster: RPK

[martinastro]

WOW, lastest c-g lightning from this storm!

[Anton]

That looks intense stuff Martin.

[JohnC]

Hope you get to it, Martin. Looks  pretty lively to me.

[martinastro]

The latest sferics chart is down so I'm blind and don't know what's going on, if the lightning was still that active then I would be tempted to drive N.

[paulster78]

Very annoying-especially when we need it. I keep trying the site every 2 minutes, lol

[martinastro]

It's really annoying Paul isn't it - and just when we need it most. I'm watching for flashes from here. Tony Gilbert has updated his forecast on UKWW, going for tornadoes across N. Ireland and N. Britain this evening and tonight with strong convective gusts.

[JohnC]

Is this of any use ?

http://www.blitzortung.org/Webpages/index.php?lang=en&page=1

[martinastro]

Thanks for the link John, I don't now how accurate it is but I've now added it to my favs for future ref so cheers for posting that 

Looks like the worst is over now, sill strong gusts and flickering lights here however the stronger radar echoes have moved east. If there have been any tornadoes from these storms then we will find out in the days ahead.

Plenty of thundersnow over Scotland last night and a possible supercell the day before.