Convective/Storm Discussion

[BFS/BHD]

T-storm just hitting Belfast atm. Constant noisy thunder!

[sammie]

TORRO TORNADO WATCH 2009/007

A TORNADO WATCH has been issued at 23:20GMT on Saturday 31st October 2009

Valid from/until: 0430-1600GMT on Sunday 1st November 2009 for the following regions:

Parts of (see map)

England & Wales

S Scotland

Isle of Man

Channel Islands

Eastern Eire

THREATS

Tornadoes and wind gusts of up to 70mph; isolated CG lightning.

Rapidly developing Atlantic depression will move NNE late tonight and through tomorrow, the most likely track is through the Irish Sea into S Scotland. Close to the storm's centre, a marked dry intrusion/frontal fracture may allow some convection to develop, in a highly sheared environment. Marked low-level shear brings the risk of isolated tornadoes - in addition, wind gusts of 60mph are possible, perhaps 70mph in places. There is a small risk that a sting-jet may develop, enhancing the wind risk.

To the south of the depression, a well-marked cold front will surge eastwards...this is likely to split, so rather intense precip, perhaps with lightning, could develop ahead of the surface front, althoug rather stable/saturated low-level air ahead of the front would limit the risk of convective gusts. The surface front looks fairly likely to be marked by a line of forced convection. Strong low-level shear ahead of this means that misocyclones may develop along this front, bringing a risk of locally damaging winds, and perhaps isolated tornadoes. At this stage it is not clear whether this convection will be deep enough for lightning.

Even at this late stage, the track of the depression is stil rather uncertain. This forecast may well be updated/amended in the morning, as the situation develops.

Forecaster: RPK.

[Jane Louise]

Estofex has us on a level 1 warning today! I wonder if we may get a Thunderstorm out of this weather today.

http://www.estofex.org/

[Coast]

I am just out of that level one area, what are the others saying?

TORRO have a huge swaith of the UK covered, UKASF have yesterdays which was:

Storm Forecast Issued: 2009-10-31 09:41:00

Valid: 2009-10-31 00:00:00 - 2009-10-31 23:59:00

Regions Affected

Northern Ireland, western & northern Scotland (including Northern Isles) and western & northern Ireland (all of the UK, excluding the far southeast, is under a WATCH)

Synopsis

A complex area of LOW pressure centred over and around Iceland, combined with a new, rapidly developing LOW to the southwest of the UK, will dominate the weather on Saturday. Scattered showers, sometimes forming distinct bands, of showers will affect many parts of Ireland, Northern Ireland and Scotland. Cloud heights look favourable for some electrification of the showers, though electrical activity should remain localised and not widespread. Favourable conditions exist for the development of a funnel or tornado across these regions.

Also, as a cold front clears eastwards across England during the morning and early afternoon, there is a low risk of an embedded thunderstorm within the front. Due to the low nature of this risk, only a WATCH has been issued.

During the late evening and night hours, the next rapidly-developing LOW pressure system will move into parts of Southwest England, Wales and much of Ireland by the end of this forecast period. Heavy bursts of rain are expected quite widely, accompanied by strong to gale force winds. It appears that there may be some convective elements possible either ahead of or along the cold front - since the cold front will affect the UK on Sunday, more details will be given in the forecast for Sunday should one be necessary by that stage.

The showers across western Scotland and Northern Ireland may remain electrified into the night.

See the note here regarding rapid cyclogenises (RACY) off the top of Wales:

[CardiffStorm]

TORRO have adjusted their forecast for later today and tonight.

TORRO CONVECTIVE DISCUSSION 2009/036

A TORRO CONVECTIVE DISCUSSION has been issued at 15:25GMT on Sunday 1st November 2009

Valid from/until: 15:25 - 07:00GMT on Sunday 1st/Monday 2nd November 2009 for the following regions of the United Kingdom & Eire:

S Eire

S Wales

S England

THREATS

Wind gusts to 40-50mph; hail to 10-15mm diameter; CG lightning; isolated brief tornadoes.

SYNOPSIS

Upper cold pool is producing numerous showers and occasional thunderstorms across S Eire and in the SW approaches at present. These will move eastwards this evening and overnight, bringing the risk of marginally severe wind/hail. In additional, coastal topography may allow brief tornadoes to develop, especially around the Bristol Channel area, where convergence is indicated.

Forecaster: RPK.

Edited November 1, 2009 by jamo_s

[Nick F]

Netweather storm forecast is available for the next 24 hours:

http://www.netweather.tv/index.cgi?action=convective;sess=c4e4ac125e83d9d0c5afa28d9f826bc7

[Coast]

Looks to be a low level risk of some minor storms for today then. ESTOFEX forecast much as NW's (if you treat the French section as covering us as well!):

Storm Forecast

Valid: Mon 02 Nov 2009 06:00 to Tue 03 Nov 2009 06:00 UTC

Issued: Sun 01 Nov 2009 21:35

Forecaster: DAHL

No threat levels have been issued.

SYNOPSIS

An intense upper trough will rapidly be moving across the Alpine regions into the Ionian-Sea region during the period. Its progression into the N Mediterranean will be accompanied by rather intense cyclogenesis over the Gulf of Genoa, moving into the central Adriatic. Otherwise, an extensive SFC low complex persists over the N Atlantic and the North Sea, with an equally large SFC high covering eastern parts of Europe and Russia.

DISCUSSION

... France ...

In the thermal-trough region over France, some instability is expected during the first half of the day. Over S France, shear will be quite intense (30 m/s in the lowest 6 km), so that some threat of at least brief linear organization and storm-scale rotation exists. This suggests that an isolated severe wind gusts and / or tornado or two cannot be ruled out. However, given the small time window and an allover marginal setup, it seems that a LVL one is not necessary.

TORRO's forecast for today is covered by Jamo's post above and the best of the rest:

[Nick F]

Netweather storm forecast for tomorrow, slight potential for severe weather across Sern counties associated with frontal wave running eastwards - GFS shows some convective potential within warm sector coupled with exceptional deep layer shear:

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

[Coast]

Thanks for that Nick, seems like some havve similar ideas, just a little more South:

Storm Forecast

Valid: Tue 03 Nov 2009 06:00 to Wed 04 Nov 2009 06:00 UTC

Issued: Tue 03 Nov 2009 05:40

Forecaster: VAN DER VELDE

A level 2 was issued for W Turkey mainly for tornadoes and severe wind gusts.

A level 1 was issued for S Italy mainly for severe wind gusts.

A level 1 was issued for N France and Belgium mainly for the chance of a tornado and severe wind gusts.

SYNOPSIS

Depressions dominates the map, with a <968 hPa low pressure center stationary north of Scotland and a <996 hPa center moving from Italy to western Turkey during the period. Blocking high pressure holds its position over Russia, with a cold stable airmass over N Balkan, Poland and Scandinavia.

The cold front and occlusion pass early in the period over the British Isles, followed by an increasingly unstable airmass. The system of Italy, Greece and Turkey is dynamically the most active.

DISCUSSION

...France, Belgium...

GFS shows signals of more than 50 J/kg CAPE with little CIN from some lower levels during the passage of the cold front after 15Z. The signals keep existing till the end of the night all the way over Germany, and significant upper support in the form of intense mid level PV values are present. At the front, large 0-2 km convergence is present in GFS. Several models currently show enhanced precipitation for extreme northern France and Belgium. All of this suggests reasonable chance for a strongly forced convective line in the level 1 area which may persist into Germany. The forecast is kept conservative but may be updated. Should convection develop along the front, it will profit from an environment with 25-35 m/s DLS, >15 m/s LLS, and 175-400 m²/s² SREH and very low LCL heights, which is sufficient for bow echos with severe gusts, and tornadoes.

...west coasts of France, Belgium and Netherlands...

There is some potential for thundery showers to cluster during early Wednesday morning (06Z) in the coastal convergence zones if storm motion becomes small and more SW-erly. The convergence should be stronger now that the temperature difference between land and sea is larger.

Storm Forecast Issued: 2009-11-02 23:34:00

Valid: 2009-11-03 00:00:00 - 2009-11-03 23:59:00

Regions Affected

All of the United Kingdom

Synopsis

A deep area of LOW pressure to the northwest of Scotland will dominate the weather across the UK on Tuesday. Various lines of showers/troughs will provide the main focus for electrical activity as they circulate anticlockwise around the centre of the LOW.

Hence, numerous showers and scattered thunderstorms are expected to affect many western coasts of both islands, perhaps with hail. Some showers may reach the eastern sides of the islands, but they will be most frequent across western areas.

Attention is also turned to the trailing cold front across southern England. A wave is expected to develop along the front, providing the focus for intense precipitation, and also an increased risk of convective activity as it moves eastwards along southern England during the afternoon. Conditions seem quite favourable for the development of a brief but moderate-intensity tornado. This risk rapidly decreases by 18z.

Showers and isolated thunderstorms will persist across many western and southern coasts overnight

Although not everyone......

and the others:

One to keep an eye on today.

[Harry]

Rain across S England has really intensified in the last half an hour!!

Could get rather soggy in the coming hours......hopefully a rogue sferic??

[weatherobsuk]

"S" Radar return now coming out of Bournemouth moving Eastwards towards Southampton. Will be hitting there in the next 20 minutes.

Edited November 3, 2009 by SNOW_JOKE

[*Stormforce~beka*]

Bloody nora that was mental that "shower". Torrential rain and wind. No T or L. Flooded the road nicely.

Will add some piccies now.

[Coast]

Squally type front just hitting us in Sussex, that green/red blob is heading straight for me!

[*Stormforce~beka*]

Here have some rain ...

[Coast]

A few strikes now showing up around North Norfolk.

[johnholmes]

ah I see-little drizzle showers!

[*Stormforce~beka*]

You got it John! We Southerners ain't we! This is the end of the world to us ...

[Flash Elvis]

Here in Thurrock we have had a very heavy shower for about 10 minutes....then as quick as it arrived its now blue sky!!!

[maidstone weather]

Not sure why UKASF have their storm risk area across the entire UK.

Seems it was appropriate though, seeing as most, if not almost all, sferics detected came from outside of ESTOFEX's region over eastern England and the North Sea?

Had a hefty prolonged downpour here at 2pm, looks incredibly black to my east as the shower moves away. Sadly no T + L :ph34r:

[fujita5]

Went jogging in Brentwood about 1pm and was watching radar just prior and was hoping the worst of the weather would just pass by. Got it dead right, main precip was just south of me - literally by a mile or so. Intensified as it passed, got buffeted by some pretty good outflow with very low ragged scud marking the OFB as it raced north over me. Lovely mammatus on north edge of shower.

Edited November 3, 2009 by fujita5

[dallas]

Just seen a report of Tornado (unconfirmed) in hamshire, near romsey and timsbury along A3057

Edited November 3, 2009 by dallas

[dallas]

DOH just seen the other reports!

[MP-R]

Thunder and lightning here in Yatton, on the edge of something big to the south.

[SteveB]

Thunder and lightning here in Yatton, on the edge of something big to the south.

Yeah best storm of the year, looks nasty on radar.

[Tn9]

Here in Thurrock we have had a very heavy shower for about 10 minutes....then as quick as it arrived its now blue sky!!!

Same here,sept that it lasted about half an hour at full tilt,pic here as the cloud moved off and the sun came out