Convective weather - 2nd-3rd November 2011

[richep]

Is it worth keeping an eye/ear out tonight or are we looking at tomorrow for any thundery activity?

[wimblettben]

All I can say is that I will be utterly SHOCKED if we get a proper thunderstorm here tomorrow or the next few day's as we have failed to have a proper one for the last 4 years.

And to be honest, my excitment is never as high now as it was last year when we had potential because it has alway's ended up being the same case of no storm after no storm after no storm.

I guess it has something to do with your brain getting used to the typical 2010s routine for storms in the SOUTHWEST!

[Nick F]

IMBY pessimism aside, it looks quite an interesting set-up tomorrow, with GFS indicating an unstable rPm airmass with several 100j/kg CAPE to the west of a cold front slowly clearing eastern England during the afternoon - as a result of a deep moist southerly flow, warm SSTs and increasingly cold air aloft. So some heavy showers and storms look to spread in across southern, central and western areas during the late morning and into the afternoon. A strong southerly jet parallels the cold front which looks to develop a wave from the south, the exact areas the wave moves north over looks a little uncertain - probably central-S England and up through the Midlands. But there could be some storm activity developing within the wave itself - certainly could be some intense rainfall near the wave.

The strong southerly winds aloft and winds backed to the SE towards the surface will generate strong vertical shear - particularly in the lowest 1km. So both along the cold front and in the unstable rPm airmass - there is potential for storm organisation and a risk of severe weather including tornadoes.

[Jane Louise]

SKYWARN UK SEVERE THUNDERSTORM WARNING #059

ISSUED: 1530UTC WEDNESDAY 2ND NOVEMBER 2011

SKYWARN UK HAS ISSUED A SEVERE THUNDERSTORM WARNING FOR THE FOLLOWING REGIONS:

NORTHERN IRELAND

SOUTHWEST SCOTLAND

NORTHWEST ENGLAND

WALES

MIDLANDS

SOUTHWEST ENGLAND

SOUTHERN ENGLAND

IN EFFECT FROM 0000UTC UNTIL 2300UTC THURSDAY 3RD NOVEMBER 2011

UNSTABLE POST-FRONTAL ENVIRONMENT WITH LOW LEVEL CONVERGENT WARM AIR ADVECTION ENHANCING CONVECTION

SEVERE THUNDERSTORMS ARE EXPECTED, OR OCCURRING, SOMEWHERE WITHIN THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

HEAVY RAIN...HAIL...STRONG GUSTS...FUNNELS...TORNADOES...FLASH FLOODING...LIGHTNING

DISCUSSION:

THERE IS GOOD MODEL CONSENSUS OF A POSSIBLE SEVERE THUNDERSTORM EVENT WITHIN THE WATCH AREAS THROUGH THURSDAY. A COLD FRONT TRANSITS THE UK OVERNIGHT SLOWING OVER EASTERN ENGLAND, BEHIND WHICH 500MB TEMPS AS LOW AS -25C WILL ENCOURAGE WIDESPREAD CONVECTION MOSTLY INITIATING OVER SURROUNDING SEAS AND ADVECTING INLAND. LOW LEVEL WARM AIR IS ADVECTED UNDER A DEEP WIND PROFILE, WITH POSSIBLE SHORTWAVING AND RESULTANT CONVERGENT ZONES THROUGH THE IRISH SEA, IN LEE OF COASTS, PENINSULAS AND HIGH GROUND, AND THROUGH CENTRAL ENGLAND. 0-6KM DEEP LAYER SPEED SHEAR IS SUFFICIENT TO ENHANCE UPDRAFT STRENGTH AND HEIGHT, WITH EQUILIBRIUM LEVELS HIGHEST OVER NORTHERN IRELAND. LOW LEVEL DIRECTIONAL SHEAR IS SUPPORTIVE OF ORGANISED CONVECTION, WITH INCREASED POTENTIAL FOR FUNNELS, TORNADOES UP TO T2 AND STRONG CONVECTIVE GUSTING. PRECIPITABLE WATER IS UP TO 2.5CM SO CORES MAY BE HEAVY WITH POTENTIAL FOR FLASH FLOODING, ESPECIALLY FOR TRAINS OF STORMS. HAIL IS ALSO A CONCERN. THIS WARNING MAY BE UPDATED.

SPOTTER ACTIVATION IS REQUESTED AND SPOTTERS ARE REQUESTED TO REPORT ALL FACTORS EXCEEDING ACTIVATION CRITERIA.

Sweet, something to watch! looks like anywhere alone the South West, South Coast and South East have a chance of something interesting over the next few days! Looks like I could in a decent area again, I hope so

Jane Ill send you a storm as well

You better do SK lol

[Stuart]

well jane that warning to good to me here

[syed2878]

Just checked the met ofice 5day forecast for birmingham. Tomorrow m cloud and lite rain. Friday thundery shower sat lite rain and heavy rain. Sun lite rain.

[Raidan]

I also will be shocked if something happens,If something does i'll class it as a late birthday or early xmas present.

[Jane Louise]

well jane that warning to good to me here

Aww Stu, it may all change! I find it hard to believe there's going to be severe thunderstorms.I just thought it'd be one or two thundery showers lol

I also will be shocked if something happens,If something does i'll class it as a late birthday or early xmas present.

I will be quite shocked too. But all we can do is wait and see. Always good to be optimistic .It's exciting that , at least we have potential there,better than nothing I say!

[wimblettben]

Well Ian Ferguson on BBC Points West this evening didn't mention any risk of thunder for tomorrow and Friday at all! Not even hail!

[A.J]

Well Ian Ferguson on BBC Points West this evening didn't mention any risk of thunder for tomorrow and Friday at all! Not even hail!

Ah, the reliable beeb forecast...lol....a very vague forecast for the masses...My 1st rule of BBC weather forecasts is simply if it's forecast, it aint happening, if it isn't forecast, it will.....lol

Humour aside, and with respect to the BBC, as posted earlier, model consensus for the potential of thunderstorms in the given watch areas are good

[Stuart]

Areas Affected:

S & W England, Wales, SW Scotland, Eire

Synopsis:

A large deep (960mb ish) area of low pressure centred several hundred miles west of Ireland will push a waving front across Britain during the day. A mild, humid southerly flow ahead of the front and associated cold air aloft behind the front will enhance the chance of rain and perhaps even some thunder. Several troughs are expected to follow the main surface front enhancing the risk of thunder.

Discussion:

Post cold front a strong southerly flow and unstable airmass with a large upper trough to the west will bring the potential for organised showers with embedded thunder. The risk for some severe weather is also possible given the combination of shear and instablity. DLS values in the region of 40kts along with LLS values around 25kts will overlap SBCAPE values of 400-500j/kg across W England, Wales and perhaps even parts of SW Scotland and Ireland (however shear values will be less in Ireland). Heavy showers will generate from sea-temps, but likely move well inland given strong southerly flow. The potential for some moderate sized hail 1-2cm with organised storms is possible, and perhaps even an isolated tornado, especally where terrian driven convergence boundaries are present.

Autumn post-cold frontal troughs in a strong synoptic flow have a history of producing isolated tornadoes and severe weather events in the UK, so this situation warrents a severe risk.

http://ukasf.co.uk/storm-forecasts/139

[DeepSnow]

That is the second time this year I have been under the red for severe, though the first time nothing happened! Would be amazing if we get some severe storms tomorrow! Better late than never

Edited November 2, 2011 by DeepSnow

[Staffordshire]

I won't be holding my breath!

[Jane Louise]

You beat me to it Stu lol. That's now 2 severe forecasts, it's really looking promising. Let's hope for an exciting and safe couple of days

[Stuart]

sorry jane but all the best for your 1st storm of the year

Edited November 2, 2011 by Stuart

[Jane Louise]

sorry jane but all the best for your 1st storm of the year

I'm hoping so Stu! what with being in a new area and remembering that when I first moved up to Glos 12 years ago we had some brilliant storms Autumn time. I have a lovely view here so I'm going to set up my camera on the tripod ready providing I get something of course. who knows I may have a video to post up if one does occur. :lol:

[Andy Bown]

Well Ian Ferguson on BBC Points West this evening didn't mention any risk of thunder for tomorrow and Friday at all! Not even hail!

Ah, the reliable beeb forecast...lol....a very vague forecast for the masses...My 1st rule of BBC weather forecasts is simply if it's forecast, it aint happening, if it isn't forecast, it will.....lol

Humour aside, and with respect to the BBC, as posted earlier, model consensus for the potential of thunderstorms in the given watch areas are good

You say that AJ, but Ian Fergusson as our local BBC forecaster is excellent when it comes to predicting thundery conditions and explaining what the atmosphere is doing. He genuinely knows the forces that come into play in this region to help things develop (also for snowy weather too) and for those of us who watch him regularly it's much appreciated.

As an example, last Tuesday there was a forecast for thundery showers. In his lunchtime broadcast he showed the current radar but said there was no lightning detected yet but that it was expected through the afternoon. Then in the evening he played the radar and showed where storms had happened, explaining why they had done so.

So back to tomorrow, I was surprised he didn't mention the possibility of thundery activity, however he did highlight the potential for very heavy rain developing in the afternoon in the East of the region while saying the exact timing/positioning was uncertain.

As usual at this time of year the greatest thundery potential will exist the nearer you are to the coast, but as last week showed, if conditions are right then thunder can spread quite a way inland.

I just think it's great to have such regular potential after a quiet summer period (the Spring was good though) and, even if nothing thundery happens I'm sure, as last week, that there will be stunning clouds to admire.

[Jane Louise]

And here's the latest from Estofex there's even a mention of supercells!!

Storm Forecast

Valid: Thu 03 Nov 2011 06:00 to Fri 04 Nov 2011 06:00 UTC

Issued: Wed 02 Nov 2011 21:08

Forecaster: GATZEN

A level 1 was issued for the British Isles and northern France mainly for large hail, severe wind gusts, and tornadoes.

A level 1 was issued for southern France and the west Mediterranean mainly for excessive rain.

A level 1 was issued for western and southern Iberia and surroundings mainly for severe wind gusts and tornadoes.

SYNOPSIS

The deep Atlantic long-wave trough will slowly enter Iberia during the period. A strong south to south-westerly flow will affect the British Isles, France, the western Mediterranean, and Iberia. The cold front will become mostly parallel to the jet and will be present from the western North Sea to France and the west Mediterranean at Friday morning. Rich low-level moisture is already present along the cold front and will even increase over the west Mediterranean given a moist south-easterly flow and strong low-level convergence. QG lift is likely from the British Isles to the west Mediterranean ahead of the eastward moving trough. This lift is expected to lead to increasing lapse rates that will overlap with the moisture.

DISCUSSION

British Isles, northern France

A tongue of very moist low-level air mass has spread into the British Isles and France and latest observations indicate surface dew points of 14°C. While the cold front crosses the Iberian Peninsula during the day, a frontal wave will be associated with backing surface winds from northern France to the British Isles in the afternoon and evening hours, associated with continuous moisture advection. Lift can be expected through-out the period given the approaching trough and mid-level jet streak as well as the frontal wave associated with warm air masses at low levels spreading northward. As a consequence, steepening lapse rates are forecast and CAPE becomes likely.

The overlap of the rich low-level moisture with strong low-level vertical wind shear (12 m/s 0-1km bulk shear) is clearly indicated by latest models. Main uncertainty will be the lapse rates and the chance of surfaced-based instability as well as the lift that may be rather weak. Current thinking is that showers and thunderstorms will develop rather isolated and will rapidly move northward. Some of these storms are expected to develop into supercells capable of producing large hail, tornadoes, and severe wind gusts. The convective activity will likely last until the night hours.

http://www.estofex.org/

[Marcus_surfer]

All this thundery activity looks further south than forecast, heading into SW France now

[staplehurst]

Worth noting land temperatures, given the warmer thicknesses etc, will be slightly warmer than that of SSTs (unlike last week) and so showers will likely hold together further land than last time, and that accompanies the chance of thunder...

[A.J]

You say that AJ, but Ian Fergusson as our local BBC forecaster is excellent when it comes to predicting thundery conditions and explaining what the atmosphere is doing. He genuinely knows the forces that come into play in this region to help things develop (also for snowy weather too) and for those of us who watch him regularly it's much appreciated.

As an example, last Tuesday there was a forecast for thundery showers. In his lunchtime broadcast he showed the current radar but said there was no lightning detected yet but that it was expected through the afternoon. Then in the evening he played the radar and showed where storms had happened, explaining why they had done so.

So back to tomorrow, I was surprised he didn't mention the possibility of thundery activity, however he did highlight the potential for very heavy rain developing in the afternoon in the East of the region while saying the exact timing/positioning was uncertain.

As usual at this time of year the greatest thundery potential will exist the nearer you are to the coast, but as last week showed, if conditions are right then thunder can spread quite a way inland.

I just think it's great to have such regular potential after a quiet summer period (the Spring was good though) and, even if nothing thundery happens I'm sure, as last week, that there will be stunning clouds to admire.

You didn't read my post properly Andy....Did you not see the 'Humour aside' part?......judging by your post, you missed that bit!

Anyhoos, not a huge fan of BBC forecasts, they are catered for the masses (it's a TV broadcast, after all) but if Ian ends up nailing this forecast for the west country, then they'll be a few eggs on a few faces on other previously posted forecasts contained in this thread (I'm also not a big fan of UKASF as forecasts are 'over the top' & rarely accurate IMHO)

a quick edit....a forecast from estofex has some potential (level 1 over much of England through tomorrow)....again, must stress that it is just potential atm, as for tomorrow, radar watching is the key

Edited November 2, 2011 by ajpoolshark

[Jane Louise]

I guess we'll all have to wait and see whether these forecasts pan out. I expect they'll move up from the South coast in a North Easterly direction lol. I also agree with AJ, radar watching is definately a must tomorrow especially to verify whether we will get the severe forecasts as mentioned.

Anyway, here's Torro's view.

TORRO TORNADO WATCH 2011/008

A TORNDAO WATCH has been issued at 22:10GMT on Wednesday November 2 2011

Valid from/until: 00:00 - 18:00GMT on Thursday November 3 2011, for the following regions of the United Kingdom & Eire:

Parts of (see map)

Eire

N Ireland

England

Wales

S Scotland

IoM

Channel Is

THREATS

Tornadoes; wind gusts to 65mph; hail to 25mm diameter; CG lightning

SYNOPSIS

A cold front will move north-eastwards tonight, introducing a returning polar maritime airmass, which has been strongly modified (warmed/moistened) in the lower levels, whilst remaining cold aloft. A large upper low to the west and high to the east will promote a strong southerly flow throughout the depth of the troposphere. One or more shortwave upper troughs will rotate around the low, and these are likely to promote some backing of the low-level flow ahead of them. The unstable airmass will move into the more south-western parts of the risk area overnight, and then up the Irish Sea, extending north and east tomorrow.

There is some uncertainty to the instability within the airmass, and how far inland instability will move, given seasonally weak insolation during Thursday. Also, low-level cloudiness may be fairly extensive, further complicating the forecast. However, given model indications of several hundred J/Kg of CAPE within a fairly strongly sheared (both deep layer and low-level), a risk of severe weather is indicated.

The highest risk would appear to be close to southern and western coastal parts of England and Wales, and throughout Eire/N Ireland, given closer proximity to the upper low. However, the brisk flow is likely to bring the risk inland, and there is a chance a new watch will be needed for areas further east and north during the day, and the risk may extend well into tomorrow night.

Enough shear is forecast to support organised convection, including the risk of supercells. Strong winds and fairly large hail are possible. There is also the risk of tornadoes, perhaps quite strong, should storms become well-rooted into the boundary layer. There is a suggestion of a push of stronger low-level winds for a time during the morning and into the early afternoon around the Irish Sea, especially into eastern Eire and across N Ireland, especially the eastern half. This could enhance the tornado risk although it must be stressed that mesoscale features during the day tomorrow are currently hard to pinpoint.

It is worth noting that similar synoptic set-ups in the past at this time of year have yielded various forms of severe convection, including tornadoes.

Forecaster: RPK

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

[Cookie]

would be a great day to be further south!!

good luck guys hope to see some good photos!

[Costa Del Fal]

Good luck all over the next 2 days. Some very interesting forecasts coming out tonight. Like the mention of possible Supercells from Estofex though probably a very low risk. Still, some pretty fantastic storm ingredients for November! SW England, Wales, The Midlands and CS England especially should be aware of not only some downpours, but perhaps a good storm. Here's hoping!

[Cheshire Freeze]

Don't know what to make of tomorrow, seems that this location is going to be wedged between two areas of potential interest (not for the first time this year) with a batch of downpours making progress up across the SW and Wales tomorrow daytime and a band of heavy rain and embedded storms pushing up across CS England, east Midlands and northeast England tomorrow evening and night. It's the same story come rain, thunder, snow- benign pretty much describes the weather here over the past year!

I fear the storm drought will push on to next year for this area.

Edited November 2, 2011 by CreweCold