General Storm Thread

[wchris_uk]

its annoying were not in for anything much i dont think...

where abouts are you?

[Ian Fergusson]

Seems that any convective activity associated with tonight and into Monday surface low and associated frontal system is rather unlikely. Though, I wouldn't totally rule out embedded cells developing near to triple point moving ENE across Sern and Eern counties during late tonight and into the early hours of Monday given greatest lift of moist air mass near to the region. However, real lack of instability and saturated profiles will limit potential greatly. Some very strong LL shear across Sern and Eern parts of England due to backed surface winds and strong veering flow aloft.

Probably have to wait a couple more model runs to see if the set-up looks a little more favourable for embedded cell development.

Hi,

Much though I'd love to share with all of you the exhaustive briefing re tonight's event from the UKMO Chief Forecaster, I can't - so let me paraphrase some key elements from his last briefing document, sent after his modifications to the 06z NAE output, etc.

That run upped the rainfall totals, generating a fairly broad swathe of 30-50mm extending from SW England to around the Wash, with sub-regional peaks of 80-90mm within it. Re your comment above, the latest run and simulated ascents does show potential instability embedded in the system, with the peak WBPT values at 850hPa. Thus, the Chief F/C notes for us to "...allow for embedded thunderstorms within (the system)"

As noted in my earlier post, much of the heaviest rain will fall in a fairly short period, when we're expecting 50mm possible in a corridor through the SW over 3hrs from 21z to 24z tonight. The Chief advises that we're probably going to see a widespread swathe of 20-40mm accumulation, with isolated spots attaining 80mm where there's convection within the rainband.

Alongside the rainfall, the winds are again important to stress as a matter of concern; my earlier post re the sting jet potential tomorrow AM in the Wash area remains valid; more broadly, the strength of the gradients around the southern and western flanks of this depression look potentially troublesome in the latest output.

Worth adding that once we're through this event, we have the temporary ridging into midweek which offers only short respite before western areas (especially) get nailed Thursday with the next deep low. BH weekend has low confidence but a further threat of heavy rain into southern England Sunday/Monday. Longer range prog from UKMO makes fascinating reading but into the 10-15d period becomes decidely tricky, due to hints of a hurricane becoming embedded into the westerly flow out in the western-central Atlantic around 40-50degN.

[camiscool]

im in tunbridge wells west kent

[Ian Fergusson]

Hi Ian, is Weston in the firing line or am I to far north?

Wet but nothing extreme - - head out east down the A303 / M4 into Wilts and it'll be a totally different story by midnight onwards. I would imagine stretches of the M4 will be wholly undriveable.

[Greeny]

Thanks for the info Ian, should be an interesting night seeings I got up at after midnight today I'm likely to be awake at those times tonight. Hehe.

[camiscool]

Hi Ian is west kent in the firing line tonight?

[Ian Fergusson]

Wet but nothing extreme - - head out east down the A303 / M4 into Wilts and it'll be a totally different story by midnight onwards. I would imagine stretches of the M4 will be wholly undriveable.

Actually, let me slightly clarify that... as I've now seen the very latest severe weather briefing from the Chief Forecaster.... his new mapping does actually take the northern edge of the swathe of heaviest / disruptive rain up to Bristol and S Glos, plus all of Somerset effectively, so it's likely you'll get a fair hosing in Weston-s-Mare. Maybe 30mm or so possible. I expect worst areas for Somerset will be around Crewkerne, Yeovil, Wincanton and NE into the borderlands with Wilts, e.g., Frome, Radstock etc.... also some of the 'flashy' catchments around Chew and environs into B&NES.

[dallas]

Hi,

Much though I'd love to share with all of you the exhaustive briefing re tonight's event from the UKMO Chief Forecaster, I can't - so let me paraphrase some key elements from his last briefing document, sent after his modifications to the 06z NAE output, etc.

That run upped the rainfall totals, generating a fairly broad swathe of 30-50mm extending from SW England to around the Wash, with sub-regional peaks of 80-90mm within it. Re your comment above, the latest run and simulated ascents does show potential instability embedded in the system, with the peak WBPT values at 850hPa. Thus, the Chief F/C notes for us to "...allow for embedded thunderstorms within (the system)"

As noted in my earlier post, much of the heaviest rain will fall in a fairly short period, when we're expecting 50mm possible in a corridor through the SW over 3hrs from 21z to 24z tonight. The Chief advises that we're probably going to see a widespread swathe of 20-40mm accumulation, with isolated spots attaining 80mm where there's convection within the rainband.

Alongside the rainfall, the winds are again important to stress as a matter of concern; my earlier post re the sting jet potential tomorrow AM in the Wash area remains valid; more broadly, the strength of the gradients around the southern and western flanks of this depression look potentially troublesome in the latest output.

Worth adding that once we're through this event, we have the temporary ridging into midweek which offers only short respite before western areas (especially) get nailed Thursday with the next deep low. BH weekend has low confidence but a further threat of heavy rain into southern England Sunday/Monday. Longer range prog from UKMO makes fascinating reading but into the 10-15d period becomes decidely tricky, due to hints of a hurricane becoming embedded into the westerly flow out in the western-central Atlantic around 40-50degN.

Ian,

That mention of a huricane in the advanced forecast, is that due to the possible route of TS6?

Hi

[Optimus Prime]

How does this advancing storm compare to July 19th/20th 2007? I seem to remember it developed from the south and moved northwards. It was later than tonight, main event here was 6AM - 1PM rather than what we have now for the early hours. I'm guessing the lack of sun the available convective energy will be lower?

I see the 'Lifted Index' has Southern England at it's lowest between 15:00-18:00 this evening. As low as -2/-3 ( Unstable, Thunderstorms Likely, Some Severe With Lifting Mechanism) before rising as the main band follows through. Typically stable conditions tomorrow away from the Tstorms towards the north.

Edited August 22, 2010 by Optimus Prime

[Ian Fergusson]

Hi Ian is west kent in the firing line tonight?

Less so - we're keeping it as 'medium risk' zone for now re rainfall, but there's still some pretty spicy totals showing there on thhe new set of outpur graphics I've got here in front of me; e.g., UKpp accumulation from 21z tonight to same time tomorrow is circa 30-40mm for you. Winds could be a bigger feature for you however, especially around tomorrow AM rush-hour as you get the 'squeeze' on the southern flank of the depression - UKpp's 10m gust prog has widely 30kts across your district; some uplands over 40kts; ditto just offshore and through entire channel crossing lanes up to or exceeding 50kts for a while. No way they'd run ferries in that, I'd wager.

[camiscool]

Thanks Ian. Shall i still keep a watchful eye tonight?

[Ian Fergusson]

Ian,

That mention of a huricane in the advanced forecast, is that due to the possible route of TS6?

Hi

Not sure, but seems possible - I will try to check with Medium Range forecaster at Ops Centre.

[Casper]

im in tunbridge wells west kent

Can you please put your location

<< Here in your avatar

Quite annoying when people give weather conditions but we don't know their locations.

[Ian Fergusson]

Thanks Ian. Shall i still keep a watchful eye tonight?

Yeah, on balance I would. If nothing else, I'd set my alarm for around 3-ish to check it all out.

But then hey, I am setting my alarm for 3-ish anyway, to get to work!! Have already put suit in car to avoid undoubted drenching around that time, althought worst will pass quickly out of Bristol by around 0400BST, so folks here won't awake to all the mayhem.... and probably wonder what the fuss was all about, albeit I'd be amazed if we haven't got some local flooding issues around the West by daybreak....

Can you please put your location

<< Here in your avatar

Quite annoying when people give weather conditions but we don't know their locations.

You're smack in the crosshairs for this one in Swindon.....

[dallas]

Not sure, but seems possible - I will try to check with Medium Range forecaster at Ops Centre.

Cheers for that, I am thinking if it is it will loose energy as it crosses colder water, but has happened before.

As for tonight, will the storms pass quickly due to wind speed?

Cheers Dallas

[Cheshire Freeze]

Hi Ian, reading through the thread it's good to see someone with some inside information on the case of this potentially nasty event. Although we wont get anything overnight up here, what are your current thoughts on thunderstorm chances tomorrow pm? GFS seems to suggest more precipitation around than the BBC graphics and the NAE seems to support the GFS too.

[vortex_liam]

I just rembered i've got a underground river going through my back garden. Offen it floods upto 90mm in my garden, think it will flood???

[SteveB]

Wet but nothing extreme - - head out east down the A303 / M4 into Wilts and it'll be a totally different story by midnight onwards. I would imagine stretches of the M4 will be wholly undriveable.

Thanks Ian,

As much as I like exteme weather events, I don't want to be flooded. Yesterdays heavy rain was intense, and caused a small amount of flooding in my back garden, which required me to go out with a broom and sweep the standing water of my patio and away from the house.

[Casper]

Yeah, on balance I would. If nothing else, I'd set my alarm for around 3-ish to check it all out.

But then hey, I am setting my alarm for 3-ish anyway, to get to work!! Have already put suit in car to avoid undoubted drenching around that time, althought worst will pass quickly out of Bristol by around 0400BST, so folks here won't awake to all the mayhem.... and probably wonder what the fuss was all about, albeit I'd be amazed if we haven't got some local flooding issues around the West by daybreak....

You're smack in the crosshairs for this one in Swindon.....

Cheers Ian i thought so, it'll be interesting watching the radar tonight.I'm up for work at 05.00am so that will be interesting!

[Wivenswold]

Is it me or is the heavier precipitation towards the South of the system?

http://www.meteox.com/h.aspx?r=&jaar=-3&soort=satradar

It's on a course for the South East at the moment.

[lottiekent]

Several rumbles of thunder in with the rain that passed over in the last couple of hours

[Wilxy]

Is it me or is the heavier precipitation towards the South of the system?

http://www.meteox.co...&soort=satradar

It's on a course for the South East at the moment.

I agree will be intresting to see what next gfs update shows where the heaviest rain hits?

[vortex_liam]

Uploaded with ImageShack.us Its vailid for Monday 0:00

[kerensa]

Actually, let me slightly clarify that... as I've now seen the very latest severe weather briefing from the Chief Forecaster.... his new mapping does actually take the northern edge of the swathe of heaviest / disruptive rain up to Bristol and S Glos, plus all of Somerset effectively, so it's likely you'll get a fair hosing in Weston-s-Mare. Maybe 30mm or so possible. I expect worst areas for Somerset will be around Crewkerne, Yeovil, Wincanton and NE into the borderlands with Wilts, e.g., Frome, Radstock etc.... also some of the 'flashy' catchments around Chew and environs into B&NES.

lol Ian, so we are going to get very wet in wincanton, a chance for me to do my cathy from wuthering heights impression!!!!!!!

[john w]

Id be interested to see Village Planks guess on Reading. Im not making any predictions though through I am expecting it to be very wet and for some flash flooding to certainly be a feature of this storm.

I do wonder ever so slightly if the main band will shift slightly East...but keep the same orientation, having looked at the latest radars...possibly entering around the bournemouth area but with the same angle of attack then affecting M3/A303, Swindon/Wilts as a West and Surrey/NW Kent as the East...with much more effect over West, SW and NW/NE London....

We shall see and I would be happy to be wrong on this one as the amounts of rainfall look set to be on a par with July 07 event...though often its the direction of travel that can have the most significant impact on flooding.

On the hurricane becoming embedded in later forecasts this does seem like a possibility. However guidance on that (and certainly not for this thread) does have difficulty getting this system to turn and become embedded in westerly atlantic flows....at the moment!