Uk Convective General Discussion & Forecasts, 11th July 2012>

[Biggin]

I did read that the storms should be on the backedge ??

[gottolovethisweather]

What started out as a sunny and bright morning as now turned progressively cloudier now. I can see areas just to the south of the main rain band doing well today, pretty sure it's not guna happen here though.

Well if you were to head south of your locality, there is a fair amount of activity growing there already. However, for my location I'm hoping you can be the breeding grounds and that the cells grow as they head eastwards along the M4 corridor. Alternatively, any development across the water from Cardiff and east of Dartmoor would IMO also favour us Central Southerners given the wind vectors.

AWS and others, where are your favoured initiation/breeding grounds for storms, especially for days with a southwesterly to northeasterly flow like today?

I think learning from the past is important here so would be interested to hear of others experiences.

Cheers, currently 14.9c AT, 86% humidity, 12.6c DP and 1001.5hpa and slowly falling barometer.

gottolovethisweather

Edited July 13, 2012 by gottolovethisweather

[Norfolk Sheep]

Drizzle now setting in big time. Might only be 10.20am but I think that's the day's weather sorted

[AWD]

Well if you were to head south of your locality, there is a fair amount of activity growing there already. However, for my location I'm hoping you can be the breeding grounds and that the cells grow as they head eastwards along the M4 corridor. Alternatively, any development across the water from Cardiff and east of Dartmoor would IMO also favour us Central Southerners given the wind vectors.

AWS and others, where are your favoured initiation/breeding grounds for storms, especially for days with a southwesterly to northeasterly flow like today?

I think learning from the past is important here so would be interested to hear of others experiences.

Cheers, currently 14.9c AT, 86% humidity, 12.6c DP and 1001.5hpa and slowly falling barometer.

gottolovethisweather

With a flow like we have today, we will be more of a "breeding ground" than the receivers. Cells will develop around Somerset, Bristol & South East Wales and become storms once they hit places like Wiltshire, the Cotswolds etc, where after travelling over land, daytime heating will have a greater chance of taking affect.

To get storms in my location, a South to South Easterly wind will be preferred, as this gives storms a chance to develop over South Eastern counties before reaching us.

A lot of cloud tends to drift up the Bristol Channel in a South Westerly, thus limiting the effect the sun has, limiting convection growth.

I still think further inland in my region, Wiltshire/Gloucs/Oxfordshire/Hampshire are good areas to be today. They will receive what cells do form over my patch.

There have been so many days like today here, where the end result is the same, we breed for places further East.

I was down in Taunton earlier where there was a relatively heavy shower, that will probably turn into a storm has it heads further East.

Edited July 13, 2012 by Active Weather Dude

[Cloudwatcher]

Drizzle now setting in big time. Might only be 10.20am but I think that's the day's weather sorted

Welcome to my drizzly world! We are in the sector marked for storm risk today, but I'm just not that hopeful. This feels like its here for the day.

[Chris K]

AWS and others, where are your favoured initiation/breeding grounds for storms, especially for days with a southwesterly to northeasterly flow like today?

Just seen AWD's response so sorry if this is a repeat.

Usually, for the best chance for us to get thunderstorms on days such as today around Bristol, I find we need to see showers initiating in North Cornwall or Devon. This allows it to develop enough as it travels NE'wards and it really is a fine line on whether it gets blown into S Wales, or too far East into Wiltshire, Dorset etc. For some reason, if it goes above the Severn Estuary & Bristol channel, things start dying.

Other days for example when winds are coming from the NW, we are more likely to see storms if they initiate around N Wales and travel down a line SE'wards through places such as Hereford. One example of a thundery shower I have had originated from Snowdonia and moved down in this way. If they breed in Central Wales, the mountains usually shield us and showers lose intensity as they approach the Severn Estuary.

The only time I've seen a massive thunderstorm was on 9th May 2008 and this is when we had a slack cold front & trough moving in from the SW, meeting humid unstable air coming up from the S/SE thanks to a Euro high and slack low to our W/NW. The front was gradually being pulled NW even though it was moving in slowly NE at the same time, so it was very slow moving.

Edited July 13, 2012 by Chris K

[gottolovethisweather]

With a flow like we have today, we will be more of a "breeding ground" than the receivers. Cells will develop around Somerset, Bristol & South East Wales and become storms once they hit places like Wiltshire, the Cotswolds etc, where after travelling over land, daytime heating will have a greater chance of taking affect.

To get storms in my location, a South to South Easterly wind will be preferred, as this gives storms a chance to develop over South Eastern counties before reaching us.

A lot of cloud tends to drift up the Bristol Channel in a South Westerly, thus limiting the effect the sun has, limiting convection growth.

I still think further inland in my region, Wiltshire/Gloucs/Oxfordshire/Hampshire are good areas to be today. They will receive what cells do form over my patch.

There have been so many days like today here, where the end result is the same, we breed for places further East.

I was down in Taunton earlier where there was a relatively heavy shower, that will probably turn into a storm has it heads further East.

Many Thanks AWD, a very thorough analysis. Now if everybody else on this forum would like to do the same please, ignore work obligations for now.

Local effects and local knowledge are invaluable and will aid to help any desperate chasers out there today.

Thanks again.

Now zoomed up to 15.4c AT with 84% humidity and a DP of 12.7c. Sunny intervals so far and some developing cumulus.

gottolovethisweather

[Karl83]

Definatley a breeding ground here as AWD says. I've seen a lot of that lately from these setups. Now its cloudy and grey. Not great.

[gottolovethisweather]

Just seen AWD's response so sorry if this is a repeat.

Usually, for the best chance for us to get thunderstorms on days such as today around Bristol, I find we need to see showers initiating in North Cornwall or Devon. This allows it to develop enough as it travels NE'wards and it really is a fine line on whether it gets blown into S Wales, or too far East into Wiltshire, Dorset etc. For some reason, if it goes above the Severn Estuary & Bristol channel, things start dying.

Other days for example when winds are coming from the NW, we are more likely to see storms if they initiate around N Wales and travel down a line SE'wards through places such as Hereford. One example of a thundery shower I have had originated from Snowdonia and moved down in this way. If they breed in Central Wales, the mountains usually shield us and showers lose intensity as they approach the Severn Estuary.

The only time I've seen a massive thunderstorm was on 9th May 2008 and this is when we had a slack cold front & trough moving in from the SW, meeting humid unstable air coming up from the S/SE thanks to a Euro high and slack low to our W/NW. The front was gradually being pulled NW even though it was moving in slowly NE at the same time, so it was very slow moving.

Many Thanks Chris K.

[Eskimo]

Going for a slightly different forecast. I have a feeling that the UHI effect will be in control of things around the London area.

[Mapantz]

Morning.

Good chance of yet more thundery activity today, and i'm hoping it stays away .. Olympic torch comes through my town today, and then there's music on the local quay through in to the evening, finishing off with fireworks.

Managed to (somehow) escape all the showers on Wednesday, when i thought i'd get something, so sods law says it will happen when you don't want it.

[A.J]

will someone please turn off the 'drizzle' tap!......In a prime area today, latest GFS & hi-res output put a LLC slap bang over the north & west midlands, sitting there until the overnight period...Should any substantial cloud breaks occur I would expect the extra forcing to aid development of heavy showers and thunderstorms right across the Midlands into parts of East Anglia, and storms will appear almost stationary on radar as they back build along outflow boundaries...A weakly sheared enviroment so I personally wouldn't anticipate well organized thunderstorms, as updrafts will be readily swamped by descending rain/cooler although the odd stronger storm isn't out of the question......The main question is, is simply will the cloud break enough along the LLC zone to allow insolation to fire convection?....I have my doubts TBH

Going for a slightly different forecast. I have a feeling that the UHI effect will be in control of things around the London area.

Your storm risk zone is too far south IMO

[Suburban Streamer]

on bbc weather just now she mentioned amber warning for wales across midlands to east anglia. nothing on metoffice website yet tho

[Luke]

on bbc weather just now she mentioned amber warning for wales across midlands to east anglia. nothing on metoffice website yet tho

Ooh that's interesting. Looks like we will wait and see.

[Mapantz]

The NAE is giving some indications that thundery downpours will develop across Wales, and push across the West Midlands in to East Anglia this evening. I suspect those areas could see the best action.

[Norfolk Sheep]

on bbc weather just now she mentioned amber warning for wales across midlands to east anglia. nothing on metoffice website yet tho

Never seen an amber warning for drizzle before

[Luke]

Give it time. We still have most the day left yet and heavy showers are expected this evening.

[matty40s]

Morning.

Good chance of yet more thundery activity today, and i'm hoping it stays away .. Olympic torch comes through my town today, and then there's music on the local quay through in to the evening, finishing off with fireworks.

Managed to (somehow) escape all the showers on Wednesday, when i thought i'd get something, so sods law says it will happen when you don't want it.

The Olympicks torch has dragged wet weather around the country with it, everywhere it has gone it has rained.

It has been intermittent drizzle, heavier showers this morning, and feels far too cold for anything exciting storm wise.

[legritter]

will try and get some royal met magazines out of the loft today ,and try to post some past events for west country and places near . looking at current detail we could have an interesting late aft /even period . especially further inland the better .reg legritter . sun out now wind dropped ,lets hope for some building ,if so i will blow them up towards any storm starved posters

[A.J]

just noticed TG's forecast at TORRO..This is interesting IMO, even though there's a lot of low level 'muck' straddling the centre of England, but some nice parameters in place for possible elevated convection?...Steep mid-level lapse rates, plenty of Multi-layer CAPE & bouyancy, a mid-level dry air incursion?....I see Dan on the thread (Staplehurst)..What's your thoughts bud?

[Stuart]

SKYWARN UK SEVERE THUNDERSTORM WATCH #041

ISSUED: 0900UTC FRIDAY 13TH JULY 2012 (GJ)

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

MIDLANDS

WALES

EAST ANGLIA

SOUTHERN ENGLAND

IN EFFECT FROM 1000UTC UNTIL 2359UTC FRIDAY 13TH JULY 2012

SHALLOW LOW PRESSURE DEVELOPMENT GENERATING STRONG, NEAR-STATIC CONVERGENCE AND PERSISTENT CONVECTIVE ACTIVITY

THERE IS A POSSIBILITY OF SEVERE WEATHER AFFECTING THE INDICATED REGIONS IN THE TIME PERIOD SPECIFIED. THREATS WITHIN THIS WATCH INCLUDE, BUT ARE NOT LIMITED TO:

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

DISCUSSION:

THERE IS GOOD MODEL AND AGENCY AGREEMENT ON THE POSSIBILITY OF A SEVERE THUNDERSTORM RISK THROUGH FRIDAY. A WEAK EXTENSION OF THE UPPER TROUGH AND UPPER COLD POOL MOVING ACROSS THE UK, COUPLED WITH SHALLOW LOW PRESSURE DEVELOPMENT, WILL GENERATE CONVECTION MAINLY BY FORCING FROM SURFACE CONVERGENCE FROM NORTH WALES TO EAST ANGLIA. INSTABILITY IS CONDITIONAL UPON CLOUD COVER THROUGH THE DAY, WITH CLEARER SKIES OVER SOUTHERN ENGLAND GENERATING CAPE OF AROUND 800J/KG AND -3 LI, BUT SUFFICIENT TO PROVIDE ENERGY FOR SUSTAINED CONVECTIVE ACTIIVTY ACROSS CENTRAL UK. SUCCESSIVE AND POTENTIALLY BACK-BUILDING STORMS MAY PROVIDE A RISK OF FLASH FLOODING, DESPITE PRECIPITABLE WATER AND LOW LEVEL MOISTURE BEING LESS THAN RECENT EPISODES. SOME CONCERNS ALSO EXIST HERE GIVEN GROUND SATURATION. STRONG SURFACE CONVERGENCE MAY GIVE RISE TO BRIEF FUNNELS AND/OR WEAK TORNADOES THROUGH THE MIDLANDS AND EAST ANGLIA. THE ZONE OF CONVERGENCE IS EXPECTED TO PERSIST WELL INTO THE EVENING

FURTHER SOUTH, LESS SURFACE MOISTURE BUT ALSO LESS CLOUD COVER MAINTAINS SIMILAR INSTABILITY, WITH STORMS EXPECTED TO OCCUR IN A MORE LINEARLY SHEARED ENVIRONMENT AND IN A LINE FROM SOUTHWEST ENGLAND TOWARDS GTR LONDON. DRIER AIR ALOFT ENHANCES THE HAIL RISK, THOUGH STILL NOT THOUGHT TO BE CLOSE TO CRITERIA VALUES, AND SUCCESSIVE PRECIP CORES TRAINING OVER AREAS OF THE SOUTHWEST MAY PROVIDE A RISK OF FLASH FLOODING. SLIGHTLY INCREASED DLS VALUES AND A DRIER PROFILE MAY ALSO ADD A RISK OF STRONG GUSTS TO ANY STORMS OVER THE SOUTH. CLOUD COVER SPREADING OVER CHANNEL AREAS THROUGH THE DAY MAY DIMINISH THE RISK LATE AFTERNOON, THOUGH THE ONSET OF THE UPPER COLD MAY PROVIDE SUFFICIENT INSTABILITY FOR STORMS TO CONTINUE INTO THE EVENING. THIS WATCH MAY BE UPDATED OR UPGRADED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

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

http://skywarn.org.uk/current.html

[AWD]

Ian Fergusson has posted the UKMO UV output for downpours this evening. Shows a band of storms across the Midlands and into East Anglia, and showers from Somerset, Hampshire into London area.

Dry slot, you guessed it, South Wales, Bristol area, Wiltshire and Gloucs.

Sorry, on phone so can't provide link.

There is good model support for cells to develop and provide for the Midlands now though, seems like say, Nottingham could be the place to be today.

Good luck all, must do some work now.

[Luke]

Lots of things still pointing to the Midlands for this event. Maybe amber warning soon?

[Coast]

Ian Fergusson has posted the UKMO UV output for downpours this evening. Shows a band of storms across the Midlands and into East Anglia, and showers from Somerset, Hampshire into London area.

Dry slot, you guessed it, South Wales, Bristol area, Wiltshire and Gloucs.

Sorry, on phone so can't provide link.

No problem:

[Thundery wintry showers]

No convective activity of note likely in N Yorkshire today as the weather is dry and cloudy, with the odd bit of drizzle further south. Not an unusual occurrence this year!