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Supacell

Storm & Convective Discussion - 02/07/15 Onward - Heat & Plumes

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Warning....strong language...

 

haha! The laughing got me laughing, very infectious!  Cracking vid, thanks for sharing.

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Estofex as I expected have put a general Level 1 around the conditional Level 2 over Northern France.

 

400 m/s of SREH Is not to be sniffed at and would be a Solid MODERATE Risk in the USA, If like GFS Suggests a Surface based Parcel can root into the boundary then I agree a strong Tornado could occur over towards Calais across to Brest Peninsular, will that cross the channel absolutely not! But...... what we might see if the after effects and structure like last year on I think it was the 18th July where what had been a Supercell over in France encroached into Kent and Sussex and gave us spectacular skies. I had a feeling the Hodo's would be sickle shaped when I saw the synoptics earlier.

 

Million dollar question for the SE Is can that Cap be overcome for a home grown surface based storm, and if so would suggest areas further north along the warm front would benefit, have no doubt numerous showers and thunderstorms will be ongoing from 20z until 00z for areas west of London stretching across to the SW Of England also.

 

Some amazing synoptics over the last few days, and 1 gripe, why of why do the Met Office persist with about 15 isobaric lines on their charts when a simple triple point, or warm front and cold front, occluded front will do, saw one earlier that had about 4 warm fronts, 3 cold fronts along it, its not needed and even one of the Mets I speak with at the BBC Cant fathom out why they use this on their fax charts.

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Warning....strong language...

 

to me thats half the fun .. not only to see and hear the storm but the reaction it gives off to people )

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Yeah tomorrow's got me all bothered now - I thought we had it in the bag but now there are quick decisions to be made nearer the time.

A big problem is that travel across the SE region of the country is nigh on impossible on a Friday between 5pm and 9pm. Chasing that elusive supercell could be difficult...

Just out of interest how quick are these storms likely to be moving? Or would the sheer size of any that do occur make this insignificant?

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Right, off to bed.

Fingers crossed that we wake to some more favourable Synoptics, cap busting ones :D

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To be honest, these situations don't often transpire well for most north of the M4 in my opinion. Looks like it will become a mess of heavy rain pretty quickly with just the odd steric and rumble at best. Seen this many a time and can't remember the last proper stormy spell from the south like this. You need discrete storm cells really, not a load of merging showers.

Edited by Costa Del Fal

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Maybe something mind boggling can happen after all. How did all the classic 90's setups occur? It's happened many times before, so it can happen again for certain.

Praying!

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Interesting storm forecasts for tomorrow.

post-17472-0-66586600-1435879319.txt

1) Convective Weather

Rapid warm air advection will develop across southern Britain through the evening hours, causing surface dewpoints to increase as a warm front lifts northwards. Meanwhile, the Atlantic upper trough will pivot NEwards, overlapping with the arrival of this plume during the evening, and providing sufficient lift. Consequently, expect thunderstorms to develop through the evening hours, initially fairly well-scattered across SW England, with activity expanding farther N and E as the evening progresses.
With the approaching trough, DLS will strengthen with favourably-backed surface winds. This combined with 800-1,200 Jkg-1 MLCAPE suggests the potential for storms to become organised, perhaps into supercells capable of producing large hail. Forecast profiles suggest most storms will be elevated above 700mb, thus limiting the tornado risk, but if any storms do become rooted within the boundary layer, then there would be the risk of a tornado developing.
There exists some uncertainty with developments farther east, namely across SE England and the Channel Isles. Capping may be too strong or upper forcing not strong enough to generate storms here (as per consistent signals in EURO4/UKV/ECMWF) while GFS is more keen to develop storms over northern France and run them northwards into CS/SE England. Given these uncertainties have opted to go for the general consensus for now (hence reducing probabilities towards the SE, the MDT placed where best agreement exists amongst most models) but cater for the risk of large hail and heavy rain (given PWAT 35-40mm) as the primary threats with any strong storms that may develop in central and southern Britain. In either case, mass ascent will see storms become more numerous as instability axis moves north, merging into an area of thundery rain and eventually losing most lightning activity during the early hours of Saturday as instability weakens and clears eastwards to the North Sea.
It is likely that this forecast will need updating during Friday with threat level areas tweaked depending on convective trends. Have also included Ireland in a SLGT for activity that may occur largely in the post-frontal environment towards the end of the night with some marginal instability present.
 
post-17472-0-64165800-1435879809_thumb.p
A level 1 was issued for a greater part of Northern and Western France and the Southern United Kingdom for large hail and extreme precipitation.
Elevated convection should move in from the south during the late evening and after midnight. There is a small risk of large hail and extreme precipitation with these storms.
 
post-17472-0-81685100-1435880079_thumb.j
Following a brief cooler period, another hot and increasingly humid airmass is expected to spread up from western Europe across England and Wales during Friday night and early on Saturday. With this airmass will come an increasing risk of thunderstorms developing during Friday night which could turn severe in places bringing torrential rainfall, large hail, gusty winds and a small chance of an isolated tornado but it is important to stress that many places will miss the storms altogether
However where any storms do occur, rainfall totals of over an inch in an hour could bring a risk of localised flash flooding, especially in areas where it has been very dry recently with C-G strikes an additional hazard
This Weather Watch will be updated as developments become clearer with uncertainties currently existing over timings and areas most at risk.
 
The convective weather (1) forecast seems promising to those in the south and Midlands (such as myself). Estofex (2) less promising though. Netweather/TORRO yet to issue forecasts if applicable.
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Looking forward to tomorrow now, heaven knows why. If storms are west of Bucks, I'm gonna hit the road. Better renew my car tax though as it ran out the other day, wouldn't want plod stopping me for doing 90+ on the M4 to only find out my car isn't taxed either. 

 

Wouldn't that be a Friday evening to die for.....parked up near some country back-road just off the motorway, with a warm breeze and lightning in the distance. Complete with an ice cold bottle of ale (but just the one, as driving)   :D

 

Damn I want a beer right now. 

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I'm sure the Met Office has removed the warnings for my area during Friday pm. They still seem to be in effect for Saturday morning, however.

 

Edit: and now the Friday warning is back again. I can barely keep up.

Edited by Damone
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I'm sure the Met Office has removed the warnings for my area during Friday pm. They still seem to be in effect for Saturday morning, however.

 

Edit: and now the Friday warning is back again. I can barely keep up.

From the latest weather forecast that I have seen, the thunderstorms have vanished from London and the SE for Friday night/Saturday morning and they are now further west. You now have more chance of storms than the SE.

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From the latest weather forecast that I have seen, the thunderstorms have vanished from London and the SE for Friday night/Saturday morning and they are now further west. You now have more chance of storms than the SE

 

I've never known a week like it. I'll be glad when the heat has gone and Friday/Saturday is over and done with, to be honest. I've tried to keep up with forecasts and charts, but it's mostly a fruitless endeavour, especially as I'm still very much an amateur when it comes to the weather.

 

Having said that, although I'm not a thunderstorm fan myself, I wish a fulfilling event to anyone who feels they need their storm-fix tomorrow evening.

 

 

I guess what will come, will come.

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I've never known a week like it. I'll be glad when the heat has gone and Friday/Saturday is over and done with, to be honest. I've tried to keep up with forecasts and charts, but it's mostly a fruitless endeavour, especially as I'm still very much an amateur when it comes to the weather.

 

Having said that, although I'm not a thunderstorm fan myself, I wish a fulfilling event to anyone who feels they need their storm-fix tomorrow evening.

 

 

I guess what will come, will come.

I prefer snow myself but it is as elusive as thunder these days. It was horrendous in London, the temperature hit 36 and the humidity was stifling. It was looking like violent thunderstorms were going to be covering most of London and the SE only yesterday, but it is all change now. It could change again as showers are notoriously hard to predict.

Edited by lassie23

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I prefer snow myself but it is as elusive as thunder these days. It was horrendous in London, the temperature hit 36 and the humidity was stifling.

I'm so glad I'm not in the south-east right now! The one thing you can usually be thankful for, if you live In Cornwall, is the sea-breeze during hot summer days. Strangely we do seem to have gotten quite thundery in recent years though.

 

I have a sister who lives In Reading (I was there during a heatwave many years ago, so I know how horrible it can be) and she almost passed-out just heading down to the local shops no more than 1/4 mile away. I can't stand oppressive heat.

 

I love snow too, but we seldom get it here, and when we do it makes getting to work a serious chore as our local public transport is bad enough in good weather. At the first sign of a snowlflake the bloody buses stop!

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A bit worried about the notion of thunderstorms merging into an area of thundery rain tonight. I am envisaging lots of rain with the odd flash and rumble whereas yesterday I was thinking an evening similar to the 28th June 2005.

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@Supacell: Brill summery, dude! Will be interesting to see which forecasts and models get it closest to the mark. Hopefully this setup will bring something to both Western/Central and South-Eastern areas and get those, who have not seen a storm yet (inducing myself), booted out of the No Storm Club. :good:

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This morning the GFS is showing a widespread storm risk across everywhere during the night and tomorrow with the risk transferring from SW to NE. The best storms are in the SE of this portion - so SE of a line from Devon to Hull. The favoured areas would be SE and EA for a more severe storm. 

 

The UKMO and BBC are totally at odds with this as they forecast the heaviest and most potent rainfall to come into the SW and move more NNE across Wales, the Midlands and up into N England. Here you could probably draw a similar line - lets say IOW to Hull and say everywhere NW of this for the best chance and pretty much nothing over the GFS favoured areas of the SE and EA.

 

The NMM favours the UKMO solution and brings the precipitation across the same areas as the BBC but the higher CAPE values are there in the SE and EA, not so much in the N and W. MLCIN is stronger in the SE though which would explain the precipitation forecast. 

 

The WRF model I am looking at agrees with the GFS solution as does the Estofex forecast - although the Estofex charts do always back the GFS.

 

The whole country benefits from deep layer shear (DLS) in the region of 20-30knts and so any storms are likely to become organised. The south east also benefits from an abundance of helicity and so storms here would have the potential to turn supercellular.

 

So, what we have here is a failure to communicate! However, my take on it is that I see a risk of thunderstorms generally across the north and west, including the Midlands, with a risk of CG lightning (at least at first) and large rainfall totals leading to localised flooding. The lack of any CIN and a lot of DLS in the western portion would indicate that thunderstorms could become very widespread and eventually merge into an area of less exciting thundery rain, dumping a lot of water but producing only a small amount of lightning. If the GFS solution is correct and storms can develop close to the SE and EA then these would remain as more isolated cells but have the potential to become supercells with more in the way of severe weather such as large hail, frequent lightning and even a tornado. 

 

As a storm chaser, I now have the decision of staying put to enjoy what I get here as the risk of seeing something is high or gambling for a lower risk of something more spectacular by heading SE.

My heart tells me to expect the worst in my part of the world, but my head says the ingredients exist and to trust in GFS. What's more, the precipitation forecast on the UKMO website clearly favours the West. However, the UKMO charts available elsewhere have continuously pointed towards much more widespread precipitation, including the SE.

If UKMO and NMM are correct (and to be honest they've hardly exactly hit the nail on the head the past few days) it would mean nothing fires over N France - over 3,000J/Kg of CAPE, LIs of -8 to -10 (SBCAPE), falling pressure from the west, shearing winds and fronts close by, eventually clattering into that instability also - as Nick F stated last night, it seems a bit hard to compute that it won't detonate.

All to play for, I'm going to try avoiding perpetual forum gazing today and try and adopt the Doris Day mantra....que sera sera! (I won't be far away though lol)

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@Supacell: Brill summery, dude! Will be interesting to see which forecasts and models get it closest to the mark. Hopefully this setup will bring something to both Western/Central and South-Eastern areas and get those, who have not seen a storm yet (inducing myself), booted out of the No Storm Club. :good:

 

Thanks mate. I am thinking I will stay put as would be more gutted if I spent petrol money and drove for hours to the SE to find nothing and Derby got hit than if I stayed at home and missed it further SE. Local Radio talking of torrential rain and large hailstones across here this evening so they don't seem to be going with the "thundery rain" idea, more severe thunderstorms.

 

In other news, Carol has mentioned that dreaded H word although did say storms would be on a par with Wednesday night and having being there under some of them I can say they definitely were h..... :D

Edited by Supacell
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Couple of charts from an 18z 3km GFS init run. The model appears to destabilise the edge of the plume again, its been fairly consistent with this approach recently but its no more accurate than any other deterministic model run. It does put a bullseye over central southern areas at midnight - make of that how you will  :D Note the big 'bite' missing from the northern edge of the elevated instability, this is likely to be where the storm is eating into the instability and it appears to ride along this moving north east out towards the Wash area. The supercell composite parameter is almost off the scale, though that could well be skewed as its a composite of a few different parameters and its also a fixed layer (not effective layer).

 

post-9921-0-83339500-1435904954_thumb.pn post-9921-0-98044100-1435904965_thumb.pn

 

Interesting to see that there is still disagreement between some of the higher res GFS models...Something, somewhere would be my guess  :unsure2:

 

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Incidentally, Euro4 holding strong with no precip at all across the SE quarter.

I'm trying to cast my mind back to last year - think it was 17th July (the day before El Shelfo across most of the SE) when the BBC forecast and UKMO forecast both ruled out storm risk across the SE (favouring SW and W), then being woken at 1-2 am by my beloved telling me there was thunderstorms.

Think I'll have a gander at those Synoptics later to see if there are any similarities.

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Couple of charts from an 18z 3km GFS init run. The model appears to destabilise the edge of the plume again, its been fairly consistent with this approach recently but its no more accurate than any other deterministic model run. It does put a bullseye over central southern areas at midnight - make of that how you will  :D Note the big 'bite' missing from the northern edge of the elevated instability, this is likely to be where the storm is eating into the instability and it appears to ride along this moving north east out towards the Wash area. The supercell composite parameter is almost off the scale, though that could well be skewed as its a composite of a few different parameters and its also a fixed layer (not effective layer).

 

attachicon.gif1hourprecip_d02_30_0307.png attachicon.gifmlcape_d02_30_0307.png

 

Interesting to see that there is still disagreement between some of the higher res GFS models...Something, somewhere would be my guess  :unsure2:

Now GFS has abandoned me ....noooooooooooo!!!!

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Charts are still going strong for my location and BBC puts a nice big torrential rain blob bang on top of me for later this evening. I am excited, that's for certain.

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