Storm & Convective Discussion - 16/07/15 onwards

[cotswoldsnow]

well, im in nw oxfordshire near chipping norton, and i think i'm going to nowcast and radar watch from tonight onwards

[Chris K]

This is different to what the EURO 4 wants and the GFS lol!

Although not to dissimilar ..

Oh look where the big gap is heading Brizzle!

I bet any lightning, if it kicks off, will flare up to the E/NE of here. That sexy persistent "thundery rain" seems most likely for the SW to my eyes.

Edited August 12, 2015 by Chris K

[AWD]

Oh look where the big gap is heading Brizzle!

To be expected mate.

A number of high res models now bring the focal point of the wave further east along the M4, leaving the W. Country largely unscathed.

However, there looks to be a possible second attack later on Friday so a lot to watch for still.

[Chris K]

To be expected mate.

A number of high res models now bring the focal point of the wave further east along the M4, leaving the W. Country largely unscathed.

However, there looks to be a possible second attack later on Friday so a lot to watch for still.

Yea I tend to expect it with these sort of setups because I find the models often underestimate the push east, as pressure systems move across the Atlantic and affect the overall flow. Like you say though, still plenty to watch out for, with rain accumulations in a relatively short space of time possibly bothersome for some.

I always try tell myself to just wait and see because of the nature of thunderstorm development. Do I listen? Nope!

Edited August 12, 2015 by Chris K

[Nick F]

Netweather storm forecast issued for next two days: http://www.netweather.tv/index.cgi?action=convective;sess=

 

Here's today's (Day 1) outlook until 06z Thursday:

 

Synopsis

Increasingly amplified upper flow, as the upper trough over the N Atlantic disrupts against upper ridge over central/eastern Europe, will form a cut-off upper low off NW Iberia which will drift NE over the Bay of Biscay towards southern UK. The flow at most levels will become backed Sly at mid-upper levels to SEly at the surface. An area of surface low pressure will develop over Bay of Biscay and western France during Weds, before drifting NE across N France & S England on Thurs. Associated warm front and shortwave trough behind it will lift north across S England/S Wales Weds night and through Thurs, with some thundery activity along it, cold front pushes north into English Channel by 00z Fri.

 

DAY 1 CONVECTIVE OUTLOOK - WEDS 12TH 06Z to THURS 13TH 06Z

Low over Biscay and increasingly backed Sly flow aloft will advect an increasingly warm/moist flow north towards S Britain later today, with a theta-w (wet-bulb potential temp) plume of 16C+ spreading across S England overnight. An EML (Elevated Mixed Layer) characterised by steep lapse aloft will also spread north with the plume, which combined with cooling aloft with approaching upper low moving in from the W/SW, will detabilise the plume ... allowing storms to erupt across N France, English Channel later Weds, before drifting N across S England and S Wales overnight into Thurs morning.

 

A cool and stable E or SEly flow at the surface will mean storms will likely be elevated and rooted well above the boundary layer, though 30-40 knts of deep layer shear and strong mid-level instabiluty developing will be sufficient for muticells and upscale growth into an MCS capable of producing large rainfall totals leading to localised flooding, hail, gusty winds and frequent cloud-to-ground lightning. A fairly broad area of marginal risk has been mapped for S England tonight for storms, given the usual model uncertainty over where storms will erupt. Greatest risk currently looks likely to be central S and SW England and perhaps S Wales.

 

And day 2 until Fri 06z:

 

DAY 2 CONVECTIVE OUTLOOK - THURS 13TH 06z to FRI 14TH 06z

Overnight elevated storms over S England will continue to spread N across Wales and the Midlands during Thurs morning before this activity wanes as it reaches N England early afternoon, with a continued risk of torrential downpours leading to flash-flooding, hail, gusty winds and frequent CG lightning. Given sufficient cloud breaks and insolation, further perhaps surface-based storms may develop across inalnd parts of S England in the afternoon in wake of this morning elevated activity heading north and surface-based thunderstorms developing over N France Thurs afternoon/evening in the warm humid airmass and high temperatures may push north across C S and SE England during the evening and overnight,all with a risk of intense rainfall bringing localised flooding, hail, strong wind gusts and frequent CG lightning. These storms pushing N across parts of the Midlands and E Anglia early Fri mornng. So have maintained a MGNL risk across S England and E Anglia.

Edited August 12, 2015 by Nick F

[Rain123]

Interesting. Thanks Nick.

[Thunderbolt_]

I'm hearing different things about these storms, embedded storms, thundery rain, the apocalypse. Which one should I believe?!

I assume you heard the "apocalypse" one from the Daily Express? If you did, then don't believe it.

Edited August 12, 2015 by Thunderbolt_

[legritter]

well all prepared here on mendip for any storms .my 93 year old mother inlaw is now living with us because of bad health [lovely lady still with a sound mind but body not so good ] .she loves a good storm so hoping for the dice to fall right for these parts .

Certainly a main and probably newsworthy 48hrs of weather coming up .

Its realy great these days having the computer so we can watch the weather with radar etc .

for any newcomers to the weather hobby ,take a look at The Science of contrails [type this in on google ] by studying contrails you can relate to the upper Atmosphere ,short trails ,long trails wide trails hardly any trails ,and different shape trails all gives clues to the upper Atmosphere .

we all contribute differently to this forum so i thank those that post charts but i havent quite mastered this yet ,a great weather forum ,best of luck all with the potential now well and truly in front of us ,sit back crack open a STElla get those cameras primed ,put away the cutlery and lets hope mother nature gives us a show ,cheers ,

[Thunderbolt_]

As much as I'd be all for this, this is certainly a bit over the top especially for this far north for the early hours of Friday morning...

 

[Azazel]

my gut feeling is heavy, thundery rain tonight into the early hours of the morning with sporadic lightning to the South East and London area. This will clear northwards, but leave a tonne of clag in its wake. Lack of cloud breaks in the south will stop anything surface-based developing in the south Thursday PM; however, the north-east will see a violent supercell, say somewhere in Lincs.

 

Bank on it

Edited August 12, 2015 by Azazel

[William Grimsley]

I'm looking forward to tonight. The latest charts and BBC forecasts show us getting thunderstorms in the early hours of tomorrow morning. It could well be a very long and exciting night for us Devonians!

[Kiwi]

Computer says ...49.79mm of rain for me (near Tadley, Hampshire) between 13.00 and 16.00 tomorrow!!  

 

 

[NO LONGER POSTING]

Well the models can do as much as they like and we can use this data to get a rough idea..

 

But it will all come down to that radar again..

 

"goes and buys net weather premium" 

[Lauren]

I am keeping a healthy amount of scepticism fr I have been burnt too many times.

[alexisj9]

Well how humid is it going to get as it's already 91% here, and hasn't really dropped at all as it should have before tonight stuff starts.

[Singularity]

Interesting how Euro4 keeps on piling those storms in from The Channel right through Thursday, while WRF has the elevated convection clearing quite sharply north to be followed by a drier interlude before a scattering of surface based storms across S. England in the afternoon.

 

The BBC forecasts this morning have resembled Euro4 quite closely, giving the impression that it will be thundering for much of the day across many parts of S. England in particular. It's been a long time since I can last remember that happening... in fact longer than I can recall to any effect! Closest I can come up with is when storms rattled in throughout an entire night while I was paying a visit to Portsmouth one weekend. The streets were full of drunken youths throwing cans into the air... as if they expected to attract lightning for some crazy reason.

 

 

I still expect the high-res models to be overdoing the totals as usually happens, but given the very high available moisture for this event, I'm not sure that the actual values will be as close to half the projected values as I have seen in past events this year (namely the two in July).

 

I'm actually amazed to have now seen 3 Euro4 runs on the trot delivering between 60 and 110 mm across CS England. Takes me back just over 8 years...

[East_England_Stormchaser91]

I am keeping a healthy amount of scepticism fr I have been burnt too many times.

Kent certainly looks favourable for something nasty tomorrow evening! I may have a chase if things look ripe.

[Summer Sun]

Updated warnings from the met office

 

Issued at: 1025 on Wed 12 Aug 2015

Valid from: 0100 on Thu 13 Aug 2015

Valid to: 2359 on Thu 13 Aug 2015

 

A developing area of heavy and thundery rain is expected to reach southern England during the early hours of Thursday before pushing further northwards during the day. There is the potential for torrential downpours in places. The public should be aware of a significant risk of localised disruption due to surface water flooding. Lightning and hail are likely to be additional hazards.

 

Chief Forecaster's assessment

 

An area of low pressure developing over Biscay pushes into southern UK during early Thursday before tracking further northwards to be centred near or just east of Scotland by Friday afternoon. With very warm air being entrained into the system, locally heavy and thundery rain is expected to develop and affect parts of England and Wales during Thursday. 20 or 30 mm of rain may fall in a relatively short space of time in some places whilst locally in excess of 50 mm is possible in just a few hours. The development of this system is relatively complex therefore the exact locations of the heaviest rainfall remain uncertain. Further updates to this warning may occur during the early hours of Thursday or Thursday morning when the location of where heaviest rain is most likely becomes more apparent.

 

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=warnings&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1439420400&regionName=uk

 

Issued at: 1045 on Wed 12 Aug 2015

Valid from: 0005 on Fri 14 Aug 2015

Valid to: 2350 on Fri 14 Aug 2015

 

An area of locally heavy rain already affecting much of England and Wales as well as parts of Scotland at the start of Friday lingers across these areas through the early hours of Friday and Friday morning. Rain is likely to be both persistent and heavy at times. Also a risk of thunder, most likely over parts of England and Wales. This rain will tend to ease through the day, probably becoming confined to eastern UK by the end of Friday. The public should be aware of a significant risk of localised disruption due to surface water flooding. Lightning may be an additional hazard.

 

Chief Forecaster's assessment

 

An area of low pressure pushing into southern UK early Thursday continues slowly northwards to be centred near or just east of Scotland by Friday afternoon. With very warm air entrained into the system, further outbreaks of locally heavy rainfall are likely during Friday, particularly during the early hours and morning, with locally in excess of 50 mm by the end of Friday. Localised thunderstorms may also develop across the south and east of England during Friday afternoon, these potentially giving 15-25 mm of rain in a few hours. The development and subsequent track of this system is very complex, therefore the exact locations of where the heaviest rainfall will occur remains uncertain. With this in mind this warning will be updated during the coming days.

 

http://www.metoffice.gov.uk/public/weather/warnings/#?tab=warnings&map=Warnings&zoom=5&lon=-3.50&lat=55.50&fcTime=1439506800&regionName=uk

[Wivenswold]

As hinted at by LukeyG, once again I can see a lot of us falling into the trap of seeing a thunderbolt on an app or a TV forecast and getting their hopes up.

 

Personally I'd ban any reference to weather apps and hourly forecasts on this forum. They're as good as useless and bring nothing to the science of forecasting.

[Stuart]

it still a bit uncertain if it will make it up to me

[NO LONGER POSTING]

As hinted at by LukeyG, once again I can see a lot of us falling into the trap of seeing a thunderbolt on an app or a TV forecast and getting their hopes up.

 

Personally I'd ban any reference to weather apps and hourly forecasts on this forum. They're as good as useless and bring nothing to the science of forecasting.

 

 Don't know how many times I have said on this forum to ignore the Iphone apps, BBC and met office symbols, a computer does this and 99% of the time it is wrong.. A meer guide! 

 

Stick the the words in the forecast and the brilliant minds on here 

[A.J]

A few handy links for storm tracking as well as the latest model output and more

 

http://www.lightningmaps.org/realtime

 

http://www.sat24.com

 

and of course, NW Extra, which costs just a couple of pounds a month for enough weather data to sink a battleship....

https://www.netweather.tv/secure/cgi-bin/login.pl?code=

[William Grimsley]

A few handy links for storm tracking as well as the latest model output and more

 

http://www.lightningmaps.org/realtime

 

http://www.sat24.com

 

and of course, NW Extra, which costs just a couple of pounds a month for enough weather data to sink a battleship....

https://www.netweather.tv/secure/cgi-bin/login.pl?code=

Let's hope this time most of the clicks are over my area, not everywhere else that's been pummelled this year!

[NO LONGER POSTING]

 

Another view on tonight tomorrow

 

This from Met Monkey  

[William Grimsley]

map.png

 

Another view on tonight tomorrow

 

This from Met Monkey

That's just typical! At least I have a risk!