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Convective Storm/Discussion thread - 02/09/16 onwards

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Forecast from estofex, and it ain't too shabby! 

UK

Within the plume of warm air, CAPE will again build during the day although steepest lapse rates will be pushed northward during the day. Rich low-level moisture and a well-developed convergence zone oriented mostly parallel to the storm motion vector can again pose a threat of excessive precipitation. Large hail is not ruled out. Storms are expected to move to the North Sea in the evening hours where they become elevated.

image.png

Edited by East_England_Stormchaser91
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Models and forecasts all differ slightly again but maybe some agreement over the SW Midlands, CS England and West Country this evening. If I were chasing (which I may still do) I would be targeting Oxfordshire/Wiltshire/Gloucestershire on current forecasts.

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The short lived electrical activity around the west Midlands (Nuneaton/Cov/Brum) last evening, looked initially promising, but died out virtually straight away.....

What/how does the atmosphere recover its cap so quickly? or were other forces to blame? (I'm talking about the ones that sprang up around 18:00-18:15)

Thanks in advance 

SS 

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32 minutes ago, Supacell said:

Models and forecasts all differ slightly again but maybe some agreement over the SW Midlands, CS England and West Country this evening. If I were chasing (which I may still do) I would be targeting Oxfordshire/Wiltshire/Gloucestershire on current forecasts.

Estofex are hinting that the most potentially convective air will be pushed northward and in the south east today's missing ingredient will be ... lapse rates!

So it will all kick off around Manchester and march northward. Yawn.

clear skies here though so solar heating should do its thing - hopefully - but not expecting anything at all for us from this.

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4 minutes ago, Speedway Slider said:

The short lived electrical activity around the west Midlands (Nuneaton/Cov/Brum) last evening, looked initially promising, but died out virtually straight away.....

What/how does the atmosphere recover its cap so quickly? or were other forces to blame? (I'm talking about the ones that sprang up around 18:00-18:15)

Thanks in advance 

SS 

I dont know why but I did see some Cu build and just explode upwards, they were North of here and looked stunning, the speed that they went up was incredible, did think when I saw them that they may have built into something.

Looking forward to today, am hopeful for a decent storm or two and hopefully some night time stuff so will get the camera ready

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Morning all

To chase it not to chase , found myself with a day off today but my windscreen wipers have broken so would have to hire a car, which is £60 

Is it going to be worth it, or is it just going to turn into a rain event? 

What do you reckon?

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8 minutes ago, Flash bang flash bang etc said:

Estofex are hinting that the most potentially convective air will be pushed northward and in the south east today's missing ingredient will be ... lapse rates!

So it will all kick off around Manchester and march northward. Yawn.

clear skies here though so solar heating should do its thing - hopefully - but not expecting anything at all for us from this.

whilst I respect all agencies that attempt convective forecasts, I don't hold estofex at the top of the tree....over the past few years I've found their forecasts either totally underplay reality or they're full of hyperbole.....I'm not sure why you're saying manchester norrthwards?....all of the short range/hi-res modelling I've seen the past 24-36 hours go for a much further south initiation (South Wales, west country) with potentially potent Sb storms drifting ESE during the evening/night :)

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15 minutes ago, Speedway Slider said:

The short lived electrical activity around the west Midlands (Nuneaton/Cov/Brum) last evening, looked initially promising, but died out virtually straight away.....

What/how does the atmosphere recover its cap so quickly? or were other forces to blame? (I'm talking about the ones that sprang up around 18:00-18:15)

Thanks in advance 

SS 

 I would say that it was because there was very little shear  yesterday, so once the cap  was initially broken you had that explosive development, but soon as the downdrafts  became established they just swamped the updrafts.  This cuts off the supply of warm air killing the cell and possibly cooling the air  in the general area,  inhibiting convection from  Breaking the cap  again.  By the time this cooler air  had dissipated, the sun had set and convection was waning  anyway. That's what I feel   Might have happened from a purely  amateur  perspective. :-) 

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The GIF above from a French weather site shows nicely how the warm humid plume across southern Britain is squeezed out both from the south and west as cold fronts approach from both directions, quite an unsual evolution, but the pincer movement of fronts into a rather unstable airmass later should hopefully create some lively storms over next 24-36hrs before the cooler and fresher Atlantic air wins out from the west:

fax_24.png

Edited by Nick F
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10 hours ago, Allseasons-si said:

Thanks buddy i will try that,i suppose if you set the manual focus on for taking pics,it should be the same for filming,i will give it a trial tomorrow

oh!,and part 4 is processing and i will post it shortly

hope you get some storms tomorrow.

2000 post's,yay:yahoo:

 

10 hours ago, Allseasons-si said:

A question

when i looked back at the clips of the storm,i noticed that the focus was dipping in and out of focus,is this because the focus is set on automatic?

would it be better filming on manual focus?

this cam is fairly new so some teething issues,not sure if i can film on manual focus though

the cam is a Sony cyber shot dsc hx60

thanks.

 

 

Just to expand the previous answers.

 

Your camera has contrast-detect auto-focus which means it looks for contrast in the picture to decide what to focus on.

 

When there is no lightening the contrast is low ( low light levels) and as such the auto-focus has to hunt for something to focus on. When there is lightning the contrast in the cloud as well as light levels improve so it can focus on the clouds. 

 

Manual focus set to infinity will mean everything from approx 1m  to infinity will be in focus assuming you are shooting at the widest available view

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have a feeling we will be too far south/the breeding ground OR it will kick off while i'm still at work and drift off north before i get home.

 

My main area of interest: (Yellow dot indicates me:( )

 

weather11.png

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5 minutes ago, Azazel said:

have a feeling we will be too far south/the breeding ground OR it will kick off while i'm still at work and drift off north before i get home.

 

My main area of interest: (Yellow dot indicates me:( )

 

weather11.png

Very difficult to predict  but seems a good assumption a  easterly flow of storms through Brum migrating east and perhaps lingering in the anglia region. i actually think it might be a tad more south than that bringing your area into the fray.  we shall see

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7 minutes ago, Azazel said:

have a feeling we will be too far south/the breeding ground OR it will kick off while i'm still at work and drift off north before i get home.

 

My main area of interest: (Yellow dot indicates me:( )

 

weather11.png

steering flows taken from modelling this afternoon/evening infer that storm motion will not be south to north, far from it

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11 minutes ago, ajpoolshark said:

steering flows taken from modelling this afternoon/evening infer that storm motion will not be south to north, far from it

Which steering flow will be the most predominant do you think AJ? Looks to be a bit of a clusterf**k in all honesty excuse my French!! 

Also, are these storms expected to be surface based? If so, this pea soup style fog needs to get a move on in clearing! 

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11 minutes ago, ajpoolshark said:

steering flows taken from modelling this afternoon/evening infer that storm motion will not be south to north, far from it

Cool - thanks for the heads up - I didn't realise the swing was occurring so this is welcome news. While Godalming / Guildford may miss out on a direct hit at least I don't have an epic journey on the chase!

finishing work at 2:30 / 3pm so I hope that's not too late to head up the M40 to Marlow /High Wicombe area and wait to see what happens from there.

Maybe even Chorleywood as its great for links in all directions (though the traffic on the western M25 can be a b1+£h!

 

Could prove to be a good day after all...

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2 minutes ago, East_England_Stormchaser91 said:

Which steering flow will be the most predominant do you think AJ? Looks to be a bit of a clusterf**k in all honesty excuse my French!! 

Also, are these storms expected to be surface based? If so, this pea soup style fog needs to get a move on in clearing! 

wow it's clear as a bell here, has been all night. Didn't expect to hear anywhere had fog off this easterly, as I'd normally be one of the first to see it, strange. Must be a lot of moisture in the air, can be a good thing.

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2 minutes ago, East_England_Stormchaser91 said:

Which steering flow will be the most predominant do you think AJ? Looks to be a bit of a clusterf**k in all honesty excuse my French!! 

Also, are these storms expected to be surface based? If so, this pea soup style fog needs to get a move on in clearing! 

lol....i totally agree, the steering winds are all over the place throughout the troposphere!....ironically the only direction not expected is south to north......looks like ESE to WNW for a few hours, then then flow changes from NE to SW as approaching fronts/troughs from the west and SE squeeze the air flow......I'm gong to stick to Nick F's & staplehurst (Dan - http://www.convectiveweather.co.uk/) .....in fact Dan's just put an updated forecast out

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2 minutes ago, alexisj9 said:

wow it's clear as a bell here, has been all night. Didn't expect to hear anywhere had fog off this easterly, as I'd normally be one of the first to see it, strange. Must be a lot of moisture in the air, can be a good thing.

Really is very thick here, although it looks to have thinned out a little. At 2am, visibility was down to at least 150M! 

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The one thing making me feel fairly positive this morning is the clear skies here. If there's no infill by this afternoon, game on.

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dan.png

Day 1 Convective Outlook

VALID 06:00 UTC Thu 15 Sep 2016 - 05:59 UTC Fri 16 Sep 2016

ISSUED 08:17 UTC Thu 15 Sep 2016

ISSUED BY: Chris/Dan

UPDATE 08:17 UTC Some adjustments to the shape of the MDT based on latest guidance - but still room for some margin of error W / E of depicted area. Some models beginning to pick up on the idea of thundery outbreaks developing towards London area late evening/overnight, which might have some disruptive impacts - treated with caution for now, but will be monitored

 

Elevated convection over the English Channel and environs on Thursday morning should gradually weaken with time - however, there is some uncertainty as to how far north precipitation (and more importantly the cloud shield) may extend, and this may have some impacts on evening developments if cloud clearance is too slow. Some sporadic/isolated lightning from embedded medium-level instability release will also be possible in Northern Ireland / western Scotland from showery bursts of rain.

 

The upper pattern on Thursday will gradually become more progressive as an Atlantic upper trough approaches from the west, causing the cut-off low over Biscay to nudge eastwards across France, while elongating - and this process may be responsible for the advection of some elevated convection into parts of SE England and coastal East Anglia on Thursday night. 

 

Elsewhere, capping will persist for much of the day. That said, strong heating and increasing low-level wind convergence, as the surface low over Brest peninsula migrates NNE to southern England by evening, may provide sufficient forcing for scattered thunderstorms to develop late afternoon into Thursday evening, particularly across the W Country / Cen S England NE to the south Midlands. Forecast profiles are quite dry, and so initial convection may struggle to develop at first, but should any storms form then the biggest concern will be local flash flooding given PWAT in the mid-high 30s mm and slow storm motion. Gusty winds and hail to 1.5cm in diameter will also be possible, which falls just shy of our SVR criteria, hence no SVR issued at this stage. CAPE values near 1,000 Jkg-1 and steep mid-level lapse rates (although these gradually weakening (in a relative sense) through the evening) suggest lightning will be quite prolific in the most active storms.

 

During the evening and night, the approaching Atlantic front will likely increase low-level convergence and provide some forced ascent, with perhaps an increase in coverage of showery precipitation in a N-S zone (highlighted by the elongated SLGT), only slowly migrating eastwards. 200-400 Jkg-1 MLCAPE overnight suggests that some occasional lightning will be possible with this activity, albeit in a rather sporadic nature, and likely to not be as frequent as initial surface-based storms on Thursday evening.

 

The exact positioning of the zone of wind convergence, and hence greatest thunderstorm potential, is subject to a little doubt and hence the MDT may need adjusting slightly as conditions become clearer through the day on Thursday.

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Just now, Azazel said:

The one thing making me feel fairly positive this morning is the clear skies here. If there's no infill by this afternoon, game on.

That's what Sat24 is currently suggesting, low level cloud slowly burning off, more cumulus type cloud moving in from English Channel.

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 I do hope things don't move ESEly  as that would be game over for me if I was ever in the game. To me it looks like wins will back  during the evening so eventually cells  would be moving NNEly. 

 On the other hand, another forecast I've looked at shows a  less complicated profile with wins Ely backing SEly  with height. 

Edited by Chris.R

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here currently in north Wilts I have to my south a bit of cirrus and some Ac Floccus from the Channel detritus drifting away to the west, but already promising signs for later with some fairly robust Cu Congestus to my north drifting slow northwestwards

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Ever so slowly now clearing up fog starting to rise. im expecting quite a bit  from the potential of tonight .  south through central midlands to east anglia and maybe London area to see the most action.  My guess would be glos area to be the sweet spot.  edit sorry Oxford  geography is rubbish

Edited by weirpig

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Calling it... My best bet, drawing a triangle from Swindon - Salisbury - Reading!

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