Convective / Storm Discussion - 31st July onwards 2013

[summer fun]

Earlier it looked really thundery out towards the prom too, im a couple of miles inland, was watching and listening for a distant rumble, apparantly it turned electric as it hit Barrow

Typical looks great till it gets past us giving nothing but rain, then explodes into life a few miles.

[Allseasons-Si]

The rain is piling into the SW now,it really needs to pep up some,otherwise it's another bust imo.

[East_England_Stormchaser91]

Just a few shots i took over the last few days

 

at work on my break,some nice Cub's firing up there,ignore the t & d as i forgot to change them on new cam lol

 

 

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these shots with my other cam,at home the other day,was waiting for some rotation,there was some

 

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and yesterday the cell can be seen at some distance clearly over lincolnshire way

 

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allthough i haven't had a direct hit from a storm in recent days i have truely enjoyed the cloud structures and the busy convective thread/media and pics that you all have posted,heres hoping that we have more this season

That Lincolnshire cell was giving off high based lightning as it exited off between Mablethorpe and Grimsby at about 21.30. Amazing thing was, I thought it was around the wash area as from Huntingdon it looked nowhere near as far as it was! Talking  nearly 100 miles!

[Mokidugway]

nothing in south Cumbria now maybe something through the night quite humid though

'

[Mark.C]

Typical looks great till it gets past us giving nothing but rain, then explodes into life a few miles.

I know mate, last August was a cracking storm, nothing since!

[Allseasons-Si]

I have thought of something,patiance is a vertue,a storm will hit you,whether it be a day,week,month or year,we will always wait for it

 

[IanR]

is that skywarn  forecast just having a laugh, the predictions for decent thundry activity over these parts of northwest very rarely comes off,, seen it many many times, this the northwest , not east midlands,.....move along, nothing to see here

I rest my case, the isolated sferics around barrow was probably the 'severe thunderstorm' risk,   ah well ,

time for bed nearly . not staying up to watch some moderate rain with heavier spells mixed in 

[Dean E]

From past experience, I've always taken a look at cloud heights to see if there is any rapid development towards PPN and especially Thunderstorms (Higher cloud tops, more likely to indicate thundery activity)

 

Cloud heights in this system are hardly increasing, which would indicate that a heavier rain maker or thundery type system is looking very unlikely. I think its more the duration of the rain that needs more attention. 12 hours of moderate rain is enough to cause some problems.

 

SM

[Mokidugway]

4 am supercell storms with inch hail I think not time for bed .....

[Sprites]

I think N.Western areas are under a high shear/low cape set-up.

Which can lead to low-topped supercells, lightning activity may not be much, but other severe weather tornadoes hail and damaging SLW can develop in that set-up.

Seems more likely in autumn with atlantic lows and fronts.

[Bobby]

The heavy rain has returned here after a lull. Latest NAE gives 80mm+ for some spots after 35mm here already.

 

 

A lot of sheer and vorticity tonight which could trigger something interest convective wise. Western parts of Wales and NW England look most at risk.

 

 

 

[Captain Shortwave]

I think western areas could get quite a drenching. East Midlands eastwards, very very unsure, could get something interesting developing or could get absolutely nothing.

GFS totally dropped any excitement for the South East on Wednesday on this run. 

[Coast]

Some isolated thunderstorms later this afternoon through London and into Northern East Anglia as the rain and gusty wind moves in?

 

[Coast]

ESTOFEX liking it!

 

 

 

Storm Forecast

Valid: Mon 05 Aug 2013 06:00 to Tue 06 Aug 2013 06:00 UTC

Issued: Mon 05 Aug 2013 01:01

Forecaster: GATZEN

 

A level 1 was issued for the southern British Isles and southern Scandinavia mainly for severe wind gusts and tornadoes.

 

SYNOPSIS

 

A very active severe weather pattern goes on across parts of Europe. A south-westerly flow has developed east of low geopotential across the north-eastern Atlantic. On Monday, a pronounced short-wave trough will move across the British Isles and the North Sea region, the trough axis will extend well into central France and the western Alps. Ahead of this trough, a warm and well-mixed air mass placed across southern France and the Alps will spread northward. Critical issue will be the boundary-layer moisture as cooler and drier air has spread into France and Germany in the wake of Sundays storms, but current thinking is that moisture recovery will be strong enough to allow for storms. In the wake of the first vort-max, another one will follow across the Iberian Peninsula that enters France at the end of the period. 

 

Given the strong south-westerly mid-level flow and backing winds in the boundary-layer, storms will have a rather high potential to organize due to strong vertical wind shear. 

 

Across eastern Europe, lapse rates are weaker in a north-westerly flow, but rich low-level moisture allows for CAPE especially across parts of Russia.

 

DISCUSSION

 

British Isles, North Sea region, southern Scandinavia

 

A strong low-level jet will move across the area from the west, associated with warm air advection. Strong QG forcing will also allow for increasing lapse rates that will overlap with rather rich low-level moisture ahead of a cold front and a following trough axis. Models indicate some surface-based instability across the North Sea and over the southern British Isles in the afternoon and evening hours. However, current thinking is that most storms will be elevated due to the rather cool and dry boundary-layer. Nevertheless, storms will likely merge into a squall line crossing the southern North Sea and moving into southern Scandinavia. Additional storms are forecast over the southern British Isles along an approaching convergence line. Due to the strong vertical wind shear, bowing segments are forecast capable of producing severe wind gusts. Additionally, tornadoes are not ruled out.

 

 

 

 

[Coast]

UKASF have:

 

 

 

Synopsis

 

A waving front will continue to affect many parts of Britain through Monday, beneath the base of an upper trough and a weakening jet aloft. At the surface, a low pressure centre will track northeastwards from the Celtic Sea, across Wales, the Midlands and northern England, and ultimately across the northern North Sea during this forecast period. To the south and east of this low and associated frontal boundary, a tongue of warm, moist air (characterised by WBPT >14C and 10g/kg 1km mixing ratio) will continue to be advected northeastwards. There is scope within this airmass for some convective activity.

 

Discussion

 

Strong DLS and LLS will be present during the first half of the forecast period, allowing embedded (probably largely non-thundery) convection to form distinct lines along both the cold front and occlusion, and hence giving large rainfall totals on some southern and western slopes across western Britain (PWAT >35mm).

 

Greatest focus for convective weather will be between 12z-20z, beginning over the West Country during the early afternoon, then shifting progressively northeastwards towards East Anglia by late afternoon and into the evening. Surface troughing underneath an upper trough axis is likely to result in a zone of low-level wind convergence or confluence. Provided sufficient insolation amongst frontal boundaries allows a build-up of 600-800 J/kg CAPE, scattered showers and thunderstorms can be expected to develop, perhaps into a distinct NE-SW orientated line. 

 

By this stage, the upper jet will have weakened but with 20-30kts DLS still present this should allow cell organisation, with perhaps a CZ-induced funnel. Perhaps of greater concern is local flash flooding, given fairly slow storm motion and/or backbuilding/training over similar areas combined with PWAT values >30mm. Some small hail is possible in any stronger cells. All activity will generally shift northeastwards offshore during the evening hours.

 

 

 

SkyWarn:

 

 

 

SKYWARN UK SEVERE WEATHER WATCH #030

ISSUED: 2200UTC SUNDAY 4TH AUGUST 2013

 

SKYWARN UK FORECASTS THE POTENTIAL FOR SEVERE WEATHER AS FOLLOWS:

HEAVY RAIN LEADING TO A RISK OF LOCALISED FLOODING - WALES, MIDLANDS, NORTHERN & SOUTHWEST ENGLAND

 

IN EFFECT FROM 2200UTC SUNDAY 4TH UNTIL 2100UTC MONDAY 5TH AUGUST 2013

 

LOW DEVELOPING ALONG A SATURATED FRONTAL BOUNDARY, GENERATING HEAVY AND PERSISTENT RAINFALL

 

DISCUSSION:

 

THERE IS STRONG MODEL AND SATELLITE DATA TO SUGGEST A SEVERE WEATHER RISK THROUGH THE NEXT 24HRS. A LOW FORMING IN THE SW APPROACHES WILL BEGIN TO FOCUS PRECIPITATION ALONG FRONTAL BOUNDARIES ACROSS NORTHERN ENGLAND OVERNIGHT, WITH AN OCCLUDED FRONT AFFECTING HERE AND THE MIDLANDS DURING MONDAY. OVER THE SOUTHWEST AND WALES, THE FORMATION OF A COLD FRONT WILL ADD HEAVY AND POSSIBLY CONVECTIVELY ENHANCED PRECIPITATION TO AREAS THAT HAVE ALREADY AND WILL CONTINUE TO SEE PERSISTENT LIGHT TO MODERATE RAIN RATES. STRONGER WINDS DEVELOPING AHEAD OF THIS DURING THE EARLY HOURS MAY ALSO SERVE TO ENHANCE ACCUMULATIONS OVER HIGH GROUND. FLASH FLOODING AND EXCESS SURFACE WATER MAY BECOME RISKS OVER THE WHOLE WATCH AREA, WHILE RIVER FLOODING IS ALSO POSSIBLE AROUND THE SOUTHWEST. THIS WATCH MAY BE UPGRADED. PLEASE MONITOR WEATHER AND TRAVEL INFO AS NECESSARY.

 

 

[Coast]

GFS is favouring Norfolk later for any potential, but still something lurking over London. Convergence seems to be setting up in windy North Sea facing areas:

 

 

Maybe up as far as Lincs?

 

[Norfolk Sheep]

 

ESTOFEX liking it!

 

 

 

 

Oh dear, Matt's Triangle of Doom is conspicuous by its absence again

[I Cumbria Marra I]

Load of crap, didn't even thunder, loads of rain though. Still waiting for my first thunderstorm of the year!

[Coast]

Oh dear, Matt's Triangle of Doom is conspicuous by its absence again

 

[Harry]

Hmm...my part of the world excluded (again) with the exception of Estofex.

 

Will be curious to see whether anything pops up again...certainly some encouraging skies on the way in this morning, with a healthy batch of Ac including some AcCas lurking.

[Captain Shortwave]

Oh dear, Matt's Triangle of Doom is conspicuous by its absence again

Oh fiddlesticks 

[staplehurst]

Load of crap, didn't even thunder, loads of rain though. Still waiting for my first thunderstorm of the year!

 

What were you expecting? 

[VillagePlank]

Looks to me as if the Estofex warning is related to cold uppers moving in late in the day,

 

 

With the jet of to our South East,

 

 

Have to wait and see I guess!

[I Cumbria Marra I]

What were you expecting? 

Thunder/lightning? Estofex had us under a level 1, meto had yellow, ukasf had SLGT, Skywarn has us under a warning, so i was atleast expecting a bit of thunder.

[Harry]

MetO precip forecast seems keen to deliver some fairly heavy precip later this afternoon, in a linear fashion as described by the issued forecasts above.