Convective / Storm Chat And Discussion

[lewisosd]

Wow! Serious downpour which flooded parts of the A14 on my drive home. Very low visibility and had to slow down to 30mph. Almost like a monsoon!

[95 Degrees]

http://uk.weather.com/weather/tomorrow-Hove-UKXX1738

Hope it becomes reality!

[Weather Wizard]

Strange stuff from Exeter HQ

This for the SE

Headline:

Heavy rain this evening, clearing to blustery showers on Saturday.

This Evening and Tonight:

A wet evening with rain, often heavy and thundery, slowly clearing northeastwards through the first part of the night, leaving clear spells and more fleeting heavy showers towards morning, as a fresh or strong westerly wind sets in. Minimum temperature 10 °C.

Saturday:

A much brighter day with sunny intervals but also showers, some heavy with a risk of hail and thunder, but generally blowing through quite quickly on a brisk westerly breeze. Maximum temperature 17 °C.

Updated: 1528 on Fri 17 Jun 2011

I definately wasn't expecting anything tonight and even after this still aren't no strikes reported on any of the detection websites.

[Costa Del Fal]

GFS 12z quite a downgrade on tomorrow. Decent cape values have gone to more average ones. The Midlands looks like missing out except perhaps the far South and the rest of Southern England. All in all nothing to shout about now.

[Supacell]

GFS 12z quite a downgrade on tomorrow. Decent cape values have gone to more average ones. The Midlands looks like missing out except perhaps the far South and the rest of Southern England. All in all nothing to shout about now.

I'm hoping its just the one run and subsequent runs bring back the excitement. Based on the 12z i would most certainly be cancelling my chase plans for tomorrow. Bring back the CAPE like the 6z and we're in business.

How i long for import storms that last all night like we used to have. Damn that jetstream lol.

Edited June 17, 2011 by Supacell

[tomp456]

http://uk.weather.com/weather/tomorrow-Hove-UKXX1738

Hope it becomes reality!

If it does I shall be drowning in my own tears

[Guest Quantumsnow]

http://uk.weather.com/weather/tomorrow-Hove-UKXX1738

Hope it becomes reality!

Hope so, would like to leave the no storms club before 2020 if I can.

[Jane Louise]

Evening all,

All this week I had a 51% chance of a storm for tomorrow and now.... it's gone down to 36% grrrrrrr.I must say though a few years back GFS were showing 0% risk at one time and I did actually get a storm lol.

The Met Office is hinting at a risk of hail and thunder for the South West tomorrow so who knows!

Don't give up yet folks, I for one will certainly be looking forward to Saturday and will be eagerly watching the NW extra radar.

[tomp456]

Evening all,

All this week I had a 51% chance of a storm for tomorrow and now.... it's gone down to 36% grrrrrrr.I must say though a few years back GFS were showing 0% risk at one time and I did actually get a storm lol.

The Met Office is hinting at a risk of hail and thunder for the South West tomorrow so who knows!

Don't give up yet folks, I for one will certainly be looking forward to Saturday and will be eagerly watching the NW extra radar.

Your are more likely to get a storm when the thing is at 31 % than 51%. Sounds odd but its true...

[biddie]

Your are more likely to get a storm when the thing is at 31 % than 51%. Sounds odd but its true...

whys that then ?

Edited June 17, 2011 by biddie

[DAVID SNOW]

whys that then ?

Sods Law.

[dave48]

An interesting heads up for Monday, a smallish area of moderate CAPE is expected across northern parts of England in an environment of strong deep layer shear. If the models were to hold up then there is the potential for multicells and potentially supercells.

Edited June 17, 2011 by dave48

[camiscool]

Are there any good storms in Thailand :s?

[Jane Louise]

From the UKASF website:

Storm Forecast Issued: 2011-06-17 22:09:00

Valid: 2011-06-18 00:00:00 - 2011-06-18 23:59:00

Regions Affected

CS & SE England, Home Counties, West Country, Northern Ireland and E Ireland (much of England, Wales, Northern Ireland and Ireland are included in the WATCH, excluding N England)

Synopsis

Behind an northward-moving occluded cold front, lowering geopotential heights associated with an upper-level trough will spread eastwards across the United Kingdom on Saturday. To the south of the front, scattered diurnally driven showers are expected to develop, and with forecast CAPE of up to 700 J/kg over Ireland, quite a few thunderstorms are expected also. Some small hail is likely in stronger cells, locally moderate in size over Ireland/Northern Ireland.

Weak deep layer shear means any showers/storms are likely to be unorganised and pulse-type in nature. It also reduces the chances of a funnel or tornado, although some low-level shear over England and Wales during the afternoon in particular may promote an increase in organisation and a chance of convergence-type funnels.

Showers will decrease slowly in coverage through the evening as daytime heating subsides.

http://ukasf.co.uk/module-Storm/mode-forecast/id-374/

Good luck all.

[Nick F]

An interesting heads up for Monday, a smallish area of moderate CAPE is expected across northern parts of England in an environment of strong deep layer shear. If the models were to hold up then there is the potential for multicells and potentially supercells.

Deep layer directional shear is rather weak tomorrow, so supercells seem rather unlikely, however fairly strong mid-upper flow (speed shear)is indicated - especially towards Sern and SW England beneath upper low over central UK, so multicell clusters possible with training of storms maybe bringing risk of flooding, along with risk some strong convective gusts. Could be quite an active day for storms over Sern parts of England and Wales.

Have issued a a storm forecast for tomorrow: http://www.netweather.tv/index.cgi?action=convective;sess=ed4f3448128cd011e35ee50c2f7e4a2b

Convective / Storm forecast - Issued 17/06/2011 22:30

Valid: 18/06/2011 06:00 - 19/06/2011 06:00

Headline: ...THERE IS A RISK OF THUNDERSTORMS FORECAST...

Synopsis

During Saturday, upper low slides east across central UK during the day, with a surface low centred over the North Sea at 12z ... an unstable rPm airmass wrapping around Sern and Wern flank.

... IRELAND, WALES, MIDLANDS, S and E ENGLAND …

Unstable rPm airmass across Ireland and Sern and SWern UK on Saturday characterised by steep lapse rates will support increasingly widespread convection during the day with surface heating, with GFS forecast soundings indicating CAPE in the range of 200-800 j/kg by the afternoon across the above areas - which suggests thunderstorms are likely here. Fairly strong mid to upper level flow (40-50 knots at 500mb) suggests some organisation of any storms into clusters with some training of storm cells which may lead to a risk of localised flooding and also some storms will produce hail and strong convective gusts. Directional shear is however fairly weak, apart from in the lowest 0-1km, so small possibility that stronger updrafts may spin to allow funnels or even an isolated weak tornado - especially where winds back ahead of troughs moving through.

Issued by: Nick F - Forecaster for Netweather

[Costa Del Fal]

An improved GFS 18z for tomorrow upon a rather disappointing 12z. Storm risk extended a bit further North again but it mainly depends on where the rain stalls tomorrow.

[dave48]

Deep layer directional shear is rather weak tomorrow, so supercells seem rather unlikely, however fairly strong mid-upper flow (speed shear)is indicated - especially towards Sern and SW England beneath upper low over central UK, so multicell clusters possible with training of storms maybe bringing risk of flooding, along with risk some strong convective gusts. Could be quite an active day for storms over Sern parts of England and Wales.

Thanks for the forecast Nick.

And to clear up the confusion if you re read my post it was a heads up for a small area of potential on the coming Monday, not for tomorrow, would agree on the weak DLS precluding supercell potential for tomorrow.

Edited June 17, 2011 by dave48

[ZONE 51]

a very interesting day coming up with a lot of activity, when i see a stormforecast by NetW i do get a little more excited!

anyway NAE 00z picks out the areas of convection shown here as areas of precipitation clumped together, looking quite widespread!

Met Office Weather - we like the word thundery..and your find it at the MetO site to! im confident all is on for today..i am expecting some nice views of distant storms even if they don't head my way! im in the risk zone!

[slinky1989]

On the train atm between swindon and bristol and already can see some lovely convection going on toward bristol

[AWD]

That's a clean window for a First Great Western train! Lol!!

Already had a number of heavy, squally showers here! Nothing more than that yet though! Hopefully something might happen today!

[chionomaniac]

First cumulonimbus cloud seen to my south /SE. Always good to see convection over the Channel - suggests good instability.

Ha, impressive. Just watched a cloud build from small cumulus into a cumulus congestus over Brighton. On the radar it has gone from no rain into a (traditional) red blob in one 5 minute update.

[WillinGlossop]

thunder and lightening very very frightening! oh i wouldnt mind a thundery shower..... lots of rain yesterday.... 30mm.... fast moving clouds today looking pretty convective.....

[Coast]

First cumulonimbus cloud seen to my south /SE. Always good to see convection over the Channel - suggests good instability.

Have issued a a storm forecast for tomorrow: http://www.netweather.tv/index.cgi?action=convective;sess=ed4f3448128cd011e35ee50c2f7e4a2b

[Nick F]

Soundings early this morning across southern England already looked pretty unstable looking at Camborne and Herstmonceux ascents:

Camborne (Cornwall) 00z ascent:

Adjust the trajectory of a rising parcel on the Herstmonceux with a surface temp of 18C, which will likely be the max in the SE today, and a some fairly decent CAPE likely:

PWAT (precipitable water) value of 25, which is fairly high, suggests some torrential dowpours likely.

[Coast]

Just need to make sure those Frenchies don't steal our thunder!!!!!

Storm Forecast

Valid: Sat 18 Jun 2011 06:00 to Sun 19 Jun 2011 06:00 UTC

Issued: Sat 18 Jun 2011 03:32

Forecaster: VAN DER VELDE

A level 1 was issued for N France, S Benelux and W Germany mainly for a chance of an isolated tornado.

SYNOPSIS

A rather vigorous low pressure area (for the season) over the North Sea, and its cold front over the Alps, Slovakia, Poland and occluded front curving back over Denmark creates two significant convective regimes over Europe. The CAPE on the warm side of the front is intersected by the southern outskirts (>30 m/s winds) of a broad jetstream rounding the upper trough, creating strong deep layer vertical wind shear conditions. The airmass near the front also features high precipitable water and column relative humidity, particularly over Poland.

On the cold side of the front, shallow convection is possible over Germany, while within the upper trough with low dynamic tropopause (PV max), deep convection will occur in conditions of weak deep layer shear, but low-level shear is enhanced by the rather tight pressure gradients combined with surface friction.

...N France, W Germany, S Benelux...

A marginal level 1 is issued where 15 m/s 0-6 km shear appears to coexist with 10-15 m/s 0-1 km shear while MLCAPE remains available in the early evening. The low level shear enhancement (from 7-8 m/s during the day) appears to be caused by decoupling due to boundary layer stabilization, but as it would favor shear, it would reduce convective potential. Except when localized dynamic lift mechanisms are able to sustain some cells/clusters. Strong but likely not severe convection-enhanced wind gusts are likely also during the day (also in Belgium and the Netherlands), as are instances of 1-2 cm large hail

TORRO CONVECTIVE DISCUSSION 2011/010

A TORRO CONVECTIVE DISCUSSION has been issued at 2345GMT on Friday 17th June 2011

Valid from/until: 0300GMT - 2100GMT on Saturday 18th June 2011 for the following regions

Parts of (see map)

Much of central and southern Eire S England Midlands E Anglia Much of Wales

THREATS

Wind gusts to 50mph; heavy rain; cloud-ground lightning; isolated tornadoes; hail to 1cm

DISCUSSION

Upper trough will move across Eire and thence Wales and the north Midlands during Saturday. At lower levels, an unstable returning polar maritime airmass will be in place. Lift associated with the trough along with surface heating will promote shower and thunderstorm development - some showers and possible storms will also move in from the Atlantic. Deep layer shear of 15-20 knots will be sufficient for some storms to organise into clusters, although much of the shear will be in lower levels, suggesting gusty winds will be a threat. These clusters will likely move inland from western coastal areas through Saturday morning, with a peak in coverage early-mid afternoon. Later on, loss of heating along with subsidence in the wake of the trough should allow storms to ease in many parts towards evening, although a few may continue in eastern parts into the evening.

Along with gusty winds, heavy rain is likely in places. Weak storm-relative upper winds will promote high precipitaion cells. Hail is possible, perhaps to 1cm.

Low-level shear will be fairly strong, especially across southern England /0-1km shear of around 15 - 20 knots/. However, directional shear looks fairly minimal. Even so, low cloud bases and fairly steep low-level lapse rates bring the risk of at least isolated, brief tornadoes, especially across southern England.

Forecaster: RPK.

UKMO and NOAAA Mid Level charts have it away from the South:

Shear to the South and East:

Plenty of convective rain:

and those lapse rates:

and finally those lovely total-totals! (Kent looking favoured here)