Storm & Convective Discussion - 01/03/15 onwards

[Noahjoe]

Very jealous hearing about anyone getting any thundery stuff today considering that here on the south coast all we have is the murk that we become accustomed to at this time of year...however tomorrow night does look decent for here

[Paul Sherman]

Strong Northerly Outflow winds to the Line to my North which seems to suggest the Line occurring to the south of the earlier right mover is initiating Outflow induced cells.

 

Only 10 miles south of the line over Essex and cant even see an Anvil, must be quite low topped

[Raidan]

First proper rain today falling now been a mostly dry day nothing thundery though

[Harry]

Strong Northerly Outflow winds to the Line to my North which seems to suggest the Line occurring to the south of the earlier right mover is initiating Outflow induced cells.

 

Only 10 miles south of the line over Essex and cant even see an Anvil, must be quite low topped

 

I thought that...when the cell was over St Albans it looked more distant than I'd expected...surprising amount of activity (if blitzortung is anything to go by) for relatively low topped cells.

 

Activity appears to be increasing around the Notts/Lincs region....unsurprisingly of course  ...in fact, ramping up really quite rapidly!

Edited May 3, 2015 by Harry

[reef]

Very humid here with a temp of 18.1C and dewpoint of 14.7C. For once the wind is not onshore so I'm hopeful those cells to the south-west of us won't die out.

 

There's an annoying gap forming though as usual!

[Mapantz]

I question blitz's 1200+ strikes over the ATD's 461..

 

[Harry]

I question blitz's 1200+ strikes over the ATD's 461..

 

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To be fair, over the past few years I've witnessed a number of storms that were considerably more electrified than ATD suggested. That said, all I've witnessed today is some early rain and nice blue skies with fair weather cumulus so I can't really comment as to how accurate either has been. But for some isolated storms on a day where nothing particularly explosive was forecast 1,200+ does seem on the high side.

[Daniel*]

A beast of a storm is inbound Ipswich with radar returns indicating rainfall rates up to 100mm/hr

[ChezWeather]

Lincolnshire taking the usual hammering 

[Guest]

Small but potent looking shower knocking on the door here. Lets see if we get any thunder

[Nick F]

Could see a cumulonimbus gleaming in the sun way off to the NE as arrived back home about 15 mins ago, could be the storm over Ipswich.

As usual, south of M4 and northern home counties missing out as is usual with SWly flow, first time this year the air's felt humid. Seems to be enough deep layer shear across southern counties this afternoon (30-40 knts) for storms to organise and develop supercell characteristics on radar.

[Allseasons-Si]

GULP!!!,MY CAMERA HAS JUST PACKED UP ,,only 6 months old

 

gone to look for receipt.

[Flipflop]

Was nice to sit back and enjoy the storm rather than panic trying to get pictures.....constant rumble for a good 20mins here   

[snowprincesspboro]

hiya peeps, any ideas if these storms will continue into the evening or die off soon after dark please. hoping to get a few rumbles here, radar looking good to the west, not so on the lightning detector thou. fingers crossed

[Allseasons-Si]

GULP!!!,MY CAMERA HAS JUST PACKED UP ,,only 6 months old

 

gone to look for receipt.

Found receipt and i was wrong,18 months old not 6,i am gutted though and i will see if i can get it fixed,storms please hold off till i get it fixed lol.

 

there is no power what so ever,anyone know where i can get it fixed,much appreciated.

 

fujifilm xp60

Edited May 3, 2015 by Allseasons-si

[Nick F]

hiya peeps, any ideas if these storms will continue into the evening or die off soon after dark please. hoping to get a few rumbles here, radar looking good to the west, not so on the lightning detector thou. fingers crossed

They will die off after dark, as they are being fuelled by surface heating of the humid SWly flow in the strong May sun.

[mike57]

Was nice to sit back and enjoy the storm rather than panic trying to get pictures.....constant rumble for a good 20mins here   

Same up the coast 4 miles north of Bridlington, constant rumbling for about half hour, but no lightning seen, and about 10 mins of heavy rain. Sun out now. At least its warmed up a lot, last 2-3 days have seen temps struggle to make 10C on the yorkshire coast. Nothing worth photographing here.

[Supacell]

I went out on a chase today but didn't see a lot to be fair. First intercepted some cells between Hucknall and Mansfield, and at this point they were producing some fairly heavy rain and blustery winds with the odd flash of lightning observed (need to check footage to see if I caught it). I chased the cells all the way past Ollerton but was losing them by this point and eventually had to admit defeat just outside Tuxford. Annoyingly it was after that whereby these cells really got going and gave Lincolnshire there normal dose of thunderstorm activity. I did get to see this classic thunderstorm cumulonimbus towards Lincoln:

 

 

A decent enough opening to the 2015 season.

Edited May 3, 2015 by Supacell

[Greeny]

They will die off after dark, as they are being fuelled by surface heating of the humid SWly flow in the strong May sun.

Feeling distinctly colder and dryer now.The storms that have been around must have probably sucked the moisture away for now. Earlier did feel hot and humid that did feel nice. I like days like that, it was the second of its kind this year. I am still doing a timelapse with my ipod touch of the small cells off the North Norfolk coast. First ever timelapse like this so all is not lost. These cells seem to be travelling slowly like a train and another builds behind it.

Picture of it from wymondham (mammatus not under a storm), line of convection about 5pm. Ashwellthorpe storms off the north norfolk coast. A line of 3 just 10 mins ago.

Edited May 3, 2015 by Greenday

[cloudsabove]

Storm approached earlier this afternoon, mostly cloud to cloud lightning a few times, few booming rumbles, exceedingly heavy rain shower. Not much structure as it approached but as it travelled away I caught this panoramic shot of the showers and some instability (correct me if wrong)

[SxK]

Anyone have any views on potential for tomorrow night?

[Azazel]

I went out on a chase today but didn't see a lot to be fair. First intercepted some cells between Hucknall and Mansfield, and at this point they were producing some fairly heavy rain and blustery winds with the odd flash of lightning observed (need to check footage to see if I caught it). I chased the cells all the way past Ollerton but was losing them by this point and eventually had to admit defeat just outside Tuxford. Annoyingly it was after that whereby these cells really got going and gave Lincolnshire there normal dose of thunderstorm activity. I did get to see this classic thunderstorm cumulonimbus towards Lincoln:

 

WP_20150503_17_06_05_Pro.jpg

 

A decent enough opening to the 2015 season.

 

 

Peach of a photo. God it's been so long since I've seen anything that even remotely resembles that:(

 

Re. tomorrow and the rain moving up from France in the evening, any chance of some sparks anyone reckon?

[Flipflop]

Second cell past with little action but i decided to air my lightning trigger to see if the damn thing still works,it did! but after letting my 16mm go 50mm (nikon) just isn't wide enough, may have to dig deep and go for tokina again or something else..

[poseidon]

Had a few flashes of lightning with thunder around here this afternoon and some very stormy cloudscapes. Also, got caught in monsoon rain from the thunderstorm west of the M11 and ended up having to pull off the road. Here's some shots from the southern end of the Cambridge line of cells....

 

         

 

And a shot of the storm west of the M11....

 

 

Not bad for early May.

Edited May 3, 2015 by poseidon

[Convective]

Well, a rather good day to really kick the convective season off! Many thanks to everyone for their live coverage and excellent photographs, keep up the good work. Hopefully a start to a hot and thundery summer

 

____________________________________________________________________________________________________

 

EDIT: Estofex forecast since issued...

 

 

Storm Forecast
Valid: Mon 04 May 2015 06:00 to Tue 05 May 2015 06:00 UTC
Issued: Mon 04 May 2015 00:03
Forecaster: VAN DER VELDE

A level 2 was issued for N Portugal and NW Spain mainly for tornadoes and severe convective wind gusts.
A level 2 was issued for SW to N France mainly for severe convective wind gusts, large hail and tornadoes.
A level 1 was issued for parts of Portugal, northern Spain, central and western France and the Benelux countries mainly for severe gust, large hail and tornado chances.

SYNOPSIS

An active depression near Portugal is advecting significantly warmer, unstable air with a SSW-ly flow into southwestern Europe. It follows in the wake of an old low with its core west of Ireland which briefly brought a surge of warm air into western and central Europe. A remnant occlusion is decaying between Czech Republic and Ukraine.
The Portuguese low is a highly baroclinic system with a marked warm front about 100 km north of the line Galicia - Switzerland during the afternoon. Strong flow veering with height is present across the warm sector and a Spanish Plume situation develops, this time separately from the Saharan Air Layer which runs over the western Mediterranean basin.
Around 12Z the cold front enters the Iberian Peninsula and reaches SW France around 21Z along with the center of the low passing west of Brittany. By Tuesday 06Z the warm front is predicted to have reached northern Netherlands and central UK.

DISCUSSION

...Portugal and NW Spain...

The northern portion of the cold front over this region around 15Z is backed by a PV lobe which causes strong upward motion. The cold front passes earlier at mid levels which creates a zone with a negative vertical theta-e gradient (potential instability) which combines with a few hundred J/kg MLCAPE. A line of discrete cells or a continuous linear convective system are thought to form. Since the flow at 1-3 km AGL averages 30 m/s, very severe wind gusts can be produced by these storms. On the other hand, very low LCLs reduce cold pool strength. This may rather benefit the tornado threat from supercells, which is significant due to nearly 20 m/s 0-1 km shear, 20 m/s 1-8 km shear and SREH over 250 m²/s² over 0-3 km. Over northern Spain, cloud bases are higher while low level winds and shear are reduced. SREH and deep layer shear do allow supercell storms with a larger chance of large hail and lower tornado/gust chance.

...France...

Initially the warm front over central France with its associated convergence line is the main focus for storm initiation. MLCAPE in the range of 500-1000 J/kg is locally possible and agreed upon by various models. Northward across the warm front, mid level lapse rates and low level theta-e drop, so storms are not likely to develop upscale here. 0-6 km shear of 25 m/s and over 200 m²/s² SREH suggest supercell mode with large hail as main threat, as low-level shear is lacking over central France (<10 m/s 0-1 km) during the afternoon. The exception is the Atlantic coast north of Bordeaux, where LCL should be low, mid level vorticity advection generates additonal lift and 0-1 km shear is over 17 m/s. A tornadic thunderstorm is quite possible under such circumstances. As southern flow increases, the warm front shall drift northward in the evening, and MCS formation is likely.

The main show appears reserved for the evening and night when the Spanish Plume lapse rates and the PV lobe trigger elevated convection with over 1000 J/kg MUCAPE over Bay of Biscay. Although extreme low-level shear and SREH will be in place across France, the severity of the storms depend on effective shear in the unstable elevated layer. This seems not a problem with GFS overlapping >500 J/kg MUCAPE with >20 m/s shear. With dry air inflow in the lee of the western Pyrenees, large hail parameter is peaking at 18-21Z along the SW France coast. If all goes well and storms formed, these will race northwards developing into an MCS with enhanced severe gusts threat. Such systems may hold themselves together on their course toward Belgium and Netherlands in the early morning due to strong dynamic support, although a not very broad and weakish CAPE region with dry air over central France might as well mean an earlier end to most nocturnal storms.

Source: http://www.estofex.org/

Edited May 4, 2015 by Convective