Storm & Convective Discussion - 01/03/15 onwards

[Arnie Pie]

Cells to the South of Leicester convecting nicely atm

[Convective]

GFS modelling widespread thundery activity on Tuesday

 

[Ben Sainsbury]

Be interesting monitoring satellite imagery late afternoon into evening tomorrow when it all kicks off over eastern France, and then into Switz, S'ern Germany, Austria, and N'ern Italy.  GFS has revised its MLCAPE progs down a touch with each consecutive run - now on the order of 1800-2000j/k (and not the 3000j/kg last week). Regardless, that sort of instability together with strong deep layer shear and low-level SR helicity favours initial supercell development, before likely MCS takes over during nocturnal hours across the entire region of interest. Large (perhaps very large) hail and damaging winds a given, with tornado potential most likely late afternoon/early evening, before low-level instability wanes and roots aloft. 

 

As for here.. 

I was going to say was viewing all the charts for tomorrow across Germany, East France etc. ESTOFEX issuing the potential for some dangerous storms around, and Supercells and MCS developing in the evening, so any webcams for that area could be a treat. Nothing as of yet but sure this afternoon it will all begin to explode, one to look out for across Europe.

 

It's just unfortunate that we don't have that heat across here, temperatures reaching 30'+ across Eastern France, cool and damp here I think.

Edited May 13, 2015 by Ben Sainsbury

[Harry]

I was going to say was viewing all the charts for tomorrow across Germany, East France etc. ESTOFEX issuing the potential for some dangerous storms around, and Supercells and MCS developing in the evening, so any webcams for that area could be a treat. Nothing as of yet but sure this afternoon it will all begin to explode, one to look out for across Europe.

 

It's just unfortunate that we don't have that heat across here, temperatures reaching 30'+ across Eastern France, cool and damp here I think.

 

I don't know about that - a stunning day here today. Can't be far of 20C with a slight breeze. 30C in May is just too premature, even for me

[Nouska]

I was going to say was viewing all the charts for tomorrow across Germany, East France etc. ESTOFEX issuing the potential for some dangerous storms around, and Supercells and MCS developing in the evening, so any webcams for that area could be a treat. Nothing as of yet but sure this afternoon it will all begin to explode, one to look out for across Europe.

 

It's just unfortunate that we don't have that heat across here, temperatures reaching 30'+ across Eastern France, cool and damp here I think.

 

Hi, here's a source for following the French storms and there should be pics from the chasers as the evening unfolds. Plenty of supercell activity already.

 

http://www.keraunos.org/actualites/fil-infos/2015/mai/orages-13-mai-2015-supercellules-grele-vent-rafales-lorraine-bourgogne-alsace-franche-comte.html

[NO LONGER POSTING]

Even though it's nothing nice to see a tiny bit of convection

Oddly moving directly south

[Mokidugway]

Nice convective looking sky here too ..

Edited May 13, 2015 by Mokidugway

[BrickFielder]

Very outside chance of a storm today mainly across southern counties.

 

Storms would be embedded in the frontal system and messy. Isle of Wight around mid day would be a key area.

 

I am not totally convinced about the risk here and models do not entirely agree.

 

Looking at the Satelite pictures there appears to be a little development towards the core of the low which is off the south west of the UK.

 

Forecasts would suggest this area will skirt the south of the UK with a slight chance of the tip of corwall being affected. Watching the satelite loops (sat24) I am uncertain about the exact trajectory, so would suggest it is worth monitoring to check.

 

Most likely there will be no storms in the UK today, but the very slight risk is worth a few words at this point.

 

[Harry]

Tuesday is looking pretty good and has now for several runs...widespread storm potential for once the SE in prime position what with the wind direction too

Edited May 15, 2015 by Harry

[Mapantz]

Tuesday is looking pretty good and has now for several runs...widespread storm potential for once the SE in prime position what with the wind direction too

Lots going on, perhaps. But, I'm not seeing what you're seeing for the SE.

North and west seeing the best of anything, perhaps some beefy showers for southern counties, as it stands now of course. It's the widespread storm bit that I can't see, maybe widespread showers?

Edited May 16, 2015 by Mapantz

[Mapantz]

I see lapse rates are quite good?! I do hope I'm wrong, lots to play for I guess? As there's a few days to run yet. Wednesday does look interesting too (on the latest run) for the east/south east.

[Supacell]

The chance of some storms over the next few days, at last!!!

 

The first chances will be seen across Scotland and N Ireland tomorrow afternoon with increasing lapse rates and a small amount of CAPE building. It is a low risk though with CAPE fairly meager and very little wind shear to speak of.  I am also drawn to the middle part of tomorrow for a brief opportunity for something a bit more interesting across the NE coast of England. GFS shows an overlap of CAPE with deep layer shear, therefore should anything develop tomorrow it could become more organised. However, it is a low risk for tomorrow that showers will develop into thunderstorms as lapse rates/CAPE values generally do not seem to support this.

 

Tuesday looks to be the main day with some decent CAPE and LI values being shown on GFS and WRF charts. Again though little chance of any organised or severe thunderstorms due to lack of wind shear and only low moisture levels, however some decent pulse type storms seem likely. It will be a good day I feel for being out and about with the camera's as some nice clear convective clouds would be visible outside of the showers. Any storms that do form could become briefly quite electrically active with hail given some very steep lapse rates with cold air aloft.The north of the country looks best placed with NE England/Humber the possible sweet spot on Tuesday on current charts (this may change). Storms will also be slow moving in the north under a centre of low pressure, but will move quite quickly further south. By Wednesday any action becomes more confined to the south and east and is generally dying out through the day as a brief ridge moves in from the west.

 

Hopefully some of us could see our first storm of the season with Tuesday's risk looking quite widespread on current charts. 

Edited May 17, 2015 by Supacell

[TropicThunder]

Impressive storms again across the the US midwest atm, seen fork lightning on this Dallas cam.

 

http://www.earthcam.com/usa/texas/dallas/reuniontower/?cam=reuniontower

 

Fingers crossed for our first storm of the year here over the net few days.

[Staffordshire]

Well Lincolnshire looks the place to be AGAIN

[Stuart]

This is for Tomorrow

 

Day 2 Convective Outlook

VALID 06:00 UTC Mon 18 May 2015 - 05:59 UTC Tue 19 May 2015

ISSUED 11:52 UTC Sun 17 May 2015

ISSUED BY: Dan

Frontal wave across southern half of Britain continues to slide eastwards through Monday morning, with embedded line convection given strong DLS across the front - however, convective depth is likely to be too shallow for any lightning activity (or at least the point probability is too low to warrant an ISOL).

... LINCOLNSHIRE TO EAST ANGLIA ...
Secondary cold front, which will likely be producing some line convection over the Irish Sea and Scottish Borders at the beginning of this forecast period, will continue to migrate SEwards across across N Wales and N England through Monday morning, while weakening. However, with the sharpening upper trough advancing from the Atlantic, coupled with surface heating and strong DLS, expect cells along this line to reinvigorate as they cross Lincolnshire and Norfolk in particular through the midday and afternoon hours. CAPE is rather meagre given that the cold pool aloft is still yet to arrive, but 50-60+kts DLS may be able to compensate for this to produce some lightning from any stronger cells, along with some small hail.

... IRELAND, NORTHERN IRELAND, SCOTLAND ...
In the post-frontal environment, a sharpening upper trough will arrive from the Atlantic, accompanied by cold mid levels. This overspreading SSTs and diurnal heating inland will generate 300-500Jkg^-1 CAPE, with scattered showers and a few thunderstorms expected to develop. Given rather weak DLS, convection is likely to be rather messy and disorganised, especially with old occlusion debris also moving through in the flow. As a result, have refrained from issuing a SLGT as it is currently difficult to pinpoint particular areas with the best lightning potential.

However, with a rather slack surface pattern over N/NE Scotland, local wind convergence and topography will combine to produce some slow-moving heavy showers/thunderstorms during the afternoon and early evening hours. Have included a SLGT here due to better, more obvious forcing mechanisms, despite a lack of DLS to aid cell organisation.

In either case, expect some small hail from stronger cells, with gusty winds too.

 

http://www.convectiveweather.co.uk/forecast.php?date=2015-05-18

[Lauren]

Lots of lovely wispy cirrus about today.

[NO LONGER POSTING]

Something imbedded in tomorrows rain? Some beefy showers around over the next couple of days so hopefully some rumbles to

[MP-R]

Monday afternoon looks the best place in the west, Tuesday looks good just about anywhere, and Wednesday looks best in the east. Fingers crossed for some surprises this week before it settles down.

[Stuart]

a bit of a head up

 

Day 3 Convective Outlook

VALID 06:00 UTC Tue 19 May 2015 - 05:59 UTC Wed 20 May 2015

ISSUED 15:49 UTC Sun 17 May 2015

ISSUED BY: Dan

Sharpening upper trough will drift slowly eastwards across the British Isles on Tuesday, coinciding with peak daytime heating. Cold mid levels atop SSTs and diurnal land temperature peak will result in 500-800 Jkg^-1 CAPE, with widely scattered showers and a few thunderstorms developing, most active across eastern Britain where longer land track to the showers, combined with slacker winds (and hence surface convergence) will aid in increasing lightning activity here - hence a broad SLGT for eastern areas. May extend SLGT farther W across the Midlands if conditions continue to look favourable nearer the time.

 

Very little shear will result in rather disorganised convection, with pulse-type storms the most favoured mode. Given cold air aloft, some small hail is possible in any stronger cells, along with gusty winds. Showers/storms will tend to dissipate during the evening hours, with the majority of any lightning activity overnight being confined to the southern North Sea.

 

http://www.convectiveweather.co.uk/forecast.php?date=2015-05-19

[NO LONGER POSTING]

Estofax level one for southeast tornado risk later today interesting..

[Supacell]

Regarding tomorrow. All models still keen on breaking out widespread showers. GFS is showing some decent CAPE and LI, along with steep lapse rates across most northern and eastern parts. NMM however does not agree and shows very little CAPE anywhere and the steeper lapse rates are kept north of the Midlands. Overall it would appear that the NE is best placed tomorrow, this is the current picture anyhow.

[Nick F]

Headline: CONVECTIVE/STORM FORECAST MONDAY 18TH MAY

 

Valid Date/Time: 18/05/2015 0600z to 19/05/2015 0600z

 

 

 

Upper trough trough to the west of Ireland and NW Britain this morning will extend across all of Britain during Monday. At the surface, a shallow low and associated frontal wave will move east across southern Britain bringing cloud and rain to much of England and Wales through the morning, a surface cold front further north across Ireland & Scotland will move SE across Britain in the morning, clearing E Anglia early afternoon followed by an unstable Polar maritime flow across northern UK.

 

...  MARGINAL RISK SOUTHEASTERN UK ...

 

Water vapour imagery shows a defined dark stripe of dry air on the forward side of upper trough along/behind the cold front moving SE, increasingly strong PVA (Positive Vorticity Advection) associated with dry air intrusion aloft and surfacing forcing along the cold front moving SE may allow line convection / squall line to develop as it moves SE across England and Wales this morning, bringing a risk of strong wind gusts (up to 55-65mph) and brief spell of torrential rainfall. Lightning and hail appear not to be too likely, given shallow surface-based nature of instability and meager CAPE forecast. However, have highlighted SE England and E Anglia for a marginal risk of severe weather, where there will be most abundant moisture combined with forcing along cold front in an environment of strong deep layer shear (60-70knts) and low-level shear (20-25knts), which suggests risk of convection organising into bowing line segments or a line echo wave pattern (LEWP) - which would support a low risk of a tornado, and this area is indicated to have strongest risk of convective gusts.

 

... THUNDESTORMS IRELAND, SCOTLAND and N ENGLAND ...

 

Following cold front moving SE, increasingly cold mid-level temps will overspread northern Britain, as upper trough to the NW moves east, which will create increasingly steep lapse rates and support heavy showers and scattered thunderstorms late morning and through the afternoon as surface heating increases in the sunny spells. Lack of warmth, moisture and weak wind shear will mean severe weather is unlikely, though showers/storms may organise near troughs in the W to NWly flow, with a risk of gusty winds and hail.

 

Issued by: Nick Finnis

Issued by the Netweather forecast team whenever there is a risk of storms or severe convective weather, these discussion based and in depth forecasts will highlight the areas at risk and give an in depth description of the risk and the factors surrounding it.

Edited May 18, 2015 by Nick F

[NO LONGER POSTING]

 

 

Developments within the main band following nicks forecast..

 

Also I note Met office rainfall prediction.. showing this..

 

 

Edited May 18, 2015 by Surrey

[Harry]

Today may hold some treats, although there appears to be a fairly strong consensus that lightning activity will be at an extreme premium.

 

Nevertheless, seems to be a good chance for a pretty active squall early this afternoon, which is always pleasing

[BrickFielder]

 Yes looks like a little bit of line convection embedded in the frontal system showing up on the rainfall radar.

 

Tomorrow

------------

 

I am not convinced by the suggestion of wide spread activity tomorrow. Firstly current modelling suggests the triggering for storms  would be mainly in the west towards North Wales, Manchester and perhaps the north east.

 

Divergent upper level winds tend to be concentrated in the west.

 

Forecast SkewT's suggest a little instability, but cloud bases are not that low due to lack of moisture. There is a hint of a low level jet but realistically with temperatures around 10 C this is unlikely to result in updrafts strong enough to utilise the jet.  Squally pulse storms are more likely.

 

There is still time for the modelling to change, so we will wait and see.