Convective / Storm Risk Discussion - 14th June 2013 onwards

[Coast]

Please use this thread to discuss the potential for convective weather in the UK from 14th June 2013 onwards

[Raidan]

Hi Coast i know this thread is for tomorrow but can I ask you or anyone else that is a lot more knowledgable than I am a question,been looking at the Storm risk charts and also the CAPE charts for Saturday,its probably me being thick plus I'm no expert but to me it looks like my part of the uk could be in with a chance of something,please correct me if I'm wrong

Edited June 13, 2013 by Raidan

[AWD]

I see where your coming from Raidan;

Worth a better look tomorrow when we have numerous high res charts available to us. Nothing special going on in Cardiff though;

So it could be a borderline thing for our location.

Edited June 13, 2013 by AWD

[Coast]

Hi Coast i know this thread is for tomorrow but can I ask you or anyone else that is a lot more knowledgable than I am a question,been looking at the Storm risk charts and also the CAPE charts for Saturday,its probably me being thick plus I'm no expert but to me it looks like my part of the uk could be in with a chance of something,please correct me if I'm wrong

 

Let me have a looky tomorrow for you if I can?

[VillagePlank]

First glance, is marginal; some risk since a small amount of CAPE is forecast to be around, but defo look at the high res charts in the morning.

[Coast]

GFS overview says no, but Saturday morning might have a rumble:

 

[Supacell]

I did highlight the risk of something during the early hours of Saturday in the previous thread. Oh and the phantom plume returns on today's GFS runs for the middle of next week

[Harry]

Errrrr...........may want to take a hop back to the 12z GFS............

 

Needlessly to say its still 7 days away blah de blah - but it's nice to see potential still never too far away. Sniff at something across the S/SE Monday afternoon/evening too looking at the precip run on GFS.

Edited June 13, 2013 by Harry

[Stuart]

yes sat look not to bad here

 

Showers on Saturday, some heavy with hail or thunder

[Jax]

Only convection here so far this "spring/summer" has been my heater!

[Supacell]

Errrrr...........may want to take a hop back to the 12z GFS............

 

Needlessly to say its still 7 days away blah de blah - but it's nice to see potential still never too far away. Sniff at something across the S/SE Monday afternoon/evening too looking at the precip run on GFS.

 

The 12z GFS is a real treat and almost brings back the storm porn charts of earlier in the week. I know its a long way off but I really hope this come off as we need a good plume event. 

[Karl83]

The 12z GFS is a real treat and almost brings back the storm porn charts of earlier in the week. I know its a long way off but I really hope this come off as we need a good plume event. 

Yes its certainly flirting with the idea. I reckon we will get something but we just gotta be patient.

[dave48]

A few thundery showers around tomorrow ahead of the approaching cold front, again affecting the midlands and the northern parts of England.

 

Worth looking out for if you live in those areas.

[Coast]

Saturday may have some possibilities for those in East Anglia and Essex, let me dig out some more specific information and charts:

 

[Coast]

Concentrating on today first, ESTOFEX show this:

 

 

 

Storm Forecast

Valid: Fri 14 Jun 2013 06:00 to Sat 15 Jun 2013 06:00 UTC

Issued: Thu 13 Jun 2013 20:14

Forecaster: SCHLENCZEK

A level 1 was issued for E Romania, S Ukraine and E Bulgaria mainly for large hail, excessive precipitation and severe wind gusts. 

 

SYNOPSIS / DISCUSSION

 

A meandering WSWerly flow is present over the western and northern parts of Europe with numerous embedded shortwave troughs. Most instability is found close to the center of each low pressure system which limits the threat of severe weather. The occurrence of isolated severe wind gusts is possible when a low pressure system moves across Ireland in the evening / night hours. Due to the fact that the convective contribution to the maximum wind speeds should be quite low, no threat level is issued.

 

 

UKASF have:

 

 

Slight

Forecaster: Dan

Last Updated: 2013-06-13 21:34:00

Valid: 2013-06-14 00:00:00 - 2013-06-14 23:59:00

 

 

Synopsis:

 

Forecast period begins with a transient upper and surface ridge across the British Isles, quickly replaced by an upper trough migrating eastwards from the Atlantic. At the surface, an area of low pressure will push a new frontal system across Britain, with two main focal points for convection - the first within the warm sector, and the latter in the post-frontal environment later in the day.

Discussion:

 

... MIDLANDS, N/NE ENGLAND ...

 

Renewed moisture advection will occur behind a northward-moving warm front, destabilising with the approach of the upper trough coupled with surface heating. This airmass will already be slightly unstable in the mid-levels, so it is possible that isolated thunder may occur from mid-level convection over SW England or Wales through the first half of the morning. However, main focus for more surface-based convection will be further north and east, most notably the East Midlands, Yorkshire and NE England during the early-to-mid afternoon hours, during the passage of a shortwave trough. 

 

Up to 600 J/kg CAPE should allow scattered showers and a couple of thunderstorms to form over these areas, capable perhaps of producing some small hail. 20-30kts DLS should allow some cell organisation, and it is possible that some showers/storms will begin to merge into more linear features through the course of the afternoon. However, lightning is expected to be less widespread/frequent compared to the activity on Thursday due to a less-unstable environment.

 

 

... NORTHERN IRELAND ...

 

Main period for convection here will be a narrow window between 09z-12z. Within the warm sector, a few hundred J/kg CAPE may allow scattered showers and an isolated thunderstorm to form, before the cold front and more dynamic rainfall approaches the area from the west quickly through the afternoon.

 

 

... IRELAND ...

 

This region poses the greatest threat for SVR convective weather, and may be upgraded to a SVR threat level if conditions continue to look favourable through Friday. Main threat period will be in the post-frontal environment, between 16z-22z, primarily over the southern half of Ireland. 

Behind the cold front, instability will rapidly increase through the second half of the afternoon and through the evening hours. Beneath the left exit region of the jet aloft, up to 500 J/kg SBCAPE coupled with cooling in the mid-levels will steepen lapse rates and generate widespread convective showers, and a few thunderstorms. Unfortunately this late development will generally occur after peak daytime heating, so this may limit the degree of instability somewhat.

Nontheless, a developing surface low near Galway will result with increasingly backed surface winds in areas further south and east of this low centre. Given 40kts DLS and sufficiently-backed surface winds, chances exist for a low-topped supercell to develop, capable of producing hail up to 2.0cm in diameter and perhaps a tornado. Greatest risk period for this will be 17z over W-C Connaught shifting slowly eastwards to SE Leinster by 21z. This situation needs careful monitoring through Friday for potential updates/upgrades.

 

 

[Coast]

Looks like we could be in for a repeat of yesterdays action with favoured areas broadly the same:

 

 

 

 

Perhaps a bit more to the North as well:

 

 

Some decent SBCAPE down the Eastern side of the country later:

 

 

Lower level lapse rates are encouraging but higher levels almost non-existent

 

 

An area of helical activity possible down around the Humber:

 

 

Let me check NMM, but if it does get going, I'll make a dedicated thread for today and move the appropriate posts over!

[Coast]

NMM in general agreement with GFS:

Aviation significant weather chart show show something at mid-levels;

Edited June 14, 2013 by Coast

[Summer Sun]

Synopsis:

 

Forecast period begins with a transient upper and surface ridge across the British Isles, quickly replaced by an upper trough migrating eastwards from the Atlantic. At the surface, an area of low pressure will push a new frontal system across Britain, with two main focal points for convection - the first within the warm sector, and the latter in the post-frontal environment later in the day.

Discussion:

 

... MIDLANDS, N/NE ENGLAND ...

Renewed moisture advection will occur behind a northward-moving warm front, destabilising with the approach of the upper trough coupled with surface heating. This airmass will already be slightly unstable in the mid-levels, so it is possible that isolated thunder may occur from mid-level convection over SW England or Wales through the first half of the morning. However, main focus for more surface-based convection will be further north and east, most notably the East Midlands, Yorkshire and NE England during the early-to-mid afternoon hours, during the passage of a shortwave trough.

Up to 600 J/kg CAPE should allow scattered showers and a couple of thunderstorms to form over these areas, capable perhaps of producing some small hail. 20-30kts DLS should allow some cell organisation, and it is possible that some showers/storms will begin to merge into more linear features through the course of the afternoon. However, lightning is expected to be less widespread/frequent compared to the activity on Thursday due to a less-unstable environment.


... NORTHERN IRELAND ...

Main period for convection here will be a narrow window between 09z-12z. Within the warm sector, a few hundred J/kg CAPE may allow scattered showers and an isolated thunderstorm to form, before the cold front and more dynamic rainfall approaches the area from the west quickly through the afternoon.


... IRELAND ...

This region poses the greatest threat for SVR convective weather, and may be upgraded to a SVR threat level if conditions continue to look favourable through Friday. Main threat period will be in the post-frontal environment, between 16z-22z, primarily over the southern half of Ireland. Behind the cold front, instability will rapidly increase through the second half of the afternoon and through the evening hours. Beneath the left exit region of the jet aloft, up to 500 J/kg SBCAPE coupled with cooling in the mid-levels will steepen lapse rates and generate widespread convective showers, and a few thunderstorms.

 

Unfortunately this late development will generally occur after peak daytime heating, so this may limit the degree of instability somewhat. Nontheless, a developing surface low near Galway will result with increasingly backed surface winds in areas further south and east of this low centre. Given 40kts DLS and sufficiently-backed surface winds, chances exist for a low-topped supercell to develop, capable of producing hail up to 2.0cm in diameter and perhaps a tornado. Greatest risk period for this will be 17z over W-C Connaught shifting slowly eastwards to SE Leinster by 21z. This situation needs careful monitoring through Friday for potential updates/upgrades.

 

http://ukasf.co.uk/storm-forecasts/249

 

[VillagePlank]

Yep, Birmingham (and surrounding area) looks to have a reasonable chance, today,

 

Here's the SE (Heathrow) for tomorrow,

 

 

Maybe. Just maybe, a thunderstorm for the SE, tomorrow, but, unfortunately (for me) much much more likely to be East Anglia,

 

 

Edited June 14, 2013 by Sparkicle

[Darren Bown]

I seem to have a higher chance today than yesterday with the areas of interest a little further North and West. That stuff over Wales currently has really pepped up showing how much moisture is available!

[Supacell]

Tonight looking very interesting. Can't post charts as at work but looks like a lot of parameters come together along the passage of a cold front which could produce some severe thunderstorms. I'll look more this afternoon if not chasing.

[pad199207]

Whats the stats for Ireland today and tonight? UKASF seems to think we could have severe potential, but I very much doubt that! Local warnings out for Flash Flooding later which I also doubt!

[Nick F]

Tonight looking very interesting. Can't post charts as at work but looks like a lot of parameters come together along the passage of a cold front which could produce some severe thunderstorms. I'll look more this afternoon if not chasing.

 

Yes, tonight/early Sat morning does looks interesting, as an active cold front sweeps through:

 

 

Left exit of a strong jet streak moving in across southern Britain tonight creating strong divergence aloft (uplift) working in tandem with the cold front moving east, so some strong forced ascent of Tm airmass ahead of front, moisture greatest across southern England - so there could be enough CAPE combined with forced ascent for some strong enough emedded convection for thunderstorms,

 

Winds backing ahead of CF before veering sharply with passage of front will generate strong low-level shear, strong winds veering with height will also mean strong deep layer shear, so convection likely to organise with possible bowing line segments with mesocyclones developing in any storms - an isolated tornado not out the question, along with strong convective gusts.

 

Unfortunately, as there will be a lack of surface heating being overnight/ early morning, true  potential may not be realised as much if this was occuring in the afternoon.

 

But nonetheless, potential there

Edited June 14, 2013 by Nick F

[VillagePlank]

Yes, tonight/early Sat morning does looks interesting, as an active cold front sweeps through:

 

fx24_sa00z.png

 

Left exit of a strong jet streak moving in across southern Britain tonight creating strong divergence aloft (uplift) working in tandem with the cold front moving east, so some strong forced ascent of Tm airmass ahead of front, moisture greatest across southern England - so there could be enough CAPE combined with forced ascent for some strong enough emedded convection for thunderstorms,

 

Winds backing ahead of CF before veering sharply with passage of front will generate strong low-level shear, strong winds veering with height will also mean strong deep layer shear, so convection likely to organise with possible bowing line segments with mesocyclones developing in any storms - an isolated tornado not out the question, along with strong convective gusts.

 

Unfortunately, as there will be a lack of surface heating being overnight/ early morning, true  potential may not be realised as much if this was occuring in the afternoon.

 

But nonetheless, potential there

 

Here's the fella,

 

 

Wow!

 

[nitro_deluxe]

Cheers guys - any show let alone a night one, wouldn't go amiss.