Convective / Storm Discussion Thread - 27th Feb onwards

[Thunderstruck]

Delete.

Edited May 25, 2017 by Jcweather

[chapmanslade]

For sure the initial crop of storms will be for the SW later on Friday night and into Saturday morning. These will be elevated in nature and may have lost their oomph by the time they reach the UK, especially further north. What happens after that may depend on how much left over clag there is.

I'll be in NW France tomorrow evening so will blow as hard as I can to send them this way!

[Harry]

Latest model output is no more revealing than previous - that is to say, a lot of uncertainty remains particularly as regards Sunday/Monday.

Pretty much anywhere could see a storm or two over the coming weekend, though what is almost certain is not everywhere will.

FAX chart is perhaps the most interesting currently - runs a trough from NW France up across the W-UK through Saturday ahead of the advancing CF. This I would suggest could be a particular focal point for thunderstorms where as the frontal zones themselves could become quite messy (still thundery rain potential for sure).

Sunday into Monday (for me in the SE) is particularly interesting as it shows a decent chunk of the SE back in the warm sector behind the shallow continental low, with a nice trough in behind, which again could potentially be a focal point for thunder. GFS modelling however not having much of it, with SB/MUCAPE staying pretty much over the continent during this period.

I may have a play tomorrow and throw some of my own risk charts out there, just because I haven't done that in a long time

Happy Days - off to catch a baking hot train.

 

[<<Ryan>>]

ESTOFEX forecast below

Storm Forecast
Valid: Fri 26 May 2017 06:00 to Sat 27 May 2017 06:00 UTC
Issued: Thu 25 May 2017 15:38
Forecaster: TUSCHY

A level 1 was issued for NW-France and SW-UK mainly for large hail and to a lesser extent for strong to severe wind gusts.

Over W-France/SW-UK, the air mass stays capped until sunset. Thereafter, initiation is expected over the NE-Bay of Biscay and far NW-France as the trough and front both approach from the SW. Forecast soundings show elevated MUCAPE in excess of 1 kJ/kg with 15-20 m/s DLS. Thunderstorms grow upscale into an organized cluster of storms quite fast. This cluster crosses the W-English Channel and affects SW-UK during the second part of the night, where large hail will be well possible. In addition, low to mid-tropospheric winds strengthen over that region during the night to 15 m/s in the lowest 3 km. Elevated nature of storms should limit the overall severe wind gust threat, but we can't exclude the chance for stronger downdrafts to penetrate through the stable layer. Therefore strong to isolated severe wind gusts are also forecast. Heavy rain is possible over NW-France but confidence decreases for SW-UK due to the progressive nature of the cluster and its late arrival.

A level 1 was issued for NW-/N-Ireland mainly for an isolated large hail risk.

... NW/N-Ireland ...

Eastbound moving cold front interacts with an air mass, which features MLCAPE of 400-800 J/kg and 15 m/s DLS. A few organized thunderstorms with isolated large hail are possible, which move off to the NE. This risk peaks during the late afternoon/evening and vanishes thereafter with decreasing CAPE. During the end of the forecast a decaying cluster from the south approaches S-Ireland but northing severe is forecast.

Over W-France/SW-UK, the air mass stays capped until sunset. Thereafter, initiation is expected over the NE-Bay of Biscay and far NW-France as the trough and front both approach from the SW. Forecast soundings show elevated MUCAPE in excess of 1 kJ/kg with 15-20 m/s DLS. Thunderstorms grow upscale into an organized cluster of storms quite fast. This cluster crosses the W-English Channel and affects SW-UK during the second part of the night, where large hail will be well possible. In addition, low to mid-tropospheric winds strengthen over that region during the night to 15 m/s in the lowest 3 km. Elevated nature of storms should limit the overall severe wind gust threat, but we can't exclude the chance for stronger downdrafts to penetrate through the stable layer. Therefore strong to isolated severe wind gusts are also forecast. Heavy rain is possible over NW-France but confidence decreases for SW-UK due to the progressive nature of the cluster and its late arrival.

Edited May 25, 2017 by <<Ryan>>

[Mapantz]

.. just a few useless charts to be getting on with..

AROME:

 

ARPEGE:

 

DWD ICON:

 

WRF:

 

NETWX:

  

Saturday afternoon looks like a whole different ball game.

 

[Sparkiee storm]

8 minutes ago, Mapantz said:

.. just a few useless charts to be getting on with..

AROME:

 

ARPEGE:

 

DWD ICON:

 

WRF:

 

NETWX:

  

Saturday afternoon looks like a whole different ball game.

 

What did you mean by a whole different ball game for Saturday afternoon, in terms of what, could u clarify a bit please :)?

[MattTarrant]

3 minutes ago, Sparkiee storm said:

What did you mean by a whole different ball game for Saturday afternoon, in terms of what, could u clarify a bit please :)?

Saturday afternoon has a wider potential in terms of convective action. The instability runs NNE/NE during the day and may combine with respectable levels of CAPE (1500 +) to produce some impressive potential. The issue is as ever the cloud amounts, thus the level of diurnal heating achieved. A safe bet would be to say Midlands north. The attached image shows the CAPE values, East Anglia may have the highest values but as always depends on whether capping is broken. Using Sounding's closer to the time will help. 

[Mapantz]

2 minutes ago, Sparkiee storm said:

What did you mean by a whole different ball game for Saturday afternoon, in terms of what, could u clarify a bit please :)?

Well, CAPE levels increase through the Midlands and in to Eastern parts of the UK - some tasty ingredients! However, i'd take a stab at capping being a problem in these areas. All to play for due to a lot of uncertainties.

I wish w09 would make an appearance, very knowledgeable member when it comes to storms.

[Cheshire Freeze]

Just now, Mapantz said:

I wish w09 would make an appearance, very knowledgeable member when it comes to storms.

He was booted from the forum a while back.

 

[Cheshire Freeze]

@Mokidugwayis also excellent at the convective side of meteorology so maybe he could take up the mantle in here 

[A.J]

2 minutes ago, CreweCold said:

@Mokidugwayis also excellent at the convective side of meteorology so maybe he could take up the mantle in here 

*ahem* cough cough....lol.......I haven't done a storm forecast for a while......I think I might have to dip my toe tomorrow 

[Cheshire Freeze]

Just now, ajpoolshark said:

*ahem* cough cough....lol.......I haven't done a storm forecast for a while......I think I might have to dip my toe tomorrow 

Oh and how could I forget AJ....

!!

 

[samadamsuk]

Hey all,

RE the cap, as usual I dont have any charts for the uk, so its a guessing game for me! Interested to know what the cinh cape forecasted is, and if theres any synoptic forcing, convergence etc that could possibly overcome this before the high based mcs trundles over us. Samos

[A.J]

3 minutes ago, CreweCold said:

Oh and how could I forget AJ....

!!

 

mind you, i've got it wrong often enough...ahahaha

[Cheshire Freeze]

1 minute ago, ajpoolshark said:

mind you, i've got it wrong often enough...ahahaha

I duno, you've always had it spot on for here when you've said I'll get nothing

[Thunderstruck]

Think a lot of nowcasting will need to be done over these next few days. Netweather now saying 0% chance of storms until Monday, when there is a 62% chance. Only yesterday it was saying 72% for Saturday. We shall see...

[knocker]

Saturday PM in the NW

[Raidan]

Everything crossed for the weekend hope something happens this time as was a bust for me last weekend...getting slightly excited when viewing charts reading members views etc could be a very good start to a week off work.

[Sparkiee storm]

27 minutes ago, MattTarrant said:

Saturday afternoon has a wider potential in terms of convective action. The instability runs NNE/NE during the day and may combine with respectable levels of CAPE (1500 +) to produce some impressive potential. The issue is as ever the cloud amounts, thus the level of diurnal heating achieved. A safe bet would be to say Midlands north. The attached image shows the CAPE values, East Anglia may have the highest values but as always depends on whether capping is broken. Using Sounding's closer to the time will help. 

 

24 minutes ago, Mapantz said:

Well, CAPE levels increase through the Midlands and in to Eastern parts of the UK - some tasty ingredients! However, i'd take a stab at capping being a problem in these areas. All to play for due to a lot of uncertainties.

I wish w09 would make an appearance, very knowledgeable member when it comes to storms.

Okay, thank you both.

Hope things will fall into place properly for most of us wanting a good proper storm though, in terms of the capping as you said being broken etc  

[SenlacJack]

17 minutes ago, CreweCold said:

@Mokidugwayis also excellent at the convective side of meteorology so maybe he could take up the mantle in here 

No offence to Moki intended but is he really ?  As much as I often appreciate his posts on various topics he's never struck me as being the 'go to' source for convective weather outlooks.

[Flash bang flash bang etc]

I'm currently in Florence after a few days over in Rome, and my personal storm shield is working overtime sending anything with rain or even cloud in it over to Greece...

Can't complain too much though - lovely weather for discovering city gems! However, as a storm enthusiast I would have expected something over the course of a week - and the only positive thing meteorologically-speaking is a small chance of a 'spot of thunder-showers' on Saturday.

Anyway... my main point for posting is the chances for storms over the central and south east from the UK heat surge this weekend - which I'm gathering is Monday night (but that's using google's weather forecast - which I really don't trust).

Having been away for a few days now and not wanting to depress myself with model watching what are the chances of a late bank-holiday breakdown overnight on Sunday? If this is likely then there is a good chance I'll be home and ready to head out in the early hours on midday for a spot of local chasing... and it would be a welcome event after a week in europe's very own 'storm alley' with absolutely nothing!

[Cheshire Freeze]

Just now, SenlacJack said:

No offence to Moki intended but is he really ?  As much as I often appreciate his posts on various topics he's never struck me as being the 'go to' source for convective weather outlooks.

You'd be surprised. I thought the same. However I've seen him post outside of NW and he would blow you away with his understanding. Seriously.

[Supacell]

Some of the charts I am seeing on Lightning Wizard are quite impressive for Saturday. If this was not still over a day away then I would be getting very excited about now. Charts below show impressive CAPE, deep layer shear, precipitation and parcel layer depth overlapping. If this does happen to come together, and is not scuppered by cloud or the ridge being too strong then this has the potential to bring severe thunderstorms across the Midlands and all of N England, this after a night of frequent lightning across the SW and Wales. Estofex charts for Saturday show hail up to 6cm in diameter!

The following two are showing supercell parameter and tornado parameter at just midday!

Charts courtesy of www.lightningwizard.com/maps

I have also just watched the Met Office forecast online and they are talking about intense thunderstorms with heavy rain, hail, gusty winds and frequent lightning.

I just hope this does come together.

 

[samadamsuk]

Well im none the wiser after looking at loghtning wizards chards. There is a cap in place, but there is also some hefty vorticity advection at 600mb - if the cap can pop it looks like deep layer shear is healthy and some very interesting helicity in the region of 200 m2 plus in the mix - significant tornado parameters reflect this. Wish I had more time to look at the synoptic scale features if there is a trough moving in - ah well, id still be none the wiser! Samos

[Chris.R]

 Wondering whether I might be close enough to get the edge of the elevated stuff on Friday night as well. Wish I was camping in Holyhead again.