End of the week & weekend storm risk

[Stormyking]

1 hour ago, tomjwlx said:

Storm risk isn't great across the south this weekend however it's looking interesting further north and west. 

Latest run looks pretty good to me if you ask me mate, Saturday night and evening sunday night shows a heavy cluster of Showers/storms moving up from the South South East, i think anywhere along the South and South West coast could be in a chance for some Elevated stuff, but again will have to wait and see as its still all up and down.

 

The stuff across the North and West does look very interesting though

[Arnie Pie]

Looking good for some activity over the weekend... more importantly are Mondays forecast for this area which looks to be giving us a clear opportunity of recording  Mercury`s transit across the face of the Sun.

13 years since the last transit....so a relatively rare event to catch

https://britastro.org/transit2016

Good luck to all for the coming days activity

Edited May 5, 2016 by Arnie Pie

[Staffordshire]

I'm meant to be in Leeds this weekend but I could travel back home to Lichfield if the potential is better, can anyone give me some guidance on where they think the potential will be better as I will realistically have to make the decision by tomorrow about 2pm

[William Grimsley]

22 minutes ago, Staffordshire said:

I'm meant to be in Leeds this weekend but I could travel back home to Lichfield if the potential is better, can anyone give me some guidance on where they think the potential will be better as I will realistically have to make the decision by tomorrow about 2pm

Most likely the best for elevated thunderstorms will be across Devon and Cornwall with most surface based thunderstorm more towards the Midlands, N England and N Wales.#

On another note, a few signs of instability starting to appear in the skies now with lots of Cirrus cloud in the sky. Looking at Sat24, you can see lots of instability showing (Altocumulus Castellanus cloud) moving NE from the Bay of Biscay up towards SW England and C S England, something to watch.

Edited May 5, 2016 by William Grimsley

[cheese]

27 minutes ago, Staffordshire said:

I'm meant to be in Leeds this weekend but I could travel back home to Lichfield if the potential is better, can anyone give me some guidance on where they think the potential will be better as I will realistically have to make the decision by tomorrow about 2pm

Looking at the NMM model, Lichfield would stand a better chance of getting something, but there's a high risk in Yorkshire as well, particularly on Sunday. Obviously there is no guarantee that a storm will occur in either location.

[William Grimsley]

5 minutes ago, cheese said:

Looking at the NMM model, Lichfield would stand a better chance of getting something, but there's a high risk in Yorkshire as well, particularly on Sunday. Obviously there is no guarantee that a storm will occur in either location.

To be honest, I think there's more chance that you'll see a thunderstorm in SW England over the coming days than anywhere else, especially as the convection will be mid-level and we have more shear to go with down here. The thunderstorms in SW England will be more organised and widespread though not as severe. However, on the other hand, even though most thunderstorms that do occur further north and east will be severe, they will be very few and far between.

I know which option I'd take.

Edited May 5, 2016 by William Grimsley

[Frosty hollows]

I know what CAPE is, but what's wind shear, how is it measured and what part does it play in storms? Sorry, if this is very basic and if I should be somewhere else to ask this.Thanks

[Convective]

6 minutes ago, Frosty hollows said:

I know what CAPE is, but what's wind shear, how is it measured and what part does it play in storms? Sorry, if this is very basic and if I should be somewhere else to ask this.Thanks

Essentially, the difference in speed and direction the wind is blowing at the different levels in the atmosphere. The greater the shear, the more likely storms are to become multicellular or tornadic, overall increasing the likelihood of severe storms. Although, many other factors need to be in place such as high dewpoints and decent lapse rates in order to sustain deep convection as the shear blows if off centre.

First potential looking to be tomorrow evening as sustainable storm conditions push out of France and into the south coast. Can't wait to take a closer look and make the first forecast of the year! Very slim risk of an isolated shower over the West Midlands tomorrow afternoon, too.

Edited May 5, 2016 by Convective

[Harry]

12 minutes ago, William Grimsley said:

To be honest, I think there's more chance that you'll see a thunderstorm in SW England over the coming days than anywhere else, especially as the convection will be mid-level and we have more shear to go with down here. The thunderstorms in SW England will be more organised and widespread though not as severe. However, on the other hand, even though most thunderstorms that do occur further north and east will be severe, they will be very few and far between.

I know which option I'd take.

Not seeing that at the moment, William.

Yes there is a potential for storms in a number of areas but current thinking is that thunderstorms are likely to be isolated rather than widespread (so I agree with you there) however the energy and instability is markedly higher further E and N of the SW. Thunderstorms in my view are most likely across the Midlands, Wales and NW England. Rain is more likely in the SW but less likely to be electrified (I'm simply not seeing enough instability here compared to other areas at this stage).

 

[William Grimsley]

Just now, Harry said:

Not seeing that at the moment, William.

Yes there is a potential for storms in a number of areas but current thinking is that thunderstorms are likely to be isolated rather than widespread (so I agree with you there) however the energy and instability is markedly higher further E and N of the SW. Thunderstorms in my view are most likely across the Midlands, Wales and NW England. Rain is more likely in the SW but less likely to be electrified (I'm simply not seeing enough instability here compared to other areas at this stage).

 

Not sure how you're not seeing that? There's quite a bit of mid-level instability moving in right now overhead! It's unlikely to be just rain, most likely thundery showers at least!

[AWD]

Perhaps I'm missing the point here but surely the focal point of any potential convective activity will be along the upper wind vectors over the weekend.

Thus I would have the convective activity focusing on a SSE - NNW profile from say Hampshire, West Sussex up towards Oxfordshire, Wiltshire, Cotswolds and up into the West Midlands, East Wales & NW  England.

Cape values and lifted indices look most favourable in this broad area and whilst other areas, such as SW England, East Midlands and SE England will have their chance too, I feel factors such as solar heating and mid level shear will prohibit much more than the typical UK "thundery shower" scenario, i.e. a couple of rumbles of Thunder and its over.

We will see though, UK thunderstorm activity is always hard to profile and never plays out exactly like NWP output forecasts.

Edited May 5, 2016 by AWD

[Frosty hollows]

4 minutes ago, Convective said:

Essentially, the difference in speed and direction the wind is blowing at the different levels in the atmosphere. The greater the shear, the more likely storms are to become multicellular or tornadic, overall increasing the likelihood of severe storms. Although, many other factors need to be in place such as high dewpoints and decent lapse rates in order to sustain deep convection as the shear blows if off centre.

First potential looking to be tomorrow evening as sustainable storm conditions push out of France and into the south coast. Can't wait to take a closer look and make the first forecast of the year! Very slim risk of an isolated shower over the West Midlands tomorrow afternoon, too.

Thank you!

[William Grimsley]

Just now, AWD said:

Cape values and lifted indices look most favourable in this broad area and whilst other areas, such as SW England, East Midlands and AS England will have their chance too, I feel factors such as solar heating and mid level shear will prohibit much more than the typical UK "thundery shower" scenario, i.e. a couple of rumbles of Thunder and its over.

That's good enough for me!

[cheese]

There's a Europe-wide view of the WRF-NMM model, which goes out to 120 hours..

It looks different to the UK version but I think it's because this one is more detailed? Not sure. 

[Harry]

4 minutes ago, AWD said:

Perhaps I'm missing the point here but surely the focal point of any potential convective activity will be along the upper wind vectors over the weekend.

Thus I would have the convective activity focusing on a SSE - NNW profile from say Hampshire, West Sussex up towards Oxfordshire, Wiltshire, Cotswolds and up into the West Midlands, East Wales & NW  England.

Cape values and lifted indices look most favourable in this broad area and whilst other areas, such as SW England, East Midlands and SE England will have their chance too, I feel factors such as solar heating and mid level shear will prohibit much more than the typical UK "thundery shower" scenario, i.e. a couple of rumbles of Thunder and its over.

We will see though, UK thunderstorm activity is always hard to profile and never plays out exactly like NWP output forecasts.

Agreed

3 minutes ago, cheese said:

There's a Europe-wide view of the WRF-NMM model, which goes out to 120 hours..

It looks different to the UK version but I think it's because this one is more detailed? Not sure. 

This is what I'm basing some of my analysis on as I have limited access to MUCAPE charts.

[Rickoza]

Quick question.  Here in Motherwell, just south-east of Glasgow, we've been almost completely starved of storms for a good number of years now.  Set to continue, or should we cop one over the weekend?

[Harry]

6 minutes ago, William Grimsley said:

Not sure how you're not seeing that? There's quite a bit of mid-level instability moving in right now overhead! It's unlikely to be just rain, most likely thundery showers at least!

Have you got any pics??

I'd be surprised if they were true AcCas, only on the basis that you don't often see these under marginal instability...and as far as I am aware, there is little or no instability around our shores until tomorrow evening at the earliest.

[Mapantz]

Looks like a dodgy period of weather coming up.. 

 

[Harry]

1 minute ago, Mapantz said:

Looks like a dodgy period of weather coming up.. 

 

OMG I was about to say that is a pretty good forgery...only to see that it is actually on the MetO website!!!!!

[William Grimsley]

10 minutes ago, Harry said:

OMG I was about to say that is a pretty good forgery...only to see that it is actually on the MetO website!!!!!

Where? I can't see it anywhere.

Re your other post, there is no Altocumulus Castellanus cloud in the area at the moment.

[timeless]

its gone now, but l did receive a snow warning to my email.. was laughing my ass off thinking how unlikely it would be for snow considering how warm its been..

tho l would prefer the snow over thunderstorms.. not looking forward to the possibility..

[William Grimsley]

1 minute ago, timeless said:

tho l would prefer the snow over thunderstorms.. not looking forward to the possibility..

You gotta be kiding, right?

[Greeny]

17 minutes ago, Convective said:

Essentially, the difference in speed and direction the wind is blowing at the different levels in the atmosphere. The greater the shear, the more likely storms are to become multicellular or tornadic, overall increasing the likelihood of severe storms. Although, many other factors need to be in place such as high dewpoints and decent lapse rates in order to sustain deep convection as the shear blows if off centre.

First potential looking to be tomorrow evening as sustainable storm conditions push out of France and into the south coast. Can't wait to take a closer look and make the first forecast of the year! Very slim risk of an isolated shower over the West Midlands tomorrow afternoon, too.

 

13 minutes ago, Frosty hollows said:

Thank you!

Just to add if I may, the last few convective days have been within a weak sheared environment. This means that storms can fire and intensify rapidly however the updraft, usually at the rear of a storm sucking in moisture and heat is quickly cut off by the cold air downdraft at the front of the cell. Giving storms a pulse like effect. Intensifying and then decaying within a short timeframe. The fuel is basically cut off by the downdraft. However get some strong shear in the mix, the storm then tilts seperating the updraft from the downdraft, the updraft can continue to fuel the storms getting more and more intense. Get both strong speed shear and directional shear, storms can begin to rotate with the presence of a mesocyclone. These storms become supercells. Not only can they last for hours, they can in turn produce strong tornados, giant hail, strong RFD (rear flank downdraft) and strong winds.

[William Grimsley]

@Greenday, what do you think for us? I know you got it right last time (2014). XD

[Harry]

8 minutes ago, William Grimsley said:

Where? I can't see it anywhere.

Re your other post, there is no Altocumulus Castellanus cloud in the area at the moment.

It was either a hack or simply a computer error I'm guessing...funny though