Convective/Storm Discussion Thread - 8th July onwards

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Wed 19 Jul 2017 - 05:59 UTC Thu 20 Jul 2017

ISSUED 21:00 UTC Mon 17 Jul 2017

ISSUED BY: Dan

... MORNING ELEVATED THUNDERSTORMS ...

Scattered elevated thunderstorms may be ongoing at the beginning of this forecast period, mainly over northern England. Through Wednesday morning these should continue to move northwards into southern Scotland by midday, but probably with a decaying trend since the main axis of instability by these latitudes will have shifted east to the North Sea. Nonetheless, some lightning will still be possible across Scotland, but probably not as active as areas farther south earlier in the morning.

... AFTERNOON / EARLY EVENING SURFACE-BASED THUNDERSTORM POTENTIAL ...

Attention then turns to the warm sector where warm, moist low level airmass will reside and subject to strong heating should sufficient breaks develop in any cloud cover. Surface troughing and low-level wind convergence beneath the upper trough, combined with diurnal heating, may allow isolated surface-based thunderstorms to develop, which would be capable of large hail and localised flash flooding - the focus for these being primarily in a zone from the West Country - Midlands - E England. In general, would prefer better shear but an upgrade to SVR may be possible here - though very much dependent on if any surface-based convection can develop on Wednesday afternoon / early evening given probably large amounts of cloud.

... REPUBLIC OF IRELAND / NORTHERN IRELAND ...

Eastern portions of the Republic of Ireland and into Northern Ireland could also see a few heavy showers and / or thunderstorms on Wednesday afternoon / early evening, ahead or along the eastwards-moving cold front.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-19

[Gordon Webb]

3 minutes ago, Summer Sun said:

Day 2 Convective Outlook

VALID 06:00 UTC Wed 19 Jul 2017 - 05:59 UTC Thu 20 Jul 2017

ISSUED 21:00 UTC Mon 17 Jul 2017

ISSUED BY: Dan

... MORNING ELEVATED THUNDERSTORMS ...

Scattered elevated thunderstorms may be ongoing at the beginning of this forecast period, mainly over northern England. Through Wednesday morning these should continue to move northwards into southern Scotland by midday, but probably with a decaying trend since the main axis of instability by these latitudes will have shifted east to the North Sea. Nonetheless, some lightning will still be possible across Scotland, but probably not as active as areas farther south earlier in the morning.

... AFTERNOON / EARLY EVENING SURFACE-BASED THUNDERSTORM POTENTIAL ...

Attention then turns to the warm sector where warm, moist low level airmass will reside and subject to strong heating should sufficient breaks develop in any cloud cover. Surface troughing and low-level wind convergence beneath the upper trough, combined with diurnal heating, may allow isolated surface-based thunderstorms to develop, which would be capable of large hail and localised flash flooding - the focus for these being primarily in a zone from the West Country - Midlands - E England. In general, would prefer better shear but an upgrade to SVR may be possible here - though very much dependent on if any surface-based convection can develop on Wednesday afternoon / early evening given probably large amounts of cloud.

... REPUBLIC OF IRELAND / NORTHERN IRELAND ...

Eastern portions of the Republic of Ireland and into Northern Ireland could also see a few heavy showers and / or thunderstorms on Wednesday afternoon / early evening, ahead or along the eastwards-moving cold front.

http://www.convectiveweather.co.uk/forecast.php?date=2017-07-19

looks like tonight could be the best chance for most in England as tomorrow could possibly be inhibitied by a lot of cloud

[Windblade]

Morning guys and girls,

There seems to be continuity in the forecasts for overnight imports tonight which is good news. Not going to get my hopes up (only for them to be let down) until I actually see things kick off and move towards me on the radar later, but with any luck a lot of us will see some decent multi cell storms this evening in the south east. Tomorrow looks good for other parts of the country. Good luck to all. 

Edited July 18, 2017 by Windblade

[Harry]

7 minutes ago, Windblade said:

Morning guys and girls,

There seems to be continuity in the forecasts for overnight imports tonight. Not going to get my hopes up (only for them to be let down) until I actually see things kick off and move towards me on the radar later but with any luck a lot of us will see some decent multi cell storms this evening in the south east. Tomorrow looks good for other parts of the country. Good luck to all. 

Very sensible @Windblade

There is a wholesale disagreement across key models this morning, based on my reading.

NMM 5K model and NetWx SR models are very prominently favouring the SW/ C/ W Midlands/ Wales regions, with very little if nothing for eastern parts.

The UKMO invent model is producing virtually no thunderstorms this evening, but sends a batch NE up the Channel grazing the far SE.

The GFS and Euro4 model going for something much more widespread across southern parts, with initial storms across the SW before developing more widely further East.

I'm going to try and maintain some sanity and only pop in here sparingly through today. It is clearly going to be one of those nights where it's anyone's game. This is clear by the broad risk areas shown on forecasts issued by @Nick F, @staplehurst and the MetO. I would suggest similar uncertainty exists for tomorrow (daytime) but for it seems very unlikely there'll be thunder anywhere east of Hereford, south of the M4 and west of IoW to Lincoln.

Edited July 18, 2017 by Harry

[Windblade]

2 minutes ago, Harry said:

Very sensible @Windblade

There is a wholesale disagreement across key models this morning, based on my reading.

NMM 5K model and NetWx SR models are very prominently favouring the SW/ C/ W Midlands/ Wales regions, with very little if nothing for eastern parts.

The UKMO invent model is producing virtually no thunderstorms this evening, but sends a batch NE up the Channel grazing the far SE.

The GFS and Euro4 model going for something much more widespread across southern parts, with initial storms across the SW before developing more widely further East.

I'm going to try and maintain some sanity and only pop in here sparingly through today. It is clearly going to be one of those nights where it's anyone's game. This is clear by the broad risk areas shown on forecasts issued by @Nick F, @staplehurst and the MetO.

Hey Harry, how are you?

Thanks for the update. I think that's the best thing to do, try not to get too excited/hopeful but if anything does kick off sit back and enjoy it.  I'm fairly confident the south/ southeast coast will see some action (even if its out to sea) but not sure how far inland things will travel.

Edited July 18, 2017 by Windblade

[Azazel]

Looked like the action could arrive quite early for me if the Met office forecast video is anything to go by. Showed storms on the south coast by 3pm, spreading north shortly thereafter. Hope I'm either at work or have made it home and not caught out in the rush hour.

[Harry]

Just now, Windblade said:

Hey Harry, how are you?

Thanks for the update. I think that's the best thing to do, try not to get too excited/hopeful but if anything does kick off sit back and enjoy it. 

I'm good mate, ta. Hope you are also. Dreading the sticky trains this evening.

While it is obviously clear that the main humid air is not here yet, it already feels increasingly warm and vaguely humid outside, with gorgeous Ac fields evident this morning. I suspect come home time it will be a little more "phwoar"

[Summer Sun]

30 minutes ago, Gordon Webb said:

looks like tonight could be the best chance for most in England as tomorrow could possibly be inhibitied by a lot of cloud

Yes could be a disturbed night for some if the storms arrive during the night

[BrickFielder]

1 hour ago, Nick F said:

Thinking that storms could arrive across SW England as early as late morning / early afternoon. Already storms off Brittany. A look at the 00z Brest radiosonde ascent shows plenty of mid-upper level instability, warm / dry nose 800-950mb keeping convection well elevated.

 

  I was thinking much the same thing. Satellite imagery to me looks like it is lifting the trough out slightly quicker than modelling suggests. It could bring storms to the south west earlier than forecast.  The lobe of Vorticity out over the Bay of Biscay does not have quite the tail to the south that I was expecting.  Think it is definitely a case for now casting while still bearing in mind that 9 times out of 10 the models get it right. Will probably wait to have a look at the 06 modelling.

[tomp456]

Declaring a bust at 9:13 am.

Just can't see a storm happening near the west sussex coast 

 

This is of course reverse psychology.

Bring on the storms.  

[richep]

Regarding storms, the bbc are terrible at forecasting them.

[tomp456]

1 minute ago, richep said:

Regarding storms, the bbc are terrible at forecasting them.

Agreed. 

It's fake news. 

 

Can't remember the last time they got a storm forecast right! 

[Chris K]

1 minute ago, tomp456 said:

Agreed. 

It's fake news. 

 

Can't remember the last time they got a storm forecast right! 

To be fair they are presenting a broad risk area for the storms - It's not worth taking the rainfall locations literally as shown on the map.

 

Considering there are still disagreements within the key models, there is still plenty of uncertainty, as always.

Edited July 18, 2017 by Chris K

[Methuselah]

3 minutes ago, richep said:

Regarding storms, the bbc are terrible at forecasting them.

Along with everyone else aye, they are...But, at the end of the day, who can pinpoint the precise location for storm development, 12 hours into the future?

[tomp456]

2 minutes ago, Chris K said:

To be fair they are presenting a broad risk area for the storms - It's not worth taking the rainfall locations literally as shown on the map.

 

Considering there are still disagreements within the key models, there is still plenty of uncertainty, as always.

True.... the computers haven't got a clue what is going to happen! 

[Nick L]

1 minute ago, Chris K said:

To be fair they are presenting a broad risk area for the storms - It's not worth taking the rainfall locations literally as shown on the map.

 

Considering there are still disagreements within the key models, there is still plenty of uncertainty, as always.

And this is the source of many people's frustrations and tantrums when they don't get storms. I think some expect a mass of thunderstorms affecting most people in that area. That's not how it works unless you get a messy clusterf***. 

The BBC, the Met Office, the SPC in the US - they all highlight a broad area of risk. In the case of the US, they can put a storm/tornado watch for several times the area of the UK, and 99% of places will see nothing!

Although the insistence of the Met Office and BBC of calling thunderstorms "thundery showers" does my nut in

[Nick L]

Just now, tomp456 said:

True.... the computers haven't got a clue what is going to happen! 

That's not true at all though is it? 90% of the time they have an excellent grasp of the broad area. The computing power required to pin point exact cells is utterly enormous and unrealistic to expect.

Edited July 18, 2017 by Nick L

[Gordon Webb]

15 minutes ago, BrickFielder said:

  I was thinking much the same thing. Satellite imagery to me looks like it is lifting the trough out slightly quicker than modelling suggests. It could bring storms to the south west earlier than forecast.  The lobe of Vorticity out over the Bay of Biscay does not have quite the tail to the south that I was expecting.  Think it is definitely a case for now casting while still bearing in mind that 9 times out of 10 the models get it right. Will probably wait to have a look at the 06 modelling.

The lobe of Vorticity out over the Bay of Biscay does not have quite the tail to the south that I was expecting

If I may ask what's the implication of this ?

[Nick L]

Dew point is surging here. 10c at dawn and now it's 16c. Sticky sticky sticky!

[jamesthemonkeh]

2 minutes ago, Nick L said:

The computing power required to pin point exact cells is utterly enormous and unrealistic to expect.

One day it will happen!  Didn't the JMA release something quite detailed and localised for Japan last year?  I could be wrong.

And does anyone have a link to the AROME precipitation model?  I have a link to 10pm tonight but think there is a 24 hour run?

[Nick L]

Just now, jamesthemonkeh said:

One day it will happen!  Didn't the JMA release something quite detailed and localised for Japan last year?  I could be wrong.

And does anyone have a link to the AROME precipitation model?  I have a link to 10pm tonight but think there is a 24 hour run?

There are models in the US that are incredibly high resolution and sometimes they do get them bang on, but other times they are hopeless. The Euro4 can pick out individual cells just about in its hourly precip rate, but I can't say its accuracy or consistency is great.

[Marcus_surfer]

Good luck everyone today! It looks good for southwestern areas, but i reckon the heaviest thundery activity will be midlands/northern england/south scotland as we go into wednesdays early hours. Just my thoughts.

[Paul Sherman]

7 minutes ago, Nick L said:

That's not true at all though is it? 90% of the time they have an excellent grasp of the broad area. The computing power required to pin point exact cells is utterly enormous and unrealistic to expect.

Yh Nicks correct here! And a few points to make as well!

1. This Plume was forecasted last Thursday which would be a Day 6 Highlight Area on the SPC - Now thats pretty damn accurate

2. There are computer models that CAN predict 12 hours in advance (HRRR) in the States

3. You simply cannot even compare this model with UK models for the fact it is sooooo much easier predicting 12 hours beforehand in a Continental Climate as opposed to our little Island which has a body of water between us and where the Plume is coming from.

Its totally unfair and I think the models have done a GOOD job at predicting this plume

[philglossop]

That's a strong gusty SE wind here at the moment. Good to see storms over Lorient and Carnac but looking at that storm in the channel at the mo. Seems to heading our way but with Torbays name on it.

[Harry]

28 minutes ago, BrickFielder said:

  I was thinking much the same thing. Satellite imagery to me looks like it is lifting the trough out slightly quicker than modelling suggests. It could bring storms to the south west earlier than forecast.  The lobe of Vorticity out over the Bay of Biscay does not have quite the tail to the south that I was expecting.  Think it is definitely a case for now casting while still bearing in mind that 9 times out of 10 the models get it right. Will probably wait to have a look at the 06 modelling.

Thanks for the update @BrickFielder

Two queries;

1. What do your red and green zones represent on the marked up satellite image?

2. "9 out of the 10 models get it right".....any models in particular I should put more faith into as they are very disparate at the moment