Storms and Convective Discussion - 20th April 2019 onwards

[Chris.R]

GFS 6Z Quick glance at raw data seems weird to me. A double peak plume. 

[Harry]

7 minutes ago, Chris.R said:

GFS 6Z Quick glance at raw data seems weird to me. A double peak plume. 

The Low that will be anchored to SW and the High to the NE will inevitably wobble about, which bring in waves of at times slightly fresher/drier air (whether continental or maritime). This will mean that ‘plume’ airmass will occasionally get squeezed. What this could mean however is that with each wobble we could see a number of rounds of storms (possibly severe) right through next week.

If the current weather patterns hold it could be a potentially very memorable period indeed and (without too much exaggeration) serious for some! 

 

Edited June 21, 2019 by Harry

[lizzieloo202]

That storm in Hinckley (Burbage) really impacted my folks. They had to have lots of roof tiles replaced, the car was swiftly put into the garage so wasn't badly damaged. 

My mum is petrified about next week, she hates storms now 

Edited June 21, 2019 by lizzieloo202

[BrickFielder]

 Still a bit early to be looking at too much detail for Sunday into Monday, but there are a few points which we can think about ahead of a more detailed look.

The first thing to look at is where the low level moisture and heat is coming from for the UK. It looks to me like the low level air is coming from deep within the continent over Germany. This direction of wind is not known for particularly moist air, although with the amount of thunderstorms recently in this region the moisture should be there.

The next thing to look at is the mid level lapse rates which really don't really start to increase until Sunday evening and into the night. This means convection will struggle to reach the heights needed for a thunderstorm until the best daytime heating is over.

Looking at the forecast SkewT's for that period then I can see an elevated mixed layer towards the east of the Country which only just reaches the UK after convection can be rooted in the boundary (Nice lightning show but limited thunderstorm severity). Further west shows a bit more of a maritime air flow but is more saturated all the way up (Messy convection without discreet storms, limiting storm severity). Wind sheer looks to be significant Sunday evening , so super cell development is possible ,but without convection rooted in the boundary layer you wont really have an updraft region again limiting thunderstorm severity.

Conditions for thunderstorms on Monday look better with steeper lapse rates, and convection rooted in the boundary layer, but wind sheer has begun to drop away significantly.

What this shows is that timing is very critical to the severity of storms and small changes in the speed of the approaching low pressure and jet streaks make a big difference. This is why looking at high thunderstorm indications three days before hand is often considered Fantasy Land forecasting.If past modelling performance is any guide then we should expect convective potential to move a little eastwards and speed up, which would probably increase the severe thunderstorm risk but move it eastwards. Current modelling suggest we will get thunderstorms but it might be a close miss for a more severe thunderstorm (OK maybe there is a insy winsy tiny window)(Dew points above 16C are usually questionable for the UK )

[Mapantz]

This mornings 03Z run on the UKV looks interesting for Southern areas of England on Monday night. 

Edited June 21, 2019 by Mapantz

[TJS1998Tom]

Just watched this video by Met Office and the way they describe the possibility of these storms are interesting by saying intense beasts compared to what we've seen recent weeks. Radar watching this week could be eventful 

 

 

Edited June 21, 2019 by TJS1998Tom

[The PIT]

Two flashes of lightning here would be a beast these days.

Anyway local forecast by met has one of those wonderful conflicting forecasts with some rain late Sunday dry Monday and a light shower possible Tuesday yet a yellow warning for severe storms for all those days.

 

[Summer Sun]

Day 4 Convective Outlook

VALID 06:00 UTC Mon 24 Jun 2019 - 05:59 UTC Tue 25 Jun 2019

ISSUED 15:50 UTC Fri 21 Jun 2019

ISSUED BY: Dan

On Monday morning, elevated thunderstorms may be ongoing in a zone from Ireland across the Irish Sea to NW England and the north Midlands. This will continue to lift northwards into southern Scotland as the day progresses.

In its wake, strong surface heating of a very warm, moist low-level airmass may occur, yielding strong instability. Forecast profiles look very warm with depth, suggesting there may be too much of a cap to allow surface-based convection to occur. However, there is a risk of isolated thunderstorms developing on Monday afternoon, particularly across the Midlands and/or eastern England. Where these do occur, hail and flash flooding may be problematic.

Scattered showers and a few thunderstorms will also be possible over parts of Northern Ireland and the Republic of Ireland on Monday afternoon / early evening in the post-frontal environment - although here instability will likely be weaker.

On Monday evening, a shortwave over Biscay combined with isentropic upglide as a renewed pulse of very warm, moist low-level air advects north/northwestward will resulting in destabilisation of increasing mid-level instability. As a result, scattered elevated thunderstorms are likely to develop close to NW France and expand in coverage as they migrate across the Channel Islands / English Channel towards southern England during Monday night. There is some uncertainty as to the exact track these thunderstorms may take, ultimately related to the exact shape of the upper pattern and therefore the direction of the (bifurcating) steering flow. 

This extended outlook provides an overview of the most likely forecast evolution during this forecast period - destabilising plume events are often fraught with uncertainty, and it is very likely certain aspects of the forecast will change as the event draws closer. However, provided guidance continues to remain relatively consistent, upgrades to higher threat levels are possible in future outlooks.

http://www.convectiveweather.co.uk/forecast.php?date=2019-06-24

[The PIT]

All eyes down for Saturday 12 oz me thinks and again for Sundays 12oz. Recent trends dictate that we won't see any storms but one day we've got to get one here. Still love to know what has changed to kill activity here. Has the urbanization to the south of us grown enough to reduce moisture or is just a natural temporary blip?

Edited June 21, 2019 by The PIT

[Thunder and Lightning]

1 minute ago, The PIT said:

All eyes down for Saturday 12 oz me thinks and again for Sundays 12oz. Recent trends dictate that we won't see any storms but one day we've got to get one here. Still love to know what has changed to kill activity here. Has the urbanization to the south of us grown enough to reduce moisture or is just a natural temporary blip?

I dont know but UKMO obviously seems to be going for 'violent' storms  . Generally the GFS hasn't been the model promising the most storms.  

[The PIT]

Just now, MetWeather said:

I dont know but UKMO obviously seems to be going for 'violent' storms  . Generally the GFS hasn't been the model promising the most storms.  

We also know that storms have also broken out away from areas showing the best cape so even with the best computer models it's still a case of nowcasting. I think storm predicting is even harder than telling when snow is going to fall or not.

[Thunder and Lightning]

5 minutes ago, The PIT said:

We also know that storms have also broken out away from areas showing the best cape so even with the best computer models it's still a case of nowcasting. I think storm predicting is even harder than telling when snow is going to fall or not.

I agree because thunderstorms are more convective and in shower form and snow is generally frontal

[Flash bang flash bang etc]

I’m hoping to see lots of pre-event cloudscapes like this

 

[Thunder and Lightning]

I feel   because the most severe threat looks to be to the west and I live in the East!!  

[Thunder and Lightning]

depressed*

[Flash bang flash bang etc]

10 minutes ago, MetWeather said:

depressed*

That’s why Henry Ford invented the internal convection engine

Edit: to chase storms, I mean

Edited June 21, 2019 by Flash bang flash bang etc

[Andy Pepler]

On 19/06/2019 at 09:53, Harry said:

How did my mate’s dad’s video do for the Fb ratings in the end @Andy Pepler?

500 likes 39 shares lol

[StormLoser]

I know it is early yet, but I don't suppose the charts show the usual ridge of intense high pressure residing around Reigate during unstable weather? It's quite small, about 3 miles across.

Curious to know what next week will bring....   

[Thunder and Lightning]

36 minutes ago, Flash bang flash bang etc said:

That’s why Henry Ford invented the internal convection engine

Edit: to chase storms, I mean

Yes good Idea, always wanted to chase storms in UK, Thursday might be the day!

[TJS1998Tom]

Sunday certainly looking interesting for some storms over night, could be a good light show

[Flash bang flash bang etc]

19 minutes ago, MetWeather said:

Yes good Idea, always wanted to chase storms in UK, Thursday might be the day!

I’ve asked for Tue, Weds and Thurs off - just waiting for confirmation

So tricky when no information is present about which days will offer the best potential

[Another Kent clipper]

25 minutes ago, Flash bang flash bang etc said:

I’ve asked for Tue, Weds and Thurs off - just waiting for confirmation

So tricky when no information is present about which days will offer the best potential

My four days off have fallen on yesterday, today, tomorrow, and Sunday!  

... however, having just checked the GFS, tue-wed-thu are already scaled down for Cape from what they were. Can't speak for other charts

Edited June 21, 2019 by Another Kent clipper

[Zak M]

CAPE values now downgraded

[Ben Sainsbury]

22 minutes ago, Another Kent clipper said:

My four days off have fallen on yesterday, today, tomorrow, and Sunday!  

... however, having just checked the GFS, tue-wed-thu are already scaled down for Cape from what they were. Can't speak for other charts

That is for SB CAPE and not ML CAPE as we're likely to see more elevated storms rather than surface based.

[ChezWeather]

2 minutes ago, zmstorm said:

CAPE values now downgraded

What did you expect? they were absolutely through the ceiling, showing values that chasers in the heart of Tornado Alley would be happy to see!

 

 

Edited June 21, 2019 by ChezWeather