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Storms and Convective Discussion - 25th June 2019 onwards


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4 minutes ago, Oliver Wyndham-lewis said:

Clouding over where I am south of London, few spots of rain and temperature has dropped significantly by nearly 3 degrees! 

 

1391E270-64A7-4FD4-9232-4CEC88AE2810.jpeg

West of London clouds building but the wind feels like a blast furnace compared to indoors. No lightning on the maps yet so I don't expect anything from this until later if it keeps building like the previous storms except this time it's inland building not over any water.

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You wait a lifetime for a funnel cloud and then two come at once!

A few from last night, just South of Salisbury. Mostly intracloud stuff, but an impressive light show none the less.  

Well that was a pretty awesome night. Although I cant help but feel slightly disappointed for not getting any SLR shots. And now I'm left wanting more and more ?. Anyway a very impressive light show w

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4 minutes ago, Ronnie said:

Sun and cloud here very hot, would love a storm today with lots of rain, veggie garden needs it. Tuesday's storm was great but hardly any rain. Don't think we are in the firing line today. I am new to this could someone explain to me what a cap is without being to technical please.

a cap basicly stops clouds towering and forming thunderstorms,i'm sure some one with better knowledge that me can explain better.found this 

Cap

(also called "Lid") A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability. However, if the cap is removed or weakened, then explosive thunderstorm development can occur. 

The cap is an important ingredient in most severe thunderstorm episodes, as it serves to separate warm, moist air below and cooler, drier air above. With the cap in place, air below it can continue to warm and/or moisten, thus increasing the amount of potential instability. Or, air above it can cool, which also increases potential instability. But without a cap, either process (warming/moistening at low levels or cooling aloft) results in a faster release of available instability - often before instability levels become large enough to support severe weather development.

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14:00 Update 

Added back in Northern England to the 70% Risk area. Thunderstorms have developed in an area around the Welsh Marches in what appears to be an area of 925mb, 850mb confluence (SSW winds over SW England and increasing SSE backing SE Winds over England) This confluence focusing the moisture within the western edge of the plume as it advects Northwards. These storms further developing as they move into NW England as the rest of the afternoon progresses. 

I now have something of a headache, The Hirlam 06Z has this area as the main area of development, EURO4 has the area to the east of Greenwich and the Arpege and AROME models are somewhere between. No one model is handling the plume completely correctly and its very complex thermodynamic structure and subtleties in Temperature, Dewpoint and Wetbulb. 

I like aspects of the HIRLAM, but suggest its probably overdoing the convection a little bit, I also think storms will fire in the plume over England during the afternoon, but it wont be until this evening that there is sufficient uplift, cooling and spin from the trough and the 925/850mb confluence zones will also be aligned to take advantage of the very high 20-23C Theta-W 850mb plume

image.png.5207d5a8793bad3ffdb1f1a33a0b6400.png

fromPJB UKWW

 

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9 minutes ago, Ronnie said:

Sun and cloud here very hot, would love a storm today with lots of rain, veggie garden needs it. Tuesday's storm was great but hardly any rain. Don't think we are in the firing line today. I am new to this could someone explain to me what a cap is without being to technical please.

John Hammond explains it well by using a bottle of Coke. If you imagine, the heating of the land is like shaking the bottle but the lid on the bottle is holding it all inside, this is the cap. If the cap weakens (by cooler air moving in over the top such as when a cold front approaches) or the temperature exceeds that necessary to break the cap then it is like taking that lid off the bottle. Boom! ? The longer that lid can hold, the more explosive it is, providing the lid comes off.

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8 minutes ago, Ndc Ozzie said:

a cap basicly stops clouds towering and forming thunderstorms,i'm sure some one with better knowledge that me can explain better.found this 

Cap

(also called "Lid") A layer of relatively warm air aloft, usually several thousand feet above the ground, which suppresses or delays the development of thunderstorms. Air parcels rising into this layer become cooler than the surrounding air, which inhibits their ability to rise further and produce thunderstorms. As such, the cap often prevents or delays thunderstorm development even in the presence of extreme instability. However, if the cap is removed or weakened, then explosive thunderstorm development can occur. 

The cap is an important ingredient in most severe thunderstorm episodes, as it serves to separate warm, moist air below and cooler, drier air above. With the cap in place, air below it can continue to warm and/or moisten, thus increasing the amount of potential instability. Or, air above it can cool, which also increases potential instability. But without a cap, either process (warming/moistening at low levels or cooling aloft) results in a faster release of available instability - often before instability levels become large enough to support severe weather development.

14 minutes ago, Ronnie said:

 I am new to this could someone explain to me what a cap is without being to technical please.

CIN https://en.wikipedia.org/wiki/Convective_inhibition  https://study.com/academy/lesson/convective-inhibition-cin-definition-role-in-forecasting.html http://www.theweatherprediction.com/habyhints3/905/ basically like a loaded gun the atmosphere is primed for thunderstorm development but with some areas seeing CIN (quite high in some areas) storms try to develop but dont manage to unless you have a trigger like a trough / front like we have today or convergence zones and sea breezes etc here is a chart for CIN values at 3pm (now) with moderate - high CIN values especially near the coasts nmm_uk1-23-7-0.thumb.png.a53f1f33e4b7cfaf9151fdb17fa7f321.png 

Edited by Kirkcaldy Weather
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Seems to be some showers developing in the channel that may have parts of the W country's name on it. We were just outside most warnings but unless steering winds start shifting it more east (or they fizzle out), they look to be heading this way later.

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Looks to me like the Met Office forecast is pretty good. We have showers already breaking out and there’s a reasonable chance of more substance coming soon.

Liverpool area looks interesting.

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Just now, Ndc Ozzie said:

yup looks like wrexham gonna have some fun and games very shortly

They already are by the look of it. Ah well...will have to make do with another dip in the pool, another beer then back to my air conditioned room for a spell...

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3 hours ago, james ley said:

I hope so  will be up all night watching think us wendoverians have a fair chance of something maybe later thisafternoon as well enjoy

Ahh wow another Wendovian! 

Ok I'll keep an eye out, I was going to take my little to the dairy today in castle park but it's too hot!

Thank you mate 

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