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Storms and Convective Discussion - 20th April 2019 onwards

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4 hours ago, Weather-history said:

I noticed that, what  caused that? 

It looks to me like it was almost a funnel, the scud briefly appears underneath and rotates too, but there’s not enough to develop properly. The cloud base was lowering too

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50 minutes ago, Flash bang flash bang etc said:

It looks to me like it was almost a funnel, the scud briefly appears underneath and rotates too, but there’s not enough to develop properly. The cloud base was lowering too

Interesting. Certainly something was afoot. 

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Crazy crazy hail storm here easily pea sized hail!!! 

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Suns out here, temp up to 15c, few showers moving in from the NW 

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Lots of convection going on around here today. I don’t think it’s gonna go bang for me, but I think it could well do for anyone east of me. :bomb:🌩️:oldgood:

B712764D-9595-4006-8099-5251CCBD822B.jpeg

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YES! i heard my first distant thunder of the year so far earlier! 🙂

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23 hours ago, Mapantz said:

Potential Vorticity

Can be deduced on relative vorticity charts, 850/925hPa

Thank you mate 👍

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Posted (edited)
15 hours ago, Weather-history said:

I noticed that, what  caused that? 

I suspect strong updrafts, you may have seen it but I took some footage of rotation in just a normal batch of dark clouds  heading to and building towards me. A total surprise, the day was nothing special stormwise. I will have to try and dig it up again.

Edited by Greeny

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10 hours ago, Greeny said:

I suspect strong updrafts, you may have seen it but I took some footage of rotation in just a normal batch of dark clouds  heading to and building towards me. A total surprise, the day was nothing special stormwise. I will have to try and dig it up again.

I have clipped out the section and it could be strong updrafts. Be interesting to see your footage

 

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Some potential this coming week perhaps ?

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1 hour ago, Biggin said:

Some potential this coming week perhaps ?

Friday looks pretty heroic on the Cape front.  Tomorrow, Monday and Tuesday don't look too shabby either.  But I'm only looking at Cape, I understand you also need shear, convergence, lift, cinnamon, nutmeg, and some wet bulbs to make a storm.

IMG_20190518_102422.png

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Day 1 Convective Outlook

VALID 06:00 UTC Sat 18 May 2019 - 05:59 UTC Sun 19 May 2019

ISSUED 06:05 UTC Sat 18 May 2019

ISSUED BY: Dan

Broad upper trough covers much of central and western Europe on Saturday. Provided sufficient cloud breaks develop, heating of a very moist low-level airmass will yield 100-200 J/kg CAPE. This combined with low-level convergence and orographic forcing will likely lead to scattered showers developing during the late morning / afternoon / early evening hours across many (largely inland) parts of England / Wales / S Scotland / Republic of Ireland.  Weak shear, meagre instability and a warm nose acting as a cap at 700mb suggests the risk of lightning is rather low, but ample low-level moisture and slow-moving nature of showers could lead to some localised surface water issues.

Showers will tend to weaken during the second half of the evening as daytime heating subsides. However, elevated instability will run northwards up the North Sea towards Shetland, and may produce some eleveated thunderstorms here late in the night towards Sunday morning. A small risk this may also affect parts of NE Scotland and Orkney.

http://www.convectiveweather.co.uk/forecast.php?date=2019-05-18

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Some intense showers forming north west of London.

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Looks a dead duck again today with cloud stopping most of any warming.

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Day 1 Convective Outlook

VALID 06:00 UTC Sun 19 May 2019 - 05:59 UTC Mon 20 May 2019

ISSUED 06:57 UTC Sun 19 May 2019

ISSUED BY: Dan

Broad upper trough covers the British Isles on Sunday, with a rather slack pressure pattern. Early in the forecast period some remnant elevated instability will pass close to Orkney and Shetland. Thereafter, provided there are sufficient cloud breaks, diurnal heating of the moist low-level airmass will yield 300-500 J/kg CAPE, with scattered showers likely to develop forced by low-level convergence and orographic forcing. As was the case on Saturday, weak steering flow (and hence weak shear) will lead to very slow movement of showers, bringing the risk of some local surface water flooding. 

 

Forecast profiles are slightly cooler aloft compared with Saturday (when a warm nose at 600-700mb limited convective depth) and so it seems plausible there is a greater chance of a few sporadic lightning strikes on Sunday - main focus will be central southern England where sufficient moisture pooling will likely occur late afternoon as sea breeze convergence meets inland convergence zone. A low-end SLGT has been introduced to better highlight the area of interest. However, lack of any notable shear and rather saturated profiles will tend to result in pulse-type convection with restricted buoyancy of air parcels - which may serve to reduce lightning potential. A couple of funnel clouds will be possible given low cloud bases and areas of low-level convergence.

http://www.convectiveweather.co.uk/forecast.php?date=2019-05-19

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Rain was forecasted for my area today. Haven't had a drop yet 🤨 

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The clouds building up look really ominous but not a drop of rain at all let alone anything more thundery.

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Posted (edited)

Day 2 Convective Outlook

VALID 06:00 UTC Mon 20 May 2019 - 05:59 UTC Tue 21 May 2019

ISSUED 20:57 UTC Sun 19 May 2019

ISSUED BY: Dan

Similar to the past few days, broad upper troughing covers the British Isles on Monday, with a slack surface pressure pattern. Diurnal heating of the moist low-level airmass will yield 300-500 J/kg CAPE, with scattered showers likely to develop forced by low-level convergence and orographic forcing. Weak steering flow will lead to slow movement of showers, bringing the risk of some local surface water flooding.

 

Forecast profiles are slightly cooler aloft compared with the weekend (when a warm nose at 600-700mb limited convective depth) and so convection may be somewhat deeper on Monday, and hence capable of producing a few sporadic lightning strikes - this perhaps more likely over southern England and / or the East Midlands. However, confidence of lightning activity is not particularly high given weak shear and skinny CAPE, and so refraining from introducing a SLGT at this stage. A couple of funnel clouds will be possible given low cloud bases and areas of low-level convergence.

 

Elevated instability will also exist over the North Sea, though this activity will likely weaken before approaching the Northern Isles on Monday evening. It could also get close to the coast of East Anglia for a time late morning / early afternoon Monday.

 

IMG_20190519_222344.png

http://www.convectiveweather.co.uk/forecast.php?date=2019-05-20

Edited by Another Kent clipper

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It is a bit tricky forecasting convective activity today and I am struggling a little bit to point to specific areas to watch for storms. The forecast charts show marked low level convergence zones from North Yorkshire to London and along the south coast and parts of Wales.

Looking at the forecast SkewT's for London then it becomes clear that weak mid level lapse rates are likely to limit cloud tops.

Looking at the forecast SkewT's for Cardiff then mid level lapse rates are even worse, but you can definitely see some drier air moving in to the upper mid levels.

Looking at the west midlands SkewT's then you can see similar problems with a cap at about 550hPa as that drier air starts to move in aloft.

Lightning Wizard cloud top charts suggest perhaps an area of extended cloud tops as that drier air aloft starts to move in.

What I am having particular difficulty with is steerage winds and although they are generally fairly light there appears to be a marked southward steerage across the midlands this morning below 650hPa. This is comparison to a generally steerage from the south west above that with very little movement below 700hPa apart from the midlands. This suggests to me that a strong convergence zone will setup along the south coast later.

Key area in my opinion is likely to be along the south coast between Southampton and Brighton from mid after noon. My confidence is not very high and weak mid level lapse rates are likely to prevent storms.

nmmukwind.png

sound-London-12.png

sound-London-18.png

sound-Caerdydd-Cardiff-12.png

sound-Caerdydd-Cardiff-18.png

sound-WestMidlands-12.png

gfs_el_eur18.png

gfs_pvort_eur18.png

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Day 1 Convective Outlook

VALID 06:00 UTC Mon 20 May 2019 - 05:59 UTC Tue 21 May 2019

ISSUED 10:17 UTC Mon 20 May 2019

ISSUED BY: Dan

UPDATE 10:17 UTC Low-end SLGT added to English Channel coast, where some localised flooding may be possible this afternoon / early evening

 

Similar to the past few days, broad upper troughing covers the British Isles on Monday, with a slack surface pressure pattern. Diurnal heating of the moist low-level airmass will yield 300-500 J/kg CAPE, with scattered showers likely to develop forced by low-level convergence and orographic forcing. Weak steering flow will lead to slow movement of showers, bringing the risk of some local surface water flooding.

 

Forecast profiles are slightly cooler aloft compared with the weekend (when a warm nose at 600-700mb limited convective depth) and so convection may be somewhat deeper on Monday, and hence capable of producing a few sporadic lightning strikes - this perhaps more likely over southern England and / or the East Midlands. However, confidence of lightning activity is not particularly high given weak shear and skinny CAPE, and so refraining from introducing a SLGT at this stage. A couple of funnel clouds will be possible given low cloud bases and areas of low-level convergence.

 

Elevated instability will also exist over the North Sea, though this activity will likely weaken before approaching the Northern Isles on Monday evening. It could also get close to the coast of East Anglia for a time late morning / early afternoon Monday.

 

http://www.convectiveweather.co.uk/forecast.php?date=2019-05-20&fbclid=IwAR1Sn7ZbHsgtrOSibWWsnIGmIvc-XL9m0PBYx9s3tR8JN-0igySqLubeO6k

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Signs of convection to the east of here. First time in quite a while I’ve seen skies like this here. 

129FB1CA-28C9-416F-AF00-CE57BAC20595.jpeg

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