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Storms and Convective Discussion - 20th April 2019 onwards

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  At low levels we have moisture advection from out in the bay of Biscay whilst the fringes of the jet stream run across the south at high levels. At the surface we have a number of convergence zones which look to spark off convection.

  Steering winds and winds aloft suggest to me a possibility of back building convection which could give rise to localized flooding. With temperatures at best reaching around 16 degrees we should not expect very strong updrafts, but rear flank downdrafts and outflow boundaries could provided conditions for an isolated more potent storm.

  Forecast skewT's even from a conservative view could produce more instability than suggested by models, but there does seem to be very moist mid levels which could make convection messy.

  Overall cloud tops look somewhat limited, so we should not expect widespread thunderstorms and wind shear although having some directional shear at the very lowest level is pretty weak. Strong winds aloft may also shut down convection as tops shoot ahead of convection. Instability through the zero degree isotherm looks quite strong which could help to sustain some moderate hail.

  Slight chances of thunderstorms with main risks being hail and localized flooding.With very slack winds at the surface there is always the chance of some localized anomalies especially with a south feed of moisture (perhaps a hint of a low level jet on some charts as well). Something to keep a close eye on with an outside chance of a more severe isolated storm.

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moistureadvection.png

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Posted (edited)

Now that was an impressive flash of lightning, and good clap of thunder! 🌩️⛈️

Hailstones as well now! Storm almost right overhead! :yahoo:

 

964EAAEF-4626-4A82-8475-2B01396BA89E.png

32F509EE-0A74-411F-A423-7871CDF63165.png

Edited by Dangerous55019
Forgot to add lightning strike images

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 Wow! Just been woken up by loads of lightning alarms. Wasn’t expecting this today. Hopefully it holds together. 

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Rumbles in Shrewsbury from a couple of cells south of the town. 

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No thunder here but some pretty heavy hail which was starting to lead to a covering.

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I do believe I just heard two rumbles of thunder. And it's just started raining

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Just now, Summer of 95 said:

I do believe I just heard two rumbles of thunder. And it's just started raining

No-it's hail!

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1 minute ago, Summer of 95 said:

I do believe I just heard two rumbles of thunder. And it's just started raining

We are sort of in a ring of developing showers/cells... the most powerful is north of town. Have had rumbles in the town from one to the south though. 

No rain in the TC so far though....

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Posted (edited)

Had some heavy rain earlier but no lightning closer than 30 km for a while. There does seem to be more around 30–40 km now though. I see steering winds are only around 10 kM/H which isn’t good. 

Edited by Chris.R

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We seem to be under a convergance zone atm with a strong cell to the north of brum looking as if its backbuilding

worth keeping an eye on

IMG_8255.thumb.jpg.10fb40c8062f24178f6bad64f0cd8c87.jpg

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Posted (edited)

Heavy showers passing here but nothing sparky.

Temp 7c

Edited by Polar Maritime

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Heavy downpour with the odd bit of thunder and lightning at Birmingham International! ⚡

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Posted (edited)

Just heard thunder with lightning to my East..

Edited by Polar Maritime

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30 minutes ago, Flash bang flash bang etc said:

Builders?

Thunder and lightning.

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Posted (edited)

Wow! I had thrown in the towel long ago but  just had a cell electrify  unexpectedly as it hit land. One strike and a heavy shower. Not bad, definitely more instability than WRF says. 

Edited by Chris.R

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Day 2 Convective Outlook

VALID 06:00 UTC Sat 11 May 2019 - 05:59 UTC Sun 12 May 2019

ISSUED 20:13 UTC Fri 10 May 2019

ISSUED BY: Dan

Upper trough axis will be over the North Sea and Germany on Saturday, placing the British Isles on the rear side (and hence forward side of the approaching upper ridge). Residual cool air aloft, dry mid-levels and heating of moist low-level air, combined with orographic forcing and low-level convergence, will help generate a few scattered showers during the day, capable of a few sporadic lightning strikes and some hail in the most intense cells. There may also be a few funnel clouds.

In terms of lightning, the greatest risk appears to be over SE England, and to a lesser-extent over the Pennines and points southeast from there - a couple of low-end SLGTs have been introduced to better highlight the main areas of interest. Any showers/storms that do form will generally decay during the evening hours as daytime heating subsides, though may persist a little longer over the East Midlands as a PV filament slides southeastwards across the area.

http://www.convectiveweather.co.uk/forecast.php?date=2019-05-11

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Does the PV stand for Positive Vorticity?

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Loud crash of thunder this afternoon, the loudest thunder that I have heard since 2007

 

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19 minutes ago, Greeny said:

Does the PV stand for Positive Vorticity?

Potential Vorticity

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

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Posted (edited)
8 hours ago, Flash bang flash bang etc said:

Look at that rotation at 2:16 😮😮😮

I noticed that, what  caused that? 

Edited by Weather-history

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Sun's out.. Looks good for a few hefty showers today 

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