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Convective/Storm Discussion Thread - 1st August onwards

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Evening all. Just back in from a little stormwatch stroll watching the south coast cluster of storms gingerly work its way up the M3 towards me. There is some fantastic lightning tonight, it's as good, if not better, than some of the summer thunderstorms we've had in the last few years. Starting to hear more frequent thunder now I'm back in the house and the lightning is now more clearly visible, which must mean its close (I live on a street that backs onto a thick tree line; any view westward is atrocious, so being able to see lightning now is a very good sign).

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feel sorry for my friends hen party in the new forest, not sure what they are doing but they were right under some great action in the last hour. 

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Get on this y’all. Thunder is getting louder 

 

 

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got some nice anticipation going, looks like it's about 30 mins away from Reading as it stands. 

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Piddling down outside now, lightning brighter, thunder louder, partner scared, cat not bothered. Standard thunder evening.

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2 minutes ago, Robert Lewis said:

got some nice anticipation going, looks like it's about 30 mins away from Reading as it stands. 

Can you see any lightning from Reading? We have lightning very close by now, within a few miles. You should be able to see something. 

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2 minutes ago, Paul Roberts said:

Can you see any lightning from Reading? We have lightning very close by now, within a few miles. You should be able to see something. 

i'm going to pop out the front and look south west as the action looks to be moving a bit more to the west of my location based on the current lightning mapper.

Looks like Basingstoke might get something out of this wave that's out to your south at the moment. More east than what's currently moving by.

Edited by Robert Lewis

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Day 2 Convective Outlook

VALID 06:00 UTC Sun 22 Apr 2018 - 05:59 UTC Mon 23 Apr 2018

ISSUED 21:51 UTC Sat 21 Apr 2018

ISSUED BY: Dan

... SHETLAND ...

Remnant elevated convection associated with destabilising plume over the North Sea could bring a high-based thunderstorms over or to the east of Shetland on Sunday morning - low confidence on lightning activity precludes the issuance of a SLGT.
 
... EAST ANGLIA ...
Ahead of a SE-moving cold front, diurnal heating will allow 500-800 J/kg CAPE to be generated. Forecast profiles suggest a cap will exist around 950mb, but provided there is sufficient insolation combined with breeze convergence then a few heavy showers or thunderstorms will be possible during the 2nd half of the afternoon. 40-50kts (fairly uni-directional) DLS would allow cells to become well-organised, capable of producing hail up to 1.5cm in diameter and local wind gusts 40-50mph.
Greatest uncertainty exists over whether the cap can be eroded, with several model solutions not particularly keen on convective initiation - for now a low-end SLGT has been issued and trends will be monitored. Broad consensus would place Norfolk and NE Suffolk at greatest risk.
 
 

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Couple of cells firing to the west of the main stuff, which I'm surprised about, looks like there's still plenty of energy around.

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1 minute ago, Robert Lewis said:

i'm going to pop out the front and look south west as the action looks to be moving a bit more to the west of my location based on the current lightning mapper.

We have lightning to our west within 1-2 miles. Infact its very close by, just had some lightning and shotgun thunder. Have a look, you should easily see something. 

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New storms firing in lyme bay, from the south devon coast to weymouth....defo worth keeping an eye on NE of these to see how they develop!

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*UPDATE 22Z* to Thunderstorm Outlook covering tonight thru Sunday, as widespread thunderstorms spread NE across England overnight before clearing Sunday morning. More thunderstorms possible for SE Britain on Sunday afternoon.

Storm & Convective Forecast

Issued 2018-04-21 21:54:57
Valid: 21/04/2018 2200z - 23/04/2018 0600z

THUNDERSTORM OUTLOOK - DAY 1 UPDATE (SAT 21ST) & DAY 2 (SUN 22ND)

Synopsis

An upper trough moving will continue to move east into western Britain from Saturday night into Sunday, a shortwave trough moving NE on the forward side of the upper trough will bring a swathe of thunderstorms, locally strong, NE across parts of England tonight, before clearing NE into the N Sea Sunday morning. During Sunday, occluding cold front moving east ahead of low moving NE between Iceland and Scotland will bring a band of cloud and rain across country with cooler and more stable conditions of Atlantic origin following. However, warm, humid and unstable airmass will hang on across SE England and E Anglia into the afternoon, - which may trigger isolated thunderstorms with surface heating.

DAY 1 THUNDERSTORM OUTLOOK

Valid 21/2200z - 22/0600Z

stormmap_210418_22z.thumb.png.0547abc4469239b32c6872d42715e5bd.png

… N WALES, ENGLAND AND SE SCOTLAND TONIGHT …

* Risk of ...

hail (isolated large), strong wind gusts, flash-flooding, frequent cloud-to-ground lightning

Through the rest of the evening and overnight, increasing large scale ascent and cooling aloft from approaching Atlantic trough from the west interacting with WBPT plume advecting north across England will support scattered elevated thunderstorm activity. One area of scatteres storms will continue to affect N England which may drift NE into the Scottish Border region. Another more extensive area of storms, forming one or two MCS (mesoscale convective systems) will push NE across S England, Midlands, SE England, E Anglia,Lincs and Yorks - driven by a shortwave trough moving NE out of France noted on WV imagery through the day. These elevated storms may produce hail, strong wind gusts, localised flooding and frequent cloud-to-ground lightning. 

DAY 2 THUNDERSTORM OUTLOOK

VALID: 22/0600Z - 23/0600Z

stormmap_220418.thumb.png.2abfeeb4ab5f28f2c3921e22a5b812c0.png

... SE ENGLAND and E ANGLIA ...

*Risk of ...

Hail, flash-flooding, gusty winds and frequent lightning

Warm and humid airmass ahead of cold front moving in from the west will become unstable with surface heating in sunny spells aided by continued cooling aloft steepening lapse rates, surface breeze convergence ahead of approaching front the west combined with large scale ascent of approaching upper trough may support the development of a few thunderstorms with peak heating in the afternoon, provided there is some sunshine. 30-40 knots of deep layer shear, strong SWLy flow aloft and 300-600 j/kg CAPE may allow storms to organise, perhaps strong enough to bring some isolated large hail, localised flash flooding, gusty winds and with LCLs lower than today, a brief funnel or weak tornado can't be ruled with storms forming or crossing along wind shift.

Issued by: Nick Finnis

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Heard my first thunder from the cells pepping up in West Yorkshire,might Be worth keeping an eye on?

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just did a sweep, saw three flashes and some lightning, not all the thunder was reaching us, then just as i went away managed to catch something on my phone. It's closing in gradually but not very intense.

Think i'm seeing the stuff that's just south of Burghfield Common right now.

Edited by Robert Lewis

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Looks like it's really getting going west of Horsham right now and got much quieter off the cell that battered the south coast and mainly Southampton earlier on.

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Thunder here in East Leeds.

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15 minutes ago, Nick F said:

*UPDATE 22Z* to Thunderstorm Outlook covering tonight thru Sunday, as widespread thunderstorms spread NE across England overnight before clearing Sunday morning. More thunderstorms possible for SE Britain on Sunday afternoon.

Storm & Convective Forecast

Issued 2018-04-21 21:54:57
Valid: 21/04/2018 2200z - 23/04/2018 0600z

THUNDERSTORM OUTLOOK - DAY 1 UPDATE (SAT 21ST) & DAY 2 (SUN 22ND)

stormmap_210418_22z.thumb.png.0547abc4469239b32c6872d42715e5bd.png

… N WALES, ENGLAND AND SE SCOTLAND TONIGHT …

* Risk of ...

hail (isolated large), strong wind gusts, flash-flooding, frequent cloud-to-ground lightning

Through the rest of the evening and overnight, increasing large scale ascent and cooling aloft from approaching Atlantic trough from the west interacting with WBPT plume advecting north across England will support scattered elevated thunderstorm activity. One area of scatteres storms will continue to affect N England which may drift NE into the Scottish Border region. Another more extensive area of storms, forming one or two MCS (mesoscale convective systems) will push NE across S England, Midlands, SE England, E Anglia,Lincs and Yorks - driven by a shortwave trough moving NE out of France noted on WV imagery through the day. These elevated storms may produce hail, strong wind gusts, localised flooding and frequent cloud-to-ground lightning. 

Issued by: Nick Finnis

I'm not convinced that what we have just south of Reading is an MCS

Can you explain why it is an MCS, as to me CAPE values are nothing exceptional and lack of DLS and SRH values, result in lack in organisation and structure. Not to add the area of intense precipitation isn't completely huge and lightning activity isn't anything significant.

I'm open to learning, which is why I'm asking thanks!

Edited by Ben Sainsbury

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2 minutes ago, Ben Sainsbury said:

I'm not convinced that what we have just south of Reading is an MCS

Can you explain why it is an MCS, as to me CAPE values are nothing exceptional and lack of DLS and SRH values, result in lack in organisation and structure.

Yes, the vertical shear is not particularly strong, 20-30 knots, but the mid-upper flow is fairly strong and, combined with forcing from a shortwave trough, enough to organise storms into clusters forming a few convective systems IMO.

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18 minutes ago, TJS1998Tom said:

Tweet from UK Weather Updates

image.png

Yep just been out the front door watching a few sparks to the NE, thundery but nothing intense.

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anyone watching whats going on below Guildford, seems to be moving much more westerly than anything else happening tonight. Any reason for this?

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WOW! 85.png

Best storm I've ever experienced in my life, I live right in the center of the red zone and we've been getting back to back flashes, with full forks. The wind was pretty strong as well! Two storms in one day, the first was just a taste and then this one came along and left me speechless. 

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