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Storm & Convective Discussion - 7th August Onwards

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Staying down in looe Cornwall for the week and have just been treated to a distant storm moving towards Plymouth 

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16 minutes ago, wimblettben said:

Are you sure its not fireworks as there can be some this time of year?

If it is lightning, then I do wonder what may come as I no there is suppose to be a risk tonight but its not great.

May be too far inland here anyway. 

Nope a proper high level thunderstorm. The radar was interesting as well. 

 

We we had a shower of biblical levels of rain at 7pm before this little beauty started about 835pm. 

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Day 2 Convective Outlook

VALID 06:00 UTC Mon 05 Nov 2018 - 05:59 UTC Tue 06 Nov 2018

ISSUED 17:02 UTC Sun 04 Nov 2018

ISSUED BY: Dan

No areas have been issued for this forecast period because the risk of lightning is considered very low, below our 5% threshold. However, there is still some potential convective interest. 

As the sharp upper trough digs across Iberia, on the forward side continued gradual warm air advection is likely from the nearby Continent and across southern and eastern Britain. Mid-level lapses will steepen, which combined with the passage of a northward-moving shortwave (arriving late afternoon over the English Channel, and reaching Shetland towards Tuesday morning) will encourage some elevated convection to develop during the evening and night hours, spreading northwards - generally from the Isle of Wight to Cumbria, and points east of there. Weak instability and rather saturated profiles suggests lightning is rather unlikely, but some showery bursts of rain will be possible.

http://www.convectiveweather.co.uk/forecast.php?date=2018-11-05

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Day 2 Convective Outlook

VALID 06:00 UTC Tue 06 Nov 2018 - 05:59 UTC Wed 07 Nov 2018

ISSUED 21:25 UTC Mon 05 Nov 2018

ISSUED BY: Dan

A complicated upper pattern exists on Tuesday, with an upper low over the Pyrenees weakening allowing elements of upper forcing to be drawn northwards across the British Isles on the forward side of the main Atlantic upper trough. At the same time, the next Atlantic upper trough will pivot such that it becomes more negatively-tilted as it crosses Biscay on Tuesday night into SW England by Wednesday morning. 

Through Tuesday daytime, elements of elevated convection from mid-level instability release will produce some sporadic bursts of showery rain across some central and eastern parts of the British Isles - but similar to Monday, the risk of lightning is considered very low (below 5%), and hence no threat level has been issued.

A series of frontal zones will provide pulses of occasionally heavy rain northwards over Ireland and western Britain throughout this forecast period, which may produce some localised sporadic lightning, but the vast majority will probably remain lightning-free at this point.

The main interest is during Tuesday evening and night as stronger upper forcing approaches, overlapping warm, moist low-levels (and atop warm SSTs), helping to generate 400-700 J/kg CAPE. Cyclogenesis is also expected to occur close to or over SW England, encouraging a wrap-around occlusion to develop. Given this environment, an increase in lightning activity seems likely amongst a rather messy precipitation pattern. Strong gusts of wind and hail up to 1.5cm in diameter will be possible with the most intense cells, while an isolated tornado cannot be ruled out. There is a risk of localised flooding where convergence zones develop across SW England and/or west Wales, providing prolonged heavy downpours.

http://www.convectiveweather.co.uk/forecast.php?date=2018-11-06

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Day 2 Convective Outlook

VALID 06:00 UTC Wed 07 Nov 2018 - 05:59 UTC Thu 08 Nov 2018

ISSUED 21:48 UTC Tue 06 Nov 2018

ISSUED BY: Dan

Main Atlantic upper low remains to the west of the British Isles during this period, but with a succession of shortwaves / impulses running northeastwards on the forward side to provide episodes of stronger forcing and hence some convective interest.

On Wednesday morning, pulses of showery rain will be affecting SW England and S Wales, with the potential for some isolated to sporadic lightning, especially close to windward coasts. During Wednesday daytime and evening hours, most of the lightning activity will likely be reserved for the English Channel where cold air atop warm SSTs will generate 500-800 J/kg CAPE. Southwesterly steering flow will serve to push these heavy showers into S / SE England for a time during the afternoon / early evening, before ridging aloft results in a gradual decay in shower activity here during Wednesday night. A SLGT has been introduced where there is a reasonable chance for some sporadic lightning activity.

On Wednesday night, a strongly-forced convective band (occlusion on FSXX) will develop and move across Ireland and the Celtic Sea, towards west Wales and SW England during the latter stages of the night. While some guidance suggests a transition to more dynamic precipitation may occur, given the strongly-sheared environment, warm SSTs and abundance of CAPE, some broken line segments seem possible, with sporadic lightning in places. There are subtle differences among NWP as to the timing of this feature, but nonetheless some squally winds would be possible with the most intense cells.

http://www.convectiveweather.co.uk/forecast.php?date=2018-11-07

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Day 2 Convective Outlook

VALID 06:00 UTC Fri 09 Nov 2018 - 05:59 UTC Sat 10 Nov 2018

ISSUED 20:49 UTC Thu 08 Nov 2018

ISSUED BY: Dan

The main interest during this forecast period will be during Friday evening and night as the next Atlantic frontal system sweeps across the British Isles. Upper forcing coupled with a strong low-level wind field ahead of, and marked wind veer along, the frontal boundary will be favourable for some elements of line convection to develop on the rear side of the precipitation envelope. In general, profiles look very saturated which combined with weak instability will significantly limit the potential for lightning - though a few isolated strikes cannot be ruled out. Main threat will be squally winds and bursts of heavy rain.

The post-frontal environment will then see cold air advecting over warm seas, generating 400-700 J/kg CAPE. Scattered showers will move across Ireland initially, and then other southern and western coasts of Britain late on Friday night. Some sporadic lightning and gusty winds will be possible, along with hail up to 1.5cm in diameter. 
 
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Day 2 Convective Outlook

VALID 06:00 UTC Sat 10 Nov 2018 - 05:59 UTC Sun 11 Nov 2018

ISSUED 21:46 UTC Fri 09 Nov 2018

ISSUED BY: Dan

Atlantic upper low slowly drifts towards western Ireland during Saturday, maintaining a feed of cold mid-levels atop warm seas around the British Isles, steepening lapse rates and generating 400-800 J/kg CAPE. Numerous showers are likely over open water, these then moving inland to exposed southern and western areas. Organised troughs / occlusions will push showers well-inland at times, and where such features become aligned with the steering flow may result in consecutive showers training over similar areas and hence the potential for localised surface water flooding - particularly southern coastal counties of England, but such convergence lines may extend well-inland too.

 

Forecast profiles look rather saturated at times, which combined with limited shear may reduce the lightning potential somewhat. Nonetheless, a low-end SLGT has been issued for S / SE England and adjacent English Channel for sporadic lightning at various times during this forecast period. Some lightning also seems likely over the Celtic Sea, and close to the coasts of SW England and S + W Wales - this area may require an upgrade to SLGT if confidence on coverage improves. In either case, hail up to 1.5cm in diameter and gusty winds will be possible from the most intense cores.

http://www.convectiveweather.co.uk/forecast.php?date=2018-11-10

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Could be a decent show in the eastern part of the channel at the moment. 

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Day 2 Convective Outlook

VALID 06:00 UTC Sun 11 Nov 2018 - 05:59 UTC Mon 12 Nov 2018

ISSUED 21:16 UTC Sat 10 Nov 2018

ISSUED BY: Dan

Broad upper low continues to slowly migrate from the Atlantic towards Ireland, the associated cold mid/upper-levels atop warm SSTs steepening lapse rates and generating 400-800 J/kg CAPE. Once again numerous showers will develop over open seas, then transferring inland to exposed southern and western coastal counties, and occasionally well-inland as organised troughs / occlusions swing through.

Given lack of any notable shear, both SLGTs should be treated as low-end to highlight areas where periods of better forcing may exist - the main interest for S / SE England will be on Sunday morning, whereas for the Irish Sea this is mainly Sunday evening and overnight. In both cases, the most intense cells may produce hail up to 1.5cm in diameter, accompanied by gusty winds. Showers training over the same areas could produce some localised flooding.

http://www.convectiveweather.co.uk/forecast.php?date=2018-11-11

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Well today's small thunderstorm was the first since May here - that's how bad this year has been! Nevertheless, an rPm setup in November very rarely doesn't give thunder at some point in this neck of the woods. 

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Woken at 630am to some shot gun thunder and a nice monsoon style spell of rain.Two or three further more distant rumbles and flashes followed.

SE LONDON.

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Active thunderstorms in the Irish sea now

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Couple of rumbles of thunder from a cell which is over Plympton/Ivybridge way. 

 

Nice start to a Monday

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Just had a big dumping of hail and a couple of nearby lightning strikes just North of Bristol 😍

Edited by Chris K

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that is potent storm going off over the cotswolds right now - can see it building from oxford.

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Out of reach.....distant convecting storm clouds moving to the NE.... East of Birmingham

 

IMG_3431.thumb.JPG.9073799355e6ef6588ea66df7c35b878.JPG

Edited by Arnie Pie
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