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Convective / Storm Discussion Thread - 31st May 2017 onwards


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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Brief hail shower here at Heathrow. Same line of showers that stretches along M4 corridor, sferics currently on cells over Wiltshire.

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Posted
  • Location: Hawkhurst (TN18) Kent
  • Weather Preferences: All weather extremes
  • Location: Hawkhurst (TN18) Kent

Hail shower passed here a short while ago, heard a distant rumble of thunder after it had passed

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Posted
  • Location: on a canal , probably near Northampton...
  • Weather Preferences: extremes n snow
  • Location: on a canal , probably near Northampton...

Incredibly strong winds round the storms over Northamptonshire, large branches down everywhere and quite dangerous driving conditions.

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Posted
  • Location: Cirencester
  • Weather Preferences: Supercells
  • Location: Cirencester

Hey all, 

Nice views of that cell near oxford.from Cirencester - could see the anvils streaming off earlier in the jet. Samos

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Posted
  • Location: Ampney Crucis, Nr. Cirencester
  • Location: Ampney Crucis, Nr. Cirencester

T&L here, only 4 rumbles so far. Very impressive convection this afternoon.

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Posted
  • Location: Hoyland,barnsley,south yorkshire(134m asl)
  • Weather Preferences: severe storms,snow wind and ice
  • Location: Hoyland,barnsley,south yorkshire(134m asl)

Explosive developments in Wales on the last few radar returns:)

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Posted
  • Location: Watford, Hertfordshire, 68.7m ASL
  • Weather Preferences: Humid Continental Climate (Dfa / Dfb)
  • Location: Watford, Hertfordshire, 68.7m ASL

Just spotted this tiny bit of mamatus on that Heathrow hail shower.

image.jpeg

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Posted
  • Location: Bedfordshire 33m above mean sea level
  • Weather Preferences: Snowy and thundery.
  • Location: Bedfordshire 33m above mean sea level

Not amazing pics, but they are anvils of storms that are missing me. 

 

WP_20170606_18_36_35_Pro.jpg

WP_20170606_18_39_25_Pro.jpg

WP_20170606_18_39_49_Pro.jpg

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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

Any thoughts about tomorrow? Low centred just west of Ireland and some storm potential?

CAPE LI 07-06-17.png

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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

Day 2 Convective Outlook

VALID 06:00 UTC Thu 08 Jun 2017 - 05:59 UTC Fri 09 Jun 2017

ISSUED 21:15 UTC Wed 07 Jun 2017

ISSUED BY: Dan

A complex pattern on Thursday with a broadscale upper trough slowly migrating eastwards across Ireland thence the British Isles later and overnight into Friday. Several areas of possible thunderstorms exist...

... IRELAND / NORTHERN IRELAND ...

Behind the frontal wave / occlusion on Thursday morning, cloud breaks should allow better insolation to occur. Given cold air aloft courtesy of upper trough and steep mid-level lapse rates, 600-900 Jkg-1 CAPE will be present provided there is sufficient post-frontal heating, with dewpoints in the 11-14C range. As a result, scattered showers and thunderstorms are expected to develop across portions of Ireland, moving NE-wards and expanding in coverage with time.

Deep convection that occurs earlier on in the afternoon will benefit from 20-30kts DLS (this generally reducing through the afternoon as the upper trough moves overhead) helping to aid some organisation, which given the degree of instability may produce hail of 2.0-2.5cm in diameter - such a risk therefore warrants the issuance of a SVR threat area, although worth stressing that perhaps only 1 (or even 0) reports of hail this size may occur. Given some reasonable cross-model agreement, and convective parameters likely in place, an upgrade to MDT may also be required across northern portions of Ireland into southern Northern Ireland - but some uncertainties exist at present over extent of cloud cover from earlier frontal wave.

... SE WALES / GLOCS to LINCS ...

Low-level convergence, perhaps along the cold front, during the afternoon hours may aid the development of scattered showers, running NE-wards with time along the front. Instability is marginal, but given falling heights aloft and reasonably-steep mid-level lapse rates in a strongly-sheared environment (30-40kts DLS) a low-end SLGT has been issued for some sporadic lightning activity.

... SE ENGLAND ...

During the evening hours, forced ascent will likely help destabilisation of the plume residing over France / BeNeLux. While the bulk of any notable thunderstorms (with prolific lightning) will remain over the nearby Continent and adjacent southern North Sea, a few thunderstorms could develop close to or over SE England and close to the coast of East Anglia - subject to some (W-E) positional errors given the spread in NWP guidance at present. This area may need revising (either expanded or removed) depending on developments during Thursday.

... CELTIC SEA to SW WALES / SW ENGLAND ...

During the evening and night hours, an increase in deep convection coverage is expected over the Celtic Sea spreading eastwards towards SW Wales and SW England as the upper trough and associated steep mid-level lapse rates migrate east over relatively warm SSTs. 20-30kts DLS should aid in some cell organisation, and lightning coverage seems worthy of a SLGT.

http://www.convectiveweather.co.uk/forecast.php?date=2017-06-08

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Posted
  • Location: Norwich, Norfolk, East Anglia
  • Weather Preferences: Sunny, stormy and I don't dislike rain only cold
  • Location: Norwich, Norfolk, East Anglia

Ah nice, thats pretty close to what I was thinking for the UK. Apart from some capping in places I think that any storm that do fire over the continent will be pretty severe, given high CAPE values and some strong deep layer shear. Good luck for the Kent clipper.

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Posted
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67
  • Weather Preferences: Winter - snow, Irish sea convection. Summer - thunderstorms, hot sunny days
  • Location: Pemberton, Wigan, 54 M ASL. 53.53,-2.67

800 J/kg CAPE and -3 LI showing for my area tomorrow afternoon on the 18z, nice. 

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Posted
  • Location: Lincoln, Lincolnshire
  • Location: Lincoln, Lincolnshire

00z looks very interesting for storm activity and heat, of course it's a fair distance away but it would be nice if it came off ;)

00z.png

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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Storm & Convective Forecast

convmap_080617_png_pagespeed_ic_OBQLf5WPys.thumb.png.6371e4e8861342375404f9adfbbcaefc.png

Issued 2017-06-08 12:17:39

Valid: 08/06/2017 12z to 09/06/2017 12z

DAY 1 CONVECTIVE / STORM FORECAST - 8TH JUNE 2017

Synopsis

Two upper vortices/lows are present over the far N Atlantic on Thursday, one just east of New Foundland will dig SE over the NW Atlantic, the other further east will move in across Ireland this evening and UK tonight. At the surface, a low pressure system to the west of Ireland will slide east to be across Scotland by 00z Friday, associated frontal system moving NE will bring rain NE across northern and western areas on Thursday, cold front clears east across Sern UK this afternoon, an unstable showery flow follows cold front across Ireland and western UK this afternoon, cold front clearing SE UK early hours Friday

... EIRE / N. IRELAND ...

Behind cold front now moving E over Wales and SW England, an increasingly unstable SWly flow will follow, as lapse rates steepen from the west in response to upper vortex/low and associated colder air aloft spreading east. GFS shows 400-800 j/kg CAPE this afternoon/early evening across EIRE/N. Ireland as colder/drier aloft spreads atop moist airmass (dew points of 12-14C) combined with surface heating in sunny spells. This will support increasingly heavy showers and thunderstorms which will spread NE. 30-40 knot 500mb SWly flow and 20-30 knt deep layer shear will tend to organise storms into linear or bowing line segments, capable of producing large rainfall totals in a short space of time leading to flash-flooding. Also there could be some isolated marginal large hail (up to 1 inch) in some of stronger storms, given fairly large CAPE values indicated, though weak shear will tend to limit this risk. Also, low LCLs (Lifted Condensation Level) and low dew point spread combined with some locally enhanced low-level shear may support isolated brief tornado / waterspout with more bouyant updrafts. 

... SW ENGLAND, WALES, NW ENGLAND and SW SCOTLAND ... 

Cold front may produce sufficient lift for some shallow convection which may locally produce isolated lightning, heavy rainfall and gusty winds. Also post front, steepening lapse rates from the west will promote some modest instability with late afternoon / early evening surface heating to support scattered heavy showers and isolated thunderstorms. No severe weather is expected from these. These showers and storms may continue into the night near coastal areas.

... SE ENGLAND ...

Low level convergence and surface heating of moist airmass ahead of the cold front and the front itself moving from the west may support some heavy showers and isolated thunderstorms later this afternoon and into the evening. Some hail and localised flooding is possible with any of this activity. Although this activity may ease for a time, further showers with isolated lightning may arrive from the west later in the night

Edited by Nick F
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Posted
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)
  • Location: Caterham-on-the-hill, Surrey, 190m asl (home), Heathrow (work)

Quite a few sferics over Ireland now, line convection along cold front crossing Wales and SW England atm. though no sferics as yet, probably too shallow convection for charge separation.

1335.thumb.JPG.37da79c365021268142a5a10bdd4ff4f.JPG

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Posted
  • Location: Birmingham, Harborne 160 asl
  • Weather Preferences: Columus Bigus Convectivus
  • Location: Birmingham, Harborne 160 asl

yep..the line that Nick has pointed out looks to be heading our way.....the extra bit of cape over the area might just spark them into life......fingers crossed

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