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Convective/Storm Discussion Thread - 1st August onwards


Supacell

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

Wind gusts in excess of 60mph for some tonight along with a period of heavy rain and still no warnings from the met office

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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington
28 minutes ago, Summer Sun said:

Wind gusts in excess of 60mph for some tonight along with a period of heavy rain and still no warnings from the met office

And right on cue warnings are out

Between 21:00 Wed 4th and 09:00 Thu 5th

Westerly winds will bring gusts of 40-50 mph, and locally into 60s of mph. In addition, rain will be heavy at times, especially over northwest England and north Wales. Whilst this weather is not unusual for the time of year, it brings the potential for disruption to transport, tree damage and temporary power cuts.

An area of low pressure crossing northern UK overnight will bring a swathe of strong winds on its southern flank, clearing latest from eastern areas.

b16c9829-812e-4884-a691-c2471556f89e.thumb.png.c93bc63c8893c2002a7a377db2362417.png

https://www.metoffice.gov.uk/public/weather/warnings

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland

^^^^ wrong thread Gavin :)

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Posted
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.
  • Location: Derbyshire Peak District South Pennines Middleton & Smerrill Tops 305m (1001ft) asl.

Yes let's please keep this thread strictly for "Convective storm" discussion only. As Mapantz has pointed out there is already an unnamed storm thread open for tonight's offering..

Thanks.

Edited by Polar Maritime
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Posted
  • Location: Darlington
  • Weather Preferences: Warm dry summers
  • Location: Darlington

Storm Forecast
Valid: Wed 11 Oct 2017 06:00 to Thu 12 Oct 2017 06:00 UTC
Issued: Tue 10 Oct 2017 20:46
Forecaster: PUCIK

No threat levels have been issued.

SYNOPSIS and DISCUSSION

Synoptic scale situation will be dominated by a deep trough residing over much of eastern Europe, followed by a ridge over France, Germany and a trough affecting British Isles. These features will translate eastwards during the course of the forecast period. Despite seemingly active large-scale pattern, lack of either abundant lower tropospheric moisture and/or of steep mid tropospheric lapse rates will preclude any DMC risk over most of the forecast area. Two areas may see isolated, weakly electrified DMC.

The first one being the Northern Sea behind the cold front passing overnight towards Thursday morning. Marginal CAPE may build up in the core of the trough thanks to the steep lapse rates. Seemingly favourable synoptic scale forcing will occur along the cold front close to Denmark, in the left exit region of a jet-streak in the upper troposphere. Due to the lack of moisture, chances for strongly forced squall line seem quite low atm.

The second area with isolated DMC will be over the Ionian Sea with marginal CAPE on the order of hundreds J/kg under the base of the large trough.

http://www.estofex.org/cgi-bin/polygon/showforecast.cgi?text=yes&fcstfile=2017101206_201710102046_0_stormforecast.xml

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

Extended Forecast
Valid: Mon 16 Oct 2017 06:00 to Tue 17 Oct 2017 06:00 UTC
Issued: Sat 14 Oct 2017 18:59
Forecaster: TUSCHY

A level 1 was issued for parts of NE-Sweden und N-Finland mainly for severe wind gusts.

A level 1 was issued for parts of Ireland, UK and Scotland mainly for severe wind gusts.

SYNOPSIS

An extensive high pressure area with a pronounced positive 500 hPa geopotential height anomaly (compared to the 79-00 climatology) remains in place with a gradual drift to the east until 06 UTC. Weak waves circle that dome of high pressue but the lack of an overlap of ingredients precludes thunderstorm chances for most places.

DISCUSSION

... Ireland, W-UK and Scotland...

During the start, a powerful warm seclusion is placed west of the Bay of Biscay with an high-end near BL flow next to the center (850 hPa winds in excess of 50 m/s). Phase diagrams support the idea of an ongoing transformation from tropical to post-tropical during the forecast period although a deep warm-core could persist until this cyclone approaches Ireland during the day from the SW. Intense vertical shear likely results in an enhanced vertical tilt of the warm core betimes but baroclinic dynamics (including a coupled jet configuration) delay any rapid weakening. Numerical guidance still indicates the idea of extratropical transformation (e.g. development of a pronounced vorticiy advection couplet and rapidly increasing baroclinic gradients (fronts) in the surrounding area of the cyclone) but confidence in how fast this transformation occurs remains low.

Between 06UTC and 12 UTC, a surge of dry low-stratospheric air wraps cyclonically around the cyclone's center, probably ending the stage of a potential offshore sting jet event but with an ongoing cold conveyor belt jet event. This jet finally approaches Ireland beyond noon from the SW. This extreme wind field remains confined to the immediate region south of the center and probably avoid of deep moist convection. Hence no level assessment for this event. This scenario is dependant on how fast the extratropical transformation occurs but latest guidance continues to support the painted idea.

This surge continues during the day and the dry air at upper-levels circles the depression's center. Numerical guidance (especially limited area models) show the development of numerous vorticity filaments spreading N/NE. A rapid change of lift and subsidence accompanies this activity (similar to moats in tropical cyclones). In combination with the natural broadening of the depression's wind field during extratropical transformation, the overlap of dry air atop the warm/moist marine layer results in a broad area over E-Ireland, Scotland and W-UK with slim chances for enhanced convection (especially along the interface of the dry slot and the northward fanning warm conveyor belt) . A few convective-allowing models indicate an increase in convection during the noon/afternoon hours in the highlighted area.

Forecast soundings show low LCLs and intense LL shear (30 m/s 0-1 km shear and SRH-1 in excess of 400 m^2/s^2) . This is enough for rotating updrafts with an isolated tornado risk. The limited depth of the CAPE layer (up to 750 hPa) with the temperature in excess of 0°C probably keep the chance for lightning activity on the very low-end side due to lack of substantial graupel. Still a low probability lightning area was added for parts of the level 1, where best chances for sporadic lightning activity exist. Beside the tornado risk, downdrafts may bring severe wind gusts to the BL, which can occur well inland.

Right now the gradient wind risk will dominate the general severe risk and hence we will stay with a broad level 1 area for now. With respect to the further development of the hurricane and a potential delayed extratropical transformation (given current intensity boost to a major Cat.3 hurricane), a decrease or increase of convective probabilities is well possible. Please stay informed with your national weather agencies.

Elevated convection with a strong differential WAA regime occurs from the Bay of Biscay to UK and isolated thunderstorms are forecast. A strong inversion at 850 hPa should suppress downdraft momentum and hence limit the severe risk to near zero (excluding an isolated hail risk due to 400-600 J/kg MUCAPE and 20 m/s DLS). A few thunderstorms are also possible over Portugal, parts of Spain and N-Morocco. Heavy rainfall remains the main risk with this activity.

http://www.estofex.org/cgi-bin/polygon/showforecast.cgi?text=yes&fcstfile=2017101706_201710141859_1_extendedforecast.xml

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Posted
  • Location: South Norfolk, 44 m ASL.
  • Weather Preferences: Varied and not extreme.
  • Location: South Norfolk, 44 m ASL.
11 minutes ago, Andy Bown said:

What's with the thundery activity in Devon/ Cornwall!?

Instability ahead of the hurricane/extratropical windstorm.

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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)

Sferics kicking off now in the BOB ahead of Ophelia.

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

Day 1 Convective Outlook

VALID 06:00 UTC Sun 15 Oct 2017 - 05:59 UTC Mon 16 Oct 2017

ISSUED 20:53 UTC Sun 15 Oct 2017

ISSUED BY: Dan

Observed and forecast soundings depict a well-developed elevated mixed layer that will cover much of England and Wales by the end of tonight. Radar and satellite imagery highlight destabilisation of the mid-levels is already occurring as incredibly steep mid-level lapse rates begin to move gradually north, ahead of what is left of Hurricane Ophelia, with a few recent elevated showers and thunderstorms over SW England. Given a large area of potential, it is possible a few more showers/thunderstorms could develop through the remainder of the night almost anywhere within the LOW threat level - although the risk in any one place is relatively low. Very dry air just above the surface should limit rainfall accumulations somewhat.

http://www.convectiveweather.co.uk/forecast.php?date=2017-10-15

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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)

Just looking at latest obs on thack of the sferics,Plymouth looks to get a direct hit from the storm in the BOB if the intensity keeps up.

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Posted
  • Location: Hanley, Stoke-on-trent
  • Location: Hanley, Stoke-on-trent

As the light comes and cloud breaks are visible, there are some very tall towers out there. Fingers crossed for surprises maybe?

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland

just been perusing the high-res 06  & 12z outputs, and ponder the possibility of thunderstorms tomorrow night over southern and SE counties?

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Posted
  • Location: Sunderland
  • Weather Preferences: Hot Summer, Snowy winter and thunderstorms all year round!
  • Location: Sunderland

just to add, modelling indicates shallow low pressure in the BoB and associated warm front/trough WAA overnight tuesday and into early wednesday....parameters show some elevated instability with high PWAT values....one to possibly watch as modelling breaks out a considerable amount of convective ppn for southern and south eastern England

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

Day 1 Convective Outlook

VALID 06:00 UTC Tue 17 Oct 2017 - 05:59 UTC Wed 18 Oct 2017

ISSUED 13:43 UTC Tue 17 Oct 2017

ISSUED BY: Dan

Upper trough migrating into Iberia will cause the flow over France to subtly back, allowing advection of a higher WBPT airmass back into southern Britain. On the eastern edge of this plume, some elevated instability will be present across NE France / BeNeLux, drawn into SE England and East Anglia during the early hours of Wednesday. It is questionable whether there will be sufficient forcing to destabilise the mid-levels, but there could be scope for isolated lightning from any showery outbreaks of rain that develop here.

http://www.convectiveweather.co.uk/forecast.php?date=2017-10-17

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

Day 2 Convective Outlook

VALID 06:00 UTC Sat 21 Oct 2017 - 05:59 UTC Sun 22 Oct 2017

ISSUED 21:03 UTC Fri 20 Oct 2017

ISSUED BY: Dan

Upper trough will migrate progressively eastwards on Saturday, marked by cooling aloft and associated steeper lapse rates in response to SSTs / diurnal heating inland. Modest instability will exist, with numerous showers expected over sea and windward coasts initially, extending inland during the day as diurnal heating develops some instability inland.

 
Greatest risk of lightning exists for southern and western coastal counties where onshore flow will drive frequent showers, though lightning is unlikely to be widespread enough in coverage to warrant a SLGT - hence the broad LOW threat level. Setup is complicated further by occlusions bringing a more dynamic flavour to the rainfall pattern.
 
Strong, gusty winds will be possible with some showers. Reasonable low-level shear combined with topographical features has in the past lead to the development of waterspouts and / or tornadoes from deep convection - one notorious area where this tends to happen is the Isle of Wight eastwards to West and East Sussex.
 
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Posted
  • Location: NW Bexley, Kent
  • Weather Preferences: Storms, rain, tornados, funnel clouds and the northern lights
  • Location: NW Bexley, Kent

Thanks Summer Sun. I see netweather have also issued a storm forecast and agree with convective weather about the possibility of waterspouts and tornados :shok:.

I've only just seen these forecasts but we did have a very intense shower this morning about 8.45. I was lying in bed and heard it pounding on the window...so relaxing. Later on about 10.45am we had a little, much lighter shower which produced a beautiful, massive rainbow. I was looking at the next lot of clouds on the horizon which were rapidly coming my way and thought to myself it feels stormy today. We keep getting clear spells in between the next shower to arrive. I see the southern coast have had a few strikes a while ago and there are loads of little cells constantly moving from southwest to northeast along the bottom curl of the low. We will see what the rest of the day brings! :)

Edited by Windblade
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Posted
  • Location: Mynydd - Isa , Nr Mold - North Wales
  • Weather Preferences: Foggy autumn days are the best! Although I does enjoy a good thunderstorm.
  • Location: Mynydd - Isa , Nr Mold - North Wales

Yesterday afternoon, once the main band of rain had passed through, we have some weakly convective cloudscapes, I didn't think much of it, apart from how pleasant it looked in the sun compared to our normal grey gloomfest... Then Yesterday evening the hail showers started.
But when I woke up this morning we have got fantastically convective skies, and the app on my phone telling me that there were a couple of lightning strikes around 03.00 (ish)! Can anyone confirm these lightning strikes please? :)

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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

Error

Edited by Chris.R
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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
39 minutes ago, Dangerous55019 said:

Yesterday afternoon, once the main band of rain had passed through, we have some weakly convective cloudscapes, I didn't think much of it, apart from how pleasant it looked in the sun compared to our normal grey gloomfest... Then Yesterday evening the hail showers started.
But when I woke up this morning we have got fantastically convective skies, and the app on my phone telling me that there were a couple of lightning strikes around 03.00 (ish)! Can anyone confirm these lightning strikes please? :)

I heard them on the radio as I was listening at the time but too far away for me to hear thunder. No hail here either, kept missing the heavier showers. 

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