Storm & Convective Discussion - 7th August Onwards

[Another Kent clipper]

The skies are beginning to look rather satisfying in north Manchester.  Presumably it's not even a convective day though.

 

[TheFlyingDuck]

Some pretty impressive cloud structures today. 

 

Spent two hours fly down canyons SFC-8000ft. Tried to get above it but was hemmed not by controlled airspace. 

 

Photo was from down over Exmoor 

[Windblade]

Halfway through September and not a peep. I get the feeling that could be it for storm season.

[Mokidugway]

25 minutes ago, Windblade said:

Halfway through September and not a peep. I get the feeling that could be it for storm season.

To late now , any plumes will get wiped out by the awakening Atlantic 

[sunnijim]

1 hour ago, Windblade said:

Halfway through September and not a peep. I get the feeling that could be it for storm season.

Advancing cold front thrown our way BY  Helene on Monday night "may" produce something....

[Chris.R]

 Friday is looking very interesting now and it’s not disappearing. The coldest 500mb temperatures of the season. Yet another convective Friday. 

[Mokidugway]

25 minutes ago, Chris.R said:

 Friday is looking very interesting now and it’s not disappearing. The coldest 500mb temperatures of the season. Yet another convective Friday. 

Looks like a classic set up , a blustery hail day 

[Lauren]

We had a couple of great storms in May but it's been absolutely dead since then. Hardly had any rain either.

Still hoping to see some good night storms in Cuba, not during the day, mind.

[Mokidugway]

11 minutes ago, Lauren said:

We had a couple of great storms in May but it's been absolutely dead since then. Hardly had any rain either.

Still hoping to see some good night storms in Cuba, not during the day, mind.

Can remember  a good one overnight  in Varadero  in  August 2010 , great light show

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Wed 19 Sep 2018 - 05:59 UTC Thu 20 Sep 2018

ISSUED 20:05 UTC Tue 18 Sep 2018

ISSUED BY: Dan

A deep area of low pressure will track northeastwards from the Atlantic across NW Scotland on Wednesday, with very strong winds on its southern flank. Cold air wrapping around the rear side atop warm SSTs will steepen lapse rates and generate a few hundred J/kg CAPE. This, within a strongly-sheared environment, suggests some sporadic lightning will be possible as numerous showers move through the area. Strong gusts of wind will be possible with the most intense cores.

Farther south, strong unidirectional shear (and limited convective depth) will lead to line segments along the cold front, but the lightning risk is considered very low.

http://www.convectiveweather.co.uk/forecast.php?date=2018-09-19

[Supacell]

I will look in more detail when I get home from work but it looks like an intense feature could pass through parts of England and Wales on Thurs eve/night. Looking like the possibility of a vigorous squall line bringing a period of damaging wind gusts, torrential rain along with some thunder and lightning.

Met Office have already issued a yellow warning for winds. 

Edited September 19, 2018 by Supacell

[Summer Sun]

Between 09:00 Sun 23rd and 09:00 Mon 24th

• East Midlands
• East of England
• London & South East England
• North East England
• North West England
• South West England
• Wales
• West Midlands
• Yorkshire & Humber

Potential for another very windy spell across parts of the UK on Sunday and into early Monday.

What to expect

• There is a small chance of injuries and danger to life from flying debris
• There is a slight chance of some damage to buildings, such as tiles blown from roofs or through falling trees and branches
• There is a small chance of longer journey times or cancellations as road, rail, air and ferry services are affected
• There is a slight chance that power cuts may occur, with the potential to affect other services, such as mobile phone coverage
• There is a small chance that injuries and danger to life could occur from large waves and beach material being thrown onto sea fronts, coastal roads and properties

Further details

During Sunday there is the potential for a deep area of low pressure to develop and track over the UK bringing a spell of very strong winds and heavy rain. At this stage developments are very uncertain but there is a small chance of disruptive winds developing with parts of England and Wales currently looking most at risk. Any strong winds should gradually clear eastwards early on Monday with more settled conditions looking likely to follow next week.

https://www.metoffice.gov.uk/public/weather/warnings#?date=2018-09-23

 

[weirpig]

Quite a bit of action going on over the next few days.  The storm on Sunday looks very nasty and needs to watched. Friday early hours is also looking rather troublesome  The Aperge (sometimes known for overcooking wind speeds)  shows  60mph+ inland over central areas  and maybe winds gusting over 70mph in the northwest.    certainly not boring weather.  Edit   the Icon 6z also shows very strong winds in these areas  maybe a touch higher

 

                   

Edited September 19, 2018 by weirpig

[Mapantz]

Wrong thread folks. This is the convective thread.

 

[weirpig]

5 minutes ago, Mapantz said:

Wrong thread folks. This is the convective thread.

 

Moved to other thread.   apologises

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Thu 20 Sep 2018 - 05:59 UTC Fri 21 Sep 2018

ISSUED 20:37 UTC Wed 19 Sep 2018

ISSUED BY: Dan

Very little lightning activity is expected through Thursday daytime - mainly over the far NW of Scotland and the Northern Isles, but even here probably rather isolated. Elsewhere, a near-stationary warm front will bring increasingly persistent and heavy rain to Wales, northern England and the north Midlands.

 

During Thursday evening, a sharpening upper trough and associated strong forcing will cause the warm front to buckle, developing a frontal wave and rapid cyclogenesis. A notable warm, moist low-level airmass will exist across England and Wales south of the warm front and ahead of the sharpening cold front - consequently, a few hundred J/kg CAPE will develop ahead of the cold front, and close to the triple point. Strong, largely unidirectional, deep layer shear will exist across the area, though the thermally-active cold front will be marked by a notable wind veer at the surface.

 

The environment, therefore, will be favourable for convective elements to develop during the evening and night hours as the frontal system crosses England and Wales to the North Sea. Embedded line convection / squalls are likely along the cold front, which may also exhibit some sporadic lightning - though difficult to say exactly how frequent this may be given rather saturated profiles and weak instability. An extension to the SLGT may be required across parts of the Midlands. Nonetheless, some damaging gusts of wind will be possible, and perhaps a tornado where any marked bow echoes can develop.

 

The best overlap of shear, instability and forcing appears to evolve over Wales initially during the first half of the evening, then into northern England before clearing to the North Sea quite quickly during the early hours. As a result, have issued a SLGT here where lightning seems more probable (with limited confidence given some uncertainty as to how far north the triple point may reach). Near this feature, forecast soundings yield curved hodographs, and given the pre-existing environment, this zone carries the greatest risk of a tornado.

 

Farther west, beneath the upper trough, a classic autumn/winter scenario will unfold with cold air aloft overspreading warm SSTs of the Atlantic to generate steep lapse rates and a few hundred J/kg CAPE - hence numerous showers and some sporadic lightning will be possible near the coasts of Ireland initially, and then W Scotland and Irish Sea coasts later in the night. Gusty winds will also be possible with this activity.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-09-20

[Chris.R]

Wow what a taf from Liverpool. Looks like a thundery squall line cold front as well as post frontal thundery showers. 

The report was made 1 hour and 10 minutes ago, at 11:04 UTC

Forecast valid from 20 at 12 UTC to 21 at 12 UTC

Wind 8 kt from the South/Southeast

Visibility 10 km or more

Few clouds at a height of 3000 ft

Becoming
from 20 at 12 UTC to 20 at 14 UTC

Wind 10 kt from the East

Visibility: 5000 m

rain

Temporary
from 20 at 12 UTC to 20 at 22 UTC

Visibility: 3000 m

Broken clouds at a height of 1200 ft

heavy rain

Probability 30% :

Temporary
from 20 at 12 UTC to 20 at 18 UTC

Broken clouds at a height of 800 ft

Becoming
from 20 at 18 UTC to 20 at 21 UTC

Wind 14 kt from the South

Probability 40% :

Temporary
from 20 at 18 UTC to 20 at 23 UTC

Wind 17 kt from the South with gusts up to 30kt

Visibility 10 km or more

Probability 30% :

Temporary
from 20 at 22 UTC to 20 at 24 UTC

Visibility: 3000 m

Broken clouds at a height of 1000 ft 
Broken clouds at a height of 1800 ft, Cumulonimbus.

thunderstorm, heavy rain

Becoming
from 20 at 23 UTC to 21 at 02 UTC

Wind 20 kt from the West with gusts up to 32 kt

Visibility 10 km or more

Probability 30% :

Temporary
from 21 at 00 UTC to 21 at 05 UTC

Wind 28 kt from the West/Northwest with gusts up to 42 kt

Visibility: 3000 m

Broken clouds at a height of 1400 ft

heavy rain

Temporary
from 21 at 02 UTC to 21 at 12 UTC

Visibility: 6000 m

rain showers

Probability 30% :

Temporary
from 21 at 05 UTC to 21 at 12 UTC

Visibility: 3000 m

Broken clouds at a height of 1400 ft 
Broken clouds at a height of 2500 ft, Cumulonimbus.

heavy rain showers, thunderstorm, small hail or snow pellets

 

Edited September 20, 2018 by Chris.R

[Nick F]

Storm & Convective Forecast

Issued 2018-09-20 12:10:49
Valid: 20/09/2018 12z - 21/09/2018 06z

THUNDERSTORM OUTLOOK - THURSDAY/FRIDAY 20/21 SEPT 2018

Synopsis

Broad upper troughing covers higher latitudes of N Europe / N Atlantic with ridging over southern Europe, a strong westerly jet stream continues to plough over UK and Ireland and on through to Scandinavia, a potent shortwave in the strong upper westerlies will interact with frontal zone lying across southern Britain and out across the N Atlantic, allowing a wave then developing low to form and track NE across England and Wales, deepening as it does so. A squally cold front sweeps SE across England and Wales later, clearing SE England in the early hours. There is potential for strong convection with isolated thunder, damaging convective gusts, intense rainfall and possibly an isolated tornado with the front and also near the deepening low as it exits NE.

… ENGLAND and WALES …

A warm and rather moist airmass conveyor, with Precipitable Water (PWAT) values approaching 35mm, will be present to south of buckling frontal zone stretching through Wales and central/northern England, which will feature a deepening low moving NE across N England this evening. The warm/moist airmass will become modestly unstable as large-scale ascent and cooling aloft occurs with approaching upper trough and developing surface low. Some embedded convection is likely to develop within pulses of increasingly heavy rainfall spreading NE across Wales, central and N England through the afternoon and evening along buckling frontal zone, although lightning is expected to be isolated, limited by warm layer aloft creating weak lapse rates, intense burst of convective rainfall may lead to some flash-flooding.

As the cold front begins to shift S and E through the evening before clearing SE England/E Anglia in the early hours of Friday morning, as the low continues to deepen as it moves out to the North Sea, line convection appears likely to develop along the front – bringing a risk of squally intense rainfall accompanied by lightning locally and strong perhaps damaging wind gusts (50-60mph, locally more with exposure) just ahead of the front. Some flash-flooding and localised wind damage is possible with passage of the squally cold front. Given strong veering of surface winds with frontal passage and strong vertical shear – there is potential for a tornado too with any broken line segments along the cold front, but this potential isolated.

... WESTERN COASTAL AREAS EARLY FRIDAY ...

Post cold front polar airmass atop of warm SSTs will create steep lapse rates which will support scattered heavy showers and some weak thunderstorms producing small hail, gusty winds and perhaps localised flooding across western coastal areas.

Issued by: Nick Finnis

https://www.netweather.tv/weather-forecasts/uk/convective

[Chris.R]

This warm front is relentless. Constant heavy rain all afternoon and temperature down to 10.9°C. 

[Another Kent clipper]

Rhetorical question: what happened to the lightning?  Nonetheless, this rain's actually quite nice

[Chris.R]

1 minute ago, Another Kent clipper said:

Rhetorical question: what happened to the lightning?  Nonetheless, this rain's actually quite wqnice

 Only ever a very low risk of lightning from this warm-front I believe. We want to be keeping an eye on the cold-front/triple point around 22:00 where there are likely to be Squall-lines  with sferics. Then early hours of tomorrow morning post frontal showers with modest CAPE and Steep lapse rates so good chance of sferics with them as well especially on the coast.  

[Windblade]

Still haven't seen a drop of rain all week. The forecast is for us to get rain, strong winds, maybe a storm and even the possibility of a tornado in the small hours. 

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Fri 21 Sep 2018 - 05:59 UTC Sat 22 Sep 2018

ISSUED 13:44 UTC Thu 20 Sep 2018

ISSUED BY: Dan

Upper trough will swing eastwards across the British Isles on Friday, with cold air aloft atop warm SSTs steepening lapse rates and generating a few hundred J/kg CAPE. Numerous showers will affect many parts, generally most frequent in exposed western areas. A few isolated lightning strikes, gusty winds and small hail will be possible from the most intense cells. Increased ridging from the west will result in weakening convection by the evening hours.

http://www.convectiveweather.co.uk/forecast.php?date=2018-09-21

[Nick F]

Storm & Convective Forecast

Issued 2018-09-21 07:06:59
Valid: 21/09/2018 06z to 22/09/2018 06z

THUNDERSTORM OUTLOOK - FRIDAY 21 SEPT 2018

Synopsis

Broad upper troughing overspreads higher latitudes of northern Europe and far N Atlantic with upper high over SW Europe - with a strong westrly jet stream flowing across the N Atlantic and UK, a deep surface depression (Storm Bronagh) continues to move away NE toward Norway. A polar westerly or northwesterly flow covers the UK, which will be unstable to SSTs and diurnal surface heating, supporting heavy showers and a few thunderstorms.

... S SCOTLAND, S IRELAND, N ENGLAND, WALES, MIDLANDS, LINCS ...

A pool of unseasonably cold air aloft will shift east across the UK this morning on the back of shortwave in strong upper westerlies / jet moving out over the N Sea - creating steep low level lapse rates. This cold air atop seasonally warm SSTs will generate instability that will support scattered showers, some heavy with hail, spreading off coastal areas and well inland this morning across the above areas. As diurnal heating warms the ground, surface heating inland may allow strong enough convection to support isolated thunderstorms too, particularly into the afternoon. These storms accompanied by hail, gusty winds and perhaps localised flooding exacerbated by recent heavy rain. Any storms should fade after dark.

Issued by: Nick Finnis

[Chris.R]

 Think it’s not gonna happen here today. The flow is too strong so cells have not got chance to develop before they hit land and instead are developing further inland with the aid  of aurographic lift.  Seen this happened before especially in winter.