Convective/Storm Discussion Thread - 1st August onwards

[Ellozee]

I'm hoping for a Kent clipper later on, but nothing seems to be electrifying today. Storms seem to be early in the season, but then I remember it is already April and we just had a very late winter!

[Dangerous55019]

1 hour ago, Weather-history said:

I am not sure it is going to go bang anywhere. Still no sferics anywhere.

 

 

Afternoon @Weather-history, sadly I have to say you're right, it looks like today is a bust.

I’ve just checked the radar and all I can see is one strike around the Leeds area... Can anyone confirm this?

Edited April 4, 2018 by Dangerous55019
Missed bits out

[Chris.R]

10 minutes ago, Dangerous55019 said:

Afternoon @Weather-history, sadly I have to say you're right, it looks like today is a bust.

I’ve just checked the radar and all I can see is one strike around the Leeds area... Can anyone confirm this?

L&B METAR recently reported thunderstorm. :-)

Edited April 4, 2018 by Chris.R

[toggerob]

High precip totals west of Durham at the moment, not going anywhere too fast across the north Pennines around the Alston area.

[Windblade]

We had a few breaks in the cloud but overall it's been mostly cloudy which seems to have limited the potential for today. Oh well, it's still very early in the season, plenty of time to go.

[Weather-history]

 

[alexisj9]

Only light showers here, had plenty of sun though. Been a rather nice day, and warm.

[Flash bang flash bang etc]

People’s thought on tomo evening? Temps up to 16° possibly during the day so maybe there’s some energy about for the forecast showers later?

[Ted Striker]

21 hours ago, Dangerous55019 said:

Afternoon @Weather-history, sadly I have to say you're right, it looks like today is a bust.

I’ve just checked the radar and all I can see is one strike around the Leeds area... Can anyone confirm this?

Yes, I was on Armley gyratory in sudden torrential downpour. Bright flash, couple of seconds later two distinct very loud gunshot sounds. Nearby roads flooded.

[Flash bang flash bang etc]

Looks like potential for tonight - albeit uncertain

[Mapantz]

The way recent forecasts have gone, I would be inclined to say that it will be a no-go... which means all hell will break loose during the early hours. 

[Ben Sainsbury]

1 hour ago, Flash bang flash bang etc said:

Looks like potential for tonight - albeit uncertain

Agreed and to admit whilst the uncertainty remains for tonight into tomorrow morning, I haven't been this excited in a long time...

Whilst CAPE levels aren't particularly big by any means, we are looking at some significant values of DLS across CS England earlier tomorrow morning and SRH values of 300 to maybe 500 moreso across the East Midlands.

When we see low CAPE values and high DLS and SRH values, I wouldn't be surprised if we didn't see any significant lightning activity however I do expect some very well structured and organised thunderstorms albeit very very isolated.

In any organised storms, there is a chance for multicelluar and supercelluar characteristics given the large vertical shear values in excess of 40knts.

These may bring some nice photogenic skies as we move towards rush hour tomorrow morning, however these may bring a risk of some very severe wind gusts, medium sized hail and a few funnel clouds and possibly a tornado.

I personally think ESTOFEX are underplaying the risk for much of Southern UK, however these may be analysed within the next ESTOFEX forecast.

Whilst there are large amounts of uncertain and possible isolated nature of storms, I can understand why the likes of ConvectiveWeather are reluctant to issue anything of a higher risk.

EDIT: Still an amateur opinion, so please correct me if you want to do so!

Edited April 6, 2018 by Ben Sainsbury

[Flash bang flash bang etc]

28 minutes ago, Ben Sainsbury said:

Agreed and to admit whilst the uncertainty remains for tonight into tomorrow morning, I haven't been this excited in a long time...

Whilst CAPE levels aren't particularly big by any means, we are looking at some significant values of DLS across CS England earlier tomorrow morning and SRH values of 300 to maybe 500 moreso across the East Midlands.

When we see low CAPE values and high DLS and SRH values, I wouldn't be surprised if we didn't see any significant lightning activity however I do expect some very well structured and organised thunderstorms albeit very very isolated.

In any organised storms, there is a chance for multicelluar and supercelluar characteristics given the large vertical shear values in excess of 40knts.

These may bring some nice photogenic skies as we move towards rush hour tomorrow morning, however these may bring a risk of some very severe wind gusts, medium sized hail and a few funnel clouds and possibly a tornado.

I personally think ESTOFEX are underplaying the risk for much of Southern UK, however these may be analysed within the next ESTOFEX forecast.

Whilst there are large amounts of uncertain and possible isolated nature of storms, I can understand why the likes of ConvectiveWeather are reluctant to issue anything of a higher risk.

EDIT: Still an amateur opinion, so please correct me if you want to do so!

I like your outlook - well worth taking on board the general reluctance to suggest anything significant - but a potential night like this can be very enjoyable if Synoptics play out right...

Best bit is that we don’t have to endure rain until much later in the night - and it being a Friday i’d like to enjoy being out and about without getting soaked!

[Nick F]

A new look to the storm forecast maps on Netweather storm forecasts. Got rid of the severe categories on the old maps and forecasts and replaced with just one for severe weather while other categories for thunderstorms are isolated, likely and strong. Also now including symbols to put over areas where there could be risk of heavy rainfall leading to flooding, large hail, strong wind gusts and a tornado risk.

Isolated risk of thunder tonight and through Saturday over parts of England, east Wales and also across Ireland:

Storm & Convective Forecast

Issued 2018-04-06 16:41:04
Valid: 07/04/2018 00Z AM to 08/04/2018 00Z

THUNDERSTORM OUTLOOK - SATURDAY 7TH APRIL 2018

Synopsis

An amplifying upper trough will continue to dig south over western Britain / Ireland and across western Iberia during Friday – before disrupting into an upper low off Iberia over the weekend.

At the surface, a cold front will move in across mainland UK today, ahead of low pressure system to the west, the frontal boundary will stall as it approaches eastern this evening, with waves developing along it, as increase baroclinicity develops along the front from France in response to sharpening upper trough to the west. Heavy rainfall will develop along frontal wave / surface low drifting north from northern France, with perhaps sufficient instability on eastern edge of rain for isolated thunder.

... THERE IS AN ISOLATED RISK OF THUNDERSTORM FORECAST ...

... HAZARDS 

... Heavy rain / localised flooding & strong wind gusts

... DISCUSSION

IRELAND

An ongoing risk of isolated thunder with heavy showers likely to affect parts of Ireland overnight and through Saturday in post frontal returning Polar maritime airmass – characterised by steep lapse rates as cold air spreads aloft with upper trough edging east. Some of these heavy thundery showers may produce localised flooding.

E WALES, CENTRAL, S and E ENGLAND

Confidence is low over the detail for the potential for convection to develop in warm air advection regime on eastern side of waving cold front and associated dynamic rainfall moving north out of France, particularly the area if may develop. If strong enough mid-level instability does develop in warm moist conveyor destabilised by increased lift of developing wave/surface low and steepening lapse rates of cooler air overrunning aloft form the upper trough to the west, then there is potential for isolated thunder. Strong deep layer shear will support organised convective cells, bringing mainly a risk of localised large rainfall rates leading to isolated flash flooding and also a risk of isolated strong wind gusts. However, given the uncertainty, will only depict area of isolated thunderstorms drifting north during Saturday across above areas.

Issued by: Nick Finnis

Also on website here: https://www.netweather.tv/weather-forecasts/uk/convective

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Fri 06 Apr 2018 - 05:59 UTC Sat 07 Apr 2018

ISSUED 19:39 UTC Fri 06 Apr 2018

ISSUED BY: Dan

UPDATE 19:39 UTC Latest data over the past 24 hours has continued a westward shift in the frontal wave later tonight and into Saturday morning, and hence a subsequent expansion of the SLGT has been issued - though still with low confidence with regards to how much lightning may actually occur

A sharp and gradually disrupting upper trough to the west of the British Isles on Friday will gradually drift over Portugal by Saturday morning. At the surface, a complex low will sit over the Atlantic, with one centre drifting north close to western Ireland during the day. A weakening cold front will drift eastwards across the Irish Sea into western Britain, while ahead a southerly flow will introduce a warmer airmass across England.

... IRELAND ...

As the cold front clears to the northeast, some marginal instability will develop in response to diurnal heating and slight cooling aloft. A few scattered showers are expected, perhaps weakly-electrified - despite marginal instability, strong DLS may be enough to compensate to produce some sporadic lightning activity. In fact, given backed low-level winds, notable SREH and LLS and relatively low cloud bases, it is possible the strongest cells could exhibit some supercell-characteristics. A tornado is not completely ruled out in these low CAPE / high shear scenarios.

While nocturnal cooling usually results in a decay of convection, the approach of a shortwave from the southwest may allow deep convection to persist into the night hours, especially in the west.

 

... S + E ENGLAND ...

Main interest here is during Friday night, as backing of the mean flow increases warm air advection, with some mid-level instability being generated. Deep convection aside, increasing baroclinicity and the development of a surface low will allow a wave on the cold front to bring a pulse of heavy, more widespread rain northwards across southern Britain. The best potential for any lightning activity will be on the eastern flank - and hence getting the exact track and shape of the frontal wave will be crucial in determine which areas are at greatest risk, and as such the forecast may need to be modified slightly nearer the time.

 

Most NWP guidance suggests 100-300 J/kg MLCAPE, so somewhat marginal instability, but this will be in a strongly-sheared environment on the forward side of the upper trough. Some lightning activity is possible, but not certain - and since a Marginal (MRGL) threat level does not exist in our forecast system, have reluctantly issued a low-end SLGT to try and highlight the area where the best overlap of conditions currently looks to take place during the early hours of Saturday.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-06

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Sat 07 Apr 2018 - 05:59 UTC Sun 08 Apr 2018

ISSUED 20:22 UTC Fri 06 Apr 2018

ISSUED BY: Dan

... ENGLAND / WALES ...

On the forward side of a sharp upper trough, which will continue to dig across Iberia, a frontal wave will drift northwards across England and Wales - bringing an area of rain across Wales and W England eventually into S Scotland. On the eastern flank, and points east, elements of medium-level instability will exist which may be sporadically destabilised in association with the passage of a shortwave, moving northeast through the morning/early afternoon. Some high-based showers will be possible, capable of producing lightning - though given rather marginal instability, confidence on lightning coverage is too low to upgrade to SLGT.

 

... REPUBLIC OF IRELAND / NORTHERN IRELAND ...

Under the upper trough, cold air aloft will produce some reasonably steep mid-level lapse rates. Diurnal heating will allow 400-800 J/kg CAPE to build, with topography and low-level convergence aiding the development of numerous heavy showers and a few thunderstorms for the afternoon and early evening hours.

 

Limiting factors will be a lack of shear, resulting in messy pulse-type convection in the main, and perhaps also a hang back of cloud associated with the frontal wave over England/Wales, which may serve to dilute insolation somewhat. Nonetheless, the strongest cells could produce hail up to 1.5cm in diameter, while low-level convergence could produce a couple of funnel clouds.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-07

[Convective]

Tentative signs of something a little more engaging towards the end of next week across a couple of the models. These being some of the better graphics taken from the 18Z GFS for next Friday. Caution as always..!

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

[Flash bang flash bang etc]

14 hours ago, Convective said:

Tentative signs of something a little more engaging towards the end of next week across a couple of the models. These being some of the better graphics taken from the 18Z GFS for next Friday. Caution as always..!

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

 

07/04/18 GFS Flickr

Banked ?

cant wait for the season to start proper at last!

[convector]

Possibility of a kent clipper/channel storms monday night into tuesday, early hours. Only really showing up on the WRF and GFS, however. Other models don't seem to be very good at forecasting CAPE, at least in early spring. ICON, for example, doesn't show any CAPE for the times given but performs well when it comes to precipitation. I only have a few years of experience, so if anyone can explain why i'd be very interested. Anyway, next week looks promising in general, albeit marginal, but I'll take what i can get at this time of year. 

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Sun 08 Apr 2018 - 05:59 UTC Mon 09 Apr 2018

ISSUED 15:18 UTC Sat 07 Apr 2018

ISSUED BY: Dan

Sharp upper trough will continue to disrupt over Iberia on Sunday, while a piece of energy drifts northeast across Ireland to Scotland. This will be associated with cool air aloft and hence relatively steep mid-level lapse rates. Diurnal heating, orographic forcing and low-level wind convergence will aid in the development of several scattered showers, some perhaps weakly-electrified.

Deep convection potential may be contaminated somewhat by an area of cloud and showery rain moving into southern Ireland from the Celtic Sea. Given lack of any significant shear, messy pulse-type convection is most likely and hence any lightning will be rather sporadic and not particularly widespread - therefore reluctant to issue a SLGT for now.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-08

Edited April 7, 2018 by Summer Sun

[Summer Sun]

13 hours ago, Summer Sun said:

Day 2 Convective Outlook

VALID 06:00 UTC Sun 08 Apr 2018 - 05:59 UTC Mon 09 Apr 2018

ISSUED 15:18 UTC Sat 07 Apr 2018

ISSUED BY: Dan

Sharp upper trough will continue to disrupt over Iberia on Sunday, while a piece of energy drifts northeast across Ireland to Scotland. This will be associated with cool air aloft and hence relatively steep mid-level lapse rates. Diurnal heating, orographic forcing and low-level wind convergence will aid in the development of several scattered showers, some perhaps weakly-electrified.

Deep convection potential may be contaminated somewhat by an area of cloud and showery rain moving into southern Ireland from the Celtic Sea. Given lack of any significant shear, messy pulse-type convection is most likely and hence any lightning will be rather sporadic and not particularly widespread - therefore reluctant to issue a SLGT for now.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-08

UPDATE 08:46 UTC LOW threat level added to SE England for this evening - a build-up of some marginal instability is possible over NE France this afternoon to the east of the frontal zone, with the potential for some showers (perhaps weakly-electrified) to drift close to or over SE England during the evening hours

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-08

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Mon 09 Apr 2018 - 05:59 UTC Tue 10 Apr 2018

ISSUED 19:09 UTC Sun 08 Apr 2018

ISSUED BY: Dan

Upper low to the west of Ireland will slide SE-wards, eventually merging with an upper low over northern Iberia / southern France by Monday night. Diurnal heating over Ireland in particular will lead to a few scattered showers developing during the afternoon, though with unimpressive mid-level lapse rates and warming aloft this will tend to limit convective depth - so a few locally heavy showers are possible, but lightning will be isolated (if any).

Instability will build over The Netherlands, Belgium and NE France on Monday afternoon. A shortwave is expected to lead to destabilisation here on Monday evening, and with the approach of the Iberian upper trough merging with the Atlantic upper low ultimately backing the flow across central and southern Britain, any thunderstorms that do develop over the nearby Continent associated with moisture plume will begin to drift west or northwestwards across the North Sea. 

 

At this stage there is some spread as to the exact track of these thunderstorms - general consensus would put the risk higher over East Anglia and perhaps NE Kent, but some model guidance offers a more southerly option, even as far south as Sussex (and a minority of models keep any deep convection offshore to the NE of East Anglia). In either case, it is questionable as to how much lightning will actually occur over land (assuming deep convection does move inland) given the gradual reduction of instability through the evening/night. The risk (albeit lowering) will continue to migrate NW-wards along eastern coasts of England through the early hours of Tuesday.

 

For now, a low-end SLGT has been issued to cover the threat of weakening thunderstorms arriving late Monday evening / early hours of Tuesday over East Anglia / Kent, but it is certainly possible this SLGT area may need to be altered or perhaps even removed, depending on trends during Monday.

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-09

[Stuart]

day 2 Convective Outlook

VALID 06:00 UTC Mon 09 Apr 2018 - 05:59 UTC Tue 10 Apr 2018

ISSUED 19:09 UTC Sun 08 Apr 2018

ISSUED BY: Dan

Upper low to the west of Ireland will slide SE-wards, eventually merging with an upper low over northern Iberia / southern France by Monday night. Diurnal heating over Ireland in particular will lead to a few scattered showers developing during the afternoon, though with unimpressive mid-level lapse rates and warming aloft this will tend to limit convective depth - so a few locally heavy showers are possible, but lightning will be isolated (if any).

 

Instability will build over The Netherlands, Belgium and NE France on Monday afternoon. A shortwave is expected to lead to destabilisation here on Monday evening, and with the approach of the Iberian upper trough merging with the Atlantic upper low ultimately backing the flow across central and southern Britain, any thunderstorms that do develop over the nearby Continent associated with moisture plume will begin to drift west or northwestwards across the North Sea. 

 

At this stage there is some spread as to the exact track of these thunderstorms - general consensus would put the risk higher over East Anglia and perhaps NE Kent, but some model guidance offers a more southerly option, even as far south as Sussex (and a minority of models keep any deep convection offshore to the NE of East Anglia). In either case, it is questionable as to how much lightning will actually occur over land (assuming deep convection does move inland) given the gradual reduction of instability through the evening/night. The risk (albeit lowering) will continue to migrate NW-wards along eastern coasts of England through the early hours of Tuesday.

For now, a low-end SLGT has been issued to cover the threat of weakening thunderstorms arriving late Monday evening / early hours of Tuesday over East Anglia / Kent, but it is certainly possible this SLGT area may need to be altered or perhaps even removed, depending on trends during Monday.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-09

 

 

Edited April 8, 2018 by Stuart

[Summer Sun]

16 hours ago, Summer Sun said:

Day 2 Convective Outlook

VALID 06:00 UTC Mon 09 Apr 2018 - 05:59 UTC Tue 10 Apr 2018

ISSUED 19:09 UTC Sun 08 Apr 2018

ISSUED BY: Dan

Upper low to the west of Ireland will slide SE-wards, eventually merging with an upper low over northern Iberia / southern France by Monday night. Diurnal heating over Ireland in particular will lead to a few scattered showers developing during the afternoon, though with unimpressive mid-level lapse rates and warming aloft this will tend to limit convective depth - so a few locally heavy showers are possible, but lightning will be isolated (if any).

Instability will build over The Netherlands, Belgium and NE France on Monday afternoon. A shortwave is expected to lead to destabilisation here on Monday evening, and with the approach of the Iberian upper trough merging with the Atlantic upper low ultimately backing the flow across central and southern Britain, any thunderstorms that do develop over the nearby Continent associated with moisture plume will begin to drift west or northwestwards across the North Sea. 

 

At this stage there is some spread as to the exact track of these thunderstorms - general consensus would put the risk higher over East Anglia and perhaps NE Kent, but some model guidance offers a more southerly option, even as far south as Sussex (and a minority of models keep any deep convection offshore to the NE of East Anglia). In either case, it is questionable as to how much lightning will actually occur over land (assuming deep convection does move inland) given the gradual reduction of instability through the evening/night. The risk (albeit lowering) will continue to migrate NW-wards along eastern coasts of England through the early hours of Tuesday.

 

For now, a low-end SLGT has been issued to cover the threat of weakening thunderstorms arriving late Monday evening / early hours of Tuesday over East Anglia / Kent, but it is certainly possible this SLGT area may need to be altered or perhaps even removed, depending on trends during Monday.

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-09

UPDATE 10:31 UTC SLGT reduced in size given decreasing risk of lightning tonight - primarily focussed on Norfolk, but perhaps even staying offshore to the NE of Norfolk

 

UPDATE 07:42 UTC No changes to the map for now, but trends in guidance over past 12 hours would reduce the risk of lightning somewhat tonight due to a much later arrival, and tending to restrict it more to N + E Norfolk, or even offshore from there. Adjustments may be required to the SLGT area if these trends continue through today

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-09

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Tue 10 Apr 2018 - 05:59 UTC Wed 11 Apr 2018

ISSUED 20:06 UTC Mon 09 Apr 2018

ISSUED BY: Dan

... E ENGLAND ...

Residual marginal mid-level instability may exist on Tuesday morning associated with the passage of a shortwave drifting NW-wards across eastern England. Given saturated profiles and weak instability, little lightning is expected (but not impossible) from Lincolnshire northwards, the risk reducing through the morning hours. Otherwise, pulses of occasionally heavy rain are expected.

 

... S ENGLAND / S MIDLANDS / WALES ...

An upper low over the Bay of Biscay will drift slowly southwards to Iberia during Tuesday, with a shortwave rotating around the northern edge across northern France / English Channel / southern England. At the surface, a moist airmass with dewpoints of 10-11C will reside over southern Britain, which provided there is sufficient insolation will help yield 300-600 J/kg CAPE in response to diurnal heating (Tmax 16-17C).

A combination of increased upper forcing and low-level convergence could allow a few scattered heavy showers or thunderstorms to form, particularly during the late afternoon into the evening hours. Forecast profiles exhibit some reasonable directional shear with height, which may allow such cells to become organised for a time, capable of producing hail up to 1.5cm in diameter. Biggest uncertainty will be cloud cover (and perhaps a subtle warm nose aloft) which may inhibit deep convection somewhat. Any showers/storms that do develop will drift to the W or WNW, slowly weakening during the evening hours.

 

... EAST ANGLIA / LINCOLNSHIRE ...

Increasing instability over the nearby Continent will likely lead to scattered thunderstorms developing over Belgium, the Netherlands and western Germany on Tuesday afternoon/evening. These will drift westwards with time while decaying as they cross the North Sea on Tuesday night, but the remnants could reach as far as East Anglia or Lincolnshire during the early hours of Wednesday.

 

http://www.convectiveweather.co.uk/forecast.php?date=2018-04-10