Storms and Convective discussion - 20th March 2023 onwards

[Raindrops]

Nice Squall line heading into Northern Ireland now, when will it trigger is the question.

Edit: spoke too soon.

Edited May 8, 2023 by Raindrops

[Raindrops]

Kicking of now in Dublin mostly CC, the Squall line in Northern Ireland fell apart, but activity has increased.

[Raindrops]

Nice storm in Dublin pasted, now in the Irish Sea, disappointed about with the activity in the North.

[Jamie M]

 

Edited May 8, 2023 by Jamie M

[Raindrops]

1 minute ago, Jamie M said:

https://twitter.com/vxlks/status/1655646291559346176?s=20

Nice , just have to love that sound.

[Metwatch]

 

Some amazing lightning from those storms in Dublin. 

 

[Kirkcaldy Weather]

[Eagle Eye]

Convective Outlook ️

On the western tip of a moisture tongue, a PV lobe along a shortwave trough will act as a forcing for either clustering pulse-storms or a weak squall line. This will depend on the exact maxima of the forcing.

If we assume a squall line forms then it'll move in the direction of highest MUCAPE and if we assume pulse-storms then they will form strongest potentially in areas of highest CAPE-kinematics forcing. A moderate has been issued in that area based off CAM guidance. Convection depth appears to be about 9KM in these areas but will be increased by kinematics so a low-end moderate has been issued. SBCAPE in excess of 1000 J/KG appears possible in areas and with the tallest storms, they may create other storms from their gravity waves so clustering of frequent lightning in the area of tallest storms is plausible. However, its difficult to forecast those.

Some quite bouyant air parcels around London area are most likely to force these strongest storms and that's certainly right in the middle of our moderate risk but that's purely based off GFS. Some could be similar to Fridays storms in terms of strength if they can get close to maximising CAPE availability.

Some hail is possible given supportive LLLR's and slightly supportive hodos with decent below zero CAPE but that will be nowhere near maximised given little to no support for Supercells. Therefore non-severe hail is certainly possible but above 2cm is extremely unlikely. Cloud heights are quite low for hail as well in most (but not all) areas.

Similar risk in Ireland with surface heating but less forcing and strength of CAPE therefore its only a slight risk. Lightning there should only really be sparodic.

So occasionally frequent lighting, small hail and torrential rainfall is possible. Non-severe wind gusts may occur as well.

[Thunders]

29 minutes ago, Eagle Eye said:

Convective Outlook ️

On the western tip of a moisture tongue, a PV lobe along a shortwave trough will act as a forcing for either clustering pulse-storms or a weak squall line. This will depend on the exact maxima of the forcing.

If we assume a squall line forms then it'll move in the direction of highest MUCAPE and if we assume pulse-storms then they will form strongest potentially in areas of highest CAPE-kinematics forcing. A moderate has been issued in that area based off CAM guidance. Convection depth appears to be about 9KM in these areas but will be increased by kinematics so a low-end moderate has been issued. SBCAPE in excess of 1000 J/KG appears possible in areas and with the tallest storms, they may create other storms from their gravity waves so clustering of frequent lightning in the area of tallest storms is plausible. However, its difficult to forecast those.

Some quite bouyant air parcels around London area are most likely to force these strongest storms and that's certainly right in the middle of our moderate risk but that's purely based off GFS. Some could be similar to Fridays storms in terms of strength if they can get close to maximising CAPE availability.

Some hail is possible given supportive LLLR's and slightly supportive hodos with decent below zero CAPE but that will be nowhere near maximised given little to no support for Supercells. Therefore non-severe hail is certainly possible but above 2cm is extremely unlikely. Cloud heights are quite low for hail as well in most (but not all) areas.

Similar risk in Ireland with surface heating but less forcing and strength of CAPE therefore its only a slight risk. Lightning there should only really be sparodic.

So occasionally frequent lighting, small hail and torrential rainfall is possible. Non-severe wind gusts may occur as well.

Got a nice chance for something tomorrow! Got school tho

[viking_smb]

it will be interesting in work tomorrow eve as will be sat on a rib in the middle of cardiff bay for the yacht racing, 

 

[Jamie M]

Day 2 Convective Outlook by Dan Holley

VALID 06:00 UTC Tue 09 May 2023 - 05:59 UTC Wed 10 May 2023

ISSUED 21:33 UTC Mon 08 May 2023

ISSUED BY: Dan

It is worth stressing from the outset this is a potentially very messy forecast evolution that carries a lot of uncertainty and is subject to updates/adjustments. In a broad sense, an upper trough will migrate eastwards across the British Isles on Tuesday, with a cut-off upper low within its base that will tend to drift eastwards through the English Channel. This will be associated with a fairly significant cold pool aloft (T500 around -26C, for example) with a cyclonically curved jet streak rounding the base of this upper low and placing the left exit region in the vicinity of southern England. The exact shape/evolution of this mid-level feature will be, at least partly, instrumental in how things develop through the day, and various NWP output varies in its handling of this feature. Therefore, the forecast evolution is highly sensitive to subtle changes in forcing aloft and/or the thermodynamic/kinematic profile which may not be fully resolved in NWP. At the surface, a moist low-level airmass will be present across England and Wales (having originated over eastern Ireland on Monday afternoon), with dewpoints typically around 10-13C. A rather diffuse cold front will migrate eastwards through the day, with a slight reduction in dewpoints likely accompanied by a veering of the low-level winds. Despite the fairly large spread in possible evolution over central and southern England in particular, key themes are outlined using a multi-model blend approach.

Fairly extensive cloud is likely during the morning across much of England and Wales, with some hill and coastal fog. Through the day this should thin and break, with increasing insolation then resulting in better surface heating. A selection of forecast soundings in central/southern Britain, while fairly moist through much of the troposphere, do appear to become unstable with only modest surface heating and as such a few heavy showers may develop around 11z-13z (in addition to an area of showery rain drifting across SW England with the potential for a few odd lightning strikes with this feature). Exactly how unstable profiles become will depend on both the amount of surface heating that can be achieved, and also the exact thermodynamic profile. Most model guidance suggests 500-800 J/kg MLCAPE may be achievable (with SBCAPE potentially in excess of 1,000 J/kg). Showers may initially be fairly scattered, eventually evolving into the thunderstorms with time, and with PV lobes in the vicinity of the upper low aiding synoptic-scale ascent then thunderstorms may tend to grow upscale into a large multicell complex across parts of the Midlands and central southern England, drifting into East Anglia and SE England later in the afternoon and into the evening. This may also coincide with a modest increase in effective bulk shear as the aforementioned jet streak rounds the base of the upper trough and shifts northeastwards into SE England (12z GFS more keen/further north than 12z ECMWF, for example). The relatively slow movement may lead to local surface water flooding, potentially very disruptive when coinciding with the evening commute for the likes of London and the Home Counties. This may be exacerbated by local strong downburst winds, gusts typically 40-50mph (and therefore below SVR criteria). Hail may accompany the strongest cells, but probably no larger than 1.0-1.5cm in diameter. In addition, a small surface low may linger close to or over East Anglia, maximising low-level convergence and forced ascent and potentially resulting in quasi-stationary heavy dowpours/thunderstorms here that may also lead to local flooding away from the larger complex of thunderstorms further to the west.

 

Elsewhere, an arguably simpler evolution is anticipated with scattered heavy showers and a few thunderstorms developing in Ulster and Leinster through the day, and also along the east coast of Britain (perhaps also NE Scotland) in response to sea breeze convergence and some orographic forcing. Reasonably strong updrafts may aid vorticity stretching along low-level CZs to produce a few funnel clouds.

[Eagle Eye]

2 minutes ago, Jamie M said:

 

Very similar to me and Jay's forecast as well

[Raindrops]

8 minutes ago, Eagle Eye said:

Very similar to me and Jay's forecast as well

Both forecasts were on the ball for today.

[Eagle Eye]

Europe gets soaked and we get storms. I like that idea.

[Raindrops]

Some clips from today, ignore me talking to Thor.

 

Forgot to add the ending

 

Edited May 8, 2023 by Raindrops

[Raindrops]

UPDATED

Convectiveweather.co.uk

Day 1 Convective Outlook  VALID 06:00 UTC Tue 09 May 2023 - 05:59 UTC Wed 10 May 2023  ISSUED 06:23 UTC Tue 09 May 2023  ISSUED BY: Dan  It is worth stressing from the outset this is a potentially very messy forecast evolution that carries a lot of uncertainty and is subject to updates/adjustments. In a broad sense, an upper trough will migrate eastwards across the British Isles on Tuesday, with a cut-off upper low within its base that will tend to drift eastwards through the English Channel. This will be associated with a fairly significant cold pool aloft (T500 around -26C, for example) with a cyclonically curved jet streak rounding the base of this upper low and placing the left exit region in the vicinity of southern England. The exact shape/evolution of this mid-level feature will be, at least partly, instrumental in how things develop through the day, and various NWP output varies in its handling of this feature. Therefore, the forecast evolution is highly sensitive to subtle changes in forcing aloft and/or the thermodynamic/kinematic profile which may not be fully resolved in NWP. At the surface, a moist low-level airmass will be present across England and Wales (having originated over eastern Ireland on Monday afternoon), with dewpoints typically around 10-13C. A rather diffuse cold front will migrate eastwards through the day, with a slight reduction in dewpoints likely accompanied by a veering of the low-level winds. Despite the fairly large spread in possible evolution over central and southern England in particular, key themes are outlined using a multi-model blend approach. Fairly extensive cloud is likely during the morning across much of England and Wales, with some hill and coastal fog. Through the day this should thin and break, with increasing insolation then resulting in better surface heating. A selection of forecast soundings in central/southern Britain, while fairly moist through much of the troposphere, do appear to become unstable with only modest surface heating and as such a few heavy showers may develop around 11z-13z (in addition to an area of showery rain drifting across SW England with the potential for a few odd lightning strikes with this feature). Exactly how unstable profiles become will depend on both the amount of surface heating that can be achieved, and also the exact thermodynamic profile. Most model guidance suggests 500-800 J/kg MLCAPE may be achievable (with SBCAPE potentially in excess of 1,000 J/kg). Showers may initially be fairly scattered and particularly tied to sea breeze convergence zones, such as near the Dorset/Hampshire coast for a time before lifting further north, eventually evolving into thunderstorms with time. PV lobes in the vicinity of the upper low aiding synoptic-scale ascent may encourage thunderstorms to grow upscale into a larger multicell complexes across parts of the Midlands and central southern England, drifting into East Anglia and SE England later in the afternoon and into the evening. This may also coincide with a modest increase in effective bulk shear as the aforementioned jet streak rounds the base of the upper trough and shifts northeastwards into SE England (12z GFS more keen/further north than 12z ECMWF, for example). Outflow from thunderstorms will significantly impact where new cells develop, and this will undoubtedly lead to a lot of uncertainty in locations with the greatest lightning coverage. Fairly moist profiles casts some concern over exactly how much lightning activity will occur. The relatively slow movement may lead to local surface water flooding, potentially very disruptive when coinciding with the evening commute for the likes of London and the Home Counties. This may be exacerbated by local strong downburst winds, gusts typically 40-50mph (and therefore below SVR criteria). Hail may accompany the strongest cells, but probably no larger than 1.0-1.5cm in diameter. In addition, a small surface low may linger close to or over East Anglia, maximising low-level convergence and forced ascent and potentially resulting in quasi-stationary heavy downpours/thunderstorms here that may also lead to local flooding away from the larger complex of thunderstorms further to the west.  Elsewhere, an arguably simpler evolution is anticipated with scattered heavy showers and a few thunderstorms developing in Ulster and Leinster through the day, and also along the east coast of Britain (perhaps also NE Scotland) in response to sea breeze convergence and some orographic forcing. Reasonably strong updrafts may aid vorticity stretching along low-level CZs to produce a few funnel clouds.

[ChannelThunder]

What an interesting set up today. Rare to see two 'yellows' from CW from homegrown storms within a few days! 

I've got a lot going on with work today, so if anything amazing comes out of this down here, I'd appreciate it waiting til 5pm!

[Eagle Eye]

9 minutes ago, ResonantChannelThunder said:

What an interesting set up today. Rare to see two 'yellows' from CW from homegrown storms within a few days! 

Without a big plume involved either. Early season has started quickly and though last season we had a plume in a week's time, I'm fine without the plumes for now. They don't make for good structure most of the time pictures as they are at night plus got my GCSE's starting next Monday. They end mid June so we can have the plumes from then .

[Windblade]

Well, absolutely bugger all from fri - this morning. Really desperate for some action now.

[Jamie M]

Day ruined now

[ChannelThunder]

22 minutes ago, Jamie M said:

Day ruined now

Did they end up releasing one for Friday? If they didn't, perhaps that's why it ended up being so eventful!

[Liam Burge]

24 minutes ago, Jamie M said:

Day ruined now

Haha! It skirts around Bristol so my hopes are still high! 

[CoventryWeather]

Don't know if I've ever been here - I can walk back home and be in the warning, whilst at sixth form, I am not in the zone....

[JR319]

Looks like we’re on knifes edge here in Leicester. Could end up being a very frustrating day 

[Gordon Webb]

To be fair to the met office there risk map does tie in more or less with Dan's moderate risk area and other forecasts I have read whether it kybosh s the whole thing remains to be seen