Convective Storm/Discussion thread - 11/06/16 onwards

[Summer Sun]

Day 1 Convective Outlook

VALID 06:00 UTC Sun 12 Jun 2016 - 05:59 UTC Mon 13 Jun 2016

ISSUED 13:05 UTC Sun 12 Jun 2016

ISSUED BY: Dan

UPDATE 13:05 UTC SLGT added over Ireland / Northern Ireland, while expansions made to existing SLGTs over England. Expectations remain more-or-less as depicted in original forecast below, with convection subject to saturated profiles across N England this afternoon, and therefore uncertain as to how much lightning activity there will be. Farther south, SMZ showing signs of cloud breaking to produce insolation, which should enable isolated to scattered thunderstorms to develop here, especially late afternoon and through the evening. Have added a MDT to highlight areas where thunderstorms may be a little more organised / have better coverage (but not guaranteed given uncertainties in cloud cover). These could produce quite frequent lightning. A further expansion of this SLGT over S England into more of the Midlands / East Anglia may be required - trends will continue to be monitored.

Another messy day is expected on Sunday with a mix of dynamic and convective precipitation across the country. Various weak(ening) frontal boundaries will attempt to nudge NE-wards, but eventually decaying before becoming the required forcing for deep convection given some strong surface heating. In particular, wind convergence along a cold front will allow a line of scattered heavy showers and perhaps a few thunderstorms to form from Norfolk curving NW-wards to Cumbria - however, instability is marginal (couple hundred Jkg-1 CAPE) with hints in forecast soundings of slight capping in the mid-levels, which may limit overall convective depth.

Given PWAT in the order of 26-28mm, scope exists (like Saturday) for slow-moving heavy showers capable of local flooding, but perhaps with limited amounts of lightning. Have issued a SLGT for now to highlight main zone at risk, but may require a downgrade if lightning potential continues to look marginal.

Farther south, heating of the shallow moist zone (SMZ) with surface dewpoints of 13-15C coupled with falling heights and the approach of a dry intrusion will yield an environment with 700-1,000 Jkg-1 MLCAPE. Provided there are sufficient cloud breaks to allow some insolation to develop, then a few isolated to well-scattered thunderstorms may form during the afternoon/evening hours, capable of producing hail locally over 1.0cm in diameter and quite frequent lightning. DLS begins to increase from the SW towards evening, and so this may enable storms to become better organised later in the day with perhaps late initiation in some areas.

Low LCLs, wind convergence (especially close to the south coast from sea breeze, and perhaps also in a separate zone across the south Midlands / Home Counties towards evening as a small surface low forms) and modest CAPE may produce one or two funnels or weak tornadoes. Cells that develop earlier on in the afternoon will pose the greatest threat of excessive rainfall / minor flash flooding given reducing PWAT values as the afternoon/evening progresses. This zone will need monitoring for perhaps either an expansion of the SLGT farther north into the central Midlands and/or the introduction of a MDT.

http://www.convectiveweather.co.uk/forecast.php?date=2016-06-12

[SteveB]

1 minute ago, Mapantz said:

Showers are cropping up all over the place but you may be a bit too far West. Pixels popping up Slightly East of Bristol and South of Swindon, a slow burner, but that's good.

Yeah I feel  it might be the case

[Flash bang flash bang etc]

decent window of clear sky to the west of London at the mo - looks to be steadily growing too

[STORMGUY]

some cauliflower top cloud in the distance.

[East_England_Stormchaser91]

All eyes on that lot approaching West Midlands for East Anglia later. 

Looks good for central southern England too with a multi cluster developing by the looks of it. 

[Nick F]

Skies clearing out nicely here in west London, with growing patches of blue skies, should spark some good storms in a few hours hopefully.

[Harry]

Still cloudy here with the rain having on recently stopped. Perhaps worth mentioning is in spite of the cloud cover you can still feel some heat of the sun.

[SteveB]

Suns been out for over an hour here, and nothing doing.

[Greeny]

Clouds are thinning out here and can see some low level Cu around. Probably earlier instability still hanging about.

Edited June 12, 2016 by Greeny

[Chris.R]

 Sun is out a bit. Temp has shot up to  19.5°C . Worried i'm too far West, and i'm not liking the  steering wind direction. 

[Greeny]

Its certainly feels warm and humid here. I like the feeling of it.

Edited June 12, 2016 by Greeny

[Joey.G]

Cant go out yet, may chase later. Otherwise id be shooting up the M5 to intercept whats by Hereford & Ross-on-Wye, expect it to develop a bit more shortly..

[Gordon Webb]

37 minutes ago, East_England_Stormchaser91 said:

All eyes on that lot approaching West Midlands for East Anglia later. 

Looks good for central southern England too with a multi cluster developing by the looks of it. 

at least today they are moving along when you get it it's not going to be a long affair well not hours on end anyway

Edited June 12, 2016 by Gordon Webb

[Gordon Webb]

52 minutes ago, Summer Sun said:

Day 1 Convective Outlook

VALID 06:00 UTC Sun 12 Jun 2016 - 05:59 UTC Mon 13 Jun 2016

ISSUED 13:05 UTC Sun 12 Jun 2016

ISSUED BY: Dan

UPDATE 13:05 UTC SLGT added over Ireland / Northern Ireland, while expansions made to existing SLGTs over England. Expectations remain more-or-less as depicted in original forecast below, with convection subject to saturated profiles across N England this afternoon, and therefore uncertain as to how much lightning activity there will be. Farther south, SMZ showing signs of cloud breaking to produce insolation, which should enable isolated to scattered thunderstorms to develop here, especially late afternoon and through the evening. Have added a MDT to highlight areas where thunderstorms may be a little more organised / have better coverage (but not guaranteed given uncertainties in cloud cover). These could produce quite frequent lightning. A further expansion of this SLGT over S England into more of the Midlands / East Anglia may be required - trends will continue to be monitored.

Another messy day is expected on Sunday with a mix of dynamic and convective precipitation across the country. Various weak(ening) frontal boundaries will attempt to nudge NE-wards, but eventually decaying before becoming the required forcing for deep convection given some strong surface heating. In particular, wind convergence along a cold front will allow a line of scattered heavy showers and perhaps a few thunderstorms to form from Norfolk curving NW-wards to Cumbria - however, instability is marginal (couple hundred Jkg-1 CAPE) with hints in forecast soundings of slight capping in the mid-levels, which may limit overall convective depth.

Given PWAT in the order of 26-28mm, scope exists (like Saturday) for slow-moving heavy showers capable of local flooding, but perhaps with limited amounts of lightning. Have issued a SLGT for now to highlight main zone at risk, but may require a downgrade if lightning potential continues to look marginal.

Farther south, heating of the shallow moist zone (SMZ) with surface dewpoints of 13-15C coupled with falling heights and the approach of a dry intrusion will yield an environment with 700-1,000 Jkg-1 MLCAPE. Provided there are sufficient cloud breaks to allow some insolation to develop, then a few isolated to well-scattered thunderstorms may form during the afternoon/evening hours, capable of producing hail locally over 1.0cm in diameter and quite frequent lightning. DLS begins to increase from the SW towards evening, and so this may enable storms to become better organised later in the day with perhaps late initiation in some areas.

Low LCLs, wind convergence (especially close to the south coast from sea breeze, and perhaps also in a separate zone across the south Midlands / Home Counties towards evening as a small surface low forms) and modest CAPE may produce one or two funnels or weak tornadoes. Cells that develop earlier on in the afternoon will pose the greatest threat of excessive rainfall / minor flash flooding given reducing PWAT values as the afternoon/evening progresses. This zone will need monitoring for perhaps either an expansion of the SLGT farther north into the central Midlands and/or the introduction of a MDT.

http://www.convectiveweather.co.uk/forecast.php?date=2016-06-12

thank god I'm not in the moderate zone

[William Grimsley]

1 hour ago, weather09 said:

Hail formation is more tied to how much CAPE there is and/or how steep lapse rates are in the mid-levels, where more CAPE means potential for strong updraft speeds and likelihood of keeping hail suspended aloft for any length of time. ELTs will give you possible cloud top height, and a tall storm is more likely to have some hail associated with it, but there are factors that can inhibited hail formation and it reaching the ground.  Instability, moisture and shear the three main factors to look at when gauging storm severity and all hazards they may pose.

Interesting, do you know why even though we had biblical rainfall, there was no lightning here?

Just been out for a walk down the local river, incredibly humid but convection seems to be capping round here even though earlier it was awesome!

Edited June 12, 2016 by William Grimsley

[William Grimsley]

Lovely convection setting off here! https://video.nest.com/live/OIJL3I

Noticing that most showers round here seems to be developing very quickly but not necessarily dying quickly either, good stuff!

Edited June 12, 2016 by William Grimsley

[TropicThunder]

Even though it's mostly cloudy here it feels very humid. Nice to be in that moderate warning area, hopefully we get something later as we've barely even had any rain here in this spell.

[Arnie Pie]

Cells approaching from the West....looking at the low level wind vectors I'll be keeping an eye out for any funnel developments

[Joey.G]

View to the NW just now, would be Cinderford/Mitcheldean way

[Greeny]

4 minutes ago, Arnie Pie said:

Cells approaching from the West....looking at the low level wind vectors I'll be keeping an eye out for any funnel developments

Yeah, lightning now being detected by lightning maps from that cell near you.

Edit: ooh didn't realise it was the one to the southwest near Hereford, can see the ones that were detected from earlier on the one approaching Birmingham.

Edited June 12, 2016 by Greeny

[Supacell]

A lot of strikes being detected around Ledbury.

[Greeny]

1 minute ago, Supacell said:

A lot of strikes being detected around Ledbury.

Yep thats the one I saw.

[Bolt from the Blue]

Torrential rain in Shaftesbury just now

[Gordon Webb]

10 minutes ago, Arnie Pie said:

Cells approaching from the West....looking at the low level wind vectors I'll be keeping an eye out for any funnel developments

heaviest rain at the moment seeming to just be to your south

Edited June 12, 2016 by Gordon Webb

[East_England_Stormchaser91]

Another strike north of Worcester now. 

Right, time to hit the road !!