Convective Storm/Discussion thread - 16/07/16 onwards

[Tom dewey likes thunder]

I want it thurder over here in warminster in Wiltshire to night or tomorrow !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[weather09]

Interesting the 00z Euro4 modeling further surface based storms tomorrow afternoon over N/NE England ahead of the cold front before it clears warm and moist air mass away.  Before that, no real change on meso. models regarding destabilisation of very moist and unstable air mass tonight and into tomorrow morning. Arome and Euro4 developing main round of storms over Wales moving NNE/NE into N England then into southern and eastern Scotland. For me, the environment here is favourable for nearly all severe convective hazards - frequent CG lightning, intense RF, low-end large hail, and strong convective winds. 

Certainly looks like an interesting period coming up over next 36 hours. 

Edited July 19, 2016 by weather09

[Weather-history]

24hr FAX chart has a trough running from the Midlands to the Lleyn peninsula at midnight.

[Tom dewey likes thunder]

But i  can feel going thunder over Wiltshire and south and west and south and east  

[Stuart]

Day 1 Convective Outlook

VALID 06:00 UTC Tue 19 Jul 2016 - 05:59 UTC Wed 20 Jul 2016

ISSUED 08:02 UTC Tue 19 Jul 2016

ISSUED BY: Dan

UPDATE 08:02 UTC Small tweaks to existing highlighted areas, and some additional text added below

 

A few isolated to well-scattered showers or thunderstorms may form this afternoon over high ground of Northern England and Scotland. However, the majority of activity will begin this evening and persist overnight, as outlined below...

 

Shortwave trough is likely to engage with instability axis as it crosses NW Ireland / Northern Ireland on Tuesday afternoon/evening, with an environment with Tds in the high teens Celsius, yielding 1,000-2,000 Jkg-1 MLCAPE. Scattered thunderstorms are expected to erupt late afternoon through the evening hours, drifting to the N/NE. Given high CAPE, 30-40kts DLS and backed surface winds, any discrete storms may become supercells, at least for a time, with an associated risk of hail to 3.5cm in diameter, strong, gusty winds and perhaps a tornado - SVR issued to cover all three threats. Some parts of C and W Scotland may require an upgrade to MDT for activity expected this evening/tonight - trends will be monitored.

 

Elsewhere, falling heights in advance of the upper trough will lead to destabilisation during late Tuesday evening and through early hours of Wednesday, with scattered thunderstorm development occurring during the evening hours, these moving NE-wards through the night while expanding in coverage - MDT issued where risk of thunderstorms is considered higher, but as is often the case in such situations, this area may need to be modified in placement/size as convective trends become more clear nearer the event.

Given nocturnal cooling will have occurred to a certain extent before any significant convection develops, most cells will be elevated but still pose a risk of local flash flooding from heavy downpours and elements of backbuilding, and also a hail threat - SVR then issued to cover the greatest risk of flooding / large hail. Significant CAPE and steep lapse rates suggests lightning could be quite prolific in places.

 

http://www.convectiveweather.co.uk/forecast.php?date=2016-07-19

[P-M]

2 minutes ago, Stuart said:

Day 1 Convective Outlook

VALID 06:00 UTC Tue 19 Jul 2016 - 05:59 UTC Wed 20 Jul 2016

ISSUED 08:02 UTC Tue 19 Jul 2016

 

ISSUED BY: Dan

UPDATE 08:02 UTC Small tweaks to existing highlighted areas, and some additional text added below

 

A few isolated to well-scattered showers or thunderstorms may form this afternoon over high ground of Northern England and Scotland. However, the majority of activity will begin this evening and persist overnight, as outlined below...

 

Shortwave trough is likely to engage with instability axis as it crosses NW Ireland / Northern Ireland on Tuesday afternoon/evening, with an environment with Tds in the high teens Celsius, yielding 1,000-2,000 Jkg-1 MLCAPE. Scattered thunderstorms are expected to erupt late afternoon through the evening hours, drifting to the N/NE. Given high CAPE, 30-40kts DLS and backed surface winds, any discrete storms may become supercells, at least for a time, with an associated risk of hail to 3.5cm in diameter, strong, gusty winds and perhaps a tornado - SVR issued to cover all three threats. Some parts of C and W Scotland may require an upgrade to MDT for activity expected this evening/tonight - trends will be monitored.

 

Elsewhere, falling heights in advance of the upper trough will lead to destabilisation during late Tuesday evening and through early hours of Wednesday, with scattered thunderstorm development occurring during the evening hours, these moving NE-wards through the night while expanding in coverage - MDT issued where risk of thunderstorms is considered higher, but as is often the case in such situations, this area may need to be modified in placement/size as convective trends become more clear nearer the event.

Given nocturnal cooling will have occurred to a certain extent before any significant convection develops, most cells will be elevated but still pose a risk of local flash flooding from heavy downpours and elements of backbuilding, and also a hail threat - SVR then issued to cover the greatest risk of flooding / large hail. Significant CAPE and steep lapse rates suggests lightning could be quite prolific in places.

 

http://www.convectiveweather.co.uk/forecast.php?date=2016-07-19

I seen this but I can't work out which areas they've tweaked...can you shed any light on it?

[P-M]

Updated from Metcheck - still going for Western areas (North Wales and NW England)  initially for storms then moving N/NE in to N England and Scotland

 

Weather Watch For Thunderstorms/Flash Flooding/Hail/Tornadoes

An exceptionally moist/unstable plume of air will head Northeast during the course of Tuesday evening and overnight into Wednesday across parts of the British Isles.

This Weather Watch has been updated to move the trajectory of the plume slightly further East and reduce risk of large hail/tornadoes due to higher rainfall values which may impede the updraft capability.

Tuesday evening will see the highest risk of thunderstorms across parts of Northern Ireland and Western fringes of England and Wales.

On Wednesday, the plume fully engages with warm air across the UK bringing torrential downpours across parts of Wales, Northwest and Northern England and Scotland.

Rainfall totals of 50-75mm (2-3") of rainfall is possible in a short period of time leading to the risk of local flash flooding and fast swelling rivers across higher ground.

Frequent cloud to ground lightning is expected within these systems, especially where they become better organised during Wednesday afternoon across Northern England and Central/Eastern Scotland.

Upper air data this morning has reduced the risk of large hail with 2-3cm possible. Higher rainfall totals within the systems are also forecast which will reduce the potential for updrafts which assist in developing tornadoes. That said, where storms become well organised there is a risk of funnel cloud/tornado development. This is most likely around Southeast Scotland on Wednesday morning and across parts of Northeast England on Wednesday afternoon.

Disruption to transport/power supplies is possible as well as local flooding overnight Tuesday and into Wednesday.

This Weather Watch will be updated on Wednesday morning.

FORECASTER : MARSH
---END---

Site Tools

http://www.metcheck.com/UK/warnings.asp

 

[Summer Sun]

8 minutes ago, P-M said:

I seen this but I can't work out which areas they've tweaked...can you shed any light on it?

Initial forecast on the left

Current one

 

Scotland, Ireland and NI has the main changes

[P-M]

Just now, Summer Sun said:

Initial forecast on the left

Current one

 

Scotland, Ireland and NI has the main changes

Cheers Mate - I seen the current one with the MDT areas before the update though?  Then they released an update at 7.55am to say they'd tweaked the areas slightly and added text but I can't see any tweaks to the MDT / SVR areas?

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Wed 20 Jul 2016 - 05:59 UTC Thu 21 Jul 2016

ISSUED 22:37 UTC Mon 18 Jul 2016

ISSUED BY: Dan

This is an advance forecast, issued to give a broad indication to areas with potential to see thunderstorms - given the early lead time, it is inevitable changes will be made to this forecast as new data becomes available in the run-up to this particular event(s)

As is often the case, this forecast period relies heavily on developments that occur on Tuesday / Tuesday night. However, current thinking is areas of thunderstorms will be ongoing on Wednesday morning across much of northern England and parts of Scotland, associated with an area of low pressure initially over the north Midlands, generally clearing to the NE through the morning to affect Shetland for a time. Provided cloud debris clears sufficiently to allow strong surface heating and a recovering of temperatures, then there will be potential for scattered thunderstorm development in the afternoon and evening - particularly across eastern England.

While DLS will be sufficient for at least some organisation of convection (should deep convection develop, which in itself is questionable / uncertain as this range), the most favourable environment for severe thunderstorms (forward side of surface low) will have shifted out over the North Sea and is therefore not best placed for peak diurnal heating. Nonetheless, high CAPE and PWAT suggests any isolated thunderstorms that can develop have the potential to produce large hail and local surface water flooding - and may require a SVR in later updates.

It is quite likely the shape / areas covered by SLGT / LOW threat levels will change over the coming days as confidence improves on a more likely forecast evolution.

http://www.convectiveweather.co.uk/forecast.php?date=2016-07-20

[staplehurst]

1 minute ago, P-M said:

Cheers Mate - I seen the current one with the MDT areas before the update though?  Then they released an update at 7.55am to say they'd tweaked the areas slightly and added text but I can't see any tweaks to the MDT / SVR areas?

Small tweaks were made to the SVR to extend it farther north across Scotland, the MDT was also extended a little bit more over NW England, and the SLGT was shrunk from E Ireland.

[Summer Sun]

1 minute ago, P-M said:

Cheers Mate - I seen the current one with the MDT areas before the update though?  Then they released an update at 7.55am to say they'd tweaked the areas slightly and added text but I can't see any tweaks to the MDT / SVR areas?

This is the first one I have seen myself with MDT so I can't really comment on any tweaks they've made between 21:45 last night and just now

[P-M]

Just now, staplehurst said:

Small tweaks were made to the SVR to extend it farther north across Scotland, the MDT was also extended a little bit more over NW England, and the SLGT was shrunk from E Ireland.

Ah OK cheers mate

[P-M]

3 minutes ago, Summer Sun said:

This is the first one I have seen myself with MDT so I can't really comment on any tweaks they've made between 21:45 last night and just now

No problem - either way here's hoping for an active 24 hrs!

[Darren Bown]

The BBC national forecast on the website seem to specifically mention N England for severe storms tonight and then N England and Scotland for tomorrow

[Nick F]

Storm & Convective Forecast

Issued 2016-07-19 09:04:37

Valid: 19/07/16 1800z to 21/07/16 0600z

DAYS 1 & 2 CONVECTIVE FORECAST - TUES 19TH and WEDS 20TH JULY

Synopsis

Upper ridge across western Europe including the UK begins to decline southeastward to allow the edge of upper trough over the Atlantic to move in across the far west of British Isles. A hot and humid plume spreading north across much of the UK will become increasingly unstable across the north and west as the upper trough edges in from the west over the next 24-36 hours. Forcing for ascent of hot and humid air by approaching upper trough and developing surface low moving NE ahead of a surface cold front moving in from the west will lead to an increasing extent of thunderstorms across northern and western areas from Tuesday evening through to Wednesday evening, some of these storms may be severe given favourable convective parameters.

DAY 1 CONVECTIVE FORECAST – TUES 19TH-JULY-2016

Valid 19/07/16 1800 to 20/07/16 0600z

… EIRE, N. IRELAND, N WALES, N ENGLAND and SCOTLAND …

Hot and humid plume spreading north across the UK over the last 24hrs will yield quite large amounts of CAPE (by UK standards) today with surface heating, GFS indicates 1000-2000 j/kg CAPE across large areas of  the UK and EIRE this afternoon. This potential energy will be strongly capped by upper ridge, but heights will weaken across the NW this evening with approaching upper trough from the west as ridge declines. Increasing large scale ascent this evening across EIRE, N. Ireland into western Scotland created by approaching upper trough and additional ascent from shortwave trough rounding the upper trough to the west and moving NE will likely trigger scattered thunderstorms. Storms increasing in coverage and extending NE to affect more of Scotland and also north Wales and northern England.

Given the large CAPE values forecast, 30-40 knots of deep-layer shear and surface winds backed SEly from SWly flow aloft … any storms that form are likely to organise into multicell clusters, a few supercells can’t be ruled out initially before storms tend line out into clusters. As storms will tend to be elevated, main severe threat from storms this evening and overnight will be excessive rainfall (30-40mm per hour or up to 50mm over a few hours) which may lead to flash-flooding locally. Strong and perhaps isolated damaging wind gusts are also possible. Given high CAPE values – isolated large hail (2 to 3cm diameter) can’t be ruled out with evening storms before hail risk subsides. Frequent lightning will also be a hazard. Therefore have issued a SLIGHT risk of severe weather for the above areas.

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

DAY 2 CONVECTIVE FORECAST – WEDS 20TH-JULY-2016

Valid 20/07/16 0600 to 21/07/16 0600z

… N WALES, MIDLANDS, N ENGLAND and SCOTLAND …

Thunderstorms, perhaps locally severe, will be ongoing to start the day across EIRE, N. Ireland, N Wales, N England and Scotland. These storms may wane through the morning across these areas, before drier and fresher conditions  spread across EIRE, N. Ireland and western Scotland in the afternoon and Wales in the evening, as cold front moves in from the west. Storms re-developing across eastern Scotland, N England, N Wales and parts of the Midlands ahead of cold front as temperatures rise combined with increased forcing for ascent from approaching upper trough and as surface low across SW UK in the morning moves NE and deepens slightly. Despite modest deep layer shear (20-30knts) – fairly strong low-level shear combined with 1000-1500 j/kg CAPE across Midlands, N England and S Scotland may favour the development of strong and perhaps severe thunderstorms capable of producing large hail (2 to 3cm in diameter), damaging wind gusts, frequent lightning and flash-flooding. Given backed SEly flow initially across N Sea coasts, high CAPE and low LCLs (cloud base) …  there is a small risk of a tornado or waterspout across NE England and SE Scotland. Have issued a SLIGHT risk for now, but may upgrade to MODERATE risk if severe storms look to be more extensive.

Issued by: Nick Finnis

[weirpig]

41 minutes ago, Darren Bown said:

The BBC national forecast on the website seem to specifically mention N England for severe storms tonight and then N England and Scotland for tomorrow

Yes it certainly does seem like a northerly affair perhaps central midlands upwards.   however as we know storms can develop anywhere  so a few may be surprised

[Ben Sainsbury]

And my forecast right here... Moderate Risk of Thunderstorms! (Poss Severe)

[Guest]

Thanks Nick for that excellent forecast

[Chris K]

6 minutes ago, Ben Sainsbury said:

And my forecast right here... Moderate Risk of Thunderstorms! (Poss Severe)

I believe this is incorrect and there should be a red high risk circling the Bristol region. 

I joke obviously. It will be interesting to hear what happens tonight/tomorrow. Don't think I will be staying up though...well not on purpose anyway.

[Hodgheg]

Well i wish i was north this week but i don't get moody when we miss out from storms, like i used to. I look forward to seeing photos and videos over the coming days. Heres a couple of pics from 2 years ago in hull to wet your appetite. Was unlike anything i've seen. 

[Ben Sainsbury]

CAPE projections increasing on every run, as I've noticed for my area! Precipitation looks to cover West Midlands as well!

[MP-R]

2 minutes ago, Ben Sainsbury said:

CAPE projections increasing on every run, as I've noticed for my area! Precipitation looks to cover West Midlands as well!

Fantastic chart mate, I just can't help but think that things will kick off just north of Bristol and become absolute bombs as they trundle up the M5. Meanwhile, we have a sunny day that gets progressively fresher. Hope I'm wrong of course.

[Costa Del Fal]

Yes, 6z is pretty good for the W Mids but I have my doubts. Most hi res modelling showing little promise.

Edited July 19, 2016 by Costa Del Fal

[SP1986]

2 minutes ago, Ben Sainsbury said:

CAPE projections increasing on every run, as I've noticed for my area! Precipitation looks to cover West Midlands as well!

For he UK that's insane. Unfortunately at this time of the day thunderstorms will not be liberated from the energy. The CAPE and LI so have decreased by the time the precipitation occurs .. still enough for strong thunderstorms  if course but if thunderstorms occurred in the highest energy area it would go mental.