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

[Windblade]

16 minutes ago, Farmer Dave said:

I'm a fruit grower in north Kent and I can remember some mega storms over the years but not recently. We did get hail damage on our fruit crops last year though from two storms - one storm had hail the size of a 50p. The irony is I love a good storm but my crops can be ruined in seconds!

Ah, I'm sorry to hear that your crops were ruined. Its very easy to forget the damage violent storms can cause to others. Beautiful, yet destructive at the same time.

Edited June 20, 2016 by Windblade

[Nick F]

Trailing front of a split cold front clearing SE looks to be forcing line convection across Midlands to Lincs currently, maybe be some isolated lightning in this line as surface cold front moves SE this afternoon and creates forced ascent of a shallow moist zone (SMZ) characterised by quite rich surface moisture, current dew point obs of 16-17C across central and southern England. Models show little instability, so be lucky to see this line produce much if any thunder.

Storm & Convective Forecast

Issued 2016-06-20 13:27:40

Valid: 20/06/2016 12z to 21/06/2016 06z

CONVECTIVE / STORM FORECAST - MON 20TH-JUNE-2016

Synopsis

The UK and Ireland is on the southeastern edge of upper and collocated low pressure system over mid-N Atlantic just south of Iceland. A split cold front feature clears SE from England and Wales Monday afternoon, the trailing cold front forcing a line of convection that will clear SE across central, southern and eastern England this afternoon.

… CENTRAL, SOUTHERN AND EASTERN ENGLAND …

A shallow moist zone (SMZ), between split cold fronts clearing SE, is characterised by dew points of 15-17C looking at recent observations. Trailing cold front stretching from SE Wales to the Humber is creating forced ascent of the SMZ and generating line convection across Midlands and E England. This narrow line of convection will continue to clear SE across central S/SE England along with East Anglia this afternoon and early evening. Although models generate little instability, there may be sufficiently strong ascent and cloud depth along the line of convection/front for isolated lightning … main risk will be temporary risk of flash-flooding as brief line of heavy rainfall moves through, also squally winds and small hail are possible from this line. A few isolated heavy thundery showers may also develop well ahead of the cold front too.

Issued by: Nick Finnis

Edited June 20, 2016 by Nick F

[Chris.R]

Nice. 

"Outlook for Wednesday to Friday:

Sunshine and showers on Wednesday. Turning cloudier, but warmer and more humid on Thursday and Friday, with a chance of thundery showers."

There is a bit of CAPE even this far West. Who knows, the plume might be pushed West  over the next few days, you never know. 

[Tim Bland]

A couple of strikes around the wash now.

Trusty Meteogroup going for storms on and off all day on Thursday! 

[Nick F]

Some healthy looking updrafts popping up around west London as the sun gets to work on the SMZ

 

[East_England_Stormchaser91]

12z showing yet another very slight shift west! These slight shifts however could make a vital difference to the all or nothing game as ever in these scenarios. Let's hope it is going to be a continuing trend. 

What we need to look and hope for is the current low in the Atlantic to keep digging further down in the meantime and to stay further west, in order to create more amplification to enable a steeper more S-N advection of the plume as opposed to SW-NE. 

[Windblade]

Looks like east anglia (imo one of the stormist places in the uk) had a few strikes.

[Windblade]

2 hours ago, Nick F said:

Some healthy looking updrafts popping up around west London as the sun gets to work on the SMZ

 

One that rain cleared off around midday it felt like both the temperature and in particular the humidity shot through the roof. Getting out of the car (air con on coldest setting) felt like stepping into a tropical rainforest.

[James_southampton]

Mass of pitch black clouds rolling by, suggests something could happen but not a drop of rain or any sparks. 

[Harry]

59 minutes ago, East_England_Stormchaser91 said:

12z showing yet another very slight shift west! These slight shifts however could make a vital difference to the all or nothing game as ever in these scenarios. Let's hope it is going to be a continuing trend. 

What we need to look and hope for is the current low in the Atlantic to keep digging further down in the meantime and to stay further west, in order to create more amplification to enable a steeper more S-N advection of the plume as opposed to SW-NE. 

Well that's promising, considering it was the 12z yesterday that looked depressing!!  

[Greeny]

3 hours ago, Nick F said:

Some healthy looking updrafts popping up around west London as the sun gets to work on the SMZ

 

Wasn't expecting that. Got to Tesco (other supermarkets are available) and saw dark clouds ahead. Felt nice and humid (i like that feeling) and pretty hot with the sun out. Wasn't sunny for most of the morning. Was in for about 30 mins and when I came out it was another surprise (as pictured) For the first time this year there was some reasonable motion and nice updtafts. Couldn't chase as with the kids but it moved away pretty quickly.

[stainesbloke]

4 hours ago, Speedway Slider said:

Was this a Friday?

Black Friday? Sorry..... I think the storms were on a Thursday (with newspaper reports on the Friday).

[Harry]

18 minutes ago, stainesbloke said:

Black Friday? Sorry..... I think the storms were on a Thursday (with newspaper reports on the Friday).

Too right - Thors-day and all that

[Summer Sun]

Day 2 Convective Outlook

VALID 06:00 UTC Tue 21 Jun 2016 - 05:59 UTC Wed 22 Jun 2016

ISSUED 18:02 UTC Mon 20 Jun 2016

ISSUED BY: Dan

Sharpening upper trough over the Atlantic, but with rising heights / weak ridging over the British Isles, suppressing deep convection in many areas. However, greater proximity to the upper trough will allow some convective potential across portions of Scotland, Northern Ireland and Ireland. Here, scattered showers / outbreaks of showery rain are likely to affect western extremities in particular, but overall the environment does not look particularly conducive to producing lightning. Chances increase more in the evening hours as lapse rates steepen a little due to an advancing shortwave and marginal cooling aloft, but by this stage peak heating will have passed and so given the very low potential for lightning, have refrained from issuing any threat levels for now.

As the upper trough continues to sharpen and dig southwards towards the west of Iberia, the resultant backing flow will lift a warm front (which will be straddling northern France on Tuesday) northwards across southern counties of England through the early hours of Wednesday, associated with advection of a high WBPT airmass into S/SE Britain by Wednesday morning. This may bring some better potential for deep convection later on Wednesday and into Thursday, for which other forecasts will be issued if necessary.

http://www.convectiveweather.co.uk/forecast.php?date=2016-06-21

[weather09]

Still small discrepancies on timing/positioning of low/frontal boundary between ECM/GFS and UKMO-GM, but, as things stand, ever increasing likelihood of possible severe convective episode late Weds and particularly into daytime Thurs across far E/SE, where initial storms/MCS earlier in the period would transition to surface-based risk during afternoon/evening period Thurs. 12z GFS modeling NE'wrd surge of fairly high low-level moisture over the region:

 

Large scale ascent with upper trough/divergence with under left-exit jet, and upper disturbances all releasing moist and potentially moderately unstable air mass.

 

Those fairly strong SW'erly mid-level winds generating a good sheared environment for storm clusters/MCS early period, then supporting more strong, organised storms when combined daytime heating. 

Three days out a long way in convective forecast terms, but given agreement between models, and likely severity of storms if current outputs verify, worth the detail.

Edited June 20, 2016 by weather09

[stainesbloke]

Starting to look rather interesting Wed into Thu....hopefully a further shift NW of the plume, thus engaging more of the UK than Dover! 

[Harry]

2 hours ago, stainesbloke said:

Starting to look rather interesting Wed into Thu....hopefully a further shift NW of the plume, thus engaging more of the UK than Dover! 

Coming into 48 hour range now... 

...if only! Have seen some massive swings in the models at this range so all usual caveats, terms, conditions and consumer warnings apply

 

As Weather09 points towards above, there is the potential for any storms which may develop to be severe, given a fairly active jet being in play (which more often than not lacks in these sorts of setups for the UK)...stark contrast to some of the similar plume events of yester-year. 

Edited June 20, 2016 by Harry

[A.J]

18z GFS moves things back east again....still pretty good for the SE quarter though it has to be said....swings and roundabouts

[Harry]

6 minutes ago, ajpoolshark said:

18z GFS moves things back east again....still pretty good for the SE quarter though it has to be said....swings and roundabouts

Indeed...think it's going to wobble continually back and forth over the next runs. The WRF-NMM however I found pretty sharp last year in these events so am keen to see how the 18z looks compared with GFS (might check in the morning)

[Harry]

OMFG...another Estofex Lvl 3, 5 in as many days. Unprecedented I think I'm right in saying 

[Harry]

Last one from me tonight...

Day 3 Convective Outlook

VALID 06:00 UTC Wed 22 Jun 2016 - 05:59 UTC Thu 23 Jun 2016 

ISSUED 20:36 UTC Mon 20 Jun 2016

ISSUED BY: Dan

This is an extended outlook issued to highlight the potential for convective weather - given the early lead time, it is inevitable that changes will be required to the forecast as the forecast evolution becomes clearer with time.

A sharpening upper trough to the west of Ireland will continue to dig southwards towards Portgual, backing the flow over western Europe and allowing advection of a notably warm, moist airmass northwards into parts of the British Isles. At this stage there is some uncertainty as to how much of (primarily) England will be affected by this rich low-level airmass - at least parts of SE England and East Anglia seems likely, but this may extend farther W across Cen S England / Midlands perhaps. Certainly trends in 12z models are beginning to shift a little more westwards, but there is still plenty of time for this to change.

In either case, during this forecast period there are 2 main aspects to consider:

(1) Should cloud begin to break in the wake of morning showery rain (associated with a frontal wave), then given modest surface heating of an airmass with Tds of 15-16C, there may be scope for isolated thunderstorm development over East Midlands / East Anglia / SE England during the afternoon and early evening, especially if any sea breeze component can aid lift. This is currently treated a low probability and generally ignored for now in the attached graphic.

(2) Forced ascent during the evening and night hours from the approach of a shortwave trough over N France / English Channel will likely lead to thunderstorm development that eventually grows into an organised cluster / MCS given strong DLS, being steered generally to the NE through the night across at least the highlighted SLGT area. Given modest instability, lightning could be quite frequent - especially on the eastern flank of any thunderstorm complex that does develop. Heavy rain and hail up to 1.5cm in diameter will be the primary hazards. There is scope for parts of these regions to be upgraded to MDT with an expansion of the SLGT westwards if recent trends continue - but there is still a fair amount of uncertainty at the moment.

[Mapantz]

Dangerous posting this, but it is only a probability after all..

Get your large condiments out.

[Norfolk Sheep]

My only beef with an MCS is that generally these days it just means left over clag and murky conditions! 

[Polar Maritime]

Cape predictions for Thursday from the in-house Net/Wx hi res suite.

And GFS in isolation.

 

Edited June 21, 2016 by Polar Maritime
No excuse..

[Harry]

Following on from my posting of the 12z WRF-NMM last night, this is the 00z from midnight.

Bit of an eastward shunt but still all to play for - I think most would agree any westward adjustment would be welcome.