Convective/Storm Discussion Thread 25/5/16 onwards

[William Grimsley]

Sorry, AJ. Yes, I admit it was very IMBY and I hate to be like that, apologies. Even though the BBC really want to go for the lightning graphics, they're only forecasting isolated showers on most days...

[Harry]

1 minute ago, ajpoolshark said:

But this is so factually incorrect unless you're talking from a totally IMBY perspective...many places in the SW had a very good 2015 season.......On a bigger scale, I feel the problem some have is that if they don't have numerous thunderstorms dropping CG's on their houses then it's been a bad season for their entire region! 

Hence my earlier exclamation of surprise...

[Harry]

Day 1 Convective Outlook

VALID 06:00 UTC Sat 04 Jun 2016 - 05:59 UTC Sun 05 Jun 2016 

ISSUED 04:21 UTC Sat 04 Jun 2016

ISSUED BY: Dan

High WBPT airmass will continue to advect westwards from the nearby Continent through Saturday, with hints perhaps of elements of elevated convection possible first thing across C to SE England (low probability). Profiles initially exhibit a notable warm nose inversion around 850-900mb, acting as a cap to any surface-based convection until sufficient diurnal heating combined with low-level convergence / orographic forcing enables air parcels to rise to form deep convection - particularly so mid/late afternoon and through the evening hours, assuming adequate clearance of existing stratus and fog trapped beneath inversion.

 

Given initial cap and CAPE values of 700-1,000 Jkg-1, convective development could be fairly rapid. However, relatively dry profiles and a lack of any notable shear will probably result in isolated to well-scattered marginally-organised showers and thunderstorms, particularly focussed over areas where low-level forcing is most prominent (sea breeze through Thames Estuary environs, orographic forcing over Wales / W Midlands / NW England / C + W Scotland etc). Instability is greatest towards the SE, and so here cells may be quite electrically active. Have highlighted areas at greatest risk with SLGTs, but it is plausible isolated cells may develop elsewhere within the LOW.

 

Overall evolution sees instability axis shifting slowly southwestward through the evening hours, and hence the zone with thunderstorm potential will be shifting SW-ward towards southern and western parts of Britain - some uncertainty as to how long through the evening hours convection can be sustained given nocturnal cooling of the boundary layer, but it certainly seems possible that some (isolated) thunderstorms could perhaps survive until 00z. There may also be elements of elevated convection approaching SE England later in the night.

 

Although some hail is possible in the strongest cells, main risk will be local flash flooding given slow storm motion in an environment characterised by PWAT values of 27-30mm - potential for 16-18mm to fall in just 1 hour.

[Harry]

I have been out this morning and the warm and humid air has certainly arrived - just have to patiently await the clearance of the horrid cloud and murk now!!

[10 Days Away]

On 30/05/2016 at 21:18, Mark wheeler said:

 

 

Mmm Lightning strike near bury st Edmunds but no rain???. Do we have lightning anprop

No idea why I'm replying to this post. Forum glitch?

 

Strike south of Cambridge!

[Speedway Slider]

Quick question.....

Do thunderstorms seed thunderstorms?

What I mean is that when a storm has tracked a particular path, does that path then have a higher chance of further thunderstorms?

[Nick F]

2 minutes ago, Speedway Slider said:

Quick question.....

Do thunderstorms seed thunderstorms?

What I mean is that when a storm has tracked a particular path, does that path then have a higher chance of further thunderstorms?

The outflow from thunderstorms (the downdrafts in a storms fanning out) can trigger 'daughter' cells around it where the outflow comes up against the synoptic flow to form convergence zone to force air upwards to form new storms. In America these are known as outflow boundaries.

 

[Mapantz]

It's not a glitch, it's how the forum works now. It saves any text that you start writing, whether it is a quoted reply or a normal one, in case you accidentally close the page or navigate away.

To delete a quotation box, just place and click your cursor at the bottom of the quote (the inside of it will have a blue box) - click between that and the outside box, then press delete.

25 minutes ago, TN26 said:

No idea why I'm replying to this post. Forum glitch?

 

Strike south of Cambridge!

 

[MattTarrant]

10 hours ago, ajpoolshark said:

But this is so factually incorrect unless you're talking from a totally IMBY perspective...many places in the SW had a very good 2015 season.......On a bigger scale, I feel the problem some have is that if they don't have numerous thunderstorms dropping CG's on their houses then it's been a bad season for their entire region! 

I'm talking about Devon in particular, it was poor last year!! Occasional rumble but nothing substantial. 

[William Grimsley]

16 minutes ago, MattTarrant said:

I'm talking about Devon in particular, it was poor last year!! Occasional rumble but nothing substantial. 

I can only remember 2 overhead thunder claps here last year and there was one thunderstorm but I was in Exmouth!

[William Grimsley]

1 hour ago, Harry said:

I have been out this morning and the warm and humid air has certainly arrived - just have to patiently await the clearance of the horrid cloud and murk now!!

Yes, it's arrived here too!

[A.J]

25 minutes ago, MattTarrant said:

I'm talking about Devon in particular, it was poor last year!! Occasional rumble but nothing substantial. 

again, it seems IMBYisms it has to be said....on the other side of the coin, Torbay and south hams had more than average amounts of thunder days, as my family can attest to 

[A.J]

11 minutes ago, William Grimsley said:

Yes, it's arrived here too!

not quite yet William, the humid air is making its way westwards over from the near continent encroaching into eastern districts of England........I'm in Bristol at the moment and it feels quite fresh and cool under cloudy skies 

[William Grimsley]

4 minutes ago, ajpoolshark said:

again, it seems IMBYisms it has to be said....on the other side of the coin, Torbay and south hams had more than average amounts of thunder days, as my family can attest to 

AJ, how specific do we need to be? What about East Devon? Is that still being "IMBY"?

[A.J]

??....I'm simply referring to the posts stating that 2015 was a poor year for the South West in terms of storms.........it wasn't

anyways, this is going nowhere, so back on topic I reckon (yes me too )

Edited June 4, 2016 by ajpoolshark

[Nick F]

Storm & Convective Forecast

Issued 2016-06-04 09:22:18

Valid: 04/06/2016 0600z to 05/06/2016 0600z

DAY 1 CONVECTIVE FORECAST - SAT 4TH-JUNE-2016

Synopsis

During Saturday, a deep upper low over the mid-North Atlantic will drift very slowly east, while further NE an upper high will be centred close to/north of northern UK with weak flow aloft across the UK. At the surface, pressure is high towards northern Scotland, lower towards near continent and SW of the UK. A weak NEly flow cover the UK, a warm front moving west overnight has introduced a humid airmass from the near continent that will become increasingly unstable with surface heating across England and Wales.

… E WALES, NW ENGLAND, MIDLANDS, S ENGLAND, E ANGLIA …

Morning low cloud, mist and drizzle is expected to break up by late morning and into the afternoon from the east, so strong surface heating of humid airmass (dew points rising to around 14-16C) should generate 300-900 j/kg CAPE by late afternoon. Despite ridging and light winds aloft along with a lack of upper forcing, breeze convergence or orographic lift of increasingly humid airmass will overcome the cap of surface instability locally to trigger isolated heavy showers and storms in parts of the above areas. Given light winds aloft, tall cloud growth and PWAT (precipitable water) values forecast between 1/ 1.4 inches – there is a risk of localised flash flooding where storms occur. Also there a risk of hail and gusty winds. Given isolated risk of storms, will refrain from issuing a MARGINAL risk but will highlight areas that may see thunderstorms, though most places will miss them.

... W SCOTLAND and NERN EIRE / N IRELAND ...

Sea breeze convergence and orographic lift of increasingly moist airmass combined with surface heating could trigger a few isolated thunderstorms this afternoon, with a risk of localised flooding, hail and gusty winds

 

Issued by: Nick Finnis

[Flash bang flash bang etc]

Forecast looks great for general (albeit short-lived) storms around this general area. I'm not able to travel too far today so will pop out and find higher ground if storms occur nearby - also any rain will be good for clearing our decking of dirt so if the weather is reading this - bring it on!

[Speedway Slider]

The warm humid stuff hasn't yet reached the Leicester area, still clag-laden grey sky.... temp stuck at 15.4c 

 

 

[andymusic]

looks like early next week when the real fun will start - although already had some storms this year

[weather09]

GFS instability progs considerably down on previous outputs, likely as a result of it predicting less clearing of murk aloft meaning suppressed sfc temps, therefore inhibiting build-up of CAPE. Where good insolation does occur, which still looks reasonable, likely good instability to tap into for any storm(s) that can develop afternoon/evening period. 

[Supacell]

16c DP's now showing up in East Anglia, that must be feeling pretty humid! Here in Derby it is still overcast and fairly cool although DP's are on the increase.

I think here in Derby I will have to wait until around Tuesday for any storm risk. Today's risk looks in a line from the SE to the NW but to the west of here. Tomorrow still looking good on GFS for SW England, especially close to the Bristol Channel and Severn Estuary. However, BBC don't seem too interested with the forecast of a sunny day and just the odd shower. Next week looks more interesting with Tuesday being the day I am currently watching with most interest.

[Greeny]

Blue sky showing here in Norwich now, just a thin layer of cloud moving across. By the looks of SAT24 I should think it will be clearing pretty soon here. Warmer than the last few days although was in Scotland during the week until I arrived back Thursday I was told it was cloudy, windy and cold which we caught the last couple of days of, until today we were lucky to have got the best of the weather up in beautiful Scotland. First visit and it was amazing, why did I wait 40 years to visit! We expected rain and we got great weather, just a couple of overcast mornings.

I think the clouds will clear soon enough and the fun (hopefully) will start for this afternoon.

Good luck to all.

[Flash bang flash bang etc]

Just gotta shift this last layer of cloud and we're off!

[weatherobsuk]

If anything pops off in the NW storm-wise today i'd say places like Sponds Moor or Lyme Park would be the best places to go to, watch the cells build over the peaks and then reach mature-stage over Cheshire and into Wales. Being to the East on the inflow side would give some nice clear views for observation.

[Richard Taylor]

BBC reports lightning has injured 51 (8 serious, 2 needed resuscitation) at the Rock am Ring music festival, Germany earlier today. Careful what you wish for if storms of similar magnitude ever make it to the UK!