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Convective / Storm Discussion Thread - 27th Feb onwards


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Lovely looking storm this afternoon! 

Here's the one that didn't get away. Taken at Crawley, West Sussex.

All bark but no bite down here on the south coast! 

Posted Images

23 minutes ago, xSnow said:

Cannot believe how badly the Midlands has done these past days. No thunder whatsoever, and now the rain has fragmented. Perhaps isolated thunderstorms tomorrow with higher CAPE values but overall one of the biggest disappointments I have ever seen thunderstorm-wise with only the far East getting all the action this evening. Oh well, enjoy it if you get the chance.

All Lightning in the past 72 hours.

IMG_4954.PNG

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Lights flickered, MASSIVE rumble that shook the whole house, and seemed to vibrate the glass and whatever else could vibrate in the structure of the house. Not heard anything like that before!

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36 minutes ago, TN26 said:

Just got back from Dungeness and Camber. I can honestly say I have never seen anything quite like that before. A mixture of CTG and intercloud lightning of varying colours from pink through to golden through to green. Booming thunder but sometimes almost throttled by comparison. Genuinely lightning every half a second as the main cell past up the channel. Roads flooded on the way back to Ashford. A memorable night for sure.

Was on the sea wall at camber,absolutely phenomenal

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Just got home from the Sussex coast, Amazing display. I can't say the M25 & M23 wasnice to drive on, so much water!!!!!!!!!. Left at 23.15, took a stop at Gatwick to check and reply to the forum and just confirm my options again, then headed down towards Eastborne, the display was mental along the whole of the coast road. On the way home had some nice lightning around the Heathrow area. Now im back in damp old Aylesbury in the storm starved Home Counties lol

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5 hours ago, Sparkiee storm said:

Keep us informed of what u see :D

Got back almost one hour ago, and I gotta say....very hit and miss night! In general, I'm very disappointed, but it could've been worse. I did witness about 40-50 flashes, and drive through absolutely torrential rain just north of Brighton, but in terms of watching a frequent light display, it wasn't the case this time. 

Ultimately, two lessons to learn from tonight: 

1. I left at midnight. Had I left about 1 hour or so earlier, I'd probably have caught a bit more where I ended up, which was some pier front beach in Eastbourne, though I did try Beachy Head too but didn't see all that much....I delayed my departure though as frankly I wanted to be damn sure these storms weren't just going to die over the channel as has happened before....

2. No doubt had I left earlier, I'd have caught more lightning from the beach spot I found, but next time.....if in doubt, choose Kent! Had I gone to Folkestone or Dover (which were only 15-20 mins more in the car!!!) I'd have seen far more than in East Sussex. 

 

So there we are, disappointing but not terrible. I have a dash cam and will scan through my footage on there tomorrow, as it should have caught at least a dozen or so decent lightning strikes, otherwise, I got damn all on my Iphone and DSLR camera. 

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Well the forecast was a flop everything massively shifted east. dunno if they updated the forecast as the evening went on. Was hoping for  some heavy rain this morning but even that is of the cards now.

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Woken up twice by rough lightning, one of the strikes must have been positive because the thunder from it was ridiculously loud.. 

Other than that, a huge flop by the models. 

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my local BBC has more showers forecast today than they did yesterday moving up from the south , I can only assume they think that stuff in the channel with move N , they did mention the odd rumble of thunder but I think it's best to take any forecast with a large pinch of salt because their graphics shows a lot of rain around this morning and there really isn't much

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Morning all,

Pretty decent storm came through about 1:30am, with some lovely strobe lightning and what I think were couple of positive CG's! Some nice long rumbles too. Didn't last all that long though I don't think, though I must confess to having dozed off halfway through! 

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11 minutes ago, Darren Bown said:

Seems to be a risk of some pop up storms and showers this afternoon in the midlands and N England today?

yep highest instabily in modeled for East Anglia which Nick F highlights with a moderate in his assessment and convectiveweather not showing anything , a lot of this though depends on sunshine and that may be in limited supply

 

edit - BBC Breakfast is forecasting sporadic storms as they call it for N Wales and N England also down into the midlands also a lot of cloud

Edited by Gordon Webb
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A few showers here overnight, Enough to wet the ground.. Thick Fog which may take time to shift and temp 11.6c here this morning.

20170529_073630.thumb.jpg.3e3074e08b51c1059f769e98a5f4f710.jpg

 

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14 minutes ago, Polar Maritime said:

A few showers here overnight, Enough to wet the ground.. Thick Fog which may take time to shift and temp 11.6c here this morning.

20170529_073630.thumb.jpg.3e3074e08b51c1059f769e98a5f4f710.jpg

 

I've got drizzle,get it every day without fail .....

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got to admire the Beebs confidence , any showers / storms if you do get any won't be as severe as the ones that were seen overnight , REALLY

Edited by Gordon Webb
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15 minutes ago, Mokidugway said:

I've got drizzle,get it every day without fail .....

Yes light drizzle here to Moki, Maybe later this afternoon thinks may pep up once the sun breaks through and showers push East.

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Storm Forecast
Valid: Mon 29 May 2017 07:00 to Tue 30 May 2017 06:00 UTC
Issued: Mon 29 May 2017 07:00
Forecaster: PISTOTNIK

A level 1 and level 2 were issued for Belarus and NW Russia mainly for tornadoes, severe wind gusts and large hail.

A level 1 was issued for central Poland, the NW Czech Republic and parts of Germany for large hail, excessive precipitation and severe wind gusts.

A level 1 and level 2 were issued for parts of England, BeNeLux, parts of France and N Spain mainly for large hail, severe wind gusts and to a lesse extent for excessive precipitation.

A level 1 was issued for W Turkey mainly for excessive precipitation.

SYNOPSIS

A subtropical ridge stretches from Algeria towards central Europe. It is flanked by two weak long-wave troughs over eastern Europe (with a cut-off low over Greece and Turkey) and from Ireland to Spain, yielding an ill-defined, stationary omega pattern. To its north, a strong zonal flow is in place from N Scandinavia into NW Russia, where a surface cyclone intensifies at the southern rim of a body of arctic air.
A long, wavy frontal boundary from NW Russia across Belarus, Poland, Germany and France into Spain is the main focus for possible thunderstorm development. Further south, warm to hot and mostly dry conditions prevail.

DISCUSSION

... Belarus into NW Russia ...

The frontal boundary becomes ingested into the circulation of the Russian cyclone. Aided by insolation, warm air advection and delayed vertical mixing, a strong rise of 2m temperatures and dewpoints is predicted in the warm sector across Belarus and adjacent Russia. Though the sparse surface observations make it difficult to validate the model forecasts, the WRF solution with values around 23/15°C by afternoon appears realistic. It would result in CAPE up to 1000 J/kg over a large area, maximized ahead of the cold front.
A small but intense upper-level trough travels from the Baltic States eastward into the area of interest. The westerly flow increases ahead of that feature and on the southern flank of the surface cyclone. As a result, 0-3 km shear around 15 m/s and even 0-1 km shear in excess of 10 m/s will likely overspread the robust CAPE reservoir of the warm sector.
Storms are expected to initiate by noon, aided by sufficient lift near the frontal boundary and ahead of the upper-level trough. Due to the trailing nature of the cold front, a convective line appears rather unlikely and convection could stay discrete for some hours. It will likely organize into supercells with a risk of large hail, severe wind gusts and tornadoes. If strong diurnal heating extends all the way northward to the occlusion point, where vertical wind shear is strongest, even one or two strong and long-lived tornadoes are not ruled out!
Storms will cluster later on and move eastward. Their severe weather risk will gradually decrease overnight. Stronger capping will likely preclude initiation further south over the Ukraine, though CAPE is present and vertical wind shear would still suffice for organized convection.

... Poland, Czech Republic, Germany ...

The westward continuation of the frontal boundary lies under quiescent synoptic conditions or even large-scale subsidence near the upper-level ridge. A cool maritime boundary layer with sea fog will be advected inland from the Baltic Sea, which will quickly cut any thunderstorm options on its northern side.
Similar to Sunday, a belt of rich low-level moisture will be trapped and maintained by the convergent flow near the frontal boundary. Its arc will stretch from central Poland across north-central Germany into BeNeLux and N France on Monday. 2m dewpoints around 18°C beneath steep lapse rates aloft (remnants of a "Spanish plume") will likely support CAPE on the order of 1000 to 2000 J/kg (see Sunday 12z Trappes and Idar-Oberstein soundings). Vertical wind shear is weak.
With a lack lift mechanisms, breaking the strong cap may be a difficult venture. High-resolution models uniformly show isolated to scattered convective initiation, but do not agree on the stretch of the frontal boundary where it shall happen. Pulse storms that form in this high CAPE / low shear environment can bring isolated large hail, severe downbursts and flash floods. Convection may continue into the night with an erratic, cold-pool-driven motion if one or two larger clusters form.

... England across BeNeLux and France into N Spain ...

The tail of the frontal boundary fans out over western Europe. Vertical wind shear increases again ahead of the next long-wave trough (rising from 10 to 20 m/s across the lowest 3 km from S to N). The plume of the richest low-level moisture is advected into N France and Belgium, where 2m dewpoints slightly above 20°C may even support CAPE up to 3000 J/kg. Otherwise, CAPE is expected mostly on the order of 500 to 1000 J/kg and its overlap with the increasing shear regime appears quite solid.
Scattered storms will initiate when diurnal heating manages to erode and break the cap, or aided by sea breeze fronts or outflow boundaries. They will organize into multi- and supercells with a primary risk of large hail, severe downbursts and excessive precipitation. Low-level shear is not particularly enhanced, but a tornado is not ruled out in case of favorable interaction of outflow boundaries with the sea breeze front or with each other.
Upscale growth into an MCS may occur and excessive precipitation may become another hazard at this later stage in the evening. The timing and placement of such a cluster are still uncertain, but the level 2 area with the most plentiful low-level moisture appears to be at the highest risk. It could continue into the night and may travel into the Netherlands and westernmost Germany with an ongoing, slowly decreasing severe weather threat.

... SE Europe ...

Scattered, mostly daytime-driven showers and thunderstorms will form in the well-mixed airmass beneath the upper-level low over Turkey, the S Balkans and Greece (including some Aegean islands). High storm coverage may result in one or two flash floods in W Turkey. Otherwise, severe weather is unlikely under limited CAPE and weak vertical wind shear.

http://www.estofex.org/cgi-bin/polygon/showforecast.cgi?text=yes&fcstfile=2017053006_201705290700_2_stormforecast.xml

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25 minutes ago, Polar Maritime said:

Yes light drizzle here to Moki, Maybe later this afternoon thinks may pep up once the sun breaks through and showers push East.

Hope so PM so hard entertaining grandchildren with this set up !

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My convective/storm forecast for today, just updated.

Storm & Convective Forecast

convmap_290517_2.thumb.png.abae8f6cf410a3f5081d16e05f085391.png

Issued 2017-05-28 22:08:52

Valid: 29/05/2017 06Z to 30/05/2017 06Z

CONVECTIVE/ STORM OUTLOOK- 29TH MAY 2017

Synopsis

Upper trough axis approaches western Britain from the west, as upper ridge extending north from the Mediterranean across Central Europe begins to relax. A plume of warm, moist and unstable air will be present across central, southern and eastern England on Monday, ahead of cold front moving in from the west, which will clear eastern England Monday night, diurnal heating of this warm humid air combined with breeze convergence could trigger some isolated thunderstorms.

DAY 1 OUTLOOK - 06Z MONDAY 29TH MAY - 06Z TUESDAY 30TH MAY 

... S ENGLAND,  E WALES, MIDLANDS, LINCS AND E ANGLIA ...

Atmosphere in the morning will likely be largely turned over by overnight storms, with a cap in place. However, abundant mositure (dew points 16-17C) and surface heating combined with breeze convergence ahead of cold front moving in from the west across England and Wales may trigger isolated thunderstorms during the afternoon across the above areas. 30-40 knts of deep layer shear should favour organisation of storms, bringing a risk of localised torrential rainfall leading to flash-flooding, isolated large hail and gusty winds. Also, an isoalted tornado can't be ruled out with storms forming along breeze convergence zones

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44 minutes ago, Gordon Webb said:

got to admire the Beebs confidence , any showers / storms if you do get any won't be as severe as the ones that were seen overnight , REALLY

Looking forward to severe drizzle and aggressive fog then. Would be confident if it wasn't for this cold damp misty rubbish.

The problem is going to be the need for warmth to trigger anything. That at the moment isn't looking likely.

Edited by The PIT
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quality of lightning last night = epic

quantity of lightning last night = pathetic 

probably only had about 8 lightning strikes last night but each was pretty special - some of the longest (distance) and longest duration C-C crawlers I've ever seen - epic thunder associated with it

pity not a lot of it

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