Convective / Storm Discussion Thread - 31st May 2017 onwards

[poseidon]

Getting dark round here as showers approach. But I'd prefer the showers to s*d off and let the sun come out for a prolonged period as this looks a bit like the all too frequent plume scenario at present when u have a day of white milky cloud and nothing happens.

[staplehurst]

3 minutes ago, Summer Sun said:

Some torrential rain in west Ireland

Looks like a radar is down in SW Ireland and so the echoes here are being detected much higher in the atmosphere than at ground level by a radar further away - in other words, unlikely to be as heavy as radar suggests

[Ben Sainsbury]

Watch the line of cloud develop from Exeter to Cambridge on Sat24, possible convection could be started here in connection with the approaching cold front? http://en.sat24.com/HD/en/gb/visual

[Gordon Webb]

41 minutes ago, Had Worse said:

Ironic that Tony Blair is in the news. Common theme WMD in 45 minutes.

Weather of mass destruction

could also be weather of minuscule distribution

[tomp456]

There's only one certainty with UK storm setups...and that is that storms are a certainty in France. 

[Ben Sainsbury]

Some promising areas of Cumulus to my south now, exciting ahah!

Really continuing to grow to good heights now.

Edited July 6, 2017 by Ben Sainsbury

[<<Ryan>>]

Back end of the storm off the Kent coast

[Mapantz]

5 minutes ago, Ben Sainsbury said:

Watch the line of cloud develop from Exeter to Cambridge on Sat24, possible convection could be started here in connection with the approaching cold front? http://en.sat24.com/HD/en/gb/visual

That's an upper trough I think?!

[Chris K]

Definitely a tiny bit more eastward shift again in model outputs, with the emphasis of thundery showers across NE England and then later down into C/E/SE England as convection kicks off. I think some people are perhaps writing this off too early though, as there is always a lot of uncertainty with storm development. Some forecast to see storms may end up with zilch, whereas some who thought they had no chance get one!

I know I use them extensively but precipitation charts are not always the best tool to use in isolation.

2 minutes ago, Ben Sainsbury said:

Some promising areas of Cumulus to my south now, exciting ahah!

Really continuing to grow to good heights now.

The skies certainly looked unstable on my drive into Bristol this morning - but I think it'll be developing east/NE during the afternoon, rather than staying over here. Interesting to watch it develop nonetheless...

[Joneseye]

The lightning activity has really died down now across NW Europe compared to a couple of hours ago. The Strike rate was up around 140 per minute and now its around 40. Plenty of time for things to get going throughout the rest of the day.

The reality so far today illustrates how difficult it is to accurately model thunderstorms in this country.  

 

[Had Worse]

Oh to have this in the UK right now, I wish.

 

Across the pond in Minesota right now, lucky buggers. 

 

[Ben Sainsbury]

Precipitation beginning to form just south of Oxford along the line of developing cloud.

[tomdewey]

Warnings affecting Warminster

Yellow warning details

Rain

Between 06:00 Thu 6th and 02:00 Fri 7th

Isolated thunderstorms are likely to develop across parts of England and Wales from early Thursday morning before clearing by early Friday. While these storms may miss many places, where they do develop intense downpours are likely, bringing the threat of sudden flooding of roads, transport routes, homes and businesses. Lightning and hail may be additional hazards.

[Gordon Webb]

update

 

Day 1 Convective Outlook

VALID 06:00 UTC Thu 06 Jul 2017 - 05:59 UTC Fri 07 Jul 2017

ISSUED 08:57 UTC Thu 06 Jul 2017

ISSUED BY: Dan

UPDATE 08:57 UTC MDT removed from SE England based on latest trends (see update below). Still quite a bit of uncertainty, but general consensus is for zone of wind convergence to be the primary trigger for a few scattered thunderstorms this afternoon and evening - given better insolation likely farther south now, have extended the MDT (and SVR) to cover this risk later today. Here, the environment will be more conducive for severe conditions compared with areas farther north - with large hail and perhaps a tornado possible, while localised flash flooding will be a risk with any thunderstorm that develops. Again, stress storms will be scattered and not everywhere within the MDT etc will be affected...

 

UPDATE 07:19 UTC No changes to the map for now - elevated thunderstorms now developing over NE England as outlined below, moving offshore later this morning. However, elevated thunderstorms have largely failed to materialise over SE England so far, against the vast majority of NWP guidance (even 00z runs). AROME, while not perfect, seems to be handling this better with many runs yesterday suggesting a mid-late morning event for the far SE corner. For now retain the MDT risk here, but it is likely this will need to be removed based on latest trends. With less activity over the SE this morning, this perhaps brings a greater chance of thunderstorms over the northern Home Counties and into East Anglia later today, which could be severe

 

Summary: Active cluster of thunderstorms likely S/SE England Thursday morning, perhaps extending into S Midlands / East Anglia, clearing NE-wards. Showery precipitation with embedded lightning possible NE England for the first half of the morning, clearing into the North Sea. Elsewhere, scattered thunderstorms may develop during the afternoon hours from E Wales / W Midlands through NW/C N England, these could be severe as they drift east through the evening hours. As is often the case in these situations, uncertainty exists and is detailed below... 

 

... NE ENGLAND - THURSDAY MORNING ...

Good agreement for a developing area of showery precipitation over N/NE England for the first half of Thursday morning at least, with perhaps some embedded lightning - this eventually moving out over the North Sea by late morning.

 

... S/SE ENGLAND / S MIDLANDS / HOME COUNTIES / EAST ANGLIA ...

Elevated thunderstorms will likely be ongoing at the beginning of the forecast period over portions of S/SE England, these producing frequent lightning. General trend is for these to drift NE-wards with time, perhaps into parts of East Anglia and the south Midlands, though some uncertainty as to the northern and western extent, and whether they may start to weaken towards late morning and into the afternoon. There is a low risk that these storms could become rooted in the boundary layer if clearance is slow, and in which case they may begin to pose greater hazards from large hail and flash flooding.

 

... E WALES / N ENGLAND / MIDLANDS / EAST ANGLIA ...

Provided sufficient insolation occurs and cloud cover from early developments is not too extensive, then scattered thunderstorms may develop in a zone from E Wales / W Mids to NW Eng to NE Eng during the afternoon hours given dewpoints in the high teens coupled with forced ascent as a developing cold front begins to advance eastwards (and marked wind convergence).

 

Given 1,000-1,500 Jkg-1 CAPE and some reasonable deep layer shear, large hail up to 3.0cm in diameter would be possible, along with strong gusts of wind and localised flash flooding. A tornado could not be ruled out, though the risk is generally low. In a broad sense, the greatest risk of severe hazards (hail, flooding and tornado) increases towards the southern end of the SVR threat area, but here storms are more likely to be isolated given stronger capping and perhaps a hang-back of cloud following morning elevated convection. Any storms that do develop will drift towards the east, perhaps a little more south of east by the evening hours, and could survive into the night as they exit across the North Sea.

 

Worth stressing storms will be scattered in nature and so inevitably some places will stay dry, despite a large geographical area potentially at risk.

I've now been removed from moderate and into slight zone

Seems BrickFielder was right in his assessment

 

Edited July 6, 2017 by Gordon Webb

[Andy Bown]

Definite line of mid level convection drifting N/NE across Warminster. Very clear ahead and behind so makes me wonder if it's a trough forming.

[AL.]

11 minutes ago, Ben Sainsbury said:

Precipitation beginning to form just south of Oxford along the line of developing cloud.

I've noticed this too, just over Abingdon. Just developed out of nowhere.

 

[Had Worse]

Apologies in advance.

This is happening in Minesota http://www.duluthharborcam.com/p/two-harbors-boat.html

Cant find a thread that it should go in as its not european.

[Flash bang flash bang etc]

Stifling here in Maidstone - clouds bubbling up nicely too, but seems odd since the channel stuff has moved on through already.

[Another Kent clipper]

Meanwhile. Here's a scudnado I took on Tuesday afternoon. I've been anticipating some action ever since, still waiting..

[dave reid]

Time to get in my chosen position and wait!!!!

 

Heading mid way up the A34, Tothill services to use / steal Mcdonalds electricity.

Like the look of any tail end charlies that can form in this area with a fair bit of wind shear and bucket loads of CAPE as the move East 

 

Woooo-Hoooo  

[MattTarrant]

Plenty of Altocumulus Cas continuing since 8AM 

[karyo]

Sunny and boring here...

[Harry]

Thunderstorm erupted in Kent (cue fury from elsewhere lol)

[seb]

Just now, Harry said:

Thunderstorm erupted in Kent (cue fury from elsewhere lol)

Yeah came out of nowhere within 10-15 minutes. Massive tower right above me. 4 lightning strikes & loud thunder in the last few minutes. 10 seconds of huge tropical rain drops... 

[Summer Sun]

Few more heavy showers breaking out now down south