Convective/storm Discussion

[Tony Gilbert]

9.45pm Mon

Slight Risk Thunderstorms SW UK through to central east regions. Also Southern Ireland. 09Z-21Z Weds 10th June 09

Slight Risk of Weak CZ Tornado Development Same region (UK only) 12Z-20Z

Some variations in the models might suggest a shift in the risk boxes by Tues morning. Current forecast synopsis shows the development of a surface trough with weak troughing aloft. Heavy rain looks in place for northern UK regions with a secondary surface feature building to the south within a rather unstable climate. A very moist lower level profile looks in place for central UK regions with dew point ratio putting LCL very low indeed. Whilst vertical shear looks weak at lower & mid levels it is noted that a strong confluent zone is likely to develop along a SW to NE boundary along the moisture axis. 400mb upwards shows a moderate divergent rear exiting jet stream. The combination of the two could well develop upper lift from the jet with stronger isolated cells running over a pronounced boundary at surface. Hense the Slight Risk for tornadoes.

ATM negative factors are heavy saturation at mid levels, weak mid level shear with dry air spreading east from 450mb upwards. The net result could see the stronger isolated cell development occurring much later in the time range as potential instability is realised.

All in all certainly one to keep an eye on.

Edited June 9, 2009 by Tony Gilbert

[Nick F]

Thanks Tony, have turned this thread into discussion thread now and shut the other one as it was getting long ...

N-W have a forecast for thunderstorms out for tomorrow: http://www.netweather.tv/index.cgi?action=convective;sess=

[pottyprof]

Well hopefully we'll get something..

Thanks to Tony for the update. Appreciate that.

Got the cams charged so we may go out for a drive into the Peaks..

Edit.. Just been told to not stick my head out the back door... LOL

Ok Ill try and get the weather cam working too.. :huh:

[VillagePlank]

Looking OK for t/storm formation in the areas Tony has already mentioned. Perhaps not great amounts of CAPE available, and certainly marginal LI's, but as we all know, that's not the whole story ...

Both these charts correlate well with the 'lift' in the atmosphere charts ...

Note the areas near the S/E of the country. Made me look further, that did ... Looks like an organised area of rain moving NE from France, clipping the S/E perhaps later ... but although it might be thundery rain, I don't think it will be an MCS, unfortunately - conditions in France don't look that good at all today

BBC have just reported some slow moving showers expected across the south which will 'certainly' be thundery. Not sure to make of that one, to be honest.

[Tim B]

Looks like this could turn out to be an interesting day.

[SteveB]

Hoping to get my first Tstorm of the year.

[Coast]

Some disagreement between sources this morning with ESTOFEX having none of it, just a central band through France being the closest they forecast for storms, but a level 1 none the less. UKASF also going with a 'no show' today, odd as both the above are normally on the case and would back up Nick and Tony's forecasts as detailed/linked above.

Of course Carol Kirkwood has a hint at possible thundery showers, but I'm not going down that whole Met O/BBC route again!

My hunch, something isolated later across the Midlands down as far as London and the home counties.

But that's just a hunch.......

[Harry]

Again, those charts looking quite good...for certain areas of the UK anyway :huh:

[dogs32]

fast development of heavy showers down South

[VillagePlank]

Again, those charts looking quite good...for certain areas of the UK anyway :huh:

Nah, don't be too disheartened, you can see where the ideas are coming from, here's the skew-t for lunchtime in our area ...

Low LCL, big (ish) clouds, and shear at around 600hPa. Not too bad, but perhaps a nice surprise on the cards. The real worry is lack of moisture with moderate amounts of Tdd most of the way up (you need a difference, I think, and it's never very helpful if it's moist all the way up, or dry all the way up)

(Yeah, I know my dry adiabat line is a bit wonky, but, hey, it's 8:21am!)

Edited June 10, 2009 by VillagePlank

[Harry]

Nah, don't be too disheartened, you can see where the ideas are coming from, here's the skew-t for lunchtime in our area ...

Reduced 84%

800 x 700 (130.68K)

Low LCL, big clouds, and shear at around 600hPa. Not too bad, but perhaps a nice surprise on the cards

Will keep my eye out then :huh:

I never realised that the showers would be kicking off so soon - its more a case of heavy rain at the moment rather than showers! Early brightness here is very swiftly giving way to some darker, ominous looking clouds to the South and Southeast at the moment

[maidstone weather]

UKASF also going with a 'no show' today, odd as both the above are normally on the case and would back up Nick and Tony's forecasts as detailed/linked above.

That's odd, because I thought someone posted the UKASF forecast last night. I just had a look at their site and they have issued one at 19:16 last night :huh:

Storm Forecast Issued: 2009-06-09 19:16:00

Valid: 2009-06-10 00:00:00 - 2009-06-10 23:59:00

Regions Affected

East Anglia, West & East Midlands, Home Counties, West Country and much of Wales ( most of the UK, excluding the Northern Isles, Western Isles and Northern Ireland, are included in the WATCH )

Synopsis

A trough over north Wales and southern parts of Northern England will provide outbreaks of heavy, locally torrential, rain during Wednesday, moving slowly northeastwards and developing during the day. Scattered showers are forecast to develop to the north of this area of rain, especially across inland parts of Northern England and Scotland, although these showers are not expected to be thundery. However, to the south of this area of rain, across much of England, Wales and perhaps southeast Ireland also, scattered showers and thunderstorms are expected to develop fairly quickly during the late morning and afternoon. With a slack airflow, and light winds, the showers will be very slow moving and could give high rainfall totals in a short space of time. The south coast, and parts of the Southeast, may have a mostly dry day, especially during the afternoon. Hail, thunder and lightning may accompany the showers/storms. Any showers/storms that do develop will only slowly decay during the evening as the pulse of heavy rain continues to move northeastwards across northern England into Yorkshire and Lincolnshire.

Back here in Kent, we have extensive cloud cover

Edited June 10, 2009 by maidstone weather

[VillagePlank]

Back here in Kent, we have extensive cloud cover :huh:

16C temps should kick stuff off, if we reach that by lunchtime The low grey murk should, believe it or not, burn off ..... but we probably won't be able to see it because the cells will be moving in, merging together, by then

[dogs32]

I think there is a good chance today for many...........With showers growing very fast down the South Coast areas..

And turning heavy as they spread up on radar....This early as got to be a good sign

[Tony Gilbert]

8.20am Weds

UPDATE

As per earlier forecast with broader coverage Ireland and UK though with restriction!

Upper troughing remains rather weak. Some uncertainties regarding lapse rate potential exist. Increased solar heating thus becomes paramount to today's outcome despite the GFS continuing to develop rather higher CAPE than may be practicable for the said regions. UK continues to show a rather strong convergence zone from S.Wales through to Humber. Though some uncertainties now exist regarding the risk of tornadoes given lack of potential instability close to the confluent zones.

Enhanced boxes are added where mid level dry air and PVA combine and marginally overlay within the zone of CAPE.

[Harry]

Oooh - very much on the fringe here!

[SteveB]

This has got to be the day.

As Dogs has said showers already to the South of me. The odd break in the cloud allowing the sun to break through.

Edited June 10, 2009 by SteveB

[Coast]

That's odd, because I thought someone posted the UKASF forecast last night. I just had a look at their site and they have issued one at 19:16 last night

Ha! I stand corrected! (must be my cache, or something, maybe :huh: )

So actually quite good agreement on something for the central part of the country today Currently raining hard here in Mid Sussex but nothing in the sky to suggest anything more. Good luck to those in the areas under observation today.

[Harry]

Rapidly expanding that band of showery rain - knocking on the door here I imagine in the next half hour or so!

Be nice if we get some thunder, naturally!

[Mad Murdoch]

Taken about 8.25am this morning, looking out to sea..

and the same one but just darken..

this was only the end of it, as it took me a few mins to get my camera.. Rotation was seen.

What do you think guys??

[MP-R]

A cloudyish start here but plenty of holes around too to let the sun through and the temperature is sitting at 15.0C so feeling nice when the sun is out. Also a bit muggier than yesterday.

[loopydreamer]

A cloudyish start here but plenty of holes around too to let the sun through and the temperature is sitting at 15.0C so feeling nice when the sun is out. Also a bit muggier than yesterday.

yep! muggy here too

cloudy but sun is shining through at times

and it just feels like something is brewing here

[maidstone weather]

The rain is turning increasingly convective in nature, that is it is now coming down harder and in big splodges that you usually see in a thunderstorm. No thunder or lightning though (as always :lol: )and only 13.1C. 1.0mm already since it started about an hour ago

Edit: we've had more rain in the first 9 days of this month than we did in the whole of last month!

Edited June 10, 2009 by maidstone weather

[Paul Sherman]

Dry as a Bone here in the Sahara SE Essex :lol:

[Harry]

Few observations from London (nr Tower Bridge) -

Clouds aren't moving very quickly, but getting progressively darker. It is eerily calm, with the slightest breeze blowing on occasions. Despite the dark cloud cover, it feels as if it is getting warmer. The radar does indicate that the incoming rain band is growing increasingly in both size and intensity!

Just feels like something fun might happen - window well and truly open too just in case :lol:

Also, where is that rain band likely to go that is wandering out of northern france? Can we hope for anything from this, especially if the sun gets out behind the current showers moving in?

UPDATE - First rains have arrived - moderate I'd say at the moment with relatively decent sized drops.

Edited June 10, 2009 by Harry