Uk Convective General Discussion & Forecasts - April 2012 Part 4

[chionomaniac]

Pics or it didnt happen!

// Whats an LLJ ( or am I just being thick today )

You can see it in the form of the low level clouds racing through the sky. It is set to weaken later this afternoon.

[Chris K]

Hmmm, I'm skeptical about today. Some very unstable looking clouds around this morning and dead calm but the convergence zone looks a bit far south for here. We shall see though.

There are some pretty heavy radar returns up over Gloucestershire and surrounds at the moment, likelihood for some flooding there.

Yes I too think that I'll be too far North to see anything thundery, however the skies above me look very ominous. I drove through a torrential spell of rain on my way into work this morning that drifted in from the Severn Estuary. The Severn crossings disappeared under the rain.If anything decent starts developing along the forecasted convergence zone,I am tempted to drive south as I finish work earlier today

[Coast]

You can see it in the form of the low level clouds racing through the sky. It is set to weaken later this afternoon.

[BrickFielder]

Marked convergence zone moving slowly south is likely to be the focus of activity today. GFS and NMM suggest it is likely to be quite marked but the RASP model might suggest it slightly more broken.

Convergenc zones tend to raise the risk of very spout like formed tornados, providing there is enough lifting at the convergence zone.

Instability according to the models looks rather weak, suggesting lifting might not be that impressive. Considering that convergence zones can of themselves create some lifting and models have a tendency to under estimate surface temperatures while in some circumstances (this tends to be with winds from the direction of Spain) over estimate dew points it is difficult to determine the instability available.

Cloud tops look a bit limited or slightly better further west, while a bit of a dry slot through mid to upper levels does not quite overlap the convergence zone. Mid level vorticity looks better over the south west but appears to be receding and lapse rates begin to decline later in the day to the east.

Forecast SkewT's show the cloud top limit at 500hpa which is barely enough for a thunderstorm, with marked wind shear limited to above this region.

Over all its not that impressive at first glance, but if I had to pick some areas then I would look at an area around exeter and possibly north london. The first due to slightly better instabillity and cloud height and the second because of the wind field and possible heat island effect of London. Main risk I think will be heavy showers and hail, with perhaps a very outside risk of a weak short lived funnel.

[Lynxus]

What on earth is wrong with the jet at the moment. I dont think ive ever seen it go that far south!

[Andy Bown]

There are now 3 distinct lines of showers over the Southern 1/4 of England which are aligned SSW-ENE with a 'joinging' line of

showers at the NE end of them.

What was forecast to be the main convergence zone is now in evidence running from South Devon up towards the Swindon (ish)

area and the Southern edge of the line is bringing sporadic sharp showers to my location at BA12.

Nothing torrrential at the moment although a few small cells are nearing 20mm per hour and the furthest SW cell is touching

90mm per hour.

I would expect the cells within the line(s) to increase in intensity as the land continues to warm, there's a good deal of sunshine to

the South to aid energy and developments.

[Eskimo]

Heavy showers to my west. Dark skies as well, but nothing massively convective about the sky.

Edited April 27, 2012 by Eskimo

[Raidan]

Hmm do I take a interest in today or not,the SW getting mentioned a lot and talk of convergence lines heavy showers etc makes me want to but after years of nothing even in the right set ups is making me think not to bother,decisions decisions do I or don't I?

[Lynxus]

Hmm do I take a interest in today or not,the SW getting mentioned a lot and talk of convergence lines heavy showers etc makes me want to but after years of nothing even in the right set ups is making me think not to bother,decisions decisions do I or don't I?

Id only pay some glancing interest.

For my area, we ONLY EVER get good storms from spanish plumes and imports.

Any other storm is just weak and pointless almost lol

[Coast]

Hmm do I take a interest in today or not

I think the UKASF map I linked earlier has the potential of interest covered:

Radar watching from now on!

[SnowJoke]

Heavy showers all morning in MK, with a few breaks in between. Clouds are gaining height as the temp rises, some i've seen already with nice anvils on. No thunder from them yet, but looking at the wind convergence zone around southern england it's only a matter of time, as this will be the driving mechanism today for storms.

[Nick L]

More annoying showers today. I wouldn't mind if they were exciting but it's just moderate rain!

I've also got an outdoor practical this afternoon. That should be fun...

Edited April 27, 2012 by Nick L

[picog]

Steady old rain all morning, barely a breeze.

[DeepSnow]

Had a very heavy shower earlier today with the paths turning into mini rivers, apart from that we have had mainly light showers but Im too far north I think for any real action today!

Edited April 27, 2012 by DeepSnow

[Eskimo]

Just heavy rain, pretty standard, in fact we had heavier rain in that band on wednesday, plenty of time obviously!

[Lynxus]

Interesting developments down bristol way / along the eastern servern...

[fromey]

afternoon all,

not a great deal going on at the moment, very dark clouds coming over head with a few heavy bursts but not much else.

just going to see what happens as the afternoon rolls on.

fromey

[Andy Bown]

Still literally on the edge of the zone as BA12 has been throughout the morning from when it first started to develop at around

08.30! Sporadic sharp showery drops of rain, very dark to the N/NW and much clearer to the S/SE.

The line does seem to be widening at the Western end with the showers pulsing NE along it.

Fascinating radar watching and sky watching - not necessarily in that order!

[MP-R]

Some huge great big cbs to the east and south at the moment, the tops just visible through patchy fractocumulus below. Sun also coming out now which should help heating.

[Lynxus]

Some huge great big cbs to the east and south at the moment, the tops just visible through patchy fractocumulus below. Sun also coming out now which should help heating.

Even seeing sferics from other parts of the country now..

Never know, The ones near you might start zapping soon.

[MP-R]

And on that note, I think I just heard a distant rumble to the south. I have checked... there are no aeroplanes around.

[Andy Bown]

And on that note, I think I just heard a distant rumble to the south. I have checked... there are no aeroplanes around.

Mike, you're one side and I'm the other! Judging by the continued pulsing movement and gradual expansion of the line I think

you've a 25% more chance of catching it than me - unless the line as a whole begins to move South.

[fromey]

Mike, you're one side and I'm the other! Judging by the continued pulsing movement and gradual expansion of the line I think

you've a 25% more chance of catching it than me - unless the line as a whole begins to move South.

looking at the radar i might get clipped by whats coming up.

im just slightly to far south east!!!

fromey

[MP-R]

Mike, you're one side and I'm the other! Judging by the continued pulsing movement and gradual expansion of the line I think

you've a 25% more chance of catching it than me - unless the line as a whole begins to move South.

Now raining and haven't heard anything else but boy is it going dark!

[chionomaniac]

I reckon that there is a classic flash flood risk for Cornwall /North Devon this afternoon. Stagnant cells over the hillier regions leading to run off. If the precipitation is heavy enough, Polperro, Boscastle type floods could occur. Lets hope that there isn't too much forcing.