Convective Outlook Sun 7th June 09

[Tony Gilbert]

6pm Sat

There is a slight risk of scattered thunderstorms central south & SE UK 06Z-21Z Sun 7th June 2009

Marginal risk of brief funnel clouds

ATM a rather low risk outlook with restrictions. Unseasonally deep upper troughing edges NE with low pressure building at surface. Initial occluded front pushes NE from early Sunday morning bringing heavy rain to many areas. It is expected that a surface trough will develop within an unstable environment in the wake of the initial front bringing further scattered showers some of which could become thundery in nature. Upper shear looks minimal and moisture somewhat limited to the SE. Though the circulation within the low is stacked vertically and is open at mid levels increasing PVA lift. Convergence at surface with a layer of dry air at mid levels may create a marginal environment for CZ tornado development.

Similar outlooks have seen CAPEs rapidly diminish as a large cold pool spreads out at surface and upper cloud remains overhead within the confines of the lows circulation. So all in all some risk here but the said restrictions may win the day!

Based on the current model output the best scope for storms looks to be around Somerset during the afternoon where the best moisture pools and upper dry air combine.

Prob worth an update in the morning!

[VillagePlank]

Yup - agreed. I pointed it out late last week. Good call. GFS doesn't look, at first glance like producing the goodies, but there are real risks around for the SE, but it is dependent on convection kicking off. Once, and if, it does, the results could be quite memorable.

[ANYWEATHER]

Thanks Tony, At least we are in for, a chance of storms :lol:

[maidstone weather]

Yup - agreed. I pointed it out late last week. Good call. GFS doesn't look, at first glance like producing the goodies, but there are real risks around for the SE, but it is dependent on convection kicking off. Once, and if, it does, the results could be quite memorable.

really? i like the way you leave things on a cliffhanger

In the worse (or best) case scenario, what could we expect? :lol:

[VillagePlank]

really? i like the way you leave things on a cliffhanger

In the worse (or best) case scenario, what could we expect? :lol:

GFS has been showing the back end of this weekend (ie midday Sun onwards) as a possible. For sure, it's low risk - because convective parameters must collide on the day or moment, but, if they do, it's explosive. All sorts of minute by minute parameters come into play, and, as Tony says, if it does go, then we might see tornadic activity.

The key to it is convection kicking off, and pretty much nothing else. That is where we should look for. At the risk of the room falling apart laughing, our best bet, at the surface is insolation - ie breaks in the cloud.

IN any case I don't understand your post, nor do I understand the point of it.

Edited June 6, 2009 by VillagePlank

[maidstone weather]

GFS has been showing the back end of this weekend (ie midday Sun onwards) as a possible. For sure, it's low risk - because convective parameters must collide on the day or moment, but, if they do, it's explosive. All sorts of minute by minute parameters come into play, and, as Tony says, if it does go, then we might see tornadic activity.

The key to it is convection kicking off, and pretty much nothing else. That is where we should look for. At the risk of the room falling apart laughing, our best bet, at the surface is insolation - ie breaks in the cloud.

IN any case I don't understand your post, nor do I understand the point of it.

Thanks for replying and explaining it

I was merely enquiring what you meant by 'memorable' :lol:

[Tony Gilbert]

Agreed guys! yes this one is pretty much on the fence. Last time I gave a forecast for a similar outlook everything went 'down the pan' as so to speak, and the forecast was a complete bust!

Having said that it probably wouldn't take too much to tip the scales along the outflow boundary to the low where there is a small break in the cloud and temp rise under clear skys. So in many respects the best chance of true convection and CAPE's being realised should be around the periphery of the circulation and not the middle.

Though given the restrictions in vertical shear we can only really expect pulse cell development IMO.

Any suggestion of weak tornado genesis will be directly linked to rapid vertical development of any single convective cell.

Edited June 6, 2009 by Tony Gilbert

[Harry]

I have a fitness test in the morning, so in some ways am quite pleased rain is forecast. Also, I have nothing planned of the afternoon so COULD be a good excuse to cloud spot :lol:

Wouldn't it be ironic (fingers crossed anyway) - if the one time the risk of storms is very marginal, and many parameters have to come together at the same time, will be the day we all get our first proper storms! Unlike the previous plume set ups whereby conditions were almost perfect at times and naff all came of it.

[A.J]

Thanks Tony....I'm running the NMM12z model...the data certainly supports the potential, all of the variables (CAPE, LI, TT, Lapse et al) support your forecast

I'll certainly be looking forward to tomorrow mornings models with interest!

[A.J]

Yes, the 12z run does look promising although it also shows quite significant cloud cover so I'm not sure how things would pan out if this were to be the case. Meto forecasts for sunny spells behind the main front with Thundery showers to follow, so from that I guess there will be breaks in the cloud.

yep, cloud cover will play a factor certainly for CS counties, however, looking at the airflow , I think there will be sufficient breaks for convection to initiate....Hmm.....I smell a chase tomorrow!

[A.J]

Good luck if you do chase and if something does develop. Just hope this main rain band pushes North quickly, as the last thing I want is the remnants of that front stuck over the Midlands for a good part of tomorrow.

If I'm out & about, it wont be in the midlands, more like the home counties, south of the M4

[Tony Gilbert]

If there is some chance that cloud cover will shift further north!...then I will be taking my son (10 yrs) on a storm chase tomorrow. Though all is ATM pretty much on a 'cliff hanger' me thinks!...

Mornings model should give more detail!

Edited June 6, 2009 by Tony Gilbert

[Tony Gilbert]

Dear Moderators,

it is noted that there are at least 3 threads running for Sunday. Might be a good idea to suggest that members specify a particular day for their forecast or outlook rather than 'Day X Onwards', maybe!!.... Just a constructive thought, anyway

Edited June 7, 2009 by Tony Gilbert

[ANYWEATHER]

Dear Moderators,

it is noted that there are at least 3 threads running for Sunday. Might be a good idea to suggest that members specify a particular day for their forecast or outlook rather than 'Day X Onwards', maybe!!.... Just a constructive thought, anyway <_<

Well Tony, at least you,ll have a head start as it looks as though you,ll be one of the first to see the sun and get some storms to ignite. We are still under the main, rainband here in south Worestershire but hopefully that will push off soon :lol: Best Wishes and i HOPE you get some storms to chase today!

[Lynxus]

Can see soem lovely blue skies to my south.

Lets hope this clears away for some great convection.

Lets see what this arvo brings.

[Tony Gilbert]

10.40am Sun

As per earlier forecast; remaining low risk.

Box extended slightly further NE. Upper cold pooling looks to remains rather low across the UK increasing lapse rates primarily central south and SE (E.Anglia) UK. Mid level dry air and convergence look to be confined to the bottom left hand sector of risk box. Continued marginal risk of funnel cloud observations possible along a line of convergence Yeovil through to Watford 15Z-18Z. Slow moving cells with a blue sky back drop should make a fairly good day for chasing maybe!