Convective Weather Discussion UK

[NUT]

What's all that rain to the North of Scotland? Anything thundery there. A noticeable cloud has been developing to the back of me

[Harry]

What's all that rain to the North of Scotland? Anything thundery there. A noticeable cloud has been developing to the back of me

Looks to be orographic...few brighter echoes, so I wouldn't rule out completely a crack of thunder or two. One of the benefits of orographic rainfall...you aren't reliant on CAPE anywhere near as much as you are in flatter areas.

[Jane Louise]

I'm keeping my fingers crossed for us all. I shall be watching the skies and looking at the radar every now and then. Expect the unexpected too Lol. A beautiful day here today, clear blue sky, no sign of any clouds bubbling up as yet. I do have a 45% risk for 7pm but I wont take it to serious for today.I'm looking more at Saturday.

[Stuart]

yes Jane I got my fingers crossed here but i still

[Harry]

While there are generally, only the subtlest of differences, I am encouraged by the 06z GFS! The charts are reflecting what appears to be a setup conducive to a feed of moisture from the South. While CAPE/LI are relatively unchanged, there is a hint of a more southerly component. The FAX chart is indicating potential for a moist plume, reflected in the CAPE/LI figures on GFS. ECM is keen also to get a greater influence of Low pressure in to play.

Make no mistake, I am looking at a general trend and source for moisture, nothing more specific. This is GFS after all and it is Tuesday (likely to be the weekend before any real prospect of storms IMO). But, I am encouraged to see signs for a flow of moisture which has been rather absent of late, along with a greater influence of Low pressure

[Jane Louise]

yes Jane I got my fingers crossed here but i still

Yes Stu, I find it really confusing too. :unknw:We've got to remember it's only April and we have the whole of Summer yet. But the charts do look good for this week/end and we can't be blamed for getting a little excited at least as well as confused!

[knocker]

What's all that rain to the North of Scotland? Anything thundery there. A noticeable cloud has been developing to the back of me

It's mainly to do with the cold front that's lying across Stornaway at Midday. The high. res. MODIS at 1233UTC shows it well. Also the cloud incursions along the east coast and the Ci currently down here. Image courtesy NERC Satellite Receiving Station, Dundee University, Scotland" http://www.sat.dundee.ac.uk/

[Coast]

You know I have one lot of fingers lightly crossed at this point but the indications are growing nicely now and by Thursday, if the possibilities are still there, I might get quite excited!

Currently the NW storm risk doesn't prove too much to get interested in:

General feelings for this though?

[Sprites]

It's mainly to do with the cold front that's lying across Stornaway at Midday. The high. res. MODIS at 1233UTC shows it well. Also the cloud incursions along the east coast and the Ci currently down here. Image courtesy NERC Satellite Receiving Station, Dundee University, Scotland" http://www.sat.dundee.ac.uk/

Thats a nice satellite pic, the saharan dust plume was visable on a similar pic a few weeks ago, it shows the altocumulus that was over east anglia earlier , we need moisture from Biscay to be added into the mix before we se any decent storms

Ive found the Netweather storm risk charts to be unreliable, tending to over-hype the percentages most times

[Neilsouth]

Lots of altocumuls pumping up from the south here

[Harry]

Lots of altocumuls pumping up from the south here

Can't see that from C London, but it does feel more humid all of a sudden!!!

[Coast]

Hmmmm, slightly interested, although this is still a real long shot down here:

TTI < 44: thunderstorms unlikely.

TTI 44 to 45: isolated thunderstorms.

TTI 46 to 47: scattered thunderstorms.

TTI 48 to 49: scattered thunderstorms, isolated severe thunderstorms.

TTI 50 to 51: few thunderstorms, scattered severe thunderstorms, isolated tornadoes.

TTI 52 to 55: few to numerous thunderstorms, scattered to few severe thunderstorms, isolated to scattered tornadoes.

TTI > 56: numerous thunderstorms, few severe thunderstorms, scattered tornadoes.

The definition of the coverage terms is as follows:

Isolated: expect condition to occur in the forecast area but only expect conditions to affect about 10% of the area. (90% of the are won't have the condition).

Widely scattered:10- 20% of the area will be affected by the condition.

Scattered: 20 - 50% of the area will be affected by the condition.

Few or likely: 50 - 70 % of the area will be affected by the condition.

Numerous or just the condition: more than 70 % of the area will be affected by the condition.

TTI is used to forecast thunderstorm coverage and severity. This index is quite good with cold air aloft. It may overcast severe weather when sufficient low-level moisture is not available and with cold upper air. TTI values work best in the flatter lower elevations east of the Rocky Mountains. For operational purposes, TTI correlations need to be adjusted by region in mountainous terrain. Generally speaking the lower TTI values can indicate more severe thunderstorms in the higher terrain region. Tests on the field (in the States) showed there is a good correlation between severe weather events and TTI values >48.

[Hughsey]

Lots of altocumuls pumping up from the south here

enlighten me, this can signal the development of thunderstorms later in the day cant it?

[Coast]

enlighten me, this can signal the development of thunderstorms later in the day cant it?

If it were a little more humid.

[Harry]

If it were a little more humid.

I have to say, I am somewhat surprised by the dew point figures. Even across the continent, they're pretty poor! We have the best dew points pretty much on the entire map!! :o

Edited April 19, 2011 by Harry

[A.J]

Altocumulus Castellanus are an indicator of mid-level instability, in a plume type setup, with an area of warm, moist air advecting out of Spain/France can lead to an increase in MLCAPE which in turn, with the correct parameters can result in elevated thunderstorms as the Ac Cas 'towers'.....At this present time, I don't believe that this scenario will play out for the SE, at least in the next 48-72 hours as the air coming up from France is relatively dry, hence the lower dew points over France, whereas over Southern/Western parts of England, dew points will rise tomorrow inland, aided with the energy and lift available with converging lower level winds may result in a few home grown heavy showers/thunderstorms breaking out in these parts....In I were to guess where, I would go for somewhere in Oxon, with any showers/storms drifting NW wards, and dissapating during the evening hours.....For elevated imports, judging by the current GFS model, I would go for saturday night into Sunday as the best chance for the SE as dew points rise over France, meaning the air can hold more moisture.....I think

Edited April 19, 2011 by ajpoolshark

[Stuart]

Hope Gfs 12z can stick with the storm risk later week and in to the weekend

[Jane Louise]

Just read the Met Office update. They don't seem very optimistic regarding rain or storms for tomorrow and the weekend. Oh well, I guesss there's still a chance it could change for the better lol.:lol: Cloud is starting to bubble up here now,it's very hot out there too .

[Supacell]

I'm hoping to chase this week, but i know its going to be an all or nothing situation. With cape values of the level shown for fri and sat any storms that can set off should be quite photogenic and electrically active, especially with that lower moisture. But i fear a week of dry weather with the cap proving too strong. Here's hoping my fears are wrong.

[Andy Bown]

The NW homepage has my town's current conditions as sunshine and thunderstorm! No idea why because there are 5 fair

weather cumulus visible lol !

[Harry]

The NW homepage has my town's current conditions as sunshine and thunderstorm! No idea why because there are 5 fair

weather cumulus visible lol !

Mine did this morning - that was replaced with a sun icon pretty soon after

[knocker]

....For elevated imports, judging by the current GFS model, I would go for saturday night into Sunday as the best chance for the SE as dew points rise over France, meaning the air can hold more moisture.....I think

Well the air over France has considerable scope to hold more moisture having had a quick look at the humidity over France at midday. And another look at todays ascent at Trappes; now if you injected some moisture into that the storm lovers might be in business.

[vortex_liam]

Good healthy cell aproaching aberdeen. looks fairly good and is going up fast! shame its not heading towards me!

[ZONE 51]

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on saturday thunderstorms also breaking out and rumbling on through the night, with a possible cluster for the south east on saturday night

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thinking saturday night perfect for the south east for multi clusters forming an MCS as dewpoints increases greatly, and other areas to seeing storms at the week end!

Edited April 19, 2011 by ElectricSnowStorm

[Harry]

thinking saturday night perfect for the south east for multi clusters forming an MCS as dewpoints increases greatly, and other areas to seeing storms at the week end!

Not seeing the justification for your statement, though nevertheless I sincerely hope you're right