Convective Discussion

[chrisbell-nottheweatherman]

Where's Mr Sherman and his tripod + camera then???

Yeah. No lightning observed, though I was in the bathroom at the time () - I suspect it was IC.

[dogs32]

some beefy shower's just started in South West Wales....

[chrisbell-nottheweatherman]

Looking at the radar, it's hard to tell where the CF is. Anyone got a good idea? (I'm going to have a look at the other charts to see if I can detect it, but I've never tried that before).

[Winso]

Bit of convective rain and a strike in Norwich earlier. I'd literally just gone outside for a meeting with my boss when there was a flash which I wasn't really expecting. He's seriously scared of lightning so had a small freak out before legging it inside.

[chrisbell-nottheweatherman]

Bit of convective rain and a strike in Norwich earlier. I'd literally just gone outside for a meeting with my boss when there was a flash which I wasn't really expecting. He's seriously scared of lightning so had a small freak out before legging it inside.

Hello local member! Whereabouts in Norwich do you work?

[Coast]

Looking at the radar, it's hard to tell where the CF is. Anyone got a good idea?

I know where it was at 0900 hrs and where its likely to be later....

[chrisbell-nottheweatherman]

I know where it was at 0900 hrs and where its likely to be later....

Thanks Coast - I can't pretend I understand all of those markings, but that looks about how I imagined. Speaking of CFs, is there any rule of thumb as to how far in horizontal surface measurement that cold sector air undercuts the warm, moist air? In other words, how far infront of the indicated position of the CF will the arrival of cooler air be?

[Jane Louise]

Not many storms around today. Sorry, Harry and Pat I really thought they would happen.

[Coast]

is there any rule of thumb as to how far in horizontal surface measurement that cold sector air undercuts the warm, moist air? In other words, how far infront of the indicated position of the CF will the arrival of cooler air be?

Oh God!! Now you're asking me technical things! All I do is post hotlinks and uploads to interesting stuff and hope clever people tell us what's going on!!

Not many storms around today. Sorry, Harry and Pat I really thought they would happen

Tomorrow more likely for you Jane Louise

[chrisbell-nottheweatherman]

:o Oh God!! Now you're asking me technical things! All I do is post hotlinks and uploads to interesting stuff and hope clever people tell us what's going on!!

Where are the forecast team when you need 'em?

Anyhow, radar seems to suggest that that line of storms and showers is now heading out over the North Sea. Quite overcast here now, but dry and breezy.

Edited August 20, 2009 by chrisbell0033944

[Jane Louise]

Tomorrow more likely for you Jane Louise

[Mark.C]

The cold front seems to have passed through now, looks like some convection happening out in the Irish sea, hopefully get some downpours later and a rumble of thunder if im lucky

[chrisbell-nottheweatherman]

Hi, if you go onto the MetO website and click on 'Latest/Recent' and on 'Pressure' you will see where the CF is located. At the moment the main CF is coming out of Eern Wales and if you look at the Radar, you will see a line of showers up the spine of the UK - that is the CF. There is a another CF just ahead of the main one which has brought with it moderate rainfall for most.

On another note, Friday continues to look good for thundery showers/storms with some impressive lapses and marginal CAPE values. Certainly one of the more promising days for storm developmen this month.

Thanks 09 - didn't see your reply before. How can there be 2 CFs in succession?

Edited August 20, 2009 by chrisbell0033944

[Coast]

I feel it's my last chance for any storms for me this summer lol.

Not a huge risk, but certainly better:

[chrisbell-nottheweatherman]

Thanks! Just one more question - on the MetO pressure chats, does a purple front indictate an occluded front?

Edited August 20, 2009 by chrisbell0033944

[chrisbell-nottheweatherman]

Not sure on that one :lol: The second front has lower temperature gradient and denser air mass than the first, which is the reason another CF is following on behind, bringing with it heavy showers.

Re: Pressure Fronts - An occluded front is shown by both an Arrow and Semi-circle indicating that the colder, much denser airmass has 'caught up' with the warm front. On the MetO website, it is indeed coloured purple.

Thanks again - I know about occluded fronts, just was making sure I recognised what I saw!

MetO pressure charts are showing 2 CFs and then a trough over Ireland?

Edited August 20, 2009 by chrisbell0033944

[Thundery wintry showers]

Storm report - crashing thunder at 11.08, another crash a few minutes later and a few more rumbles associated with a short but sharp shower.

Bit of convective rain and a strike in Norwich earlier. I'd literally just gone outside for a meeting with my boss when there was a flash which I wasn't really expecting. He's seriously scared of lightning so had a small freak out before legging it inside.

Yes, the same (highly unexpected) short sharp shower passed through UEA as well. I think the electrification died out once it got north of Norwich, as there were just a few rumbles of thunder as it approached. A couple more short, sharp showers occurred afterwards from altocumulus castellanus that was developing into cumulus and cumulonimbus.

I didn't see it coming at all- I was in the office doing some work and suddenly it went very dark outside, so naturally I went to check what was up, and saw that beast.

Today's weather backs up my previous opinion that the "westerly change" is coming in too rapidly to allow much in the way of storm activity to develop. After an hour of "sunshine and showers" with Ac Cas type stuff, it's gone dry, cloudy and windy with the storms shoved out into the North Sea.

[chrisbell-nottheweatherman]

Yes, the same (highly unexpected) short sharp shower passed through UEA as well. I think the electrification died out once it got north of Norwich, as there were just a few rumbles of thunder as it approached. A couple more short, sharp showers occurred afterwards from altocumulus castellanus that was developing into cumulus and cumulonimbus.

I didn't see it coming at all- I was in the office doing some work and suddenly it went very dark outside, so naturally I went to check what was up, and saw that beast.

Today's weather backs up my previous opinion that the "westerly change" is coming in too rapidly to allow much in the way of storm activity to develop. After an hour of "sunshine and showers" with Ac Cas type stuff, it's gone dry, cloudy and windy with the storms shoved out into the North Sea.

So, with the rapid advance of the CF, the result is a line of thundery showers as opposed to a big, wide mass of them?

[Harry]

Not many storms around today. Sorry, Harry and Pat I really thought they would happen.

Lol aww don't despair Jane Louise

What was discussed in the PM did mention timing would be a significant factor, so I didnt raise my hopes though nevertheless it was a very enjoyable read :lol:

Tomorrow looking good - Estofex even giving us the decency of inclusion yay I think tomorrow would stand many people in good stead, especially central southern areas. On days like that expected tomorrow, you can get widespread areas of downpours, so unlike days like today it's one and that's it, it's one, followed by possible half a dozen more

Bring it on!!

[Ross B]

There are quite a few lightning strikes on that band moving out east of Ireland. Maybe something for some western areas in the next few hours? The general band is moving in this direction but it's not very strong in the area which is likely to hit here. I wouldn't really be able to enjoy it anyway since i'm at work in central Glasgow :lol:

[Harry]

Just been having a peruse at the charts for next week, and yet again we find a very complex system of weather around.

Low pressure (as has been the case for most of the Summer it feels like) will be stationed towards the NW/W, advecting further warm and moist pools of air up across France. Unfortunately for us, another mate in the form of a cold front is expected to skip across us and cut this off, "giving all the frogs the fun AGAIN!!" lol. Some pretty nice CAPE values and storm risks will build for our French neighbours through next week.

Indications appear to be that we will be get thrown some relatively warmer and moist air late towards the end of the Weekend, before the CF is expected to bully it's way through.

As ever, if the CF stalls, or the LP pulls away slightly, we may get thrown another plume opportunity.

It is very unlikely at this stage, and a long way off, but I am hoping the 'long way off' bit could be in our favour :lol:

NB I have attached the FAX chart for early Monday...you can then imagine what the following charts will read...CF stalling over N France allowing another plume for France and other continental neighbours to enjoy, while we painstakingly watch the thunder risk zones bend around our shores!!

Edited August 20, 2009 by Harry

[Thundery wintry showers]

So, with the rapid advance of the CF, the result is a line of thundery showers as opposed to a big, wide mass of them?

Yes- and they're all out in the North Sea now!

[Jane Louise]

Lol aww don't despair Jane Louise

What was discussed in the PM did mention timing would be a significant factor, so I didnt raise my hopes though nevertheless it was a very enjoyable read

Tomorrow looking good - Estofex even giving us the decency of inclusion yay I think tomorrow would stand many people in good stead, especially central southern areas. On days like that expected tomorrow, you can get widespread areas of downpours, so unlike days like today it's one and that's it, it's one, followed by possible half a dozen more

Bring it on!!

Thanks Harry,

I was expecting heavy rain showers today and what did I get a bit of drizzle

Oh well, there's always tommorow I suppose lol.

[chrisbell-nottheweatherman]

Yes- and they're all out in the North Sea now!

I know. :lol:

There are quite a few lightning strikes on that band moving out east of Ireland. Maybe something for some western areas in the next few hours? The general band is moving in this direction but it's not very strong in the area which is likely to hit here. I wouldn't really be able to enjoy it anyway since i'm at work in central Glasgow

Those are, I presume, associated with the trough in the Irish Sea.

[Ross B]

Those are, I presume, associated with the trough in the Irish Sea.

They are indeed, it has markedly increased in intensity as it has hit land over SW/W Scotland with areas of rain rates now up to about 50-100mm/hr mixed in. I can see a huge CB now approaching Glasgow so we might manage the odd rumble of thunder here if we are lucky.