Convective / Storm Chat And Discussion

[Coast]

Next week is looking good though.

Not currently particularly special:

[paul m]

We can but hope eh.

[Harry]

We can but hope eh.

Indeed, that GFS profile chart Coast posted this morning has updated in an interesting way.

Swathe of negative indices for the LI figures, particularly across the SE with hints of CAPE possibly building. Manchester not looking too bad in a few days time now either.

Stepping outside just now it FEELS as if there is a decent amount of moisture in the air - feeling more humid than I was anticipating...whether this is just because its a lot warmer today I don't know. High pressure dominating rules anything out for us in the next few days, but as the High recedes westwards over the weekend, it MAY just allow the areas of low pressure over the continent to encroach, or if orientation changes and we get a favourable wind flow from the continent, then storms may be a possibility - CAPE/LI figures are mouth watering just over the stream (the 'channel') for several days.

As it stands, there looks to be v little scope for my somewhat fantasy scenario to emerge...but on the edge of something I'd say, particularly if the High's orientation permits an east/south easterly flow.

Makes for more interesting chart watching than a fat High stuck over us

[Harry]

Indeed, that GFS profile chart Coast posted this morning has updated in an interesting way.

Swathe of negative indices for the LI figures, particularly across the SE with hints of CAPE possibly building. Manchester not looking too bad in a few days time now either.

Stepping outside just now it FEELS as if there is a decent amount of moisture in the air - feeling more humid than I was anticipating...whether this is just because its a lot warmer today I don't know. High pressure dominating rules anything out for us in the next few days, but as the High recedes westwards over the weekend, it MAY just allow the areas of low pressure over the continent to encroach, or if orientation changes and we get a favourable wind flow from the continent, then storms may be a possibility - CAPE/LI figures are mouth watering just over the stream (the 'channel') for several days.

As it stands, there looks to be v little scope for my somewhat fantasy scenario to emerge...but on the edge of something I'd say, particularly if the High's orientation permits an east/south easterly flow.

Makes for more interesting chart watching than a fat High stuck over us

Edit - Alex Deakin just said risk of showers moving into the se corner on Sunday evening. Thats a step in the right direction :-)

[virtualsphere]

Indeed, that GFS profile chart Coast posted this morning has updated in an interesting way.

Am I missing something here? On Coast's London chart above, labelled GFS12Z, the LI is negative throughout the period from 4 - 6 June, while on the Netweather GFS 12Z CAPE & LI chart the LI over London looks positive throughout: http://www.netweather.tv/index.cgi?action=nwdc;sess=

[pottyprof]

It probably has something to do with the various ways that different sites handle the data.

The problem is that at this range, it is only a heads up. It will change and as is usually the case for thundery conditions, it's down to nowcasting.

[Jane Louise]

It's been a gorgeous hot day here. I'm not too sure if there are any thunderstorms for my area in the near future. I do hope there is some kind of thundery breakdown soon.I know it's only been one day of hot weather but there's a few more days to go yet. Whatever happened to the old saying of 'Three fine days and a thunderstorm?' I don't think I've ever had that here in the summer Lol

[virtualsphere]

It probably has something to do with the various ways that different sites handle the data.

The problem is that at this range, it is only a heads up. It will change and as is usually the case for thundery conditions, it's down to nowcasting.

Thanks - I didn't realise these were calculated by the site, I assumed it was part of the data sent by the GFS! Shows how much I know about the models...

[Phelpsy]

Very humid here this evening, think will be a sticky night, but the mozzeys.. yes Mosquitos will keep me company lol!

[Sprites]

It's been a gorgeous hot day here. I'm not too sure if there are any thunderstorms for my area in the near future. I do hope there is some kind of thundery breakdown soon.I know it's only been one day of hot weather but there's a few more days to go yet. Whatever happened to the old saying of 'Three fine days and a thunderstorm?' I don't think I've ever had that here in the summer Lol

it's now three fine weeks and perhaps 1 rumble of thunder "mixed in" hahaha ,although that only applies during June-September...

It's been a gorgeous hot day here. I'm not too sure if there are any thunderstorms for my area in the near future. I do hope there is some kind of thundery breakdown soon.I know it's only been one day of hot weather but there's a few more days to go yet. Whatever happened to the old saying of 'Three fine days and a thunderstorm?' I don't think I've ever had that here in the summer Lol

it's now three fine weeks and perhaps 1 rumble of thunder "mixed in" hahaha ,although that only applies during June-September...

Edited June 2, 2011 by Sprites

[ZONE 51]

There is a risk of some action-or distant action 0: for the SE/S over the weekend..

[Coast]

Edit - Alex Deakin just said risk of showers moving into the se corner on Sunday evening. Thats a step in the right direction :-)

I caught that too, but still plenty to chop and change:

My fear is the French will be enjoying it all again:

[Harry]

My hopes aren't high, but I am encouraged by the rare event of there being thundery potential close by for the ENTIRE GFS run at the moment GFS in advance of 5 days (something I ignore, though nevertheless appreciate the pretty colours) shows possible potential across S UK.

I am encouraged by the indication from UKMO that the thundery lows over the continent may overspill and move up over/close to the SE/EA late Sunday into Monday. Might be a little bit too much frontal action for my liking, but it does provide a means for storms and possibly MCS' to come very close indeed

Edited June 3, 2011 by Harry

[todd1970]

I notice Estofex have a wee circle right over central Scotland today and Net-Weather have given us a 51% chance of a storm in the afternoon.

But surely with pressure so high and not a cloud in the sky hardly this seems unlikely ? or do they know something i dont know as im just a pure amateur just learning as i go along from the guys on here.

[Harry]

I notice Estofex have a wee circle right over central Scotland today and Net-Weather have given us a 51% chance of a storm in the afternoon.

But surely with pressure so high and not a cloud in the sky hardly this seems unlikely ? or do they know something i dont know as im just a pure amateur just learning as i go along from the guys on here.

High pressure often prevents the development of convection, by suppressing air which may be trying to rise. Nevertheless, under certain circumstances, convection can initiate, especially if conditions creating forcing/lift is stronger than the suppression by the High. A good example of this is orographic lift...air forced to rise up mountains/hills. Another good example is convergence zones, particularly sea breeze convergence - i.e the breeze blowing inland from the sea collides with prevailing winds from another direction. We mustn't also forget (as we tend to do) weather fronts are associated with Highs as well as Low pressure systems.

It is worth pointing out that the thunderstorms which hit the SE on Thursday last week developed under increasing atmospheric pressure, as a ridge built in across southern England.

However, directly approaching your question, Northern Scotland will not be under the influence of rising pressure this afternoon - the High is close, but the synoptics show pressure briefly falling as a developing Low pressure system moves through N Scotland later today. Furthermore, based on the GFS charts showing wind direction, a convergence zone will setup later today as the low pressure system brushes past, introducing stronger westerly winds, colliding with the more southerly winds around the High pressure system in the N Sea.

[todd1970]

High pressure often prevents the development of convection, by suppressing air which may be trying to rise. Nevertheless, under certain circumstances, convection can initiate, especially if conditions creating forcing/lift is stronger than the suppression by the High. A good example of this is orographic lift...air forced to rise up mountains/hills. Another good example is convergence zones, particularly sea breeze convergence - i.e the breeze blowing inland from the sea collides with prevailing winds from another direction. We mustn't also forget (as we tend to do) weather fronts are associated with Highs as well as Low pressure systems.

It is worth pointing out that the thunderstorms which hit the SE on Thursday last week developed under increasing atmospheric pressure, as a ridge built in across southern England.

However, directly approaching your question, Northern Scotland will not be under the influence of rising pressure this afternoon - the High is close, but the synoptics show pressure briefly falling as a developing Low pressure system moves through N Scotland later today. Furthermore, based on the GFS charts showing wind direction, a convergence zone will setup later today as the low pressure system brushes past, introducing stronger westerly winds, colliding with the more southerly winds around the High pressure system in the N Sea.

Thanks for that explanation Harry..like i says im picking up bits and pieces as i go along..every little helps.

[Coast]

Hmmmm, I'd say no more than 50/50 too according to various others:

There, that hasn't helped at all has it?

[Andy Bown]

Ok so where has Sunday's forecast come from?

I was under the impression that it would be a cooler day with a NE wind but still fine and bright/sunny in the South thanks to the

High pressure, so why did the 13.30 BBC forecast have rain/showers across much of the South?

And then the local BBC forecast had showers breaking out tomorrow afternoon/evening which he said would be from mid level cloud,

that's very intriguing because it leads me to believe tomorrow night could be thundery?

[Harry]

Ok so where has Sunday's forecast come from?

I was under the impression that it would be a cooler day with a NE wind but still fine and bright/sunny in the South thanks to the

High pressure, so why did the 13.30 BBC forecast have rain/showers across much of the South?

And then the local BBC forecast had showers breaking out tomorrow afternoon/evening which he said would be from mid level cloud,

that's very intriguing because it leads me to believe tomorrow night could be thundery?

There's increasing uncertainty over the activity of the High Pressure increasingly melting away westwards (how much it will melt, how quickly etc) and the evolution of thundery lows over the near continent.

Initially, the high to the west was going to remain dominant, introducing a change in wind direction to northerlies (NW/N/NE) but keeping the weather largely settled. A CF is still due to swing over the top of the High, introducing much cooler conditions, thicker cloud and perhaps some light rain.

However, evolving forecasts hint that the High could retreat more quickly and also further west, allowing the lows bringing thunder over the continent to drift much closer, possibly affecting the S/SE/EA. UKMO currently indicates that the low to our SE could evolve fronts bring more persistent rain, possibly thundery.

I think the message is that the forecast is potentially very changeable...showers MAY break out across the SW tomorrow afternoon where some low levels of CAPE are progged - how much convection will initiate is questionnable due to the presence of the High. There is likely to be clusters of thunderstorms, possibly forming an MCS, across Northern France tomorrow evening/night, drifting westwards on a keen easterly. At the moment, these should not affect us (may present some disco lights for the IoW at most)

Sunday though, as the High retreats and the lows to the south drift slightly closer, could throw some action towards the S/SE England and EA. GFS is indicating a massive clump of precip, possibly MCS, across the SE for Sunday but this I question at this stage. I find it unlikely an MCS would from across N France Sat night, weaken but maintain structure, drift north across the S/SE on Sunday then reintensify...more so because the winds will be prevailing northerly/easterly, rather than southerly/westerly...odd.

Will be following future forecasts though with a rather high level of intrigue that I can tell you

Edited June 3, 2011 by Harry

[Jane Louise]

Something could spark off tomorrow afternoon!

For the South West the Met Office mentions a chance of a shower later on in the afternoon and the sailing school also mentions this for Saturday:

To the south Skies are brighter with good spells of sunshine, although areas of cloud are going to be drifting along southern coasts, perhaps producing a few showers into the afternoon as the atmosphere destabilises due to the proximity of the developing low across France.

Thundery showers may well be triggered across inland parts of England and Wales later.

Fingers crossed y'all

[Harry]

Something could spark off tomorrow afternoon!

For the South West the Met Office mentions a chance of a shower later on in the afternoon and the sailing school also mentions this for Saturday:

To the south Skies are brighter with good spells of sunshine, although areas of cloud are going to be drifting along southern coasts, perhaps producing a few showers into the afternoon as the atmosphere destabilises due to the proximity of the developing low across France.

Thundery showers may well be triggered across inland parts of England and Wales later.

Fingers crossed y'all

Things do appear to be heading in a better direction am awaiting the GFS 12z with some anticipation!

EDIT - I wouldn't say 12z is a step in the right direction.

Edited June 3, 2011 by Harry

[Lauren]

I would be extremely surprised if we got anything decent this weekend.

[Sprites]

The N.E. wind over the south east is mainly a surface wind, the rain over France may ride over the N.E. wind, and move into the the south on sunday evening...

[jamesbhx]

The N.E. wind over the south east is mainly a surface wind, the rain over France may ride over the N.E. wind, and move into the the south on sunday evening...

Indeed, the jetstream (albeit rather slack) which can provide an element of steering is actually flowing in the opposite direction to the surface wind on Sunday.

[paul m]

As long there are no storms for Scarborough tomorrow i will be happy... I know you cant win with me and yes i want storms but not when out with the kids.