Convective/storm Discussion 5Th August >>

[Hurricane Andrew]

http://www.woolstonemet.co.uk/

could this been right nearly 2 inchs of rain today so far ?

[Costa Del Fal]

Lol radar says we should of had rain yet it is bone dry here.

[nwales]

No rain or storms here yet. The cloud has thickened, the breeze has picked up and the temperature has dropped to 19.9C from 21.6 earlier. Humidity is at 72%. The storms so far have been just to the west of here judging by the radar, on the other side of the Chilterns scarp.

[Noctilucid]

Looks like something weak perhaps getting going South of the river too, a bit dark and mushy to my SSW, everything seems a bit stable here though, and the convection has done the usual thing where it spills out into a big mid level layer, which suggests there is something keeping convection capped here in the SE.

Edited August 6, 2009 by jshaw

[slinky1989]

Got thunder here, and not just rumbles either

Sounds like good lightning thunder. Haven't seen any yet but can hear the thunder cracking infrequently

[❄️❄️❄️❄️❄️❄️❄️❄️❄️]

http://www.woolstonemet.co.uk/

could this been right nearly 2 inchs of rain today so far ?

The rain total is really shooting up!

[chrisbell-nottheweatherman]

Well, the CIN for S. London is around -15 to -20, but I don't know how that index works!

[saint]

BBC forecast concentrating on the rain moving in later, saying "heavy rain for IOW, Herts, Beds, Bucks" ? What do you think of this?

[NorthantsSnow]

Seems to be more of a northerly component to the flow than an easterly. Could be bad news for here later, will Leicester take all our storms away I wonder?

[chrisbell-nottheweatherman]

I found an article on CIN on the dreaded Wkipedia (sorry) that says:

CIN is an energy per unit mass and the units of measurement are joules per kilogram (J/kg). CIN is expressed as a negative energy value. CIN values greater than 200 J/kg are sufficient enough to prevent convection in the atmosphere.

Does this mean that -200 or below (i.e -200 - -400, say) is a strong cap, orthat =200 or greater is?

[Coast]

Latest METAR from Gatwick, look at that dewpoint!

METAR text: EGKK 061350Z 31010KT 9999 FEW045 26/18 Q1017

Conditions at: EGKK (LONDON/GATWICK A, GB) observed 1350 UTC 06 August 2009

Temperature: 26.0°C (79°F)

Dewpoint: 18.0°C (64°F) [RH = 61%]

Pressure (altimeter): 30.03 inches Hg (1017.0 mb)

Winds: from the NW (310 degrees) at 12 MPH (10 knots; 5.2 m/s)

Visibility: 6 or more miles (10+ km)

Ceiling: at least 12,000 feet AGL

Clouds: few clouds at 4500 feet AGL

Weather: no significant weather observed at this time

Forecasst for the next few hours at Gatwick:

Text: BECMG 0618/0620 29010KT 7000 RA

Forecast period: 1800 UTC 06 August 2009 to 1800 UTC 07 August 2009

Forecast type: BECOMING: Conditions expected to become as follows by 2000 UTC 06 August 2009

Winds: from the WNW (290 degrees) at 12 MPH (10 knots; 5.2 m/s)

Visibility: 4 miles (7 km)

Weather: RA (rain)

Current airbase warnings for the USAF in England from 21st OWS:

[StormChaseUK]

Had a few rumbles of thunder over the Chilterns this afternoon, took this one overlooking Aylesbury around 2.30pm

Shows the dividing line between the oxfordshire rain/cells and warmer air to east.

Video : Divide Line

Edited August 6, 2009 by danielreal2k

[Neilsouth]

We still may get storms tonight or tomorrow early hours , we've had more altocumulus today and alot yesterday. All it needs is that trigger and the odd storm is already firing directly south of us over france !

[MAF]

i see the RH has dropped there Coast. London is the same, humidity has fallen some 20% since this morning

[Tom Montalbano]

Looking at the Meteox 3 hour predicted rainfall sequence, it looks like an area of heavy rainfall will run up towards London from the West Sussex coast around early/mid evening, no doubt with embedded thunder. This area looks to continue to move NNE up towards E.Anglia during the rest of the evening and night.

Also the line of thundery showers running from Dorset through S.Midlands, into the E.Midlands looks to continue moving NNE towards extreme E.Yorks/Lincs during the rest of the evening.

As usual in these situations some areas will see some pretty appreciable rainfall totals, whilst other areas see relatively little.

Regards,

Tom.

Edited August 6, 2009 by TomSE20

[Noctilucid]

Looks like we have a isolated mid level storm setting up over South London, very dark that way and a huge flock of seagulls has appeared out of nowehere going mad.

[chrisbell-nottheweatherman]

Any ideas as to my CIN question, please?

[scud]

Wife just texted me "leaving thundery Swindon now"

Shes on her way home to Staines

[MAF]

Here's the Meteox 3 hour predicted rainfall sequence.Looks like an area of heavy rainfall will run up towards London from the West Sussex coast around early/mid evening, no doubt with embedded thunder. This area looks to continue to move NNE up towards E.Anglia during the rest of the evening and night.

Also the line of thundery showers running from Dorset through S.Midlands, into the E.Midlands looks to continue moving NNE towards extreme E.Yorks/Lincs during the rest of the evening.

As usual in these situations some areas will see some pretty appreciable rainfall totals, whilst other areas see relatively little.

Regards,

Tom.

pretty much in line with the BBC forecast i saw earlier Tom. i go home around 1900 tonight, might be a wet walk when i get off the train at Woolwich

[Coast]

Looks like an area of heavy rainfall will run up towards London from the West Sussex coast around early/mid evening, no doubt with embedded thunder. This area looks to continue to move NNE up towards E.Anglia during the rest of the evening and night.Also the line of thundery showers running from Dorset through S.Midlands, into the E.Midlands looks to continue moving NNE towards extreme E.Yorks/Lincs during the rest of the evening.

So by my reckoning, looking at the current sferics, two lines of storms will meet over London later

[Harry]

Looks like we have a isolated mid level storm setting up over South London, very dark that way and a huge flock of seagulls has appeared out of nowehere going mad.

Hmm, it has gone very dark here in the last half hour! Feels dead calm, air very still...and the sky looks bruised if that makes sense - mixture of greys, purples and oranges...very eerie! And still very very warm and humid!

Edited August 6, 2009 by Harry

[chrisbell-nottheweatherman]

Hi, yes CIN of -200j/kg or below is classed as a strong cap. CIN is essentially negative CAPE and is a stable layer of the atmosphere preventing convection from occuring.

So the deeper the negative value, the stronger the capping? Is it possible to have a +ve figure?

[Coast]

BTW, though you might like this from the official Eastbourne Weather Station:

Temp curve is wrong but figues above it are correct

Edited August 6, 2009 by Coast

[NorthantsSnow]

The rain is the heaviest it's been all day at present. 17c, relative humidity 100%.

[Tom Montalbano]

Hi MAF, jshaw & Harry,

Can concur with your obs, looking very dark just west of here, Lee, S.E.London. Some very slight returns on 4.00 Meto radar around the London area.

That large pulse of ppn thats moving NNE out of Cherbourg just starting to reach I.O.W/Hants/W.Sussex coast.

Regards,

Tom.