Thunderstorms and Convective Potential (Welsh imports 28/7/08)

Snowbie

Post here of all things thunderstorm related,whether it be radar,maps,charts,forecasts or just simple discussions.
Over the months you will find some variables or terms describing suitability of storms which are:
CAPE - This is the amount of potential energy in the atmosphere. High CAPE will indicate a high chance of thunderstorms.
LI - Lifted Index (LI) displays the 'trigger' potential at the surface to initiate unstable conditions. A low or negative LI will indicate conditions for thunderstorms are favourable.
Cb-Cumulonimbus or thundercloud.
Anvil-Where the top of the Cb reaches the stratosphere and spreads out like a flat top.
Cell or Supercell-An individual storm or a violent storm.
Squall line-Multi cellular organised storms forming in a line usually ahead or parallel to cold fronts.
Embedded Storms-Storms that are contained in overcast conditions
Convection-Warm air rising,cools,condenses forming cumuli clouds.
Orographic lift-Low level winds are forced to rise against rising terrain ie:mountains.Prevailing wind on a hot summers day,this lift can produce rapid convection.
Convergence zone-usually refers to a region in the atmosphere where two prevailing winds meet and interact, usually resulting in turbulent weather.
Lapse rate steepeing-is another fancy term for instability.
Sferics-Sound of low-frequency radio signals that derive from lightning strikes.Common terms would be strikes or strokes.
Some useful links
http://www.irlweather.com
http://durrow.athost.net/lightning/
http://www.gyweather.com/
http://www.isleofwightweather.co.uk/live_storm_data_sound.htm
http://www.wetterzentrale.de/pics/Rsfloc.html
http://www.estofex.org
http://www.blitzortung.org/index.php?mode=0&map=5&lang=e
http://www.nowcast.co.uk/lightning/
http://meteocentre.com/lightning/map_sfuk.php?time=0&lang=en&map=Europe
http://www.estofex.org/guide/
http://www.strikestareu.com/
If anyone has any more feel free to post them.

darkman2

Latest GFS ups the chances for tomorrow night. Might have to stay up a little late though!

Danno

Snowbie wrote:

If anyone has any more feel free to post them.

http://durrow.athost.net/lightning/ South Central Ireland Lightning detector. - How could you forget Snowbie?

Hal1

Woo a brand new thread. I'd like to see this thread packed with reports of TS's over the coming days.

Taken from Estofex: "Isolated storms are expected to develop over Great Britain and eastern parts of Ireland as well, where CAPE should be a bit lower."

Snowbie

This is the beta viewer for the new Netweather NMM Mesoscale model. This model runs at a resolution of around 12km (0.09 degrees), making it far more detailed than the GFS which runs at 0.5 degrees (around 60km). The NMM model is designed and used operationally across the USA by the NCEP, Netweather are running this UK version on our own servers, twice a day, updating at around 6am and 6pm).

Nw model being used on the latest potential. This is the 12Z Sunday output.

There is two potential setups for Monday and into the evening into Tuesday morning.
The first is an airmass setup with surface heating also with a trough moving close to the south coast during the afternoon destabilising the air further. Risk of heavy showers breaking out away from the East coast( wind from the NE) and higher risk later in the afternoon in the S midlands and SE with isolated storms west of the Wicklow mtns as the trough moves closer to that area with lift being aided by the mtns.

The second is from an occluded front moving up overnight on Tuesday morning. This feature is advecting alot of moisture up from France across southern England and later into Wales with a possible MCS (mesoscale system). Mid to high level based storms with no interaction with the channel and maybe later the Irish sea? (SST's do not effect TS development in high based storms)

We check this by using the ML Cape (mid level) model and it is over 1000j/kg moving up from France, into southern UK and later into Wales. The westward motion continues into the Irish sea and into the East and SE parts of Ireland with some few hundred to 600j/kg ML Cape by then.

As always there is a risk but Monday evening/Tuesday morning setup is still developing and 24hrs away to be exact. Could be up or downgraded.

Danno

Interesting indeed Snowbie. I will be keeping a close eye on the Castlecomer Pleatau tomorrow from Midday. Hopefully something kicks off there and then trundles down into the heat trap in the Nore Valley!

Deep Easterly

DOCARCH

Indeed DE, fairly rough stuff appraoching the south coast but there's nothing electrical in it at the moment.

maquiladora

DOCARCH wrote: »

Indeed DE, fairly rough stuff appraoching the south coast but there's nothing electrical in it at the moment.

Dannos detector is picking up strikes in it.

Snowbie

CB,s building off the coast here

http://www.sat24.com/frame.php?html=view&country=gb&sat=vis

Regarding tonights potential has downgraded somewhat (UK too) but still energy at midlevels there from 00Z.

Edit:Lightning off the coast from here moving NW in the Irish sea.

Snowbie

TS now approaching the Louth coastline, Dundalk maybe.

Here's Brens thoughts/map from over on two ( copyright bren )
He's usually on the ball given he works for a met company
He's reckoning embedded storms in the general band and thunderstorms ahead of it with the heavy showers. ( link )

Danno

Seems the current activity is being held off the Cork City coast by a few miles. Anyone down there to give us a report?

(I was in Youghal yesterday meself - lovely there - damn storms are 1 day late!!!)

darkman2

6z GFS looks good to me for tonight.

Snowbie

Back and forward in the models this morning although a couple of hundred ML cape is hardly exciting for tonights potential. It just falls into the slight risk catagory. This is still a downgrade on yesterdays output but slightly up on 00Z.

The models have done there best on tonights potential so a nowcast be the focus of attention.

Today (daylit hrs) looks good for heavy showers and storms still.

Storm 10

Really coming down here in Galway now with very heavy rain showing up on the Met Eireann Radar.

What are the chances of a Storm here today Snowbie?????

Deep Easterly

Snowbie wrote: »

The models have done there best on tonights potential so a nowcast be the focus of attention.

Really difficult to pin point, and utterly painful. I am pinning my faith in the UKMO rainfall graph for tonight as they are still showing storm potential for Ireland tonight. (I am not in the least bit surprised that there is a gap in the middle of the storms heading for me though. :rolleyes:)

Forecast graph for 1.00am Tuesday 29th July 08:



Forecast graph for 4.00am Tuesday 29th July 08:



A sweaty night ahead, and not because of the heat!

Snowbie

Storm 10 wrote: »

What are the chances of a Storm here today Snowbie?????

Very messy to pinpoint where the chances are for the west in the frontal stuff. Surface heating ahead of that may create some lift but looks to be embedded with the odd CB developing.

With later on as things get going over France and the energy being pumped up over the UK as the front moves in would destabilise the air ahead of it and overnight but i have low confidence on anything happening here in the east atm. Nothing really mouth watering but a risk is there. All can change as the models have difficulty in handling this for this country.

DOCARCH

There's a lot of very heavy rain just off the NW coast of France/Brest peninsula atm (just off the UK/IRL radar)
http://www.meteox.com/gmap.aspx?zoom=5&lat=52.908902047770255&lon=-1.845703125

and a lot lightning activity further down in the Bay of Biscay
http://www.strikestareu.com/

Seems to be some rotation now to the system?
http://www.sat24.com/frame.php?html=homepage

maybe this will all slip north west (probably not ) but worth watching and hoping anyway!

I'd love a nightime storm - any activity we've had this year has all been in the daylight just not half as dramatic.

maquiladora

Nice storm off the SW coast on Dannos detecter. Over 100 strikes in the last 30 mins. Its looking more quiet off the South coast at the moment.

DOCARCH

maquiladora wrote: »

Nice storm off the SW coast on Dannos detecter. Over 100 strikes in the last 30 mins. Its looking more quiet off the South coast at the moment.

I would question somewhat the accuracy of that detector at the moment* This activity is not showing up on any of the other detectors!

*Please please note - no disrespect intended Danno - just a comment!

Danno

Correct lads. I was up in the attic making further adjustments to the antenna. Was working with spirit levels, compasses, hammers, tie-wraps etc... and the heat was horrible. That interference was me at work! Hopefully now, my page will be showing the storms far more accurately. "Bring 'em on!"

highdef

Can see a good bit of cumlus congestus exploding to my southwest. i'm in D8 and I would imagine the clouds are somewhere around Blessington or beyond. Thats purely guesswork!!!

DOCARCH

Danno wrote: »

Correct lads. I was up in the attic making further adjustments to the antenna. Was working with spirit levels, compasses, hammers, tie-wraps etc... and the heat was horrible. That interference was me at work! Hopefully now, my page will be showing the storms far more accurately. "Bring 'em on!"

Phew!

Danno

Right on the edge of that front here, grey skies to the west and blue skies to the east with convection exploding to my north. Every so often the sun comes out and drives the temperatures up, then the cloud sits back in over us and makes it damn muggy.

Looks like a nice shower is building on the sat24 from Portlaoise to Kildare area and when it pushes over the Slieve Bloom Mountains it should kick off big time. Birr area should get hit.

nacho libre

The last time I experienced a proper night time thunderstorm was May 2001. There was fork lightning in every direction i looked. It would be great if this week gave us something like this again. Does anyone recall the event i'm talking about?

Danno

And we're off, bang goes the popcorn cloud over North Laois/South Offaly/West Kildare.

nacho libre

There seems to be a lot of activity in Galway bay at the moment

Snowbie

Nacho thats what happens when lightning is detected first if a storm is weak, ranges better when the storm becomes more organised and stronger. The storm is over Offaly atm.

Danno

Nacho, if you are reading both Snowbie and My lightning detectors you will notice that Snowbie is picking up some activity over Galway bay and I am getting strikes in Derry.

These "ARE" the same strikes!!! What is happening is...

I am south of the storm and Snowbie is east of it. The storm is over say Tullamore-Edenderry area. Because the storm is so weak the strikes are being detected further away than they really are.

When activity increases the strikes will "pull back" to the correct location and be displayed on our pages more accurately.

Currently the storm is knocking out 3 or 4 strikes at best per minute. If it gets up to 10 or better strikes per minute then the maps will display much better accuracy.

Hope this helps!

Danno

Snowbie wrote: »

Nacho thats what happens when lightning is detected first if a storm is weak, ranges better when the storm becomes more organised and stronger. The storm is over Offaly atm.

Beat me to it!!!