Thunderstorms and Convective Potential (Dublin Floods 9/8/08)

Snowbie · 29-07-2008 11:01am #1

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.

Snowbie · 29-07-2008 11:10am

Renewed risk today for some fireworks with most areas at risk of a storm.

squonk · 29-07-2008 11:20am

That's what I want to hear. It's certainly humid and warm enough anyway!

force eleven · 29-07-2008 12:03pm

This mornings murk and rain have cleared from here, and its a breezy bright morning/midday. Certainly still warm and humid in that sun,with plenty of cumulus, though they don't look like developing into anything as yet, they are blowing along nicley on the breeze. We'll have to see what today brings,certainly the ingredients are there.

maquiladora · 29-07-2008 12:03pm

Snowbie wrote: »

Renewed risk today for some fireworks with most areas at risk of a storm.

What areas are looking to be most at risk today snowbie?

maquiladora · 29-07-2008 12:08pm

squonk · 29-07-2008 12:12pm

Serious rain pushing into Kerry just now. If this moves up the country, could it have the potential to kill off any potential? The approaching cloud would kill the sun's effect anyway?

maquiladora · 29-07-2008 12:16pm

squonk wrote: »

Serious rain pushing into Kerry just now. If this moves up the country, could it have the potential to kill off any potential? The approaching cloud would kill the sun's effect anyway?

Looks like that rain is moving west/southwest. It doesn't look like its going to move up the country.

Snowbie · 29-07-2008 12:35pm

That rain is circulating around the LP just off the SE coast.

Risk areas anywhere in the CAPE and LI values in the attach. But only if there is prolonged sunshine to generate surface warming. Total airmass setup. Hit and miss.
Anywhere away from the very east and south coast at first and SW will have a chance if sun pokes through. Radar and Satellite viewing will give you an indication.

Hal1 · 29-07-2008 1:42pm

I can see some nice Culumus bubbling up outside from my front door. Still fairly cloudy overall but sun appearing now and again.

squonk · 29-07-2008 1:54pm

I was just outside to get lunch. To me it seems too fresh today for any major potential... but I could be wrong (and probably am)

shamwari · 29-07-2008 1:56pm

Just looked at StormVue, its reporting some sferics in a trail from Dublin Bay head SSE. Just off Wicklow looks particularly active, however there is nothing on any of the online rainfall radars to substantiate this. Can anyone confirm if we have a storm just off the coast?

Snowbie · 29-07-2008 2:15pm

shamwari wrote: »

Just looked at StormVue, its reporting some sferics in a trail from Dublin Bay head SSE. Just off Wicklow looks particularly active, however there is nothing on any of the online rainfall radars to substantiate this. Can anyone confirm if we have a storm just off the coast?

No storm. In laymans terms, this happens when a particular storm (in this case now over SW UK) signature sky hops untill the detector tracks the storm accurately.(depends on the strength of the storm, the more stronger the quicker the accuracy) This happens with all single point lightning detectors.

shamwari · 29-07-2008 2:26pm

Snowbie wrote: »

No storm. In laymans terms, this happens when a particular storm (in this case now over SW UK) signature sky hops untill the detector tracks the storm accurately.(depends on the strength of the storm, the more stronger the quicker the accuracy) This happens with all single point lightning detectors.

Interesting...a lightning anaprop!

Snowbie · 29-07-2008 2:38pm

shamwari wrote: »

Interesting...a lightning anaprop!

Similar but not quite. Anaprop is a false doppler return whereas you can have a false lightning strike from local interference. But on this occasion the signal is detected but ranged incorrectly.

Snowbie · 29-07-2008 3:09pm

Thunderstorms over Wales again now but depending on the track of the LP to the SE and how fast it moves up through England will not spiral them into the Irish sea or they just might if the LP becomes stationary. Interesting next few hours.

rc28 · 29-07-2008 3:11pm

We had a torrential downpour about an hour ago with a few rumbles of thunder.

Snowbie · 29-07-2008 3:51pm

Anvils clearly visible from the Wales storms from here.

force eleven · 29-07-2008 4:03pm

Plenty of cumulonimbus visible inland here, but mostly swift moving showery type clouds, its been a mainly dry bright and breezy afternoon here.
I'd be very interested to get some rainfall figures from Kerry/Cork, as Met Eireann radar has shown that front pivoting around Kerry, no let up in rain since last night.

TheGreenGiant · 29-07-2008 4:32pm

got a good storm there about 2 hours ago up here in trim co.meath.fork lightning actually hit a neighbors television mast! the whole house shock from the thunder.sky here looks very promising indeed for the rest of the day.radar shows it.hope to get a good video.pity i missed that strike earlier on in the day

29-07-2008 4:35pm

Snowbie wrote: »

Anvils clearly visible from the Wales storms from here.

Yeah I can see a good line of them and cb's out over the sea.
Checked am radio there and it's going mad with crackles.

squonk · 29-07-2008 4:36pm

Hope the house wasn't damaged and nobody was injured. It was only when the electricity went after a near overhead strike last night and I was sitting there wondering what was going to happen with the next strike that I realised that fun and all as the fireworks are, there's a dangerous side to them too.

TheGreenGiant · 29-07-2008 4:42pm

indeed.the house looks ok. i'd say who ever was in it got a fright.the flash was very bright but the clap of thunder was insane! hope more storms brew up later.wales are getting a hard pelting with them!

shamwari · 29-07-2008 5:03pm

Latest from StormVue, it looks like the storm off the Welsh Coast has blown east over Anglesey.

TheGreenGiant · 29-07-2008 5:06pm

dammit was hoping for it to head across the Irish sea since the low pressure is swinging right around

TheGreenGiant · 29-07-2008 5:07pm

gud thing is there's a storm back in Trim:)

andrewie · 29-07-2008 5:30pm

Thunder and Lightning around Kells for the last half hour.

IRISH RAIL · 29-07-2008 5:41pm

Lot of action on storm vue around south donegal but would love to be in england even on a plane to birmingham

TheGreenGiant · 29-07-2008 6:01pm

lots of anvils and distant rumbles of thunder forming around the trim area.

highdef · 29-07-2008 6:16pm

The anvil above Meath as seen from my balcony in Santry can be seen in the photo section

rc28 · 29-07-2008 6:19pm

I could hear a lot of thunder from a large anvil in Dunshaughlin direction about 20 mins ago.

Snowbie · 29-07-2008 6:22pm

highdef wrote: »

The anvil above Meath as seen from my balcony in Santry can be seen in the photo section

Yeah have a few shots of it from here with more building right behind it.

squonk · 29-07-2008 6:26pm

Some decent cumulus to my NW atm but heading NW/N as far as I can see. Nothing sounding or falling anyway!

highdef · 29-07-2008 6:54pm

Looks like convection is dying down now. I'll pop up the timelapse of the Meath storm tomorrow. Have to head to bed soon as working tonight

CIDK · 29-07-2008 6:54pm

GFS 12Z run shows good probability for a late night storm in the Munster region. I try not to get my hopes up about these as I'm normally let down.

chris2007 · 29-07-2008 7:34pm

Clouds starting to build up here in North Dublin.

chris2007 · 29-07-2008 7:39pm

Lashing rain here im in the coolock area.

Storm 10 · 29-07-2008 10:47pm

Very wet here tonight but sadly no Thunder all we can do is hope something kicks off.

squonk · 29-07-2008 11:51pm

Not too hopeful of anything kicking off myself. I had a glimmer earlier in the evening but that went to nothing very quickly. I had a light shower here about 8pm and that's all really. tomorrow looks decidedly wet and, in general crappy

shamwari · 30-07-2008 12:08am

Rain & drizzle has started here. It feels cool and a lot less humid than recently. I reckon the shows over now for a while..

Snowbie · 30-07-2008 1:29am

The slightest of chances of an embedded rumble or two in the east tomorrow within the rain band.

Some energy in the mix.
Deep wind shear very favourable
Vertical vorticity 700mb with pressure decrease rapidly as air is drawn up quick
500mb RH% indicating some cooler dryer air at altitude. Enough for the odd CB to creep up to a favourable height.

Risk is low but there is one there under all the cloudcover on Wednesday.

TheGreenGiant · 30-07-2008 1:37am

thats good news snowbie! thanks for the update

Snowbie · 31-07-2008 1:40am

GFS has picked up on a short wave trough following Thursdays heavy rain to swing up through the south and east of the country tomorrow evening and overnight (Thurs/Fri).

As the Jetstream exits the area, lapse rates(instability)will steepen with the air drying out somewhat at height and vorticity advection. This forced advection will trigger the development of CB, and possible storms with the SE highest at risk. However low level shear is minimal but deep directional wind shear is moderate across the SE making any storm moderate to strong.

Will update during Thursday if needed.

Snowbie · 31-07-2008 1:45am

The TT (Total Totals) is an index used to assess storm strength. This sometimes does not pick up on some parameters but any index over 51 is classed as severe.

IRISH RAIL · 31-07-2008 2:59am

STORMVUE at the moment has a lot of strikes over the east coast anyone awake to verify

Snowbie · 31-07-2008 9:56am

00Z has the risk there still and moving more slightly into the south midlands too. Lapse rates are not as high as the attach above but still decent.

maquiladora · 31-07-2008 10:47am

Snowbie wrote: »

00Z has the risk there still and moving more slightly into the south midlands too. Lapse rates are not as high as the attach above but still decent.

How would you rate the TS risk for the Waterford area since the 00Z?

Snowbie · 31-07-2008 12:38pm

maquiladora wrote: »

How would you rate the TS risk for the Waterford area since the 00Z?

Well like the 00z the 06z keeps the risk going. But shear has all but gone so storms shall not be severe. Instability is back on too. So if any sparks are to occur you be first to see them as the unstable conditions are pushing in from the SSW. It's looks to be around 2200-0300 for these. 12Z today should confirm better today the potential as 06z output is still too far away from the event (which is what i based the above on atm)

Snowbie · 31-07-2008 7:51pm

Last 3 runs maintain the threat of storms for later this evening and overnight. Initially, the threat is for southern areas later moving into the east in the wee hours of Friday morning. Cape values are not impressively high but looking at the satellite the arc at the back of the LP system seems to be developing.

Also to more SE areas, the trough has pepped up the precip and some towers are visible.
The IR sat does not show cloud tops reaching too high atm.

Watch the IR Sat's later to see if CBs build.

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

darkman2 · 31-07-2008 7:55pm

Snowbie wrote: »

Last 3 runs maintain the threat of storms for later this evening and overnight. Initially, the threat is for southern areas later moving into the east in the wee hours of Friday morning. Cape values are not impressively high but looking at the satellite the arc at the back of the LP system seems to be developing.

Also to more SE areas, the trough has pepped up the precip and some towers are visible.
The IR sat does not show cloud tops reaching too high atm.

Watch the IR Sat's later to see if CBs build.

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

Im not all that hopeful but would love to see a storm tonight. GFS seems ok but the UKMO is having none of it with just the mid west at slight risk and the rest of the country dry. Will keep an eye on the radar and satellite though.

Snowbie · 31-07-2008 8:32pm

Compare both GFS model at the same time. The Nw resolution is far more detailed than the US GFS version.
Though the UKMO model does not show the trough.
GFS indicates that a shortwave will develop later this evening to the south steepening lapse rates.

It's a case of which one is right.

Thunderstorms and Convective Potential (Dublin Floods 9/8/08)

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