Thunderstorms

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://www.gyweather.com/
http://www.isleofwightweather.co.uk/live_storm_data_sound.htm
http://www.wetterzentrale.de/pics/Rsfloc.html
Estofex
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/
If anyone has any more feel free to post them.

Snowbie

Cape atm is around 600j/kg over the north of Ireland falling back low throughout the rest of the country.
LI is negative at around -1 around the country.

Atm TS are at a low risk of developing(moderate up north) but the chance is there as we move through the late afternoon

Paddy.1

Quick question snowbie. Convergence zone. Clouds here are almost stagnant. I am timelapsing convection today, and just having a quick review, Lower cumlulous is moving from an increasingly S to E direction, while the higher level clouds (when can be seen) are still moving from a S to SW direction. Does this mean convergence..? as the medium and high level clouds are now almost moving at 90 degree opposites. Thanks.

My understanding of convergence Irish style is the line where a sea breeze meets a land breeze.
Central florida being the best international example of this that I know of as it has two of them side by side.
The one you are talking about paddy1 seems to be upper air going one way and lower surface air going the other.
It might lead to the same or be the same phenomenon alright.

ninebeanrows

Intense precip forming to the southwest, some really heavy rain this evening for the south/midlands and east.

Thunderstorms likely

http://www.met.ie/latest/rainfall_radar.asp

Snowbie

Most common type of convergence is a seabreeze convergence line or squall line in this country.

You are witnessing land convection whilst moving in the prevailing wind direction low level winds.
We turn now to whats called CIN or convective inhibition explained better here

Looking at the skew-t data for Velentia, CIN is playing its part in restricting convergence today. So pulse type storms cant be ruled out due to homegrown convection but on a wider scale looks unlikely.

Snowbie

Weathercheck wrote: »

Intense precip forming to the southwest, some really heavy rain this evening for the south/midlands and east.

Thunderstorms likely

http://www.met.ie/latest/rainfall_radar.asp

Cape in that clump is running at around 150/200 with a LI of 0
Thunderstorms unlikely. A rumble or two would be more at best.

Overhead in Dublin atm we have a cape of 450 and LI -1 now and with that approaching precip is making conditions unfavourable pushing northwards.
Obviously the lack of convection as its cooler under that clump is making for poor conditions for things to develop.

Snowbie

Wow that was right overhead here, one massive boom just there.Shook the house.

darkman2

Yeah kicking off here.

Morrigan

Yeah, it was a long roll and a bright flash! Interfered with the TV reception too...

ninebeanrows

Snowbie wrote: »

Wow that was right overhead here, one massive boom just there.Shook the house.

Bloody tremendous noise wasnt it?

I quickly got out of the shower when i heard it!!

Trogdor

Just seen to flashes to my North-East.

darkman2

4 flashes in total - only one could be heared. The others out to sea a bit.

Mobhi1

Bright flash and long rumble here a few minutes ago. Sounds like very heavy rain at the moment.

ninebeanrows

Small rumbles now

Snowbie

A couple of sporadic strikes off the isles of scilly and Brest NW France but nothing in the last 20mins not even detecting noise.

DOCARCH

Snowbie wrote: »

Wow that was right overhead here, one massive boom just there.Shook the house.

Had the same here at approx. the same time? A big flash - approx. 2 seconds and a loud long boom of thunder. Could hardly be the same strike?

Snowbie

Yeah why not.Couple of my coleauges from Blanch and Finglas heard the same roll but the thunder here was within 0.5sec after the lightning and is probably the loudest boom of thunder i have ever heard.

One strike is all i witnessed.

Snowbie

First couple of bolts over the Irish sea.

Hal1

Snowbie wrote: »

First couple of bolts over the Irish sea.

Bolts? sounds serious

Paddy.1

Not sure where to post this, but I was flicking through some weather vids on You Tube last night and came across this one taken in Mid West of USA. It is well captured, without timelapse. It really is an explosive and awe-inspiring site.

http://www.youtube.com/watch?v=yRgLvKCRr_8&feature=related

Does anybody know the name for this kind of event? I am not sure if it is a usual site even with the mid west, as it seems very sudden, and yet without much thunder.

Snowbie

It looks like a possible birth of a supercell, well maybe further down the line of the storms path. Notice the slanted updraft in the first minute of the clip near the wall cloud and the slight rotation. For sure it moves through the area pretty quick.

Danno

Cripes, thats a nasty one. Very little precip though.

Paddy.1

Yeah, nasty looking but nice:). Thanks for the info Snowbie. Probably is the birth of a supercell, certainly a lot of energy being sucked in hence the lack of rainfall. I have to admit that is my kind of weather. Dramatic changes within seconds. Watching vids like that makes me realise how diluted the weather here in Ireland is. With big events rare an cruelly irregular. Ah well.

I notice as well that we get a lot more interesting weather in Ireland anytime Fianna Geal is power. It sounds mad, but it is true. So lets vote this Brian what-do-you ma-call-him out right now. I demand a general election!!!:)

darkman2

Some intense activity approaching the west coast atm.

Tomorrow and the weekend look good for some very heavy thunderstorms to develope with steep lapse rates. This most likely to occur away from the West coast.

Snowbie

Detecting an embedded storm in that lot out west atm.

Paddy.1

Had to drive a friend down to Shannon airport earlier, got to see some flickers driving home just south of Gort. Nothing too spectaclar. Though it rained like mad down there.

Snowbie

The energy potential is expected to be lower than yesterday forecast which i find hard to believe with but the LI remains good for development of the odd storm today.In other words if the sun goes in the potential decreases and vicaversa.Very hard to see that in this setup.

With cold PM quickly established air in the mix and surface warming from the sun(lapse rates steepen), convective showers should get going from early on and by mid to late afternoon there should be the odd storm.CBs a plenty today with anvils and with lots of medium sized hail as the freezing level is lower.

Snowbie

Squall line developed over south UK while CBs are well established but nothing organised over our west.

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

Hal1

Metcheck weather warning here. I usually look at 'storm watch' on metcheck. It shows some predicitions of the cape and li values and reports of recent activity.

DOCARCH

Snowbie wrote: »

Squall line developed over south UK while CBs are well established but nothing organised over our west.

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

Looks now like a more orgainsed line of heavy showers has formed from Waterford up to Sligo/Leitrim?