Thunderstorm/Convective Watch - Spring/Summer 2012

Iancar29

YUP.... Su 100% on this one, clearly LI and Cape have nothing to do with these kind of setups. " Iv yet much to learn Master Su ...much to learns indeed. " :pac:

Whats even more interesting is that the cell appears even before the main band reaches us.





* Takes sticker back out of drawer *

Su Campu

I think maybe Met Eireann deserve an apology after spotting this a few days ago and sticking with it. No covering their asses at all, just doing their job.

This morning's 05Z TAFs for Dublin and Casement continue to show moderate showers, with a PROB30 (slight) chance of thunderstorms, up to 10Z. Also moderate showes for Waterford Airport this morning. Their 06Z aviation forecast chart shows an area containing a local risk of thunderstorms over the Irish Sea and encroaching the east from Waterford to Dundalk. Their 12Z chart shows this area retreating back and only barely clipping Rosslare.

Still a lovely crisp day in North Louth, has been for the last hour and a half at least that I know of.

Wild Bill

Nothing here bar a stiff easterly........

Speak Now

No showers at Waterford airport.....yet!!!

Caitriona

There was serious stuff happening over our house between 5 and 5:40. The lightning had everything electrical in the house beeping and the thunder actually shook the house, and for massively long intervals. I haven't been scared of a thunderstorm in years but this one had me nervous.

Thankfully the kids slept through it, presumably they thought the thunder was just the neighbours moving some extremely big wheelie bins.

gebbel

Another Drogheda resident here. Incredible weather last night. Started with an extremely intense hail shower at around 5am. Then came the thunder and lightning. 2 claps of thunder were so loud that the sonic waves rattled the houses and set off house alarms. I counted 4 separate alarms in my estate. 3 were deactivated soon after but 1 kept me awake for 30 minutes as obviously nobody was at home there.

It was apocalyptic weather, never experienced the likes of it.

Iancar29

Su Campu wrote: »

This morning's 05Z TAFs for Dublin and Casement continue to show moderate showers, with a PROB30 (slight) chance of thunderstorms, up to 10Z. Also moderate showes for Waterford Airport this morning. Their 06Z aviation forecast chart shows an area containing a local risk of thunderstorms over the Irish Sea and encroaching the east from Waterford to Dundalk. Their 12Z chart shows this area retreating back and only barely clipping Rosslare.

Back to the NMM model , seeing as the LI was 3 on the coast but 13 just inland , would that tight gradient have acted as a instability in itself?

Just tryin to get my head around this more.

Deep Easterly

met.ie radar animation (using old radar) for the last 12hrs or so. Shows that potent little shower that hit Louth this morning developing quite rapidly onshore:



Sferics at 5am this morning (from Meteox)

Caitriona

And it formed over the Isle of Man. For once they did us a weather favour

Su Campu

Iancar29 wrote: »

Back to the NMM model , seeing as the LI was 3 on the coast but 13 just inland , would that tight gradient have acted as a instability in itself?

Just tryin to get my head around this more.

The lifted index is the difference in temperature between the 500 hPa level and that of a parcel lifted from the surface to 500 hPa.

L.I. = T(500) - T(par)

If the L.I is negative, it means that the parcel is warmer than its surroundings and so is positively buoyant and will continue rising. The difference in the two indices you quoted is due to the difference in parcel temperatures starting off at the surface, which is due to the sea being warmer than the land at that time of the night. The warmer marine parcel will therefore have a better chance of maintaining its buoyancy for longer as it ascends. But as I said, it was all happening well below the 500 hPa level so in this case L.I. was not much use.

That shower was formed by a combination of vigorous lake-effect convection (cool northeasterly airstream moving over relatively warm sea surface and predicted by the enhanced 0-2 km CAPE values for that area posted last night) occuring under an area of coldest upper temperatures and just enough shear. Coastal convergence from the Co Down coast probably contributed to lift. Satellite imagery shows the cloud top only reached around 14,000 ft (around 4,000 ft below 500 hPa), which shows just how turbulent this shallow convection was to generate such hail and thunder. If anyone was on a flight into Dublin early this morning I'm sure they'll agree it was bumpy.

Iancar29

Su Campu wrote: »

The lifted index is the difference in temperature between the 500 hPa level and that of a parcel lifted from the surface to 500 hPa.

L.I. = T(500) - T(par)

If the L.I is negative, it means that the parcel is warmer than its surroundings and so is positively buoyant and will continue rising. The difference in the two indices you quoted is due to the difference in parcel temperatures starting off at the surface, which is due to the sea being warmer than the land at that time of the night. The warmer marine parcel will therefore have a better chance of maintaining its buoyancy for longer as it ascends. But as I said, it was all happening well below the 500 hPa level so in this case L.I. was not much use.

That shower was formed by a combination of vigorous lake-effect convection (cool northeasterly airstream moving over relatively warm sea surface and predicted by the enhanced 0-2 km CAPE values for that area posted last night) occuring under an area of coldest upper temperatures and just enough shear. Coastal convergence from the Co Down coast probably contributed to lift. Satellite imagery shows the cloud top only reached around 14,000 ft (around 4,000 ft below 500 hPa), which shows just how turbulent this shallow convection was to generate such hail and thunder. If anyone was on a flight into Dublin early this morning I'm sure they'll agree it was bumpy.

CHeers for that Su, 2nd paragraph is what i was needing.

Iancar29

London being lit up by lightning tonight! Very annoyed at some of the messages im getting from my friend over there!

EDIT : And the storm has reached london.. confirmation?... while the Net Weather sever has gone down! ha

Harps

Yeah was just gonna say that, Netweather's crashed so there must be some serious activity over there! They've been spoiled in London this month, some people reporting thunderstormsstorms for 5 or 6 days in a row last week

Not bad..

Hal1

Just reading some of the comments on UKWW: link

22z late report of a lovely in-cloud thunderstorm with at least 10-15 minutes of almost constant lightning and rumbling which never got very loud, but a wonderful night time light show.

Edit - overall the lightning lasted at least 40 mins

Seems to be fizzling out now.

Iancar29

Taken in south east london 2 hours ago.
Apparently there was a few sightings.





Convergence zone ?

My name is URL

Caitriona wrote: »

There was serious stuff happening over our house between 5 and 5:40. The lightning had everything electrical in the house beeping and the thunder actually shook the house, and for massively long intervals. I haven't been scared of a thunderstorm in years but this one had me nervous.

Thankfully the kids slept through it, presumably they thought the thunder was just the neighbours moving some extremely big wheelie bins.

Same here, it sounded and felt like a very large cannon being fired from my roof. I thoroughly enjoyed it though

The dog not so much.

gbee

skipz

strike on the south Dublin/wicklow coast.

sunbabe08

surprised that's there's nothing coming from those intense showers in the north at the moment

Iancar29

skipz wrote: »

strike on the south Dublin/wicklow coast.

What time was that at?... i cant see anything on radar all night in that area...


Anyone know why the Thread title was changed?????

DOCARCH

Iancar29 wrote: »

Anyone know why the Thread title was changed?????

Can't understand that either? There was/have been lots of other thunderstorms around the country?

I think that strike over south Dublin must have been a rouge one (or a Honda 50 ) - there was no convective activity or showers at that time.

Iancar29

DOCARCH wrote: »

Can't understand that either? There was/have been lots of other thunderstorms around the country?

I think that strike over south Dublin must have been a rouge one (or a Honda 50 ) - there was no convective activity or showers at that time.

Exactly ha, maybe it was a thread merged from someone who made another just for the event in louth.


Anyways... onwards and upwards.

Next potential seems to be on Monday.

Hopefully some embedded storms within the main band of rain forecasted to head NE across the country come Sunday night.

LI good on the last few runs with some nice SL cape too.



Deep Layer Shear ( DLS ) seems good and Low Level Shear (LLS) too.


At the moment id guess the favourable area to be would be the South and midlands .

If not any storms on the day there sure will be a good bit of rain in the south to deal with.

THoughts anyone?

Hal1

All subject to change though. I wouldn't consider the gfs to be the most reliable charts, especially out past t+72.

Iancar29

AH of course .. but its has been there in some form on the last few runs. Shall be interesting indeed to see how the next few runs take it.

MiNdGaM3

A very heavy shower in Cork the last half hour, kinda caught me by surprise.

sunbabe08

MiNdGaM3 wrote: »

A very heavy shower in Cork the last half hour, kinda caught me by surprise.

same here, wasn't expecting that

Kensington

Pretty heavy hail/sleet shower just now in Templeogue.
From calm and quiet to very heavy hail and back to calm and quiet in the space of five minutes.

Still managed to get soaked though

Iancar29

Tomorrow is still looking good for some thundery activity after the main band of rain clears away to the North.

Id say most areas are in with a decent chance of some action, mainly the Midlands .

Charts below for 3pm show some good LI values (lifted index) and a nice amount of CAPE too. Precip. chart are also picking up on some of the showers .



My only concern would be any heating would be limited if any residual cloud is left after the main rain band moves through.

Shall Update later

Su Campu

Yes, certainly looking good for tomorrow afternoon. We should also see a comma-type system form off the west coast early morning and move inland over Connaught through the day, bringing more organised showers to the west.

The US Air Force maps for 12 and 18Z tomorrow show isolated thunderstorms for much of the country.