Thunderstorms and possible tornadoes Saturday

Su Campu · 10-09-2010 10:01pm #1

As discussed in the Convective thread, this one deserves its own thread.

Things could be very interesting in the eastern half of the country tomorrow, with everything pointing to frequent thunderstorms, and even a good chance of tornadoes! Surface heating under the deepening upper trough leads to CAPE in the 500-1000J/kg range, with low eq. temperatures and strong windshear meaning frequent heavy thundery showers. The chart below shows the "Significant Tornado Parameter", which takes a lot of these parameters into account and spits out where conditions are conducive for tornadoes to develop.

I'd say ESTOFEX may give a Level 1 in their forecast later.

Deep Easterly · 10-09-2010 10:09pm

ESTOFEX 21.04 utc update:

showforecast.cgi?lightningmap=yes&fcstfile=2010091206_201009102104_2_stormforecast.xml

A strong upper trough over the NE Atlantic will shift eastwards towards the British Isles, leading to cold air convection over Ireland and parts of UK. The cold front of this low pressure system seems to be not very active on Saturday but this may change on Sunday. Isolated showers and weakly electrified thunderstorms are well possible but severe weather should be unlikely.

One to watch.

Wertz · 10-09-2010 10:10pm

Estofex showing general yellow t-storm area for Ire/UK tomorrow. No level 1.
They've been wrong before though.

the dinner · 10-09-2010 10:10pm

Deep Easterly wrote: »

ESTOFEX 21.04 utc update:

A strong upper trough over the NE Atlantic will shift eastwards towards the British Isles, leading to cold air convection over Ireland and parts of UK. The cold front of this low pressure system seems to be not very active on Saturday but this may change on Sunday. Isolated showers and weakly electrified thunderstorms are well possible but severe weather should be unlikely.

One to watch.

OH YOU BEAT ME TO IT XD
Anyways this forecast is very lenient

Deep Easterly · 10-09-2010 10:13pm

Wertz wrote: »

Estofex showing general yellow t-storm area for Ire/UK tomorrow. No level 1.
They've been wrong before though.

They have, and it could well be updated later on tonight or in the morning. I have been keeping an eye on this potential myself, and it is worth keeping an eye on for sure.

Su Campu · 10-09-2010 10:14pm

Hmmmm, I thought they'd say more than that. They're usually spot on, but yes, let's hope they've underestimated this one (but I betchya they haven't!) :rolleyes:

CAPE and LI at 15Z tomorrow, showing the situation at its peak. With upper ridging approaching from the west, any showers should die out fairly quickly as the evening wears on.

Iancar29 · 10-09-2010 10:22pm

NOT FAIR!

IM IN WORK 12-9 2moro!!

IF ANYTHING STARTS TO HAPPEN IM GOIN OUTSIDE ON A "EXTRA LUNCH BREAK! "

the dinner · 10-09-2010 10:28pm

This looks like the usual thundery showery day Ireland usually gets in the summer imo. Might do some storm chasing tomarrow if this hits Arklow

Deep Easterly · 10-09-2010 10:28pm

HIRLAM 18z cloud chart for tomorrow 13z:

potential still there, but what I think is keeping ESTOFEX erring on the side of caution is the timing of the ridge moving in (as Su noted). Still, could be an interesting day for some.

delw · 10-09-2010 11:30pm

Deep Easterly wrote: »

ESTOFEX 21.04 utc update:

A strong upper trough over the NE Atlantic will shift eastwards towards the British Isles, leading to cold air convection over Ireland and parts of UK. The cold front of this low pressure system seems to be not very active on Saturday but this may change on Sunday. Isolated showers and weakly electrified thunderstorms are well possible but severe weather should be unlikely.

One to watch.

as usual will b a non event

,on a brighter note big brother is finaly over for ever

:D:D

the dinner · 10-09-2010 11:33pm

delw wrote: »

as usual will b a non event ,on a brighter note big brother is finaly over for ever :D:D

Horray:P
In terms of the showers there is still most likely the chance of some thundery downpours occuring except probably not as widespread.
Any thunderstorms affecting anyone yet?

Elmo5 · 11-09-2010 12:11am

and I'm supposed to be taking the kids to the zoo tomorrow around lunch time.... hmmm!

DOCARCH · 11-09-2010 8:02am

ME forecast pretty muted for today, especially if you are in the east.

Bright and breezy today with sunny breaks and occasional showers. The showers will be heavy across the midlands north and west of the country with the risk of thunder, but some parts of Leinster and east Munster will remain mostly dry.

redsteveireland · 11-09-2010 9:02am

I can see those first showers arriving from the west. They will probably skirt past north and south of me as usual. Here's hoping for some action. For anyone.

M.T. Cranium · 11-09-2010 9:13am

I think the situation is still potentially volatile today.

The first batch of showers has out-run the upper support and aside from one cell now approaching Louth, the cluster has died out. The upper trough is near 12 W at 06z and will be near 10 W by 12z, 4 W by 00z. This means it should be over eastern Ireland by 18z. The strongest convection should be just ahead of that feature in a growing area of positive vorticity. Sunshine during the morning hours will be helpful in getting the lapse rates steeper.

All things considered, I think the earlier outlook from SC and others will work out well and some heavy showers and thunderstorms will develop, but for Dublin in particular the timing would be best around 3-5 p.m., so anyone looking for an earlier opportunity to chase or take pictures might be well advised to look around Athlone to Laois or western Kildare noon to 1 p.m., that's about where I would expect some good development to take place.

There might be thunder before that in western counties, and the whole situation is mildly unstable so would not rule out other clusters further south and southeast.

Not sure how long I will be watching, my forecast thread has this potential covered but I would appreciate it, if any regulars would post updates there if storms are brewing.

The other big weather story may be the very strong winds possible on Monday night and Tuesday as the jet stream is indicated on several models as being intense across far northern Ireland and Scotland by 06z Tuesday, and then this drops further south during Tuesday. Although this is not ex-hurricane Earl, it is some of the energy that broke away from that storm which tracked up west of Greenland this week.

Su Campu · 11-09-2010 9:14am

I don't get that at all. The upper trough is lying off the west coast at the moment and is forecast to deepen as it moves eastwards across the country around lunchtime. The 06Z Valentia sounding shows good cooling at upper levels, and this is a bit removed from the more unstable conditions further north, where the 00Z Castor Bay sounding showed a few hundred J of CAPE. There is an area of low cloud in the east at the moment which is limiting surface heating, but that should clear and allow the sun to do its work. I'd expect some showers showing up on radar in the eastern half of the country before midday, peaking around 4pm, then dying out after that.

Even Met Éireann's own TAFs from this morning mention a chance of moderate thunderstorms for Dublin, Casement and Shannon, and their Local Area Forecasts mention them for Galway and Donegal.

Dublin
EIDW 110500Z 1106/1206 25010KT 9999 SCT016 SCT030 PROB30 TEMPO 1106/1108 5000 BR TEMPO 1106/1111 SCT018CB BECMG 1109/1112 29015KT TEMPO 1111/1118 30015G25KT 5000 SHRA BKN012 BKN017CB PROB30 TEMPO 1111/1116 4000 TSRA

Shannon
EINN 110500Z 1106/1206 25010KT 9999 SCT015 SCT040 TEMPO 1106/1109 SCT015CB BECMG 1109/1112 28013KT TEMPO 1111/1118 29015G25KT TEMPO 1109/1117 5000 SHRA SCT012 BKN018CB PROB30 1111/1116 4000 TSRA

Cork
EICK 110500Z 1106/1206 23008KT 9999 SCT010 TEMPO 1106/1109 4000 SHRA BR BKN008 SCT018CB BECMG 1107/1110 29015KT TEMPO 1111/1118 4000 SHRA BKN010 BKN018CB

Knock
EIKN 110500Z 1106/1206 30006KT 0700 FG BKN002 BECMG 1106/1109 30012KT 9999 NSW SCT022 TEMPO 1109/1119 30017KT 4000 SHRA BKN008 BKN017CB PROB30 TEMPO 1111/1117 3000 TSRA BKN009 BKN015CB

The UKMET issue the TAFs for the north:

Belfast Aldergrove
EGAA 110504Z 1106/1206 21007KT 9999 SCT030 PROB40 1106/1110 BKN005 PROB30 TEMPO 1106/1111 9000 SHRA BECMG 1107/1110 28012KT PROB40 TEMPO 1111/1117 4000 +TSRA PROB40 1204/1206 BKN006

Belfast City
EGAC 110610Z 1106/1115 21011KT 9999 SCT030 BECMG 1106/1109 27012KT PROB30 TEMPO 1111/1115 5000 SHRA

Derry
EGAE 110627Z 1106/1115 27011KT 9999 FEW020 SCT030 PROB40 TEMPO 1110/1115 7000 SHRA

EDIT: I meant I don't get the met.ie forecast, not yours MT. I've just seen your post after I posted mine, and it may read like I was disagreeing with yours!

DOCARCH · 11-09-2010 9:39am

Nice clear slot over the centre of the country moving east in advance of the showers to the west - should get things warmed up nicely!

http://www.sat24.com/gb

ME yesterday evening were forecasting heavy showers with local downpours and spot flooding - I can't understand their turnaround this morning?

Su Campu · 11-09-2010 9:51am

Here's the GFS sounding forecast for Dublin Airport today.

The corresponding CAPE gets to 700-800J/kg at 15Z

redsteveireland · 11-09-2010 9:52am

Some clouds moving in from the west. Quality not great. I was in a hurry.

Su Campu · 11-09-2010 9:54am

redsteveireland wrote: »

Some clouds moving in from the west. Quality not great. I was in a hurry.

Yes, fleeing from the imminent carnage this severe weather is going to cast on us! :pac:

Deep Easterly · 11-09-2010 10:02am

redsteveireland wrote: »

Some clouds moving in from the west. Quality not great. I was in a hurry.

Can see a showerhead to my WNW also:

roughly centered west of Claremorris going by my bad sense of judgement.

GFS still giving good cape for this afternoon:

Su Campu · 11-09-2010 10:06am

GFS Meteogram for Dublin Airport

redsteveireland · 11-09-2010 10:29am

I know there is a picture forum but this is my best attempt at forecasting:D
Changing cloudscape in the west.

Su Campu · 11-09-2010 10:44am

With very low cloud bases and very unstable lower levels I think it's pretty certain that there'll be some funnels today. There is already some vigoruous swirling motion visible in the updrafts around here anyway. Everyone keep their eyes open and camera at hand!

skipz · 11-09-2010 12:25pm

I bet i wont even hear any thunder today here in Louth today, and if there is any action Dundalk will most likely have all the fun:)
Always happens....

Deep Easterly · 11-09-2010 12:43pm

First strike just east of Galway (Offaly?) in the last hour

http://www.meteox.nl/h.aspx?r=&jaar=-3&soort=satradar

coming from the same band of showers that passed over here earlier :mad:, but certainly, they are looking very black from the ground here as they push away eastwards, although convective cloud is building up again directly overhead.

maquiladora · 11-09-2010 12:52pm

… IRELAND, SCOTLAND, N ENGLAND, N WALES …

Moist surface maritime airmass will be overlaid by increasingly steep lapse rates as cold air advection increases aloft with approach of upper trough off the Atlantic (500mb temps falling to -20C). As a result, scattered heavy showers and isolated thunderstorms will develop across the above areas as post frontal westerly flow becomes increasingly unstable with surface heating and approach of upper trough. Upper winds will be rather light within axis of upper trough where maximum CAPE will be realised across northern UK and Ireland, so weak wind shear will minimise severe risk of any storms that develop. Main threat, given weak upper flow, will be slow-moving nature of showers/storms giving high rainfall totals leading to localised flooding. Convection may also be accompanied by hail and gusty winds. Heavy showers with isolated lightning may continue near Irish Sea/western coasts into early part of the night.

http://www.netweather.tv/index.cgi?action=convective;sess=

maquiladora · 11-09-2010 1:08pm

Saturday, 11 September 2010 11:42

Today

Sunny spells and occasional showers this afternoon and evening, the showers mainly in the western half of the country at first, but becoming more widespread during the afternoon. Many of them will be heavy, with a risk of thundery downpours. Highest temperatures 15 to 19 degrees, in a moderate to fresh westerly wind.

http://www.met.ie/default.asp

Storm 10 · 11-09-2010 1:26pm

Lots of convection activity and heavy showers around Galway City but no thunder yet, hopefully it may happen in the afternoon

redsteveireland · 11-09-2010 1:41pm

The leading band of heavy showers is just a couple of hours away from The Big Smoke. It should liven up in here by then.

Aiel · 11-09-2010 1:46pm

2 heavy downpours in Galway city just after 11am.Thick deep purple clouds so i thought might have sparked off a thunder storm but was just the heavy rain.

Thunderstorms and possible tornadoes Saturday

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