Very Heavy Rain Saturday Night with Flash Flooding/Lightning storms

darkman2

An active depression is going to sweep across the country on Saturday night quickly spreading rain to all areas which will bring exceptionally heavy pulses overnight to the Southern Half of the country in particular. Large amounts of rain are likely to fall in a short period and this could lead to flash flooding. If you are in an area prone to river flooding you should get sandbags ready and motorists should note that due to the abundance of leaves on the roads drains are liable to get blocked. Overnight large amounts of surface water are likely to accumulate with 50mm or more falling in a relatively short space of time.


Thunder and lightning is also likely especially in Southern areas with the rain.


Winds will strengthen significantly in the Southwest Sunday Morning.

Redsunset

I have to agree with you and i think people are somewhat underestimating this system.it will not pour rain it will dump it very quickly catching all by surprise.good job its not a commute to work morning.winds are being underestimated too especially around coasts.This is my view too on this and don't see it downgrading.

mike65

A wet Halloween then.

Redsunset

not really,heavy rain reaching south west bout 9ish showery elsewhere, then torrential stuff spreading as we go into sunday morning.i think a line from dundalk to limerick,basically half the country will experience the worst.

I_am_Jebus

I'll be on the North Stand at the RDS Saturday evening for the Leinster vs Blues game. Is there any chance of getting thru the game with getting drenched do you think?

Redsunset

well it seems that the system is going to pass about 150 miles further south than originally thought.we won't get the worst of it now but still plenty of wet weather to deal with especially southern counties.getting bit too reliable time frame for it to suddenly ramp up and beeline for us again, however stranger things have happened before.

Redsunset

sky news forecast

http://news.sky.com/skynews/Home/UK-Weather-Forecast-In-Video/Video/200806315009830?lid=VIDEO_15009830_UKWeatherForecastInVideo&lpos=searchresults

M.T. Cranium

I notice that the 06z GFS edges the storm track back closer to Ireland again, my take on it is that it will probably bring a fairly steady rainfall of 20-30 mms to the southeast "half" of Ireland about as discussed above, today's western showers tending to merge into the oncoming storm for some central counties but in general most places won't get too wet until the main storm arrives, some time late this evening.

With this trend in the model runs, there is certainly reason to be very vigilant as what we are dealing with is a weak system currently a long way from Ireland (it's just north of the Azores now) which means that possible development scenarios varying slightly would have considerably different results for places along the track.

It could end up producing as much as 40 mms of rain if everything comes together just right and the track were to be something like Wexford to Isle of Man to Edinburgh. If by any chance it shifts even further back to the north and west, then the heavier rain would shift back to the west and some stronger winds could reach southeast Ireland. That's probably not going to happen, but we can't rule this out yet.

As to the winds, I think they will pick up rather slowly on Sunday in Ireland, there will be strong southerly winds across parts of the UK ahead of the low. But the shape of the thing seems to indicate a gradual rise in wind speeds through Sunday afternoon from a westerly direction, but only reaching 20-40 mph for most. In fact the whole week to follow is looking rather blustery, there may be some significant gusts around Tuesday and Thursday too.

Back to watching and waiting ...

Darwin

Had an absolutlely torrential downpour in Portlaoise around 2pm - but it was very localized. Rumbling thunder at the moment - quite unusual for this time of year.

Redsunset

Met Eireann Warning

Rain warning
Rain will extend northwards across the country Saturday night, turning heavy in many areas. Totals will exceed 25 mm in places, mainly over Munster and Leinter, and may reach 35 - 40 mm locally. Clearer weather will spread from the Atlantic later Saturday night and Sunday morning.

big slap of thunder, west dublin about 10mins ago

Ciaran500

Deleted User wrote: »

big slap of thunder, west dublin about 10mins ago

Very impressive and surprising but looks like it's gone now.

milly4ever

had the very localised thunder, lightning and heavy downpour in belfast 1/2 an hour ago, started as soon id put the washing out- weather forecast said nothing until tonight! :mad:

anotherlostie

I presume that wasn't THE heavy rain? I got caught in it out for a walk:(

darkman2

No, that is not the rain in question, though it is the first sign of the system developing for tonight. The depression to the south is developing rapidly and will cross the country overnight. Some severe convection seems likely and so embedded storms are likely to occur esspecially later as the cold front crosses Ireland. Flooding is likely to occur in some places but the nature of these things mean it is very hard to pinpoint exact locations. The Southern Half of the country is most at risk of torrential downpour and flash flooding.


If you are in the Southeast, perhaps near a river, or an area prone to flooding you really should take some form of prevention like sandbags now just in case.

darkman2

milly4ever wrote: »

and how about us in the north east?

You mean Down, Antrim? Or Louth? The former - no, it should not be quite as bad there for rainfall (still a bad and wet night with some heavy rain expected though in the early hours!)....the latter it's much more difficult to say. The problem for the East coast tonight is that winds will turn to come off the Irish sea so it's going to be very wet in Eastern counties but I still think the Southeast is most at risk - though all areas at some level of risk for flooding. It's not that im trying to be vague with you but it is very hard to be specific about individual counties or towns!

Redsunset

Lots of lightning showing up on meteox site over eastern ireland at the moment.

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

milly4ever

darkman2 wrote: »

You mean Down, Antrim? Or Louth? The former - no, it should not be quite as bad there for rainfall (still a bad and wet night with some heavy rain expected though in the early hours!)....the latter it's much more difficult to say. The problem for the East coast tonight is that winds will turn to come off the Irish sea so it's going to be very wet in Eastern counties but I still think the Southeast is most at risk - though all areas at some level of risk for flooding. It's not that im trying to be vague with you but it is very hard to be specific about individual counties or towns!

thanks for the info! and i'm in belfast , the antrim side of the river!

darkman2

milly4ever wrote: »

thanks for the info! and i'm in belfast , the antrim side of the river!

NP. It should not be too bad there relative to what may happen further south. Still a rough night mind!

Iancar29

Just back from work, the main bit of rain past . My lightning detector was lettin off a few beeps of 10-15 km away, any more lightning epected wit 2nites "storm" ? , Hav 2moro off so i can stay up and watch! ha

In Dublin btw.

Redsunset

just watched weather on rte and they have it more northerly hitting munster and leinster before pushing through to scotland.

oh i give up with this one:D

Redsunset

Ill be happy enough with this during the wee hours.

Deep Easterly

Pretty violent shower here in Tuam at the moment. Has already dumped 5.2mm in the last 10 minutes.

Deep Easterly

Shower has dumped 8.0mm so far. Easing up a little now. Flooding for the second day in a row.

Redsunset

this is what you got.

Deep Easterly

A grand total of 9.8mm from that shower. 2nd day in a row of flash flooding here. Gonna take a walk around to see how the roads around town are doing.

Redsunset

A TORRO CONVECTIVE DISCUSSION has been issued at 13:30GMT on Saturday 31st October 2009

Saturday 31st October 2009 for the following regions of the United Kingdom & Eire:

Eire

N Ireland

Parts of Scotland

THREATS

Wind gusts to 50mph; hail to 10-15mm diameter; CG lightning; isolated funnels/brief tornadoes.


TONIGHT AND TOMORROW: A rapidly developing depression will move north-east later tonight and tomorrow. There is a risk of severe convection along the cold front, and around the centre of the storm, as it undergoes rapid cyclongenesis - severe gusts and isolated tornadoes will be the main threats

Redsunset

Interesting Hi res chart for rainfall total i've nicked from NW.

M.T. Cranium

I had a close look at ship reports and satellite imagery to try to get a fix on how this storm is developing. Looks to me as though the original low that was near 41N 20W has faded out and is being replaced by stronger lows in a chain east to west around 47.5 N, one centre near 18 W and another near 14 W, both around 1012 mbs. These will probably slide east-north-east and merge into one centre at 1002 mbs that will be closer to the trailing low, by about 00z, and I would place that just south of Cork and north of the Marathon platform. At this point, a secondary front that is drifting south through western Ireland will wrap around the developing centre and stall around south-central Ireland. From there, this centre of low pressure should track just across the southeast corner of Ireland (996 mbs) and perhaps slightly inland, then into north central Wales (988 mbs) and towards Newcastle at about 980 mbs (on Tyne not under Lyme unless it rains exceptionally hard).

This may sound fairly dramatic but this sliding track may tend to spread the rainfall out along a fairly long axis of moderate rain so places will need to be right under that axis to get the maximum amount. I am estimating this to be 35-40 mms and possibly the heaviest rain near Tipps, Laois, Carlow and Kildare. I think there could be a fair amount of thunder and lightning there especially, around 0200-0500.

All could change as this system is only just starting its developmental phase now and there is a large mass of 17-18 C air temps and dew points over Biscay. Wind potential for southern England is considerable given the instability likely to develop mid-morning Sunday. I would not want to be flying into Heathrow or Gatwick around lunch time tomorrow. Which is fine, because it seems very unlikely that I would be.

Well then, back to hunting for clues.

darkman2

Thanks MT. Well, the action (so to speak) has begun with the radar lighting up through the evening. Already some downpours in there toward the South Coast so we will see how this developes. I hope there is no flooding of course but the original OP still stands that there is a risk overnight.

Redsunset

TORRO TORNADO WATCH 2009/007

A TORNADO WATCH has been issued at 23:20GMT on Saturday 31st October 2009

Valid from/until: 0430-1600GMT on Sunday 1st November 2009 for the following regions:

Parts of

England & Wales

S Scotland

Isle of Man

Channel Islands

Eastern Eire
THREATS

Tornadoes and wind gusts of up to 70mph; isolated CG lightning.

Rapidly developing Atlantic depression will move NNE late tonight and through tomorrow, the most likely track is through the Irish Sea into S Scotland. Close to the storm's centre, a marked dry intrusion/frontal fracture may allow some convection to develop, in a highly sheared environment. Marked low-level shear brings the risk of isolated tornadoes - in addition, wind gusts of 60mph are possible, perhaps 70mph in places. There is a small risk that a sting-jet may develop, enhancing the wind risk.

To the south of the depression, a well-marked cold front will surge eastwards...this is likely to split, so rather intense precip, perhaps with lightning, could develop ahead of the surface front, althoug rather stable/saturated low-level air ahead of the front would limit the risk of convective gusts. The surface front looks fairly likely to be marked by a line of forced convection. Strong low-level shear ahead of this means that misocyclones may develop along this front, bringing a risk of locally damaging winds, and perhaps isolated tornadoes. At this stage it is not clear whether this convection will be deep enough for lightning.

Even at this late stage, the track of the depression is stil rather uncertain. This forecast may well be updated/amended in the morning, as the situation develops.

Forecaster: RPK.