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Storm Ellen - 19th/20th August 2020

M.T. Cranium

I just finished my forecast prep and discovered that various models are toying with strong developments in the Biscay region within 24-36 hours affecting some parts of Ireland within 36-48 hours, but details vary from model to model so at this early stage it's not possible to give a very precise alert for which regions may see the strongest winds.

The developments are somewhat similar to a near-tropical storm scenario that I recall from this time of year several years ago. That one moved into the Irish Sea.

Impacts are likely to be winds of at least 60 to 90 km/hr and possibly a lot stronger than that, possibly in more than one wave around Thursday and Friday, and locally intense rainfalls rapidly increasing in totals to reach 30-50 mm.

My expectation is that some clarity and model consensus may emerge as early as the 12z model runs later today but it may not be that straight forward.

At the moment, the ECM seems to favour the southwest for peak development while the Arpege model favours the southeast. While the GFS and some other models have considerable wind and rain in their output, they don't necessarily pick up on these particular developments from Biscay, keeping more of a southwesterly origin for their trajectory and no discrete lows.

This may of course be a false alarm so at the moment I am going with a level 1 tag although if some maps verify we will definitely be seeing level 2 impacts at least.

Heavy rainfalls over several days will be falling on top of considerable rainfall that hit similar areas in recent days and this needs to be factored into flooding potential.

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lucernarian

Little snowy old me wrote: »

Not trolling but am I correct in saying that the downgrades have already started? Its a perfectly reasonable observation to make.

There's unfortunately been no downgrades and most models are backing the extreme version of events led by the ECM output.

endainoz

Little snowy old me wrote: »

Not trolling but am I correct in saying that the downgrades have already started? Its a perfectly reasonable observation to make.

Not from what I've seen?

DOCARCH

Little snowy old me wrote: »

Not trolling....

Beg to differ! :P

If you are following certain forecasts (e.g. on Facebook) then expect downgrades or for it not to be as severe as suggested!

Advice would be to follow Met Eireann forecasts for your area.

munsterlegend

DOCARCH wrote: »

Beg to differ! :P

If you are following certain forecasts (e.g. on Facebook) then expect downgrades or for it now to be as severe as 'forecast'!

Advice would be to follow Met Eireann forecasts.

You have to admire his consistency. Every big thread without fail..

Graces7

Deleted User wrote: »

There should be definite advice given that all people occupying tents or caravans (In these orange/red warning situations) move to safe "built" shelter, ie check into a hotel, b&b, or go home well in time. I believe that was a particularly well-run caravan site and the owners
very upset by that tragedy which occurred in one of the most beautiful locations in the country.

There will likely be a run on accommodation within easy reach of the coast tonight, and it would be a good thing if caravan/camping site managers were obliged to inform occupants of the weather warning. Many people take these kind of holidays to get away from the usual bad news stories and may not have caught the weather warning.

When that happened I was looking at the possibility of renting on Omey and involved with folk there.

Whatever folk think of forecasts it is safer to err on the overhyped than the other way. Like now...;

M.T. Cranium

Will be posting forecast update soon. Rapidly deepening low centre (978 mb) is close to 50N 10W heading NNE. Most likely landfall is Cork/Cobh to Youghal at about 2100h (967 mb). Reports from Brittany buoy indicate steady increase in wind speed there already veering to SSW. A ship is heading east through the storm centre and reported at 12z and 15z (18z is 1900h). Estimate that this ship will be at 50N 9W at its next report. Also the centre will pass very close to the Kinsale energy platform around 2000h. So we will have those direct pressure and wind reports.

Red alert conditions for wind and rain may verify in parts of Cork, Waterford, Limerick, Tipps, and possibly Kilkenny and south Clare, Wexford, Carlow, and higher parts of inland Kerry. It should be noted that the red alert for wind would occupy mostly the eastern half of that composite zone, red alert for rainfall the western half. Overlapping wind and rain red alert conditions could occur in some parts of east/central Cork and possibly in an intermittent swath extending north along the track as far as Lough Derg.

Will give some thoughts on details of scenario at landfall later. Dublin region impacts fairly moderate, peak gusts likely to be around 110 km/hr (southwest around midnight) and rainfalls 10-20 mm. That can be scaled towards the major impact zone, for example, for Laois would say peak gust potential is 120-130 km/hr and rainfalls 20-30 mm, etc, until you get into a narrow swath of 140-160 km/hr gust potential and 30-50 mm rainfalls just to the west of that. If the centre misses Cobh to the east by any margin, winds will still be very strong westerly (northwesterly towards west Cork) but storm surge will likely only be an issue east of the landfall. On my proposed track, places like Youghal and Dunvargan could take the worst of the winds and storm surge, and it will remain high impact for east Waterford and Wexford coasts too.

froog

lucernarian wrote: »

There's unfortunately been no downgrades and most models are backing the extreme version of events led by the ECM output.

i must be missing something ECM doesn't look remotely like any other model i'm looking at. all the others show a tame enough offering, whereas the ECM looks apocalyptic.

DOCARCH

@Graces7. I have edited two of your posts as I would prefer not to have a specific past tragic incident discussed in this thread.

M.T. Cranium

Little snowy old me wrote: »

Not trolling but am I correct in saying that the downgrades have already started? Its a perfectly reasonable observation to make.

Yes, IWC down from 200 to 199 peak gusts. :cool:

Sephiroth_dude

leahyl wrote: »

Dead calm in cork city and quiet....

Lets hope it stays that way ;-)

leahyl

Sephiroth_dude wrote: »

Lets hope it stays that way ;-)

Ah now don’t be a killjoy! :-P

[Deleted User]

Calm in North kerry.

m17

Co galway

leahyl

Gone very misty and foggy now in Cork City - wind starting to stir a little...Jennie O’ Sullivan on RTE news just now in Garretstown and it already looks pretty miserable down there tbh!

squarecircles

m17 wrote: »

Co galway

youre actually standing in County Mayo there,thats part of the Mweelra mountain range,Mayos highest peak.

Waves*

SleetAndSnow

Standing on a beach in West cork at the moment, tide is highest I have seen it in nearly two+ years. Nearly covering the entire beach.

DOCARCH

Update from MT in the forecast thread....

Update -- Wed 19 Aug 2020 -- 6 p.m.

The core of storm Ellen is rapidly developing around 50N 10W and heading for a landfall near or just east of Cork/Cobh in east-central county Cork or at the very furthest east, western border area of county Waterford.

A red alert has been issued by Met E for county Cork and I believe that red alert conditions could verify locally in an area including parts of Cork, Limerick, Waterford, Tipps, Kilkenny, Carlow, Wexford and higher inland parts of Kerry as well as southeast Clare.

The red alert conditions would be for wind damage (130-160 km/hr) in eastern portions of that zone and for rainfall and flooding potential in the western half (rainfall will be highest about 10-30 miles west of the track of the northward moving centre). Rainfalls of 30-50 mm in twelve hour periods can produce moderate to severe flash flooding of short-cycle watersheds (the impact on larger rivers would be felt somewhat later and would include rain that might fall after Ellen). Storm surge may become an issue in east Cork and Waterford, and possibly some parts of Wexford. I don't think this would be catastrophic but could do some damage to shoreline properties.

By the time the centre reaches east Galway and Roscommon around midnight to 0300h, conditions will have moderated slightly to orange alert, winds gusting to 120 km/hr and rainfalls of 20-40 mm. This could still cause some localized damage and flooding.

Most parts of Leinster away from the southern counties, and some central and eastern parts of Ulster, will have relatively moderate impacts from winds gusting to about 110-120 km/hr and rainfalls of 10-20 mm.

For Mayo, expect some locally heavy rainfalls mainly over higher terrain and in the east, and an interval of strong wind gusts along the coast. For Sligo, Leitrim and Donegal, the effects will be most pronounced around 0300-0600h and an orange alert may be justified there also. For most of Ulster otherwise the impacts will diminish further east except in a few exposed coastal locations.

The worst of the storm should last about 3-6 hours and conditions will slowly improve after it has passed to the north by 50-100 miles of any given point.

An update around 9 p.m. on landfall parameters will be issued.

looksee

Heavy mist, rain and a brisk breeze in north Waterford.

Oscar Bravo

The latest TAF',s have downgraded max gusts.

leahyl

Oscar Bravo wrote: »

The latest TAF',s have downgraded max gusts.

Ah no! Downgraded to what?

M.T. Cranium

The reason for the calm or light winds in west Cork and Kerry is that this storm has no cold air advection, it is moving along through the broader warm sector ahead of the more distant Atlantic low. Therefore as it approaches, wind potential from northeast is cancelled by the southwest flow around the more distant low. This calm phenomenon may be noted later up along the coast into Connacht for some period of time. Eventually even where the low passes to the east, strong southwest to west winds will develop around the circulation of Ellen. The centre is most likely to hit where winds stay moderate southerly. It will be very close to a direct hit on the Cobh/Cork metropolitan region but I suspect the actual location of landfall will be something like 20 miles east of there and west of Youghal. The only good thing about that for Cork might be that coastal flooding would be somewhat reduced as the storm surge will be higher to the east of the landfall. However I understand that the coastal flooding around Cork is mainly from runoff in the river Lee backed up by higher than normal tides so that part of the equation would still be operational if heavy rain was falling all through county Cork tonight.

There will very likely be some scattered wind damage in exposed coastal and inland higher south-facing locations, this is why I suggested a wider extent of the red alert to include those exposed locations. Our forum member RobertKK is on a south-facing hill (I think I recall him saying) in Kilkenny, that sort of location could pick up higher gusts than most of the surrounding county.

garyha

https://twitter.com/CarlowWeather/status/1296134440452870144

DIF

Oscar Bravo wrote: »

The latest TAF',s have downgraded max gusts.

Sounds good, I'm in East Cork so don't wanna be shopping for roof tiles tomorrow:D

Oscar Bravo

leahyl wrote: »

Ah no! Downgraded to what?

Big downgrades on TAF's,Cork ,for example now going for max gust of 45 knots with 40 percent chance of 60 knots,way down from the 75 knots mentioned earlier.

FastFullBack

SleetAndSnow wrote: »

Standing on a beach in West cork at the moment, tide is highest I have seen it in nearly two+ years. Nearly covering the entire beach.

Which beach?

leahyl

Oscar Bravo wrote: »

Big downgrades on TAF's,Cork ,for example now going for max gust of 45 knots with 40 percent chance of 60 knots,way down from the 75 knots mentioned earlier.

Ah jeez, another damp squib? Or is it unwise to go on just the one source?

froog

ICON and GSF still showing a non event.

grinder23

Hi Guys haven't a clue about any of this but I never see Longford mentioned lol anyone any idea what we could expect?

pad199207

Oscar Bravo wrote: »

Big downgrades on TAF's,Cork ,for example now going for max gust of 45 knots with 40 percent chance of 60 knots,way down from the 75 knots mentioned earlier.

The trend is there this evening for Cork to be taken out of the highest risk zone for wind.

JCX BXC

TAF's aren't generally the best indicator, I've seen them be wrong many many times.