Storm Desmond - High Winds 4/5 December 2015

M.T. Cranium

As almost all guidance seems to agree now that wind gusts in exposed western counties may exceed 120 km/hr on Friday, I have opened up this new discussion thread for strong winds Friday into early Saturday.

The global models and the short-range specialty models seem to agree on this and you could find depictions of 120 km/hr or higher gusts near the Mayo coast on almost all models in the 00z suite.

The strongest winds should gradually move east across all regions, arriving on the south coast later Friday and on the east coast early Saturday morning.

This event does not currently look too bad for heavy rain potential but will address that later.

The GFS model also shows further windstorm potential later in the month, in particular around mid-month. This is probably the truer signal of the colder conditions likely to develop than anything you might read in a tabloid about a 2010-style cold spell and snowfall. That's not really supported in any reliable guidance although it could eventually get cold enough for wintry showers (in about two weeks).

Tactical

Thanks for the advance warning.

I'll be on the road early Saturday morning travelling from East to West. While I'll most likely miss the chance to "enjoy" the best of the wind I'll know to be alert for debris on tge roads once I leave the motorway and national primary roads.

Both recent storm have felled trees across public roads here in West Limerick so there's the potential for a similar occurance

Bigcheeze

What will conditions be like on the east coast around 6pm Friday ? Am due to fly out of Dublin.

Weatherproof79

Bigcheeze wrote: »

What will conditions be like on the east coast around 6pm Friday ? Am due to fly out of Dublin.

www.xcweather.co.uk/forecast/Dublin_airport_

Updates four times per day

Bigcheeze

Weatherproof79 wrote: »

www.xcweather.co.uk/forecast/Dublin_airport_

Updates four times per day

Crap. 60mph gusts likely to mean disruption.

RubyK

Waterford half marathon is on Saturday morning 10.00am, so it could be a rough day for runners and volunteers

maquiladora

Friday evening looking windy on the 06Z GFS. Probably a bit weaker than Barney for inland areas, but a longer period of strong winds and covering a wider area than on Nov 17th.



Also got to keep an eye on a potential low crossing the country Saturday/Sunday.

Stealthfins

Sounds good for wave watching Mullaghmore should be epic.

SEPT 23 1989

Is this part of the same system that is giving violent storm force 11 winds south east of Iceland?*

*half asleep listening to the shipping forecast early this morning:D

marvin80

Bigcheeze wrote: »

Crap. 60mph gusts likely to mean disruption.

What mph would usually cause a disruption?

(Flying early Saturday morning)

Bigcheeze

marvin80 wrote: »

What mph would usually cause a disruption?

(Flying early Saturday morning)

It's the direction that's as much a problem as the strength of the wind because cross winds make it difficult for aircraft.

This is forecasted to be south westerly and the runway is westerly so there'll be a significant cross wind. Once gusts get to 40+ knots with significant cross wind it seems to cause delays and cancellations.

Irish Steve

marvin80 wrote: »

What mph would usually cause a disruption?

(Flying early Saturday morning)

Depends on the direction and the size of aircraft you will be flying on.

The smaller aircraft (ATR sizes) are restricted to about 35 Kts cross wind component, and if it gets above 50 Kts, even if it is directly down the runway, that speed can cause issues with things like opening and closing cabin doors, especially for Ryanair, and the other carriers that don't use the jetway stands, which give some protection, if the stand is remote, or has no jetway, above a certain speed, there is the risk of damage to the doors, or the crew being physically blown out of the aircraft when trying to control the doors.

At this stage, all you can do is contact the airline to ask them if they are anticipating any disruptions, and they may not know yet if there will be issues on Saturday.

There is also the possible issue that problems on Friday may result in aircraft not being where they are supposed to be, which can disrupt early morning services.

Bigcheeze

maquiladora wrote: »

Friday evening looking windy on the 06Z GFS. Probably a bit weaker than Barney for inland areas, but a longer period of strong winds and covering a wider area than on Nov 17th.

Is the time on these charts CET ? i.e. the above is showing 90-100km/h gusts in the Dublin area at 6pm Irish time ?

maquiladora

Bigcheeze wrote: »

Is the time on these charts CET ? i.e. the above is showing 90-100km/h gusts in the Dublin area at 6pm Irish time ?

Yes thats 6pm here. 100-110 km/h gusts possible there, but of course it may turn out to be weaker than that and local topography has to be taken into account. It's just an estimate.

maquiladora

ICON showing gusts up to 70 knots on the west coast Friday night.

maquiladora

"Round 2" on Saturday evening on the 12Z GFS. May be just as strong or even a bit stronger (for some areas) than Friday night.

Oneiric 3

DMI run has wind speeds reaching the top end of its scale off the north coast of Ireland by Friday evening.



What makes this one interesting is these wind speeds are not really circulating around a classic storm low feature that we are more familiar with, but more a tightening gradient between HP to the south and LP to the NW. HH Lamb, in his study of European storms identified similar set ups over the last 150/200 years that brought periods of gale to storm force winds over northern Europe, and often for longer periods than from the more classic storm low set up that tend to whisk through more rapidly.

JCX BXC

The storms seems to be a late evening/night time event so flights shouldn't be affected too bad.

How long until Met Eireann issue a warning? My guess is Tomorrow evening.

maquiladora

Carnacalla wrote: »

The storms seems to be a late evening/night time even so flights shouldn't be affected too bad.

How long until Met Eireann issue a warning? My guess is Tomorrow evening.

Well looking at the 12Z GFS, it starts to get stormy on the west coast around noon on Friday and stays windy there until around midnight, easing off on the east coast early Saturday morning, but it never really calms down much on the south coast and then there's a second round of equally stormy/windy conditions possible on Saturday afternoon and evening.
So as the the post above mentions its as bit different from the usual 1 or 2 hours of peak winds zipping across the country, it's more extended. So even if the winds don't look like being exceptional, they will keep going for several hours, so that could cause some problems with branches and trees being weakened over time rather than in one big severe gust.

Tactical

Really looking forward to an interesting weather weekend

Hopefully there will be no significant downgrade of whats forecast.

I'm very much enjoying the various inputs from knowledgeable posters, its very much appreciated. Also enjoyable are the various opinions and discussions that take place.

Oneiric 3

EMHI 12z run showing widespread zone of 24 m/s (46 knots/BF 9) mean wind speeds approaching the NW coast by 6pm Friday.

Villain

My WXSIM forecast just updated, based on GFS

JCX BXC

Met Eireanns own 5 day forecast on their website looks interesting, quite user friendly too.
http://www.met.ie/forecasts/5day-ireland.asp

Hooter23

This wind chart is showing violent storm force 11 winds Friday evening...I think

http://www.myweather2.com/streamline/player.aspx?Streamline=2#

squarecircles

Violent storm force 11 on the west coast Friday evening on this chart.

Oneiric 3

DOCARCH

Desmond...that's the next storm name due!

maquiladora

UKMO for noon Friday. Strong winds approaching the west coast.

JCX BXC

Storm Desmond then it seems :P

Oneiric 3

The wind from this system may only be half the story, at least according the the latest ECM, which has the frontal zone wavering over the mid-west and midlands for 30 hours solid, bringing the risk of some prolonged and/or heavy spells of rain.



Looks particularly dodgy for N.Munster in through parts on N Leinster/S Ulster right through Friday night and throughout Saturday. Whether the evening's run has this nailed on though is the big question.

Chris_5339762

Vanilla GFS is showing a good lot of rain all over the weekend. Torrential for ~30 hours in places.

FWVT

The 12Z ECMWF shows 50-kt 10-metre and 80-kt 925 hPa winds off the far west coast on Friday 12Z. Over land the 925 hPa level is around 700 metres in that area but the winds are at most 60-70 kt.

For comparison, Barney, which gave a 68-kt gust at 5 pm at Oak Park, had 925 hPa winds of 80 knots over land (yellow area) but this level was lower, at around 600 metres. This Friday's system will be no match for Barney over land, however I would not like to be out to sea in it.

Tactical

Chris_5339762 wrote: »

Vanilla GFS is showing a good lot of rain all over the weekend. Torrential for ~30 hours in places.

Torrential rain for approx 30 hours? Surely that's overcooked? That would be quite serious given the recent rain we've had, even taking into account a dry day or two.

Can you elaborate on this?

FWVT

Chris_5339762 wrote: »

Vanilla GFS is showing a good lot of rain all over the weekend. Torrential for ~30 hours in places.

??

Clonmel1000

Met Eireann not quite as strong in this as I'd have thought having read this thread.

DOCARCH

Clonmel1000 wrote: »

Met Eireann not quite as strong in this as I'd have thought having read this thread.

Still a little early to call it. ME would be on the cautious side.

km79

DOCARCH wrote: »

Still a little early to call it. ME would be on the cautious side.

MTC holding off on major rainfall too
I hope they are right

M.T. Cranium

The guidance suggests heavy orographic rainfall (on south-facing hills) which might be level two rain or flood potential locally for small streams that drain those hills. Lowland rainfall does not look overly heavy. Would expect possible changes as details of the frontal stall zone become clarified.

From the guidance I looked at, would suggest 50-75 mm rainfalls on hills in west but only 15-30 mm over most lower terrain. So unless you live close to those hills or have a stream nearby that rises in nearby hills, the flood potential may not be especially great. This is not meant to be a comment on the Thursday rainfall in the southeast which is being discussed in a separate thread.

I can edit posts but I can't change thread titles so if there is a change in my thinking it will show up in posts before the thread title.

Oneiric 3

Latest HIRLAM has a zone of mean wind speeds of near gale or gale pushing into Connacht later on Friday. Here imby, it is showing a period of mean wind speeds reaching near gale for period of at least 6 hours which would be unusual event in recent climate history. Gust speeds not projected to be excessive though away from the coast.

maquiladora

18Z ARPEGE max gusts up until 6am Saturday. 130 km/h gusts shown for northwest Mayo.

maquiladora

Here's a comparison, for what it's worth, between the max gusts up until Saturday 6pm on NMM WRF and what the same model showed for Barney's max gusts.

Barney :



This weekend :

kittyn

maquiladora wrote: »

Here's a comparison, for what it's worth, between the max gusts up until Saturday 6pm on NMM WRF and what the same model showed for Barney's max gusts.

Barney :



This weekend :

Looks a fair bit worse than Barney or are my eyes deceiving me???

Isaiah

Hi folks, have a ferry crossing Holyhead to Dublin this Friday afternoon.

What's the verdict ? Look like a cancellation?

Oscar Bravo

Jerry Murphy on Radio 1 there "very wind or possibly stormy friday night", not much more detail on it.

Isaiah

Oscar Bravo wrote: »

Jerry Murphy on Radio 1 there "very wind or possibly stormy friday night", not much more detail on it.

Hopefully we get in before it kicks off.

Oneiric 3

maquiladora wrote: »

18Z ARPEGE max gusts up until 6am Saturday. 130 km/h gusts shown for northwest Mayo.

Felt a pang of excitement in my stomach looking at that chart

maquiladora

kittyn wrote: »

Looks a fair bit worse than Barney or are my eyes deceiving me???

Winds over a wider area and a longer duration than Barney but I doubt winds will be stronger than Barney in the inland areas where Barney was strongest.

ninebeanrows

Latest EC data suggests widespread 50-60mph wind gusts. Western coastal fringes ~65/70mph gusts... A small slice of 75/80mph gusts into the north-west.

Oneiric 3

Weathercheck wrote: »

Latest EC data suggests widespread 50-60mph wind gusts. Western coastal fringes ~65/70mph gusts... A small slice of 75/80mph gusts into the north-west.

I don't think gusts will be the biggest issue in this event, but more the persistence of high mean speeds, which would be more typical of warm sector conditions in similar set ups I think.

mickger844posts

I'm surprised Met Eireann/UkMo haven't come out and called this Storm Desmond yet. Looks on a par or stronger than previous named storms this season. Guess there is still time but it seemed like they named previous storms a few days earlier.

Irish Steve

Isaiah wrote: »

Hi folks, have a ferry crossing Holyhead to Dublin this Friday afternoon.

What's the verdict ? Look like a cancellation?

Depends on which company/ferry you are travelling on. If it's Irish Ferries, then the Swift fast craft is likely to be hiding in Dublin port for a number of days, but Ulysses, their largest Cruise ferry is probably going to be operating, I don't think they've cancelled a sailing because of weather with that ferry since it entered service, though some wind directions can cause issues at Holyhead when getting on and off the berth.

I have no recent experience of the Stena craft that are operating the route now, they're both decent size ships, so should be OK, but your best bet is to check with the operators for an update