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Extratropical Storm Ophelia - Technical Analysis Only - MOD NOTE post #1

M.T. Cranium

Mod note

This is a busy thread and as a result the Mod Team will be taking a zero Tolerance approach to trolling and flaming

Don’t say you weren’t warned!!

And please don’t feed
Thanks

Just briefly for now, recent model runs (12z Wed 11th) have shown a track near Ireland for strong extratropical low (Ophelia) with timing converging on Monday 16th during the daytime hours.

The GFS model was of some concern but the ECM now has a very high impact low depicted at 965 mbs just about 70 miles southwest of Valentia by mid-day Monday.

This would evidently track through Ireland and Scotland on a generally NNE to NE path, which would bring damaging wind gusts into most of Ireland.

Too early to get very specific about impacts or peak wind speeds but these maps got my interest and look as intense as storm "Darwin" in 2014.

I wanted to get a dedicated thread into existence so that we can focus on this storm rather than using the tropical seasonal thread. Also, please note, obviously if this verifies a level 3 warning would be justified and at some point we will consider upgrading the current level 1 which is appropriate mainly because of the uncertain outcome, but an event of at least level 1 status seems almost locked in given the model consensus.

The GEM model is currently an outlier, like the rest of the pack it shifted east but that took its earlier eastern Ireland windstorm into Britain instead. It would be unusual for the GEM to beat out all these other models at five days so I don't give that much weight. However, it needs to be mentioned that this storm is currently a long way away (southwest of Azores) and relatively small for a hurricane, which it is about to become later today (last advisory had it as a high end tropical storm).

We shall see how the models respond to developments. The track towards Ireland makes sense when you consider how warm it is likely to be on the weekend and the position of the long-wave trough slowly moving east from the central Atlantic.

This could be a high impact windstorm for Ireland and the forum will be buzzing from now until the event comes into clear focus, after which it may be hyperactive, so post wisely with useful info as it comes along.

Mods, I will get in touch if I feel that a higher level or title change is needed. Get ready for a very busy few days.

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s.m

Everyone keeps on about a hurricane hitting this country but there's never been any record of one affecting our lovely land. Though mind you the records do only go back to late 1961 after the original building holding the records mysteriously blew away.

On a more serious note how will Donegal fair in this situation ?

mrsWhippy

When is the worst of this supposed to hit?

Sephiroth_dude

Oneiric 3 wrote: »

Looks increasing likely that the west will miss out on all the excitement yet again. :rolleyes:

Lets hope so.

Gaoth Laidir

s.m wrote: »

Everyone keeps on about a hurricane hitting this country but there's never been any record of one affecting our lovely land. Though mind you the records do only go back to late 1961 after the original building holding the records mysteriously blew away.

On a more serious note how will Donegal fair in this situation ?

Debbie was not tropical when it hit Ireland.

https://irishweatheronline.wordpress.com/2015/10/28/blast-from-the-past-hurricane-debbie-1961/

flaneur

How does this compare to what we know of the 1839 “Night of the Big Wind” ?

KingdomRushed

mrsWhippy wrote: »

When is the worst of this supposed to hit?

It's pretty well documented but the thread has gotten long.

Worst will be daytime Monday. Very worst afternoon. Core of storm moving north through Ireland between 11am and 5pm perhaps

KingdomRushed

flaneur wrote: »

How does this compare to what we know of the 1839 “Night of the Big Wind” ?

Well one thing has happened and the other hasn't (not being funny) so who knows

flaneur

KingdomRushed wrote: »

Well one thing has happened and the other hasn't (not being funny) so who knows

I obviously mean in terms of how it is shaping up and the rest of the known data at this point vs what is assumed to have happened in 1839.

Rougies

Gaoth Laidir wrote: »

Debbie was not tropical when it hit Ireland.

https://irishweatheronline.wordpress.com/2015/10/28/blast-from-the-past-hurricane-debbie-1961/

Yeah I was very surprised at that tweet from the NWS earlier saying Debbie was tropical when it hit Ireland.

https://twitter.com/NWSEastern/status/919298032625209345

Kermit.de.frog

MJohnston

Here's that most recent Arrival Time chart (note that you need to add 5 hours to the times listed because they are in AST):

It's worth pointing out how even though the models have changed the potential tracks here and there, the timing has remained fairly consistent.

Irish Steve

s.m wrote: »

Everyone keeps on about a hurricane hitting this country but there's never been any record of one affecting our lovely land. Though mind you the records do only go back to late 1961 after the original building holding the records mysteriously blew away.

On a more serious note how will Donegal fair in this situation ?

Technically, by the time it gets here, Opehlia will no longer be a hurricane, unless it doesn't downgrade itself (which will be even worse than what's being predicted), it will have become a post tropical storm that happens to still have hurricane intensity winds circulating around it. This thread has grown so fast, I doubt I can easily find the discussion, it happened some way back, and went into the fine detail of what happens to a hurricane to downgrade it into a post tropical storm, and that's related to things like the structure of the eye, and how it is both generated and maintains its structure and integrity. The fact that Ophelia has now "collided" with the North Atlantic Jet Stream will subtly affect the vertical structure of the storm, which will modify how it develops or decays, and change the direction it moves in. That's one of the (many) reasons why the exact track can't yet be completely accurately predicted, the Jet stream is a very volatile system, and it is even more rare for a hurricane of the strength of this one to be coming towards Ireland on the track that it is, so the computer models are struggling to predict the outcome, as there is not enough historical precedents for the models to evaluate and compare against.

It's hard to be sure what's going to happen in Donegal yet, due to the likely changes to the track that this system will take, a change of only a few kilometres even could mean a massive difference, and it will vary between a "normal" unremarkable windy day, and something verging on a nightmare. The worst case scenario is that similar weather has not been seen since 1961, so there are not many people around with mature memory of that time, suffice to say that 18 deaths in that event is pause for significant thought.

Meteorite58

18Z ARPEGE rolling out at present and it aint pretty.

Mean

Gusts

TheMilkyPirate

Seems a bit further west

pad199207

I’m officially worried now for large parts of the country.

Downgrades would have happened by now, but they haven’t.

munsterlegend

Meteorite58 wrote: »

18Z ARPEGE rolling out at present and it aint pretty.

Mean

Gusts

That's some pretty high gusts. I was kind of nonchalant about this on Friday but a little worried now about structural damage inland. Our properties are not built to resist strong winds like this. The track seems no matter which way it goes east or west that Cork will be hit.

Rikand

flaneur wrote: »

How does this compare to what we know of the 1839 “Night of the Big Wind” ?

We have much better warning systems in place, better constructed housing and the ability to be better prepared... So there's no real way to compare them at all imo

Meteorite58

Icon 18Z

Gust

Rikand

TheMilkyPirate wrote: »

Seems a bit further west

The ARPEGE has been favouring a westerly track from the outset

pauldry

Some of those charts would do extensive damage to Cork City.

Slates n Trees

munsterlegend

Meteorite58 wrote: »

Icon 18Z

Gust

Where does this Icon model originate from?

MJohnston

munsterlegend wrote: »

Where does this Icon model originate from?

The Deutscher Wetterdienst

munsterlegend

pauldry wrote: »

Some of those charts would do extensive damage to Cork City.

Slates n Trees

And towns outside Cork City. This storm still has a good way to travel so despite the current models all is not certain.

[Deleted User]

Meteorite58 wrote: »

18Z ARPEGE rolling out at present and it aint pretty.

ARPEGE seems to like the more Westerly track. Heres the Euro 4. Similar placing of the centre when its near Kerry, but theres a divergence later in the timescale.

Meteorite58

Where does this Icon model originate from?

German, had thought in the past that it overestimated winds a bit, but when you look at the APERGE.

allthedoyles

Here's hoping we in Wexford can escape the worst

sword1

We haven't had a big blow in a few years so trees roots have been weakening etc are going to go.

pad199207

allthedoyles wrote: »

Here's hoping we in Wexford can escape the worst

Might take a trip down to Kilmore Quay. Worried about my humble Mobile Home.

stevenup7002

Meteorite58 wrote: »

Icon 18Z

Gust

Hmm, that white spot is right over my house (Clonmel)

Meteorite58

Mod Note : Reminder that there is a chat thread re preparations / disruptions see below . Best keep this thread for more technical discussion.

http://www.boards.ie/vbulletin/showt...p?t=2057797471