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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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spookwoman

It's only west of the Strait of Gibraltar

Gaoth Laidir

Latest structure at 2020Z, showing the eye opening to the southwest.

Windsat 37 GHz H

20171014.1940.coriolis.x.37h.17LOPHELIA.100kts-960mb-353N-251W.75pc.jpg

TheMilkyPirate

Oneiric 3 wrote: »

Hirlam continues to track the low right over the country. 18z update:

That's impressive 50-60knot (100km) mean winds at rosslare at 4pm so looking at about 4 hours of winds that speed judging by the location of the storm?

To put that in perspective the max gust here in the 1998 storm was 105km/h and I remember being on the town that day and there were slates flying everywhere and chimneys falling down. Gusts from Opehilia look like they could be much higher

dball

getting very windy down on the Dingle peninsula.

monkeynuz

Romantic Rose wrote: »

It's quite windy here already (South Donegal).

Been very windy here in southest westest kerry since early ish evening

Romantic Rose

It's quite windy here already (South Donegal).

Gaoth Laidir

Latest winds (21Z) max 87 knots east of centre.

nagdefy

This reminds me of watching Cyclone Treacy as a 12 year old in 1988. Updates on the cyclone from it's development around 20th December 1974 until it hit Darwin, Australia in the early hours of Christmas Day. The full film was on youtube but gone now. It was well done. Totally off topic but made around 1986 with Kate Ritchie (Sally in Home and Away) in it.

Dow99

crashadder wrote: »

having lived most of my life in the rather warm part of the world i dont know what to expect or do in terms of preparation. How bad is this going to hit Dublin ?

It's not going to be a cold event. Think of Florida which is also a warm part of the world and would have this kind of weather regularly. This is also an event that does not regularly hit Dublin so use caution & commonsense ( torch, charge phone, extra food, do not travel during the storm)

Oneiric 3

Hirlam continues to track the low right over the country. 18z update:

wind10mkt_046.jpg?2017101418

Donegal Storm

Jobs OXO wrote: »

Are we talking oiche na ghaoithe proportions now ?

The current forecast winds are nothing we haven't seen before, we had hurricane force storms in Donegal in 2012 and 1998 and survived to tell the tale, most guidance is suggesting storm force 10 or 11 on Monday.

Falling trees will be the main danger along with the fact that the winds are across a large and more densely populated area

sdanseo

Really not sure about ventusky forecast. Hovering over the storm in real time shows 60mph wind when we know it to be almost double that.

Gaoth Laidir

Eye probability forecast, showing the eye gone by tomorrow night.

BorneTobyWilde

“Ophelia was a cyclone, tempest
a god damned hurricane
your common sense
your best defense
lay wasted and in vain”
―Natalie Merchant 1998

spookwoman

From NOAA http://www.nhc.noaa.gov/text/refresh.../142036.shtml?

SUMMARY OF 500 PM AST...2100 UTC...INFORMATION

LOCATION...35.9N 23.7W
ABOUT 235 MI...375 KM SE OF THE AZORES
MAXIMUM SUSTAINED WINDS...115 MPH...185 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 28 MPH...44 KM/H
MINIMUM CENTRAL PRESSURE...960 MB...28.35 INCHES

Hurricane-force winds extend outward up to 45 miles (75 km) from the
center and tropical-storm-force winds extend outward up to 125 miles
(205 km). The wind field of Ophelia is forecast to expand
substantially and wind and rain effects in Ireland and the UK are
expected to reach the coast well before the arrival of the center.

The estimated minimum central pressure is 960 mb (28.35 inches).

Mech1

Eh lads,,, your rollercoaster type thingy is eh.. busted? I got on yesterday, im still goin up?

emeldc

MJohnston wrote: »

You are (sorry!) - pay attention to the force of the winds that is listed in the title of the charts, one is showing the probabilities for 34+ knots winds, and the other for 50+ knot winds. You can check out all 3 wind speed probabilities charts (the third is for 64+ knot winds) here:

http://www.nhc.noaa.gov/refresh/graphics_at2+shtml/205031.shtml?tswind120#contents

Ah right, get ya now. Complete noob at this sh1t. Thanks

Donegal Storm

Gaoth Laidir wrote: »

But the anemometer there is I think over 100 metres above the sea so really not of any use.

Will still be interesting what sort of readings we get from it, plenty of areas in Cork and Kerry above 100m so while not an official reading it'll still give an idea of what people might experience.

A shame we don't have a station somewhere in the Kerry mountains like they have in the Cairngorms in Scotland, would be quite an experience on top of Carrauntoohil on Monday!

Jobs OXO

spookwoman wrote: »

Looking at the forecast on https://www.ventusky.com/?p=51.0;-5.9;5&l=wind using the ICON and GFS models they both seem to show the south east and east getting hit

Are we talking oiche na ghaoithe proportions now ?

Gaoth Laidir

sdanseo wrote: »

Latest NHC update. Of specific note comparison between predictions 6 hrs ago and now:

1500UTC

2100UTC

Essentially, they expect it to become extratropical around the same time, and still hit 53N at around 65kt - Category 1 force - but keep going for longer afterwards before dissipating.

Note the size of the cone is much narrower, so much less uncertain. This doesn't seem to be any further west, even though it might look that way, because the cone only shows the position of the centre and not the size of the storm, as they explain.

Also those charts are Mercator projection, so areas further north appear stretched out and larger than they are on the globe. So that cone of error Ireland is not quite as wide.

FutureGuy

Thanks a million to everyone who is contributing their time and effort into breaking it down for the many of us who may not frequent the board. I really want it to be Tuesday.

crashadder

having lived most of my life in the rather warm part of the world i dont know what to expect or do in terms of preparation. How bad is this going to hit Dublin ?

Gallee

Compared with Feb 12th 2014 we had gusts around Limerick around 120kmh initially from South to South West and verring West....am I right in saying that this one on Monday has wind South to South West and not veering West or does it really make any difference. Just looking at what's around our house (tree wise).

spookwoman

More info 5pm

http://www.nhc.noaa.gov/text/refresh/MIATCDAT2+shtml/141438.shtml

sdanseo

NASlad wrote: »

Odds on this being a complete flop and not half as bad as we're expecting?
Can't say I'm too worried yet. Will make up my mind Sunday night.

We're great in Ireland for "ah, it'll be grand" so I don't blame you for seeing it like that.

But when you're looking at a chart produced by the US National Hurricane Center, probably the Gold Standard for this type of thing (although there's a huge side-conversation there about after it goes extra-tropical, UKMO having a lot more experience than NHC as usually they are concentrating on tropical), which gives a 90-100% probability of tropical-storm force sustained winds covering half the island in less than 48hrs....no, I don't think it'll be a "flop". Could well be less severe than we think. Could well be more severe. But it won't be a non-event.

Spanish Eyes

MT's update tomorrow will either terrify us, or keep us calm.

nagdefy

CloughCasey1 wrote: »

Agree with that. She usually knows her stuff. She usually comes across no more than the usual suspects on here as a total weather nerd. She looked like she was bursting to tell everyone what may/might/probably will happen and would only love to be showing the general public of the ifs and buts of what is LIKELY to happen. She looked nervous.....and rightly so....as she knows the severity of the upcoming situation and she also knows that she has to act 100% professional on the national airways.

Agree. It's very easy be critical. She has to adjust from conversation with meteorologist colleagues to addressing a nation just versed in the basics. What to say, what to withhold and then when you're live stuff can come out unintentionally as any of us who ever spoke in public know!

MJohnston

emeldc wrote: »

The charts in #1385 and #1388 seem to be the same only compleatly different as regards the position of the worst winds. Maybe I'm just reading it wrong

You are (sorry!) - pay attention to the force of the winds that is listed in the title of the charts, one is showing the probabilities for 34+ knots winds, and the other for 50+ knot winds. You can check out all 3 wind speed probabilities charts (the third is for 64+ knot winds) here:

http://www.nhc.noaa.gov/refresh/graphics_at2+shtml/205031.shtml?tswind120#contents

Rougies

Gaoth Laidir wrote: »

Looking forward to readings from Sherkin Island and Roches Point. Also, could have anomalously high Föhn readings from Valentia. Later on, Mace Head and Belmullet will be interesting.

Do you mean in terms of temperature readings?

nagdefy

MJohnston wrote: »

Not quite - you need to understand what those wind probability charts represent. Close to the current position of the hurricane, they literally represent how likely those areas are to receive particular strengths of winds.

However, the further you get along the predicted track of the storm (ie. further into the future), the probabilities change not just because areas are less likely to get hit by particular strength winds, but also because the likelihood of the forecast being correct is less certain.

Cheers MJ just after realising that now. It's probability of hitting not a forecasted track.