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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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RobertKK

channaigh wrote: »

How will Kilkenny fair in this Robert ?

I wouldn't be surprised if like with Storm Darwin, we ended up with a red warning.
We only got the red warning upgrade during that storm when we were in the middle of the worst conditions and trees were falling down everywhere, power cuts happening and conditions that were just too dangerous to be out in.

Be prepared for the worst, and hope for the best.

Meteorite58

luimneachboy wrote: »

For those that have a good knowledge, at the moment what's this looking like for West limerick /north kerry

Discodog

RobertKK wrote: »

I wouldn't be surprised if like with Storm Darwin, we ended up with a red warning.
We only got the red warning upgrade during that storm when we were in the middle of the worst conditions and trees were falling down everywhere, power cuts happening and conditions that were just too dangerous to be out in.

Be prepared for the worst, and hope for the best.

I think that power cuts could be the biggest problem.

uck51js9zml2yt

mel.b wrote: »

Just wondering what has caused this hurricane to travel east towards us, rather than west as they typically do? Is it due to where it first formed?

Interesting question.. hope someone can answer it!

Cloudio9

Weathercheck wrote: »

At present the Greater Dublin area looks least exposed so may lessen slightly the coverage of the storm.

The chart in post 894 shows a scenario where the east gets hit as hard as the west and this is going to peak around the evening rush hour.

Stephen Hawkins football boots

The weather is so warm at the moment, excuse the cliche but is this calm before storm?Is the hurricane the reason it's so warm?

Gaoth Laidir

12Z wind analysis showing 75 knots as the max winds, but the radius of 64-knot+ winds has increased out to 70 miles from the centre.

M.T. Cranium

Well that was a fast jump by ME to level 3 and a fast jump by me out of bed.

Anyway, I think we knew this was almost inevitable if models kept tracking the storm towards west Munster and the 06z GFS probably tipped the balance of near-inevitability that the storm would be high impact.

As to the impact on Azores, here's the current situation -- the cold front has moved through the western half of the Azores with 15-25 knot northwest winds reported at Flores and falling temps (to 15 C). The southeastern islands have seen winds backing from south to southeast, still moderate at Santa Maria (southeast 18 knots) with a warm and humid 25/21 temp/dew point, and Ophelia will be within 50 miles of there by about 21z so those islands including Punta Delgada may reach 120-140 km/hr northeast winds as the centre goes past to their south.

I agree it looks close to cat-3 now.

Debbie which was never moving as slow as Ophelia did for much of this past week moved through the central Azores and was at 22W when it reached 42 N, Ophelia is predicted to be near 17W by 42N so its angle of approach is more SSW than Debbie's SW, however the results may be similar although details will be different.

Some talk about Donegal -- it all depends on whether the track cuts inland far enough to take the centre east of Donegal (which would likely mean Mayo and some parts of west Galway as well) -- in that scenario, winds over those counties would be more moderate, southeast backing to northeast 60-100 km/hr then shifting rapidly around to northwest 80-130 km/hr as the centre passed. But if the centre moves up the west coast and west of Donegal, then all those areas are exposed to stronger southerly winds, albeit not as strong as Kerry, Clare and other parts of west Munster might see -- would estimate 100-140 km/hr for Donegal in that scenario, and possibly 120-160 for Mayo, 130-170 might be the peak further south.

Storm surge potential should not be underestimated. The peak winds appear to be timed close to high tides on the south coast and this is a long duration, long fetch storm that will be rolling in with 10-15 metre battering waves and a storm surge that could be as high as 2 to 2.5 metres in some places between Sherkin and Waterford, 1.5 to 2 from Waterford to Rosslare and 1.0 to 1.5 up the east coast. Storm surges on the west coast would be somewhat less than other events with most track scenarios but would increase if the track is further west than consensus.

One other note of interest, the centre of the storm will pass very close to an ocean buoy located around 49N 13W about 06z Monday so we'll get very good data from that if it survives the encounter.

4068ac1elhodqr

Cloudio9 wrote: »

The chart in post 894 shows a scenario where the east gets hit as hard as the west and this is going to peak around the evening rush hour.

Agree, (according to two charts) 4-5pm Monday could be the worst for the SE, which means going into rush-hour on the (exposed) M1, some lorries will take a tumble, again.

Peak traffic & peak population significantly increases incident exposure risks.
Screen_Shot_2017-10-14_at_15.10.08.png

Of course still early, and many think this is a storm of one part, and not two?

Nettle Soup

Kai Rotten Shipwreck wrote: »

Interesting question.. hope someone can answer it!

https://www.popsci.com/hurricane-ophelia-british-isles#page-3

Hurricane Ophelia is an odd storm. It’s a picture-perfect hurricane with winds around 90 MPH, but that’s not the odd part, of course. What makes this storm weird is its location. It’s way out in the Atlantic, where it’s usually too cool for hurricanes to develop—much less survive. Ophelia is so far off the beaten path that instead of heading for the Americas (as so many storms have this season), the system will evolve and threaten Ireland and the United Kingdom early next week.

Met Éireann—Ireland's meteorological service—is advising residents to keep a close eye on the storm as it approaches the Isles, emphasizing the uncertainty in the forecast. A statement by the agency on Thursday noted that "it won’t be possible to quantify the exact timing, nor the strength or intensity of the wind and rain, in any great detail until later in the weekend." Weather alerts issued by the U.K.'s Met Office read much the same, noting the potential for damaging winds, heavy rain, and scattered power outages in Northern Ireland and along the western coast of Great Britain.

mel.b

Nettle Soup wrote: »

https://www.popsci.com/hurricane-ophelia-british-isles#page-3

That talks about how/why Ophelia has survived but not what caused her to come east in the first place which is what I'm curious about.

511

Stephen Hawkins football boots wrote: »

The weather is so warm at the moment, excuse the cliche but is this calm before storm?Is the hurricane the reason it's so warm?

The warm southerly airflow is guiding this tropical storm into Ireland's path: https://earth.nullschool.net/#current/wind/surface/level/orthographic=-15.77,42.59,981

Gaoth Laidir

Early 12Z intensity forecast initialises it at 100 knots.

MJohnston

mel.b wrote: »

That talks about how/why Ophelia has survived but not what caused her to come east in the first place which is what I'm curious about.

The thing to know about hurricane movement is that they generally would be absolutely stationary under their own power, ie. they have no natural "inclination" to moving anywhere.

Their structure makes them very easily moved by external systems however - so they tend to get pushed around a lot. So to understand why Ophelia came east, you need to look not at the hurricane itself, but the jet stream and nearby pressure systems that pushed it along that particular course.

Kermit.de.frog

If this is not a CATEGORY 3 at the next advisory i'll eat my hat.

leahyl

Kermit.de.frog wrote: »

If this is not a CATEGORY 3 at the next advisory i'll eat my hat.

Red warning on ME site now, someone has prob already said this...so ignore me if that’s the case haha

Working class heroes

What time for the next advisory?

Kermit.de.frog

Working class heroes wrote: »

What time for the next advisory?

Just before 4 pm

JCX BXC

leahyl wrote: »

Red warning on ME site now, someone has prob already said this...so ignore me if that’s the case haha

Kermit is referencing the hurricane strength, which ranges from CAT I- CAT 5, not the Met Eireann red warning!

4068ac1elhodqr

leahyl wrote: »

Red warning on ME site now, someone has prob already said this...so ignore me if that’s the case haha

Since around 12noon, but the MetOffice in the UK only have Yellow (low) warning for wind.
Would not like to be landing a plane around 4-5pm at DUB.

enricoh

Will there be good surfing to be had Monday?! Dont want to take a day off monday n trek west for nothing!

Gaoth Laidir

Meteorite58 wrote: »

Wow !

By the looks of that this short-term intensification has been due to the effect of the approaching upper trough in aiding poleward outflow, kind of venting the storm. As the trough approaches further though it will increase shear and finally start to eat away at it.

Doltanian

enricoh wrote: »

Will there be good surfing to be had Monday?! Dont want to take a day off monday n trek west for nothing!

Yes great idea, and the darwin award goes to......

M.T. Cranium

The region where Ophelia formed about a week ago is not that unusual a location for weak, meandering storms, the ones that move west tend to form further south. In the past quite a few storms from that sector have moved more to the north than either west or east.

I could say that this one has decided to track east then northeast because it happened to start up just before a deep layer trough emerged from eastern North America into the central Atlantic, once the hurricane began to feel the outer edges of the jet stream at the base of that trough, it began to drift along and eventually it will be fully absorbed (not quite happened yet but by tomorrow west of France).

But that would not really answer the question, it just shifts the question to a different subject, why was there a deep layer trough at this particular time and was the hurricane's formation entirely independent of that. And nobody really has answers to those questions which is why our science is more empirical than exact like say astronomy where they deal in certain forecasts over long periods of time. If we knew why these things happen, we would have much more precise forecasts further in advance.

However, that's meteorology -- climatology deals with the statistical overview and that's fairly well understood, as in climatic zones, frequencies of events etc. So you could maybe look at Ophelia that way, perhaps a 1 in 3 chance of a tropical storm forming in that general area in early to mid October and a 1 in 10 chance of a deep layered trough being in the western Atlantic about the same time, so a 1 in 30 chance of the combination which leads to this unusual track (and then you would find variations in outcome from one case to the next so they would not all head for Ireland, some might head for France or Spain, or move a bit further west). That seems to match the historical record of these infrequent events.

Kermit.de.frog

Confirmed

https://twitter.com/NHC_Atlantic/status/919210698898640897

Gaoth Laidir

Sexy Ophelia

20171014.1415.goes13.x.wv1km.17LOPHELIA.100kts-960mb-342N-277W.91pc.jpg

LaVail

Do we have any sort of idea as to roughly when this storm would hit? Monday morning AM or more towards Monday night?

star gazer

Major Hurricane Ophelia

Hurricane Ophelia Discussion Number 22
NWS National Hurricane Center Miami FL AL172017
1100 AM AST Sat Oct 14 2017

During the past few hours, Ophelia's satellite presentation has
improved significantly. The eye has become even more distinct
with a temperature of 16 deg C, and has been surrounded by very
deep convection. T-numbers from TAFB and SAB have reached 5.5 on the
Dvorak scale, and the objective numbers from CIMMS have been
oscillating around T5.8 and T5.9 recently. Based on these estimates,
the initial intensity has been increased conservatively to 100 kt,
making Ophelia a category 3 hurricane on the SSHS. Ophelia is a
quite intense and rare hurricane for its location in the
northeastern Atlantic. Increasing shear and cold waters will
soon begin to impact Ophelia, and the hurricane should begin to
acquire extratropical characteristics in about 36 hours or sooner.
Although some weakening is anticipated, Ophelia is expected to reach
the British Isles as a powerful extratropical cyclone with hurricane
force winds. Dissipation is forecast in about 4 days after the
system moved over these Isles.

Satellite fixes indicate that Ophelia is moving toward the northeast
or 055 degrees at 22 kt. The hurricane is well embedded within the
southwesterly flow associated with the southern extension of a large
mid-latitude trough, and this pattern should continue to steer the
cyclone northeastward and north-northeastward with increasing
forward speed for the next 2 to 3 days until dissipation. Track
models are in excellent agreement and the guidance envelope is quite
tight. The NHC forecast is not different from previous ones, and it
is very close to the HFIP corrected consensus HCCA and the
multi-model ensemble TVCX.

Given that Ophelia is forecast to become extratropical, the wind
field should expand, resulting in impacts over portions of the
British Isles regardless of its exact location or strength.

Although the center of Ophelia is not forecast to reach Ireland or
the UK for another couple of days, wind and rains will arrive
well in advance of the cyclone center. Individuals in those
locations should consult products from their local meteorological
service for more information on local impacts.

Tropical-storm-force winds are possible throughout the Azores
after Ophelia passes to the south and east later today and tonight
as a cold front moves through the islands. Interests in the Azores
should refer to products issued by the Azores Weather Forecast and
Watch Center.

KEY MESSAGES:

1. Ophelia is expected to be a powerful extratropical cyclone with
hurricane force winds Monday while it moves near Ireland and the
United Kingdom. Direct impacts from wind and heavy rain in portions
of these areas are likely, along with dangerous marine conditions.
For more details on the magnitude, timing, and location of impacts
from post-tropical Ophelia, residents in Ireland should refer to
products issued by Met Eireann, and residents in the United Kingdom
should refer to products issued by the Met Office.

FORECAST POSITIONS AND MAX WINDS

INIT 14/1500Z 34.8N 26.6W 100 KT 115 MPH
12H 15/0000Z 36.5N 23.0W 95 KT 110 MPH
24H 15/1200Z 40.5N 18.0W 90 KT 105 MPH
36H 16/0000Z 46.5N 14.0W 85 KT 100 MPH...POST-TROP/EXTRATROP
48H 16/1200Z 51.5N 11.0W 75 KT 85 MPH...POST-TROP/EXTRATROP
72H 17/1200Z 59.0N 6.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
96H 18/1200Z...DISSIPATED

$$
Forecaster Avila

Upgraded discussion 22

Kermit.de.frog

https://twitter.com/UKWX_/status/919213500655861760

My name is URL

LaVail wrote: »

Do we have any sort of idea as to roughly when this storm would hit? Monday morning AM or more towards Monday night?

Probably gonna hit land in the AM

http://www.nhc.noaa.gov/graphics_at2.shtml?cone#contents