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

M.T. Cranium

Somebody asked if I could sum up ... I think the forum discussion to this point has been good and anyone can see the range of possible outcomes from reading it.

I feel that the situation will become much clearer around Saturday night when the hurricane moves close enough to the main jet stream to reduce model errors to almost nothing (24-36h) and then it becomes a matter of fine-tuning the dynamics which may be a little more complex than just the usual autumn low from a more traditional source (west rather than south southwest). As I mentioned in an earlier post, there will be rapid changes in structure as heights fall (meaning as the jet descends closer to the surface near the low centre). The whole thing may start to rotate and that will make the frontal zone the focus of the damaging wind gusts. Or we may get a signal for a more leisurely transition with a longer lasting warm sector, that will make the cold front slower to move inland.

I think we're as prepared as we can be for Monday and we just have to accept that this will turn into a 12-hour forecast challenge from Sunday evening to get exact details in focus. I wouldn't roll the dice and plan to travel any distance on Monday, but as with all storms this may produce a patchwork quilt of damage and not much impact, you can do your own forecast to some extent by considering how exposed you are to the south-southwest, as that's the direction most likely to occur when winds are at their peak.

George Sunsnow

I’m beginning to wish an electric shock could be wired into the post reply button anytime there’s a they’re under or over playing it post

This has the potential to be high impact nationwide and downright nasty in some parts
Certainty will be absolute enough tomorrow to make a big deal and Sunday is oceans of time for school closure texts should they be necessary in places

I know we will have extra tropical transition before the system reaches Ireland, but I'm wondering is there any chance of seeing a 'stadium effect' in the cloud structure for areas where the centre may pass over? I'm not talking about the classic structure the hurricane hunters see in the eye but any noticable bending in cloud formations due to the tight circulation that may be present there on Monday.

leahyl

Following this thread with great interest as I sweat it out in 30 degree heat in Lanzarote! Can’t believe I’m missing all this!

Dr. Kenneth Noisewater

Monkeynut wrote: »

40% of the population live in Dublin though.
where there are more people affected, it usually gets more news.
anyway, sure if its bad at your doorstep who cares of the news.

40% don't live in Dublin, they live in the Greater Dublin area which includes Meath, Kildare, Wicklow and Louth. But I agree, where there are more people affected, it'll get more coverage. I lived in Donegal during the winter of 2010 and there was a foot of snow on the ground for a week before Dublin saw any and there wasn't a word about it on RTE. It isn't that they don't care, but it garners more attention if the people that work there are affected themselves. And most of them live in the Greater Dublin area.

Jpmarn

Will there be any journalist/ metrologist coming over to Ireland from The Weather Channel to cover what is now Hurricane Ophelia. As it passes into cooler waters off the Bay of Biscay she will transform into an extra tropical Atlantic Storm. By Monday she will be no longer officially recognized by the NHC in Miami. It will be then exhurricane Ophelia.
With of all future weather we don't know what will be happening this Monday. All we can do is to batten the hatches, take care and hope for the best. Maybe do something of a religious nature like visit a church on your own or for a service on Sunday.

Screenshot of the 5pm (EDT, 10pm Ir time) NHC chart for historical reference purposes.

Kermit.de.frog

18:00 NAVGEM model

M.T. Cranium

Ophelia looks strong on the satellite imagery, I wonder if we will get a cat-3 upgrade on the next advisory? Won't make much difference to the 48-60h forecasts.

Kermit.de.frog

Newest advisory - strength (surprisingly) stays Category 2. Likely to remain a hurricane for at least 48 hours after which becomes extra tropical. That takes the hurricane force winds pretty much right up to Irish coast.






Prognosis have shifted back east for the center leaving more, if not all, of the country in the potential firing line again.

http://www.nhc.noaa.gov/text/refresh/MIATCDAT2+shtml/140233.shtml?

Kermit.de.frog

DWD 00Z

Some serious stuff starting to show



GFS 00Z





Whole country is in play now. For the South and Southwest coast this is looking really bad.

DOCARCH

Mod Note: Posts deleted, stay on topic.

M.T. Cranium

GEM same story, intense.

GFS indicates 80-100 mph gust potential in west Munster.

The steady approach of the late Tuesday early Wednesday frontal wave cuts off any miss to the west scenario (I think), so now the only way out is for the system to weaken faster than depicted.

Note, it does weaken rather steadily on the inland track models but this only spares parts of the north, the trend is much slower on Arpege which holds the centre at the coast all the way to Belmullet.

Unless the ECM is a lot different from this guidance, we can probably go to level 3.

Pa ElGrande

For historical reference - Hurricane Debbie (1961)

Hurricane Debbie is the most powerful cyclone on record to strike Ireland in September, and possibly the only tropical cyclone on record to ever strike Britain and Ireland while still tropical.

source

Hurricane Faith (1966)

The storm maintained nearly the same intensity as a Category 2 hurricane for several days, while tracking northeastward into the far North Atlantic Ocean. Faith finally weakened while north of Scotland and became extratropical near the Faroe Islands on September 6

source

Great Storm of 1987

The Great Storm of 1987 was a violent extratropical cyclone that occurred on the night of 15–16 October, with hurricane-force winds causing casualties in England, France and the Channel Islands as a severe depression in the Bay of Biscay moved northeast.

source

KingdomRushed

Maybe it's just me, but I think this storm's potential has seriously downgraded. Now we see it aimed right at Ireland, more of the country is in play but it's potential energy would appear lessened with it weakening rapidly. The charts from approximately 2 days ago with the storm centre cruising just along the west coast were showing much more destructive potential. It is even apparent on the NHC plots now that while the country is nailed on for a direct hit the probability of experiencing tropical storm force winds is reducing all of the time as it approaches

secman

KingdomRushed wrote: »

Maybe it's just me, but I think this storm's potential has seriously downgraded. Now we see it aimed right at Ireland, more of the country is in play but it's potential energy would appear lessened with it weakening rapidly. The charts from approximately 2 days ago with the storm centre cruising just along the west coast were showing much more destructive potential. It is even apparent on the NHC plots now that while the country is nailed on for a direct hit the probability of experiencing tropical storm force winds is reducing all of the time as it approaches

That's good , less destruction potential.

Hastentoadd

Max winds forecasted at 85mph for ireland should ophelia hit us directly on monday. Storm expected to totally dissipate by wednesday.

M.T. Cranium

Some guidance is stronger and some a little weaker, all outcomes still in play.

We should stick with level 2 for the time being, noting that some models have level 3 conditions in parts of Munster and Connacht (Kerry, west Cork, Clare, Galway most at risk).

Meteorite58

Good morning all, still on track and still looking very strong.

Meteorite58

Meteorite58

Note 850 hPa Chart.

All models look very consistent with this.

Liffey4A

Thanks for updates. What are the main times that the models release new charts during the day?
I've a feeling that a lot of people will be busy tidying away any garden furniture still outside this weekend!

Gaoth Laidir

I think people are still expecting something more than we look like getting. Even on the latest official forecasts it's not quite as bad as it appear, but that's still bloody bad.

The latest NHC track shows it as already extratropical by 45N (white H). That's over 350 nautical miles south of Ireland, so the chances of us getting a tropical system seem gone at this stage. Still "hurricane-force sustained winds"* at that point, so what happens to the windstrength between there and landfall is what is of interest.



*All NHC forecasts are quoting max sustained 1-minute winds. This is very different to the WMO standard 10-minute mean (the Beaufort Scale) which is what we are used to and is what the global model output quotes. In an off-sea situation, the 10-minute mean is roughly 90% of the 1-minute mean. So when the NHC quote "65 kt" in reality on the Beaufort Scale it would be around 58 knots (Force 11). That's why come Tuesday I'm pretty certain nowhere in Ireland will have recorded Force 12 sustained winds, unless there's a major upgrade.

Read more on the 1 Vs 10-minute debate here

https://www.wmo.int/pages/prog/www/tcp/Meetings/HC31/documents/Doc.3.part2.pdf

Meteorite58

Mean speeds in Kts







Note this is 850 hPa chart.

fraxinus1

Thankfully the talk this morning is of a serious downgrade. Still stormy but nothing that we don't see every year in Ireland. So am I correct in saying that there will be storm 10 on western and south western coasts and gale 8 to strong gale 9 every where else? I and many others are relieved. No one wants damage.

Meteorite58

Some other commentators.

https://twitter.com/RyanMaue/status/919082011305959424

https://twitter.com/pppapin/status/919073052784291840

https://twitter.com/JimCantore/status/919097696690102272


https://twitter.com/meteociel/status/919095075082207232


https://twitter.com/metofficestorms/status/919092095100641280

Sesame

Never ventured into the Weather forum before but fascinating to see the charts.

I'm on the south coast and there's a lot of very noisy bird activity this morning. Are they influenced by the falling pressure or been blown in from the Atlantic?

leahyl

fraxinus1 wrote: »

Thankfully the talk this morning is of a serious downgrade. Still stormy but nothing that we don't see every year in Ireland. So am I correct in saying that there will be storm 10 on western and south western coasts and gale 8 to strong gale 9 every where else? I and many others are relieved. No one wants damage.

A serious downgrade? Really? Who’s saying this?

Clonmel1000

leahyl wrote: »

Following this thread with great interest as I sweat it out in 30 degree heat in Lanzarote! Can’t believe I’m missing all this!

Lucky you but rest assured you’re missing nothing yet only the usual muck we get and Monday may be a very ordinary windy wet autumn day in Ireland.

Meteorite58

The HIRLAM short range model just coming into view

Mean




Gusts