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

tomcosgrave

NHC have isssued their last advisory, looks like the centre is going to the west.

Kermit.de.frog

Michelle_b wrote: »

Latest update just now from National Hurricane Centre in Miami;

Post-Tropical Cyclone Ophelia Advisory Number 28 NWS National Hurricane Center Miami FL AL172017 1100 PM AST Sun Oct 15 2017 ...OPHELIA NOW POST-TROPICAL BUT STILL EXPECTED TO BRING STRONG WINDS TO IRELAND AND THE UNITED KINGDOM ON MONDAY... ...THIS IS THE LAST ADVISORY FROM NHC... SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION

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LOCATION...49.2N 13.3W ABOUT 220 MI...355 KM SW OF MIZEN HEAD IRELAND MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H PRESENT MOVEMENT...N OR 10 DEGREES AT 44 MPH...70 KM/H MINIMUM CENTRAL PRESSURE...969 MB...28.62 INCHES WATCHES AND WARNINGS

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There are no coastal tropical cyclone watches or warnings in effect. Interests in Ireland should monitor products issued by Met Eireann, and interests in the United Kingdom should monitor products issued by the UK Met Office. DISCUSSION AND 48-HOUR OUTLOOK

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At 1100 PM AST (0300 UTC), the center of Post-Tropical Cyclone Ophelia was located near latitude 49.2 North, longitude 13.3 West. The post-tropical cyclone is moving toward the north near 44 mph (70 km/h). A turn toward the north-northeast with a decrease in forward speed is expected on Monday, with that heading continuing through Tuesday. On the forecast track, the center of the post-tropical cyclone will move near western Ireland on Monday and then near northern Scotland Monday night. Maximum sustained winds are near 85 mph (140 km/h) with higher gusts. Weakening is forecast during the next couple of days, and the post-tropical cyclone is expected to dissipate near western Norway by Tuesday night. Hurricane-force winds extend outward up to 70 miles (110 km) from the center, and tropical-storm-force winds extend outward up to 275 miles (445 km). The estimated minimum central pressure is 969 mb (28.62 inches). HAZARDS AFFECTING LAND

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WIND: Gale-force winds are expected to begin across southern Ireland during the next few hours and gradually spread northward across the country during the day on Monday. Hurricane-force winds are forecast to reach the southern portions of Ireland by Monday afternoon. Strong winds will then spread across the remainder of Ireland and parts of the United Kingdom into Monday night. Preparations to protect lives and property should be complete. Wind speeds atop and on the windward sides of hills and mountains are often up to 30 percent stronger than the near-surface winds indicated in this advisory, and in some elevated locations could be even greater. RAINFALL: Ophelia is expected to produce rainfall amounts of 2 to 3 inches (50 mm to 75 mm) with isolated totals near 4 inches (100 mm) through Tuesday across western Ireland and Scotland. Across eastern Ireland, rainfall amounts will average around 1 inch (25 mm) or less. STORM SURGE: A dangerous storm surge is expected to produce significant coastal flooding near and to the east of where the center of the post-tropical cyclone makes landfall. Near the coast, the surge will be accompanied by large and destructive waves. NEXT ADVISORY

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This is the last public advisory issued by the National Hurricane Center on this system. Additional information on this system can be found in High Seas Forecasts issued by the UK Met Office under WMO header FQNT21 EGRR and on the web at http://www.metoffice.gov.uk/public/weather/marine-high-seas/. Local forecasts and warnings for Ireland can be found on the website of Met Eireann, the Irish Meteorological Service, at http://www.met.ie/. Local forecasts and warnings for the United Kingdom can be found on the website of the UK Met Office at http://www.metoffice.gov.uk/. $$ Forecaster Berg

We may never see the NHC have to track a hurricane here for the rest of our lives. Historic in itself.

I salute them. Great work.

tomcosgrave

This is the wind prediction from that same NHC forecast.
It's not that much different for most of the country.
As I said above, please - do not take Ophelia lightly - this is a highly dangerous and destructive weather event.

Kermit.de.frog

ICON 00z

Xenji

Sherkin Island with a max gust of 37 kts on the 04.00 report, 26 kts max in Castlebar.

Kermit.de.frog

GFS 00z



This is now looking a good bit weaker than may have been expected.

Red warnings are not justified on current evidence.

munsterlegend

Kermit.de.frog wrote: »

GFS 00z



This is now looking a good bit weaker than may have been expected.

Red warnings are not justified on current evidence.

All over the country or further east?

M.T. Cranium

NHC track may have shifted a little too far west just as 24 hours ago it shifted a little too far east.

ICON model output shows a track only marginally further west than we were discussing several hours ago, and by marginally I mean 10-15 miles.

It maintains hurricane force gusts hitting the south coast. There is also one new wrinkle in its hourly projections, namely a secondary surge of westerly storm force winds just around the time the centre makes landfall in western Galway.

Waiting for other guidance, the NHC centre fix might be a touch west of reality too, the K1 buoy has no wind readings but pressure readings suggest it is west of the centre, and also that the centre is intense (pressure falls over 3 hours were almost off the scale at 19 mbs).

I am not expecting big changes in the official forecast but any slight shift west reduces the potential maximum windspeed on the east coast. It makes almost no difference to outcomes on the south coast and it puts more of the west into a wind damage scenario.

Back in a while with some comments on GFS and GEM.

Kermit.de.frog

munsterlegend wrote: »

All over the country or further east?

Everywhere. Not to say the ECM might say differently. But ICON and GFS suggest no red warning for anywhere is justified right now (except very initially in the far southwest).

BLIZZARD7

This is currently showing up to 150km mean winds on the southern side of the storm... This was only maxing at 130km earlier on


https://earth.nullschool.net/#current/wind/surface/level/orthographic=-6.56,49.44,1907/loc=-12.858,47.394

pad199207

Looks a bit more west alright but satellite showing its being pushed eastwards into Ireland now. Wouldn’t say out of the blue just yet.

Kermit.de.frog

Arpege 00z, 11 am



2 pm

munsterlegend

Kermit.de.frog wrote: »

Arpege 00z, 11 am

That looks a rather tight gradient!

M.T. Cranium

I can see where Kermit gets a weaker GFS, although probably more for eastern half of the country, however, the track is not that different from previous runs, still makes a grazing approach to Dingle peninsula and a landfall in Galway.

GEM guidance is unchanged generally and still has a strong phase over Ireland. I went back and checked the 00z upper air maps with their own 12 hour forecasts from 12z and found them virtually identical.

Meanwhile the wave heights at K1 continue to increase by 2 metres an hour and pressure is still dropping despite the fact low has passed by.

Jury is still out on this weaker trend, but it has to be said the level 3 outside a list of counties we had speculated about was never a suggestion made by anybody here and so I don't feel that we are committed to it. The guidance at present suggests level 3 in Munster and Galway, possibly Wexford and parts of Carlow and Kilkenny.

Don't expect any huge changes in forecasts posted earlier, I still see the same processes at work. Not sure what the met.ie forecast will be like, they may downgrade some parts.

It is not going to take very long to get early indications, the maximum wind speed at the Kinsale energy platform could occur as early as 0900 or 1000h. I am expecting maximum wind speeds on the south coast to occur around 1100h to 1300h, each hour fairly similar, and for Galway it may be around 1500h.

Kermit.de.frog

ICON gusts 3 pm

monty_python

Hastentoadd wrote: »

Can anyone say this has hit Cork/ Kerry yet?

Wind is picking up in South west cork

Sephiroth_dude

Hastentoadd wrote: »

Can anyone say this has hit Cork/ Kerry yet?

It's here in ballincollg, Cork, fecking thing woke me!

pad199207

The circulation on Ophelia is huge this morning. She’s being pushed eastwards now and tbh it doesn’t look too far off the originally track.
The northward momentum seems to have slowed considerably.

Certainly Red Warning for South and West Coastal areas. For the rest of the country it’s negotiable but if it’s for public saferty well then a good call.

Meteorite58

Mod Note

This thread is for technical analysis only please - there’s a general discussion thread available for everything else

Thanks

Meteorite58

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

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Don’t say you weren’t warned!!

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Thanks

Meteorite58

ARPEGE 0Z

Gust

Meteorite58

Tralee Winds NNE 10 min avg 14 kmh / gust 40 km/h

Bar 996.0 hPa dropping rapidly

Rain 2mm

pad199207

Just my tuppance on Ophelia’s track.

hatrickpatrick

The "false alarm" brigade are forgetting a few very important things. When a hurricane transitions to an extratropical storm, its wind field increases dramatically. Just look at the NHC's diagram - the orange oval shape is the extent of sustained tropical storm force winds. The rain will extend far beyond that boundary. Furthermore, most of the action has been biased towards the eastern side of the storm for the last day or so as it has begun to transition.

The centre making landfall in Galway rather than the southwest is only going to mean marginally less action for the southwest and marginally more for Galway. The only other real impact I can see from this westward shift (assuming the NHC isn't overcompensating in their forecast as some have suggested) is that Wexford in the southeast may be spared more of the tropical storm force winds than they were initially forecast to.

For the rest of the country and for the eastern seaboard, from my reading of that latest NHC graphic, nothing has changed, and this is still every bit as much of an extreme and dangerous weather event as it has been forecast all along.

The NHC have always been at pains to remind people not to focus too much on where the exact centre of a storm is going to track, for this very reason. It's amazing how many people ignore that advice.

Meteorite58

ICON 0Z

Meteorite58

GFS 0Z

Kermit.de.frog

Meteorite58 wrote: »

ARPEGE 0Z

Gust

Meteorite58

GFS oZ

Meteorite58

WRF - NMM Rolling out


Mean




Gust

stevenup7002

Wind has picked up in Clonmel over the past 30 minutes. About the same as your average windy night at the moment, with some sudden strong gusts.

EDIT: This is getting noticeably worse by the minute. 10 minutes later and we're into "bad windy night" territory. Hard downpours that last for about 10 seconds and then suddenly stop.