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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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Oneiric 3

WV animation over the last 12 hrs or so. Gradually losing its 'eye'.

New Home

Reggie. wrote: »

What is that string of calm wind?

I don't know, but I assume it's the place where the two weather fronts collide. Anyone with even a scrap more meteorological knowledge than I have will be able to tell you.

Drumpot

M.T. Cranium wrote: »

Having reviewed a visible satellite loop I would say the storm is still tropical and the eye has reduced in diameter to about 5 miles (current position 40N 16W). It appears to be making the turn north in the last three hours.

The waters ahead are not all that cold either, near 20 C in Biscay. And the strong southerly flow will bring a slight warming further north.

This storm may continue to be a hybrid like Sandy up until landfall.

Storm surge issues should be taken very seriously on this track (from SSW). You know the terrain better than me, but any coastal villages with exposure to the south or southwest may have inundations up to 3 metres above normal high tide and powerful waves could be bringing in debris from beaches.

Does the storm surge apply to middle/northern east coast ? I am in bettystown and my estate has flooded before in conditions that weren't as bad as this . High tide (due at 10pm tomorrow) followed by prolongued rain caused the problem. I am wondering if my estate needs to be on alert and if we should contact the council!

TheMilkyPirate

munsterlegend wrote: »

I think you had a site for predicting wind strength in a location? Could you post it again thanks?

Sure,

https://weather.us/forecast/2960964-wexford/ensemble/euro/wind-gusts

munsterlegend

TheMilkyPirate wrote: »

160-180km/h gusts in Wexford and Waterford if that icon materialised. I really don't think people understand the severity of this.

I think you had a site for predicting wind strength in a location? Could you post it again thanks?

sword1

M.T. Cranium wrote: »

Having reviewed a visible satellite loop I would say the storm is still tropical and the eye has reduced in diameter to about 5 miles (current position 40N 16W). It appears to be making the turn north in the last three hours.

The waters ahead are not all that cold either, near 20 C in Biscay. And the strong southerly flow will bring a slight warming further north.

This storm may continue to be a hybrid like Sandy up until landfall.

Storm surge issues should be taken very seriously on this track (from SSW). You know the terrain better than me, but any coastal villages with exposure to the south or southwest may have inundations up to 3 metres above normal high tide and powerful waves could be bringing in debris from beaches.

When does the surge come, before, during or after the wind. Tides are about a meter below strong tide s. High water around 4 for a lot of cork. Hopefully the surge will hit at low tide

Gaoth Laidir

12Z early intensity forecast, showing it just dipping below Cat 1 by 12Z tomorrow (24 hr). Official NHC forecast is in red. Still Beaufort 10-11 along the south coast with this.

TheMilkyPirate

160-180km/h gusts in Wexford and Waterford if that icon materialised. I really don't think people understand the severity of this.

M.T. Cranium

Having reviewed a visible satellite loop I would say the storm is still tropical and the eye has reduced in diameter to about 5 miles (current position 40N 16W). It appears to be making the turn north in the last three hours.

The waters ahead are not all that cold either, near 20 C in Biscay. And the strong southerly flow will bring a slight warming further north.

This storm may continue to be a hybrid like Sandy up until landfall.

Storm surge issues should be taken very seriously on this track (from SSW). You know the terrain better than me, but any coastal villages with exposure to the south or southwest may have inundations up to 3 metres above normal high tide and powerful waves could be bringing in debris from beaches.

cherryghost

ICON Current run vs Previous Run:

Previous:

Current:

Clear eastwards shift noticable, Wicklow looks pretty terrible especially if you live in the mountains. Dublin looks like a noticable upgrade too. Cork still looks pretty bad but Waterford now looks like its in the firing line.

Wales coast looks dodgy too.

M.T. Cranium

I always think Iberia looks like a human face looking west, and today there's quite a sight.

About the eye disappearing -- more accurate to say that the eyewall structure will dissipate in the transition, an eye will probably remain and continue to contain a zone about 20-30 miles wide where wind speeds fall off to almost zero. Some parts of Connacht (and possibly Kerry/Clare) will experience this tomorrow, it may not move right over a reporting station but we will likely get observations that confirm this.

Some remnants of the eyewall could be visible for part of the early transition. I have watched several dozen of these storms do a transition over New England or eastern Canada and it takes hours for the eyewall structure to be fully obliterated. Juan 2003 still had the northern half of its eyewall when it made landfall at Halifax despite moving over 15-18 C waters for six hours. We'll see tomorrow if there's much left of that core near Valentia.

Another thing that seems to happen a lot with landfalling tropical storms or hurricanes is that convective activity will flare near the eventual landfall spot well in advance giving a bit of a "tell" as to where that will be. I think it has to do with electromagnetic currents that are interacting the same way the atmospheric circulations of jet stream and hurricane are interacting. (this is not proven science by the way and in fact I never posted a mention of it anywhere on the internet before today -- MTC's secret recipe).

MJohnston

Gaoth Laidir wrote: »

Looks like the NHC have downgraded it to 80 knots now as the 12Z SHIPS forecast below has it initiated at that intensity. It forecasts it to be fully extratropical by 18Z this evening and at around 54 knots intensity by 12Z tomorrow as the centre moves inland over SW Kerry at around 27 knots. In the case of land interaction the LGEM forecast is likely to be more accurate.

Gaoth I know this is obvious to the more technical folks here and the more constant lurkers like myself, but might be worth mentioning when something is and isn't "expected" - I suspect a lot of newbs will read your mention of downgrading and think that applies to the forecast, and not the current conditions.

Liffey4A

What's the expected behaviour of the system now it's losing its structure?
Its going to interact with colder sea temps now and other systems, will this weaken it or strengthen it as it moves north?

Gaoth Laidir

Looks like the NHC have downgraded it to 80 knots now as the 12Z SHIPS forecast below has it initiated at that intensity. It forecasts it to be fully extratropical by 18Z this evening and at around 54 knots intensity by 12Z tomorrow as the centre moves inland over SW Kerry at around 27 knots. In the case of land interaction the LGEM forecast is likely to be more accurate.

spookwoman

SAT24 @ 13:55

Gaoth Laidir

Latest wind analysis at 12Z, showing max 1-minute winds now dropped to 74 knots. The radius of 64+ winds has further expanded to 65 nautical miles east of centre.

Latest water vapour shows it losing all structure now.

20171015.1245.goes13.x.wv1km.17LOPHELIA.80kts-973mb-401N-169W.80pc.jpg

signostic

Airport TAFS
Shannon
TAF: EINN 151100Z 1512/1612 32010KT 9999 BKN012 PROB40 TEMPO 1512/1520 BKN020 TEMPO 1520/1606 3000 -RADZ BR BKN003 BECMG 1601/1604 03015G25KT BECMG 1605/1607 06025G35KT BKN020 BECMG 1609/1612 12035G55KT

Cork
TAF: EICK 151100Z 1512/1612 21012KT 2000 -RADZ BKN002 TEMPO 1512/1603 0200 FG -DZ BKN001 PROB30 TEMPO 1512/1521 4000 SCT002 BKN004 BECMG 1518/1520 01005KT BECMG 1603/1606 07020G30KT 9999 NSW SCT025 BECMG 1607/1609 17030G45KT BECMG 1609/1611 17040G60KT

Ireland West Knock
TAF: EIKN 151100Z 1512/1612 33010KT 9999 BKN016 PROB30 TEMPO 1512/1514 BKN006 BECMG 1517/1520 01007KT BECMG 1521/1524 -RADZ BKN010 TEMPO 1600/1609 4000 RA BKN004 BECMG 1603/1606 05015G25KT BECMG 1608/1610 08025G35KT BECMG 1610/1612 12030G40KT 9999 NSW SCT025

Dublin
TAF: EIDW 151100Z 1512/1612 21013KT 9999 FEW015 BKN018 BECMG 1516/1518 35005KT PROB40 TEMPO 1514/1518 -RADZ BKN014 BECMG 1518/1521 04010KT BKN012 TEMPO 1600/1608 4000 -RADZ BR BKN006 PROB40 TEMPO 1600/1607 2000 BKN003 BECMG 1604/1607 07013KT BECMG 1608/1610 12015G26KT SCT018 BECMG 1610/1612 16025G35KT

Aldergrove
TAF: EGAA 151101Z 1512/1612 22015G25KT 9999 BKN012 BECMG 1512/1514 27012KT SCT025 PROB30 TEMPO 1512/1513 6000 -RADZ BKN008 BECMG 1515/1518 36005KT TEMPO 1522/1606 6000 RA -RADZ BECMG 1600/1603 07010KT SCT008 BKN014 BECMG 1603/1606 BKN005 BECMG 1606/1609 11020G30KT SCT025 BECMG 1609/1612 15025G40KT

star gazer

Paully D wrote: »

Forgive my ignorance, but that image appears to show Ophelia heading more to the west, and not as much to the south-east as I have seen in other models, no?

Short answer, yes and as it turned out forecasts are for the impact to be a little further East with only small changes having serious potential impact changes locally. The other chart i posted was the track chart, that chart itself shows the probabilities of wind speed which isn't necessarily going to show you the exact track of Ophelia as the winds are biased to the East side.

This post by sdanseo gives the then position changes in that forecast.
Current NHC track graphic
Eye losing distinction

NHC

WIND: Gale-force winds are expected to begin across southern
Ireland by early Monday morning and gradually spread northward
across the country during the day. Hurricane-force winds are
expected to reach the southern portions of Ireland by Monday
afternoon and spread inland across the country into Monday night.
Preparations to protect lives and property should be rushed to
completion by this afternoon.

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 makes landfall. Near the coast, the surge will be
accompanied by large and destructive waves.

Comhrá

Samaris wrote: »

Gaoth Laidir - still getting my head around sting jets. Is that section just to the west of the eye protruding down from north roughly over Galway something along those lines or is it normal swirling winds around the lowest pressure area?

Watch the second part of this video. It gives a good explanation of sting jets:

shmaupel

MJohnston wrote: »

No - the colouring of those charts is really bad, those purple patches are actually at the very low end of the scale, so very low winds.

Ah thanks. The colours are tricky.

MJohnston

shmaupel wrote: »

Are the purplish patches that develop around Sligo/South Donegal in the evening time sting jet related?

Also, a general thank to all who are interpreting these charts for the rest of us. This board is a real gem, we're lucky to have it.

No - the colouring of those charts is really bad, those purple patches are actually at the very low end of the scale, so very low winds.

shmaupel

Gaoth Laidir wrote: »

06Z Hirlam, showing Force 11 sustained winds getting into southern Cork/Waterford from around 11 am tomorrow. Peaking at around 60 knots by lunchtime.

Are the purplish patches that develop around Sligo/South Donegal in the evening time sting jet related?

Also, a general thank to all who are interpreting these charts for the rest of us. This board is a real gem, we're lucky to have it.

Gaoth Laidir

Side-by-side comparison of Arpege and Hirlam mean winds tomorrow at 13Z. The bottom right of each image shows the max winds on that chart, so the Arpege shows 66 knots out to sea south of Cork while the Hirlam has 61 knots. A few knots less along the coast in each case.

George Sunsnow

Samaris wrote: »

Gaoth Laidir - still getting my head around sting jets. Is that section just to the west of the eye protruding down from north roughly over Galway something along those lines or is it normal swirling winds around the lowest pressure area?

Sting jets wouldn’t be modeled,they are more or less a now cast situation like Squal lines

[Deleted User]

1pm image.

Samaris

Gaoth Laidir - still getting my head around sting jets. Is that section just to the west of the eye protruding down from north roughly over Galway something along those lines or is it normal swirling winds around the lowest pressure area?

Gaoth Laidir

06Z Hirlam, showing Force 11 sustained winds getting into southern Cork/Waterford from around 11 am tomorrow. Peaking at around 60 knots by lunchtime.

Donegal Storm

Even if this does take a slight easterly shift there could still be exceptionally strong winds from Kerry up to Galway, ARPEGE model is potentially showing a sting jet close to the centre giving gusts upward of 150kph right across Tralee, Limerick, Ennis and Galway. A sting jet in the Jan'12 storm in Donegal gave gusts of 170kph so potentially even more dangerous than the main band of winds further east

Lumi

Mod Note

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

Thanks

Gaoth Laidir

Core of maximum winds on landfall looks like between Roches Point and Wexford. Key observation stations to watch are Roches Point, Waterford Airport (EIWF) and Johnstown Castle.