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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

Latest image. Eye still visible but seems to be fading away over the last while:

Gaoth Laidir

OOZ ECMWF winds for 100 metres. Subtract around 5-10% to estimate surface winds. Force 10 or 11 likely at the surface in souther coastal areas.

Slight upgrade for the 09Z chart compared to yesterday's chart, showing a Cat 2 purple area inside the Cat 1 gold area south of Ireland.

12Z, the Cat 1 gold area is just on the Cork/Waterford coast.

By 15Z there is a tiny area of Force 12 in Galway bay, but otherwise it's storm force through the rest of the country.

18Z, the southeast and east still getting storm force winds.

Meteorite58

Hi Res WRF-NMM 06Z

Mean

Gust

munsterlegend

Meteorite58 wrote: »

Hi Res WRF-NMM 06Z

Mean

Gust

That is again further east.

Full Marx

How is it looking on the east coast? Louth Meath and Dublin?

I don't understand these charts at all I'm afraid. Is purple the worst?

MJohnston

munsterlegend wrote: »

That is again further east.

It seems to have slightly adjusted back to the track we were seeing on Friday, after moving a touch west yesterday.

Gaoth Laidir

I think Joanna's comment on Cat 2 winds refers to gusts, not sustained winds.

Again, when looking at NHC figures, subtract around 11% to get Beaufort 10-minute mean speeds.

Meteorite58

That is again further east.

Yes, ECM seems to have nudged a bit E as well.

Oneiric 3

Met.no (Norway met office) has the storm remaining as a tropical feature as it reaches the SW coast tomorrow, despite having occluded before that:

MJohnston

Full Marx wrote: »

How is it looking on the east coast? Louth Meath and Dublin?

I don't understand these charts at all I'm afraid. Is purple the worst?

They’re pretty simple to read - theres a colour code chart along the bottom with numbers listed in km/h, so the purple is indeed at the higher end of the scale.

amandstu

Is it just a coincidence that the eye is forecast to go up the West coast? Does the landmass act as a kind of guide for its (the eye's) course?

Gaoth Laidir

A sneaky shot of someone at Met Éireann's screen, showing the Harmonie model mean winds. Taken from the RTE website.

Hooter23

I think some places that are not in the red alert areas may get some surprises too with squall lines threatening to give severe winds to almost anywhere...

thomasj

amandstu wrote:

Is it just a coincidence that the eye is forecast to go up the West coast? Does the landmass act as a kind of guide for its (the eye's) course?

it loses its eye when it becomes a tropical storm

Meteorite58

patneve2

The greater Dublin area looks a bit more sheltered compared to other areas in the SW, South and SE although 70 kt gusts still a real possibility. Could be quite nasty with those SSE gusts tomorrow lunchtime - afternoon. Going for a 65-70 kt gust at Dublin airport, so a peak somewhere between 120 and 130 km/h. Unfortunately 80 kt + gusts look quite possible in the most affected areas further south - this could cause some serious damage.

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.

Lumi

Mod Note

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

Thanks

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

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.

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?

[Deleted User]

1pm image.

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

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.

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.

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

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.

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:

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.

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