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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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Xenji

It has been gusting close to 30kts since about 03.00 in Castlebar, touching 40kts at times in the last two hours, Ophelia is very consistent so far to say the least.

Roches Point with a max gust of 58kts on the 09.00 report.

garyha

Latest ECMWF at 9km

DOCARCH

mirrorwall14 wrote: »

Joanna talks about the potential for a stingjet and I know the structure of it (forms high, descends, high winds, lots of damage), however what I don't know is-how would we know it happened?

Local reports generally.

stevenup7002

Wind already seems very violent in Clonmel. It's already on par with how bad I remember it being in 2014. If this is just the start, I'm extremely concerned.

onmebike

Smart Buoys should make for interesting reading today...

https://twitter.com/IrishLights/lists/irish-lights-smart-buoys

Fastnet will show elevated wind speed - the sensor is at a height.

mirrorwall14

Could I ask a question of the technical "team" who are doing such a wonderful job?

Joanna talks about the potential for a stingjet and I know the structure of it (forms high, descends, high winds, lots of damage), however what I don't know is-how would we know it happened? Will satellite or short range models show it or is it a case of going by local reports?

pad199207

Have we some sort of an eye trying to redevelop again?

DOCARCH

Meteorite58 wrote: »

....with 10m gusts in the 160-180 km/h range.

*whistles*

Meteorite58

Storm Forecast
Valid: Mon 16 Oct 2017 06:00 to Tue 17 Oct 2017 06:00 UTC
Issued: Mon 16 Oct 2017 00:40
Forecaster: VAN DER VELDE
A level 1 was issued for W Ireland and W Scotland mainly for isolated tornadoes.

Note: Extremely severe winds are forecast for Ireland, produced by synoptic/mesoscale conditions which are outside the scope of our convective threat level system.

SYNOPSIS

A large part of Europe is under anticyclonic conditions with stable weather. On Sunday, the southwestern flow over the Atlantic has carried a hurricane intensifying to category 3 into European waters. This system is currently transitioning rapidly into a strong post-tropical cyclone as it moves to Ireland. Cold air mass has now wrapped around the core, forming a cold front and occlusion leading into an isolated warm core. This cold front should touch the south coast of Ireland by 06Z. The core of the low is forecast by GFS run of 18Z to track along the west coast of Ireland, with a dramatic pressure gradient of about 25 hPa across Ireland at 12Z. Models forecast the strongest winds along Ireland's south coast around 12Z of up to 40 m/s sustained with 10m gusts in the 160-180 km/h range. This should cause widespread damage, but since deep convection no longer plays a role in it, we do not issue level 3 for this. The other component is excessive rain, and models predict 30-50 mm rain mainly along the Irish west coast, with a possible convective contribution.

DISCUSSION

As we are concerned with convective severe weather threats, the occlusion north of the low is the most interesting. Although is predicted to contain only 100-300 J/kg MUCAPE, often from elevated parcels, very strong winds veering with height create 300-600 m2/s2 of 0-3 km SREH and over 17 m/s 0-1 km shear vectors. This supports tornadogenesis if convection really manages to form and stay alive. Differential theta-e advection in the low levels could destabilize the situation. The highest potential for development is along the west coast of Ireland. After this band, only shallow convection seems possible. Isolated thunder may occur elsewhere (SW UK, W France) from elevated convection.

My name is URL

Gaoth Laidir wrote: »

Joanna Donnelly on radio now just mentioned gusts >150 kph and a possible sting jet later

Realistically, what are the chances of a sting jet occurring?

How are those predicted?

Meteorite58

Getting lively in Tralee gusting 70 km/h SE

ps200306

Sunrise on Ophelia:

DOCARCH

Gaoth Laidir wrote: »

....and a possible sting jet later

She seemed quite enthusiastic about that!

Not sure realistic the prospect is for it in this storm?

DOCARCH

Sherkin gusting 55kn on 0800 reports.

emeldc

Power gone in parts of Cork already :eek:

Gaoth Laidir

Joanna Donnelly on radio now just mentioned gusts >150 kph and a possible sting jet later

REBELSAFC

How accurate/reliable is ventusky? This chart looks very worrying with gusts over 170kmph for this afternoon.

Akrasia

The winds are strongest to the east and south of the eye, and the rain is worse on the west, so if it has shifted west, this should reduce rainfall but increase the storm surge on the west coast.

Gaoth Laidir

Again, not sure if the windspeeds in this latest analysis at 7 am are accurate (77 knots). It doesn't even state a radius for the 34-knot winds but at least it shows where the centre is now (50.8N 11.5W, about 200 km southwest of Kerry).

lucernarian

http://www.meteociel.fr/observations-meteo/satellite.php

This one is easier to see the storm momentum from, but as I said earlier looking at the infrared imagery can be deceptive. Nonetheless it seems like a slightly westerly wobble happened last night and I'd expect a slightly bigger hit on the western side of the country than I had expected yesterday.

There's been some eejits thinking that the storm is meaningfully missing Ireland when the winds from this will be severe throughout the south even still. When it does make it to Ireland, the observations will paint a detailed picture of what exactly it will do. Hopefully not as bad as feared or predicted.

Edit: basically this event is going to happen and it will be bad, and it's the technical thread so can we cut out the "what about me and my random question" stuff?

Meteorite58

Mod Note

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

Thanks

DOCARCH

Highest gust for 0600 reports was 44kn at Valentia, and, for 0700 reports is 47kn at Sherkin.

flaneur

Are all the models beginning to ageee on the westerly shift or is it all a little speculative ?

flaneur

Bear in mind hurricane describes a very specific type of storm. This may no longer meet those technical criteria but it does not mean that it’s not a very powerful system.

Meteorite58

Barometer / Temp Readings Tralee

SPEKudp.png?1

Meteorite58

GFS 0Z

Mean

NPVyS32.gif?1

850hpa

Gaoth Laidir

This was the wind analysis at 4 am. I'm not sure if it's valid for extratropical systems as it works on the reduction of 700 hPa winds, which may not apply in this case. In any case it showing max winds 79 knots to the ENE.

Meteorite58

Hastentoadd wrote: »

Meteorite, what you show would suggest that this storm will miss on the West?

I think if you go back a few pages and look at the various models, there is slight variances. In general I would think it wont miss, maybe not as bad as the SW, S and SE but treat it as a Red warning. This as they have said is unprecedented.

Rikand

Hastentoadd wrote: »

Meteorite, what you show would suggest that this storm will miss on the West?

The eye of the storm. Not the storm itself