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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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emeldc

Power gone in parts of Cork already :eek:

DOCARCH

Sherkin gusting 55kn on 0800 reports.

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?

ps200306

Sunrise on Ophelia:

Meteorite58

Getting lively in Tralee gusting 70 km/h SE

Meteorite58

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

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.

DOCARCH

Meteorite58 wrote: »

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

*whistles*

pad199207

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

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?

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.

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.

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.

garyha

Latest ECMWF at 9km

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.

MJohnston

M3 Buoy data of interest:

M5 will also be worth watching as an indicator of eastward extension

patneve2

https://en.sat24.com/en

Quite impressive-looking on sat24. Looks like it will seriously pack a punch in some areas. Expecting a 120/130 gust around these parts...160/170 in the SW

flaneur

It doesn't appear to be all that far west on Sat24

Meteorite58

Discodog

What's the barometric at the centre ? Too many isobars for my eyesight

MJohnston

Anyone know if the Kinsale Energy buoy listed here:
https://www.met.ie/latest/buoy.asp
Is an actual buoy, or are they using the same elevated data as the weather station there?

DOCARCH

MJohnston wrote: »

Anyone know if the Kinsale Energy buoy listed here:
https://www.met.ie/latest/buoy.asp
Is an actual buoy, or are they using the same elevated data as the weather station there?

Not a buoy. As far as I am aware station is at approx. 100m over sea level.

Gaoth Laidir

mirrorwall14 wrote: »

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?

Water vapour imagery will show it up as a very dark small area of dry air near the tip of the occlusion.

MJohnston

DOCARCH wrote: »

Not a buoy. As far as I am aware station is at approx. 100m over sea level.

Yeah, weird that they list it on the buoys page, but surely if it is recording wave heights, it must have some sea level observation capabilities?

Donegal Storm

This is what the Arpege model shows for 9am, max gusts around 100-110kph on the south coast which is exactly what we have so far. Expecting a peak around 140-150kh around midday to 1pm if it keeps up its accuracy before the storm quickly weakens as it moves north

star gazer

https://twitter.com/MetEireann/status/919844165164392448
Gusts of 80 knots at Fastnet rock
58 knots Roches point

[Deleted User]

Thought I would add this positional graphics chart for historical reference purposes. The last advisory on Ophelia was issued at 11pm EDT (4am here) by the NHC. Not sure the next time the NHC will be issuing advisories for our part of the world. Add 5 hours to the chart times.

MJohnston

M3 latest hourly observations down to 976.4mb (from 980), wind speed largely the same at 40G53 (up from 39G49), significant wave heights up quite a bit to 5.47m (from 4.06m)

Gaoth Laidir

MJohnston wrote: »

Yeah, weird that they list it on the buoys page, but surely if it is recording wave heights, it must have some sea level observation capabilities?

I think the anemometer is at about 100 metres as this is where helicopters land but they do have wave sensors too.

From Kinsale-energy.ie...