Storm Lorenzo: October 3/4 2019 Technical Discussion Only

Gaoth Laidir · 27-09-2019 9:43pm

It's down to 110 knots in the latest update. Extratropical transition should be finished by T+120 h (at 44 N).

Hurricane Lorenzo Discussion Number 21
NWS National Hurricane Center Miami FL AL132019
500 PM AST Fri Sep 27 2019

The satellite appearance of Lorenzo has degraded further since the
last advisory, with only a hint of an eye still apparent in visible
imagery and the cold cloud tops in the eyewall becoming very
asymmetric in infrared imagery. A recent SSMI/S overpass shows
that the southern portion of the eyewall has eroded, possibly due to
shear or dry air intrusion. The microwave imagery also suggests an
outer convective band is forming, but it is not yet well enough
defined to call it an outer eyewall. Satellite intensity estimates
have continued to decrease, and the initial intensity is lowered to
110 kt as a blend of the various estimates. The hurricane continues
to have excellent outflow in the northern semicircle.

The initial motion remains 330/12 kt. There is no change in the
track forecast philosophy or the forecast confidence, as Lorenzo
should turn northward and then northeastward during the next few
days as it moves around the western edge of a mid-level ridge
centered over the eastern Atlantic. Later in the forecast period,
the cyclone is expected to accelerate northeastward in the
mid-latitude westerlies ahead of a deep-layer trough approaching
from the west. The track guidance for this advisory, while it
remains tightly clustered in direction, is a little slower than the
previous guidance. Based on this, the new forecast track is just a
little slower than the previous forecast.

Lorenzo will be passing over sea surface temperatures of 27-28C for
the next 48-72 h. However, it will be in an environment of moderate
vertical shear due to an upper-level trough not far to the west.
The intensity guidance responds to this by showing gradual
weakening during this time, and the new intensity forecast follows
the trend of the guidance. There is a possibility of fluctuations
in intensity caused by eyewall replacement cycles superimposed on
this weakening trend. After 72 h, the hurricane should encounter
stronger mid-latitude westerlies, move over cooler sea surface
temperatures, and eventually merge with the above-mentioned
deep-layer trough. As this occurs, Lorenzo is forecast to undergo
extratropical transition, with this being complete by 120 h.
Current indications from the global models are that Lorenzo will
retain hurricane strength through the transition.

FORECAST POSITIONS AND MAX WINDS

INIT 27/2100Z 20.3N 43.6W 110 KT 125 MPH
12H 28/0600Z 21.6N 44.1W 105 KT 120 MPH
24H 28/1800Z 23.3N 44.3W 100 KT 115 MPH
36H 29/0600Z 25.0N 44.0W 100 KT 115 MPH
48H 29/1800Z 26.6N 43.3W 100 KT 115 MPH
72H 30/1800Z 30.3N 41.1W 95 KT 110 MPH
96H 01/1800Z 35.5N 36.0W 90 KT 105 MPH
120H 02/1800Z 44.0N 26.5W 80 KT 90 MPH...POST-TROP/EXTRATROP

hatrickpatrick · 27-09-2019 9:54pm

NHC now show it becoming extratropical further south of Ireland than Ophelia did, but it'll be interesting nonetheless since they show it only weakening to just below Cat 2 strength by that time, so it could still potentially cross Ireland with stronger winds than Ophelia did depending on how it tracks. ECM shows it crossing the south of the country, while the UKMO cuts off just before showing that timeframe but seems to be following the ECM up until then. Going to be a very interesting few days, particularly to see how Met Eireann reports this after all the (completely bullsh!t in my view) criticism they got for "overhyping" the red weather alerts of 2017 and '18.

igCorcaigh · 27-09-2019 10:28pm

hatrickpatrick wrote: »

NHC now show it becoming extratropical further south of Ireland than Ophelia did, but it'll be interesting nonetheless since they show it only weakening to just below Cat 2 strength by that time, so it could still potentially cross Ireland with stronger winds than Ophelia did depending on how it tracks. ECM shows it crossing the south of the country, while the UKMO cuts off just before showing that timeframe but seems to be following the ECM up until then. Going to be a very interesting few days, particularly to see how Met Eireann reports this after all the (completely bullsh!t in my view) criticism they got for "overhyping" the red weather alerts of 2017 and '18.

Totally agree with that last comment.

Anyway, if this approaches anything Ophelia like, people need to be aware.

The fact that this system is the most powerful this far East makes it stand out anyway.

Interesting times!

Kermit.de.frog · 27-09-2019 10:46pm

One or two interesting evolutions starting to appear for us.

navgem-0-162.png?27-19

Johanna Donnelly will have her Ophelia face on in a few days I reckon. :P

Oneiric 3 · 27-09-2019 10:50pm

That UKMO chart posted above looks scarily Debbyesque. Different times and different methods of course, but forecasters at the time predicted that the worst of that particular storm would stay off well to the the west of Ireland. (I posted the Irish Times chart and forecast for that fateful day years back, but wound't have a hope of finding it now)

Hooter23 · 27-09-2019 10:52pm

"This is Happening" :pac:

SleetAndSnow · 27-09-2019 10:52pm

Navgem though, generally very unreliable if I remember correctly right? Regardless I’d trust the ecm most here with us possibly feeling 70kmph winds along the SW/W coasts vs a southerly direct hit

Harry Palmr · 27-09-2019 10:55pm

The jet stream is pretty volatile right now, it could push this wind away as much as it could steer it over us.

Kermit.de.frog · 27-09-2019 11:13pm

Yeah this needs watching

gfs-0-144.png?18

Gaoth Laidir · 27-09-2019 11:18pm

What happens Lorenzo after the Azores depends on how an upper trough coming off eastern Canada interacts with. The 12Z ECM has the trough not absorbing the low-level centre but giving it a shot in the arm as it continues towards us. By Thursday evening the low reaches the southwest coast with around 50-knot mean winds at 100 metres, around 40 knots on the surface, highest offshore.

Oneiric 3 · 27-09-2019 11:25pm

This is what we are dealing with... and this is just one model run.. of many.

Gaoth Laidir · 27-09-2019 11:27pm

Oneiric 3 wrote: »

This is what we are dealing with... and this is just one model run.. of many.

Meteorite58 · 27-09-2019 11:32pm

GFS 18Z has thrown in a direct hit on the latest run. My trees !

Still about 132 hrs out so very much in the unreliable timeframe but certainly starting to see charts showing it tracking close to our shores.

Has a pressure of 960 hPa this time, +30 hPa on the last run.

Oneiric 3 · 27-09-2019 11:36pm

Slightly tidier looking. EPS mean (850 hPa ws > 50 knots for time in question)

for the second run in a row now, the ECMWF op has broken free from the general consensus. Either it is onto something (it is the highest res of all the runs afterall) or it is just being mischievous.

Kermit.de.frog · 27-09-2019 11:40pm

https://www.youtube.com/watch?v=rpFfXWr_gRo

sdanseo · 27-09-2019 11:41pm

Even a 960mb low with extratropical features and 40kt sustained wind is no joke.

Note: from here on, post is borderline hyperbole based on ONE run. But still worth talking about.

GFS on the other hand. Literally off the scale with >160km/h gusts over land. I've never seen this on a GFS chart before, it's stuff usually reserved for ICON, or NAVGEM when it's had a few pints.

Edit: Portions of coastal Kerry could see 130km/h +mean wind here. Well into sustained hurricane force. (2nd pic)

ICON comes into range tomorrow night, could make for some spectacular (if speculative) charts with quite a lot of black off-the-chart type windspeeds in them.

138-289UK.GIF?28-18

Gaoth Laidir · 27-09-2019 11:48pm

12Z ECM ensembles. Look similar to the previous couple of runs?

igCorcaigh · 27-09-2019 11:50pm

Well wouldn't that be something.
Hopefully not though, as much as I love a good storm.

pauldry · 27-09-2019 11:50pm

Remember all charts look fantastical at night runs but by morning watch for the "and now its gone" comments before it reappears as a yellow warning next weekend

uck51js9zml2yt · 27-09-2019 11:58pm

I read the first post and my first thought was would you "feck off" with your hurricanes

I'm in the south west on the side of a mountain facing the Atlantic.

I nice shower would do grand and a bit of a breeze

How come Harm what's his name didn't mention hurricanes in his report on rte radio at 6 this evening?

Gaoth Laidir · 28-09-2019 12:02am

Leila Eager Blowgun wrote: »

I read the first post and my first thought was would you "feck off" with your hurricanes

I'm in the south west on the side of a mountain facing the Atlantic.

I nice shower would do grand and a bit of a breeze

How come Harm what's his name didn't mention hurricanes in his report on rte radio at 6 this evening?

It's way too early. Let the redtop rags to that.

Kermit.de.frog · 28-09-2019 12:03am

Leila Eager Blowgun wrote: »

I read the first post and my first thought was would you "feck off" with your hurricanes

I'm in the south west on the side of a mountain facing the Atlantic.

I nice shower would do grand and a bit of a breeze

How come Harm what's his name didn't mention hurricanes in his report on rte radio at 6 this evening?

lol

There won't be a "hurricane". It will be a cold core storm by the time it gets here so no eye so to speak. There could be a post tropical storm with hurricane force winds though equivalent to a Cat 1 strength storm.

At this far out the track and intensity will vary a lot though.

J6P · 28-09-2019 12:08am

A bit premature maybe but the latest GFS and some ECM ensembles would be concerning.

If the worst case scenarios were to verify would this warrant a red alert/national emergency as was the case with Ophelia, If i remember correctly there was a couple of fatalities during Ophelia.

Gaoth Laidir · 28-09-2019 12:16am

The latest microwave at 2144Z shows that outer southern eyewall that was trying to form earlier a little less defined. Overall it's not looking as healty on its southern half as earlier as dry air is wrapping around and shear is starting to pull at it.

20190927.2144.f17.x.colorpct_91h_91v.13LLORENZO.110kts-948mb-198N-433W.062pc.jpg

20190927.2144.f17.x.colorpct_91h_91v.13LLORENZO.110kts-948mb-198N-433W.062pc.jpg

20190927.2130.goes16.x.wv1km.13LLORENZO.110kts-948mb-198N-433W.100pc.jpg

Kermit.de.frog · 28-09-2019 12:25am

Can a mod update the thread title to "hurricane" rather than storm for the time being?

J6P · 28-09-2019 12:26am

https://twitter.com/andrewwulfeck/status/1177653491638112262

Gaoth Laidir · 28-09-2019 12:36am

J6P · 28-09-2019 12:40am

http://maritimebulletin.net/2019/09/27/bourbon-offshore-tug-distressed-in-atlantic-14-crew-waiting-rescue/

Offshore AHT tug BOURBON RHODE issued distress signal in the morning Sep 26 in Atlantic, in vicinity 15 35N 040 10W, some 970 nm due W of Cape Verde. The ship while en route from Las Palmas Canary islands, to Georgetown Guyana, was caught in cyclone, suffering massive water ingress in ship’s compartments, 14 crew readying for evacuation. MRCC Antilles-Guyana directed the only ship in the area around distressed tug, bulk carrier SSI EXCELLENT (IMO 9693757), to assist.

Gaoth Laidir · 28-09-2019 1:00am

J6P wrote: »

https://twitter.com/andrewwulfeck/status/1177653491638112262

What it was doing sailing right through an eyewall in this day and age is beyond me.

https://twitter.com/UCARCPAESS/status/1177686947201998848?s=19

Kermit.de.frog · 28-09-2019 1:00am

Gaoth Laidir wrote: »

Conditions look reasonably favorable for this to retain a good bit of it's tropical characteristics right up until near landfall time as it would be for us.

That depends entirely on the track of course. Early days but I wouldn't be surprised if the NHC started to reference the potential impacts here within the next 2 days. Probably be in touch with Met Eireann too.

Let's see if it stays on track over the next couple of days.

Storm Lorenzo: October 3/4 2019 **Technical Discussion Only**

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Storm Lorenzo: October 3/4 2019 Technical Discussion Only