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27-09-2019, 21:19   #31
Gaoth Laidir
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This microwave scan just in shows that eyewall replacement cycle well underway. We might see a slight weakened intensity in the 10 pm discussion.

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27-09-2019, 21:43   #32
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It's down to 110 knots in the latest update. Extratropical transition should be finished by T+120 h (at 44 N).

Quote:
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
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27-09-2019, 21:54   #33
hatrickpatrick
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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.
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27-09-2019, 22:28   #34
igCorcaigh
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Quote:
Originally Posted by hatrickpatrick View Post
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!
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27-09-2019, 22:46   #35
Kermit.de.frog
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One or two interesting evolutions starting to appear for us.




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

Last edited by Kermit.de.frog; 27-09-2019 at 22:50.
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27-09-2019, 22:50   #36
Oneiric 3
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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)
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27-09-2019, 22:52   #37
Hooter23
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"This is Happening"
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27-09-2019, 22:52   #38
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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
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27-09-2019, 22:55   #39
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The jet stream is pretty volatile right now, it could push this wind away as much as it could steer it over us.
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27-09-2019, 23:13   #40
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Yeah this needs watching

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27-09-2019, 23:18   #41
Gaoth Laidir
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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.





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27-09-2019, 23:25   #42
Oneiric 3
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This is what we are dealing with... and this is just one model run.. of many.

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27-09-2019, 23:27   #43
Gaoth Laidir
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Quote:
Originally Posted by Oneiric 3 View Post
This is what we are dealing with... and this is just one model run.. of many.


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27-09-2019, 23:32   #44
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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.









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27-09-2019, 23:36   #45
Oneiric 3
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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.
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