[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 180233
TCDAT5

Tropical Storm Odette Discussion Number   2
NWS National Hurricane Center Miami FL       AL152021
1100 PM EDT Fri Sep 17 2021

Satellite images indicate that west-southwesterly shear is taking a
toll on Odette.  Deep convection has been separating from the
low-level circulation, and the closest area of thunderstorms is now
more than 100 miles east of the center.  The circulation is rather
broad, but there is a clear center a couple of hundred miles off the
U.S. Mid-Atlantic coast.  The initial intensity is held at 35 kt for
this advisory.  A very recent ASCAT pass showed some stronger winds
in the thunderstorms more than a couple of hundred miles east of the
low-level center, but its not clear if those winds are reliable and
representative of the storm's true intensity.  Hopefully more
scatterometer data with be available soon to better assess Odette's
strength.

Although it appears that Odette has been meandering lately, a
12-hour average yields a northeastward motion at about 9 kt.  The
storm is expected to move faster northeastward or east-northeastward
off the northeast U.S. and Atlantic Canada coasts this weekend as it
moves in the mid-latitude flow.  After that time, the models show a
significant slow down as the cyclone cuts off from the progressive
flow to the south or southeast of Newfoundland.  Although there is
quite a bit of spread in the models from days 3-5, almost all of the
guidance shows the storm stalling by the end of the forecast period.
The new NHC track forecast is a little to the south of the previous
one to come into better agreement with the latest models.  This
forecast still lies to the north of the consensus aids, however.

Odette is already beginning the process of transitioning to an
extratropical cyclone, and it will likely complete the transition by
Saturday night when it is expected to be north of the Gulf Stream
Current and merging with an approaching trough.  The cyclone is
likely to reach its peak intensity as an extratropical storm in
48-60 hours when the baroclinic dynamics are most favorable.
Gradual weakening seems likely beyond that time.  The NHC intensity
forecast is the same as the previous one and in line with the
majority of the guidance.

As Odette becomes fully extratropical and gains latitude this
weekend, the wind field is forecast to expand significantly.  Odette
is expected to affect portions of Newfoundland with strong winds and
heavy rainfall Sunday and Sunday night as a post-tropical cyclone.
Please refer to products from Environment Canada for additional
information on potential impacts in Newfoundland.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 36.4N  71.2W   35 KT  40 MPH
 12H  18/1200Z 37.8N  69.3W   40 KT  45 MPH
 24H  19/0000Z 39.4N  65.7W   45 KT  50 MPH...POST-TROP/EXTRATROP
 36H  19/1200Z 41.0N  61.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  20/0000Z 42.3N  57.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 60H  20/1200Z 43.4N  53.1W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  21/0000Z 43.8N  50.0W   50 KT  60 MPH...POST-TROP/EXTRATROP
 96H  22/0000Z 44.3N  48.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  23/0000Z 44.8N  46.6W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi
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