[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 240848
TCDAT5

Hurricane Tammy Discussion Number  24
NWS National Hurricane Center Miami FL       AL202023
500 AM AST Tue Oct 24 2023

Tammy's satellite depiction has improved slightly compared to the
sheared convective pattern from yesterday evening. The latest
infrared satellite imagery depicts convective bursts are once again
wrapping around the southern portion of the system. Earlier
microwave imagery showed a well organized low-to mid-level
circulation. The most recent TAFB Dvorak satellite estimate held
steady at T4.0/65kt, which supports maintaining an initial intensity
of 65 kt for this advisory.

The hurricane is currently moving northeastward, and should
continue this motion for the next day or two. A mid-latitude trough
approaching the system from the northwest will cause Tammy to begin
to move more northward during the middle of the forecast period. It
is after this point, the model guidance becomes increasingly
divergent. Models are split on whether another mid-latitude trough
will cause the system to accelerate east to northeastward, or have
Tammy not being picked up by this trough and move the system
westward to southwestward under a building mid-level ridge. The GFS
has trended towards the west-southwest track scenario, closer to
the ECMWF. Therefore, the NHC forecast track, which already favored
the ECMWF solution, remains similar to the previous advisory and is
close to a blend of GFS and ECMWF.

There is considerably better agreement among most of the
intensity guidance, which indicates slight strengthening is possible
during the next day or two, as Tammy interacts with an upper-level
trough.  After 48 hours the system should begin to weaken and
start to transition into a post-tropical cyclone. The latest model
simulated satellite imagery depicts that this process is expected
to be complete in about 60 h, though Tammy will likely continue to
produce gale-to storm-force winds for several days even after this
transition occurs.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 23.7N  62.8W   65 KT  75 MPH
 12H  24/1800Z 24.5N  61.8W   70 KT  80 MPH
 24H  25/0600Z 25.9N  60.3W   75 KT  85 MPH
 36H  25/1800Z 27.9N  59.0W   75 KT  85 MPH
 48H  26/0600Z 29.5N  58.9W   70 KT  80 MPH
 60H  26/1800Z 31.0N  59.7W   60 KT  70 MPH...POST-TROP/EXTRATROP
 72H  27/0600Z 31.7N  60.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  28/0600Z 32.4N  62.8W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  29/0600Z 32.8N  64.8W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Kelly
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