[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 162035
TCDAT5

Tropical Depression Fifteen Discussion Number   6
NWS National Hurricane Center Miami FL       AL152023
500 PM AST Sat Sep 16 2023

The tropical depression remains poorly organized this afternoon.
However, visible satellite imagery continues to indicate a broad
region of low- and mid-level rotation, and deep convection has
increased somewhat in the northern semicircle of the disturbance.
Subjective Dvorak estimates from SAB and TAFB remain steady at 25 kt
and 35 kt, respectively. Based on the current structure and the
various intensity estimates, the intensity is held at 30 kt for this
advisory.

The initial motion is estimated at 330/14 kt. This general motion
is expected to continue for the next couple days as the depression
moves along the southern periphery of a mid-level ridge. Consensus
track guidance, as well as the global and regional hurricane models,
are in general agreement during the early portion of the forecast
period. Early next week, the track forecast uncertainty increases
somewhat as the system will begin to interact with a deep-layer
trough. This trough interaction is expected to induce a more
poleward shift in the track and eventually recurve the system toward
the northeast after 96 hours. The NHC track forecast is in agreement
with the consensus aids, TVCN and HCCA, and slightly faster than
the prior forecast.

Environmental conditions remain favorable for intensification during
the next several days, with low vertical wind shear and warm sea
surface temperatures expected to persist along the forecast track.
The timing of intensification will depend on how quickly the system
is able to consolidate into a more compact structure. The current
intensity forecast assumes that it will take 24-36 hours for this to
happen, with the system expected to become a hurricane in 48 hours.
The current forecast reaches 95 kt by 72 h, although the regional
hurricane models HWRF and HAFS indicate that a major hurricane is
not out of the question. ECMWF-SHIPS guidance continues to indicate
the possibility of rapid intensification in the next 72 hours. By
mid-week, as the system recurves to the northeast, it is expected to
gradually weaken as southwesterly shear increases. The NHC forecast
is in the middle of the guidance envelope and is similar to both the
prior forecast and HCCA.

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 20.8N  47.1W   30 KT  35 MPH
 12H  17/0600Z 22.3N  48.2W   35 KT  40 MPH
 24H  17/1800Z 24.2N  49.7W   45 KT  50 MPH
 36H  18/0600Z 25.6N  51.1W   55 KT  65 MPH
 48H  18/1800Z 26.9N  52.9W   65 KT  75 MPH
 60H  19/0600Z 28.3N  54.8W   80 KT  90 MPH
 72H  19/1800Z 30.0N  56.4W   95 KT 110 MPH
 96H  20/1800Z 34.6N  57.3W   90 KT 105 MPH
120H  21/1800Z 39.6N  52.0W   80 KT  90 MPH

$$
Forecaster Hogsett/Bucci
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