Tropical Depression Twelve Forecast Discussion

000
WTNT42 KNHC 300838
TCDAT2

Tropical Depression Twelve Discussion Number   3
NWS National Hurricane Center Miami FL       AL122024
500 AM AST Mon Sep 30 2024

Tropical Depression Twelve has become better organized overnight.  A 
29/2338 UTC ASCAT-B overpass showed a large area of 25 to 30 kt 
winds, and that the center was located near the northern edge of the 
large convective mass.  Although a 30/0334 UTC AMSR2 microwave image 
showed that the center was still located near the northern edge of 
the central convective area, curved banding has been increasing 
during the night, with a large area of cold cloud tops persisting.  
Subjective Dvorak intensity estimates are a consensus T-2.0/30 kt 
from both TAFB and SAB.  Objective intensity estimates from UW-CIMSS 
are rising and now range from 36 to 41 kt.  Based on the subjective 
Dvorak estimates, a 30 kt initial intensity is held for this 
advisory, but the depression is likely very near tropical storm 
strength.

The estimated initial motion of the depression is westward, or 275/7 
kt.  The cyclone will continue moving westward to west-northwestward 
for another couple days while a well-established subtropical ridge 
remains in place to the north of the system.  A gradual turn to the 
northwest is expected around mid-week as a deep-layer trough over 
the north-central Atlantic weakens the ridge.  At the end of the 
forecast period, an approaching upper-level trough near Bermuda will 
induce the cyclone to turn northward over the open waters of the 
central Atlantic Ocean.  Some along-track spread is noted in the 
various track model solutions, but the models are in good agreement 
on the northward turn, with little cross-track spread.  The latest 
NHC track forecast is nearly identical to the previous one, and is 
about halfway between the slower GFS solution and the faster ECMWF 
model.

Conditions are quite favorable along the path of the depression with 
29 degree C sea-surface temperatures, a moist environment, and weak 
vertical wind shear.  Given the weak shear and the gradually 
improving structure, the cyclone should begin to steadily intensify 
soon.  The depression is forecast to become a hurricane in 36 to 48 
hours and a major hurricane in about 4 days.  The NHC intensity 
forecast is similar to the previous one, and lies between the middle 
and upper end of the intensity guidance suite, near the HCCA and 
IVCN multi-model consensus aids.  It should be noted that most of 
the models indicate that the cyclone's wind and wave field will 
expand significantly over the next several days, and the system is 
forecast to become a large and powerful hurricane as it gains 
latitude later this week.


FORECAST POSITIONS AND MAX WINDS

INIT  30/0900Z 14.0N  34.1W   30 KT  35 MPH
 12H  30/1800Z 14.1N  35.7W   40 KT  45 MPH
 24H  01/0600Z 14.3N  37.9W   50 KT  60 MPH
 36H  01/1800Z 14.9N  39.8W   60 KT  70 MPH
 48H  02/0600Z 15.8N  41.4W   70 KT  80 MPH
 60H  02/1800Z 17.1N  42.7W   80 KT  90 MPH
 72H  03/0600Z 18.4N  44.1W   90 KT 105 MPH
 96H  04/0600Z 20.7N  46.5W  105 KT 120 MPH
120H  05/0600Z 23.4N  48.5W  105 KT 120 MPH

$$
Forecaster Hagen