Tropical Depression Twelve Discussion Number   1
NWS National Hurricane Center Miami FL       AL122024
500 PM AST Sun Sep 29 2024

The system we have been monitoring in the eastern Tropical Atlantic 
(AL90) has continued to become better organized throughout the day. 
After an overnight deep convective burst, outer convective banding 
has become better defined, noted by the most recent TAFB subjective 
Dvorak fix of T2.0/30 kt. GOES-16 1-minute visible imagery also 
shows that the circulation, which was more elongated this morning, 
has become better defined on the western side, suggesting a 
well-defined closed vortex now exists. Based on the above data, 
advisories are initiated on Tropical Depression Twelve this 
afternoon, with an initial intensity of 30 kt.

The motion of the new depression currently appears to be westward at 
270/8 kt. A prominent subtropical ridge to the north should continue 
to steer the system generally westward to west-northwestward over 
the next couple of days. After that time, this ridge becomes more 
eroded by a mid-latitude trough on its western side, resulting in 
the system gradually turning more poleward through the end of the 
forecast. In general the guidance is pretty tightly clustered for 
the first 48-60 h, with spread increasing a little more thereafter 
related to how quickly the system turns poleward. The initial NHC
track forecast lies near the HFIP Corrected Consensus Approach 
(HCCA), which favors the ECMWF track a little further west than the 
GFS track.  

For at least the next 2-3 days, vertical wind shear is expected to 
remain low, mid-level moisture stays high, as the system remains 
over 29-30 C sea-surface temperatures. Yet, the current large 
convective envelope of the system suggests it may take a day or so 
for an inner-core to become established. Thus, the initial rate of 
intensification is a bit slow, a little under the guidance for the 
next 24 hours, but then becomes faster and ends up near the IVCN 
consensus aid by 120 h. The initial NHC intensity forecast shows 
TD12 becoming a hurricane in 60 h and a major hurricane in 5 days.

FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 13.8N  32.5W   30 KT  35 MPH
12H  30/0600Z 13.9N  33.6W   35 KT  40 MPH
24H  30/1800Z 14.2N  35.7W   40 KT  45 MPH
36H  01/0600Z 14.5N  38.1W   50 KT  60 MPH
48H  01/1800Z 15.0N  40.0W   60 KT  70 MPH
60H  02/0600Z 15.9N  41.5W   70 KT  80 MPH
72H  02/1800Z 17.4N  42.7W   85 KT 100 MPH
96H  03/1800Z 20.0N  45.0W   95 KT 110 MPH
120H  04/1800Z 22.5N  47.5W  105 KT 120 MPH

$$
Forecaster Papin