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Tropical Depression Fifteen Discussion Number   3
NWS National Hurricane Center Miami FL       AL152023
1100 PM AST Fri Sep 15 2023
 
Deep convection has increased over the northern portion of the 
depression's broad circulation this evening, however it is still 
not particularly well organized. A recent ASCAT passed indicated 
that the circulation is still broad and that the center may be 
trying to reform farther north closer to the convection.  The 
scatterometer data revealed peak winds of 25-30 kt, and the initial 
wind speed is maintained at 30 kt for this advisory. 
 
The initial motion is a still somewhat uncertain 320/12 kt. A 
deep-layer ridge over the central Atlantic should steer the 
depression northwestward through early next week. By late 
Tuesday, a mid-latitude trough moving westward over the western 
Atlantic is expected to cause the cyclone to turn north- 
northwestward and northward near the end of the forecast period. 
The track guidance is in relatively good agreement on this 
scenario, and the latest NHC track forecast lies near the middle of 
the guidance envelope. 
 
Given the current structure of the system, only gradual 
strengthening is likely overnight. Once an inner core become 
established a faster rate of strengthening seems likely as the 
system traverses warm waters and remains in a low vertical wind 
shear conditions.  Steady to potentially rapid strengthening is 
predicted later this weekend, and the system is forecast to become 
a hurricane by late Sunday or Monday. The NHC intensity forecast is 
near the higher-end of the guidance, close to the HCCA model 
through 72 hours, and is then near the higher dynamical guidance at 
96 h. By late in the period, increasing southwesterly vertical wind 
shear is likely to cause some gradual weakening.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  16/0300Z 16.3N  44.7W   30 KT  35 MPH
 12H  16/1200Z 17.9N  45.8W   35 KT  40 MPH
 24H  17/0000Z 20.1N  47.7W   45 KT  50 MPH
 36H  17/1200Z 21.7N  49.4W   55 KT  65 MPH
 48H  18/0000Z 23.3N  50.9W   70 KT  80 MPH
 60H  18/1200Z 24.7N  52.6W   80 KT  90 MPH
 72H  19/0000Z 26.0N  54.6W   90 KT 105 MPH
 96H  20/0000Z 29.3N  57.9W  100 KT 115 MPH
120H  21/0000Z 34.1N  58.3W   90 KT 105 MPH
 
$$
Forecaster Brown
 
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