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Tropical Depression Fifteen Discussion Number   1
NWS National Hurricane Center Miami FL       AL152023
Issued by the NWS Weather Prediction Center College Park MD
1100 AM AST Fri Sep 15 2023

1-min GOES-East visible imagery indicates improved organization of 
Invest 97, with a well-defined surface center forming since 
sunrise, along with large curved banding features.  Thus the system 
is designated as a tropical depression, and the initial intensity 
is set to 30 kt, in closest agreement with the TAFB Dvorak 
classification.  

Our estimate of initial motion is northwestward at 10 kt, though 
this is uncertain due to the recent center formation.  A
subtropical ridge over the central Atlantic should be the dominant 
steering mechanism during the next several days, sending the system 
on a steady northwestward track.  For a first forecast, guidance is 
in remarkably good agreement, and the official forecast lies near 
or west of the model consensus.  Despite the good model agreement, 
there is still some long-range uncertainty in how far west this 
system moves, which partially depends on the strength of the 
subtropical ridge in the wake of Tropical Storm Margot. 

The depression is forecast to gradually intensify over the next 
couple of days as moderate northeasterly shear and the initial broad
cyclone structure could provide a check on the intensification 
rate.  By early next week, this system is forecast to move over 
near record warm sea-surface temperatures for the region in light 
shear conditions. It probably sounds like a broken record at this 
point in the season, but rapid intensification is a significant 
possibility, and the official forecast could be conservative below. 
The intensity forecast is near or above the intensity consensus, 
only leveling off at 120 hours due to gradual SST cooling and the 
possibility of eyewall replacement cycles, as suggested by the HAFS 
model suite.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/1500Z 14.4N  43.8W   30 KT  35 MPH
 12H  16/0000Z 15.5N  44.7W   35 KT  40 MPH
 24H  16/1200Z 17.2N  46.0W   40 KT  45 MPH
 36H  17/0000Z 18.9N  47.9W   50 KT  60 MPH
 48H  17/1200Z 20.5N  49.6W   60 KT  70 MPH
 60H  18/0000Z 22.0N  51.2W   70 KT  80 MPH
 72H  18/1200Z 23.4N  52.9W   85 KT 100 MPH
 96H  19/1200Z 26.0N  56.8W  105 KT 120 MPH
120H  20/1200Z 29.0N  60.0W  100 KT 115 MPH
 
$$
Forecaster Churchill/Blake/Lamers
 
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