Tropical Depression Seven Discussion Number   8
NWS National Hurricane Center Miami FL       AL072024
500 AM AST Fri Sep 13 2024

The depression has an asymmetric structure due to moderate 
west-northwesterly shear, with the center lying west of generally 
shapeless convective clusters.  Because there has largely been 
little change in the system's organization, and there is quite a 
range among the subjective and objective estimates, the intensity 
remains 30 kt out of respect for continuity.

The initial motion is a little slower toward the west-northwest 
(290/12 kt).   A weakness in the subtropical ridge to the north of 
the depression is becoming more pronounced, and the track guidance 
indicates that the system should turn westward by tonight and slow 
down further through much of the forecast period as it moves across 
the central tropical Atlantic.  In fact, by days 4 and 5, an 
amplifying shortwave trough to the north is likely to cause the 
cyclone to crawl at speeds near or less than 5 kt and gradually turn 
northwestward.  The official forecast is close to the previous 
prediction during the first 60 hours, but then is adjusted westward 
on days 3 through 5 following the latest model trends.

In terms of moisture, the environment across the tropical Atlantic 
has not been kind to weather systems over the past couple of months. 
The official forecast still allows for the possibility of the 
depression becoming a tropical storm today or tonight, however an 
even drier air mass to the west is likely to cause the cyclone to 
continue struggling convectively.  In fact, all of the global models 
show the cyclone's wind field weakening over the weekend, with the 
GFS suggesting the depression could degenerate into a remnant low.  
For now, the NHC forecast keeps the system as a tropical cyclone for 
the entire forecast period, but it does show weakening in a couple 
of days.  Some recovery is possible by days 4 and 5 when the system 
reaches a slightly more moist and low-shear environment. 


FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 19.0N  38.2W   30 KT  35 MPH
12H  13/1800Z 19.4N  39.7W   35 KT  40 MPH
24H  14/0600Z 19.7N  41.6W   35 KT  40 MPH
36H  14/1800Z 19.8N  43.4W   30 KT  35 MPH
48H  15/0600Z 19.7N  45.0W   30 KT  35 MPH
60H  15/1800Z 19.5N  46.7W   30 KT  35 MPH
72H  16/0600Z 19.3N  48.0W   30 KT  35 MPH
96H  17/0600Z 19.2N  49.7W   35 KT  40 MPH
120H  18/0600Z 20.5N  50.6W   40 KT  45 MPH

$$
Forecaster Berg