Tropical Depression Seven Forecast Discussion

000
WTNT42 KNHC 122022
TCDAT2

Tropical Depression Seven Discussion Number   6
NWS National Hurricane Center Miami FL       AL072024
Issued by the NWS Weather Prediction Center College Park MD
500 PM AST Thu Sep 12 2024

Tropical Depression Seven appears somewhat more organized on 
satellite imagery this afternoon, with a compact circulation 
and a couple bursts of deeper convection near the center, though it 
has been exposed for portions of the day.  Subjective and objective 
Dvorak numbers indicate the system is close to becoming a tropical 
storm. However, the initial intensity will stay 30 kt, at the lower 
end of the estimates, until we get a little more definitive 
evidence of a tropical storm.

The cyclone continues on a west-northwestward heading, and the 
general motion is expected to continue over the next 2-3 days. The 
forward speed should gradually slow as the subtropical ridge to the 
north of the system weakens. Track guidance diverges considerably 
early next week, related to uncertainties with an amplifying trough 
over the north-central Atlantic Ocean and another ridge centered 
northeast of the Leeward Islands.  The GFS-based guidance has 
trended much farther west and faster, showing a weakening system at 
long range.  However, the ECMWF and its ensemble members still show 
a risk of a stronger system, so the forecast will stay on the 
northeastern side of the track guidance.  The new NHC forecast is 
faster and left of the previous one owing to the bulk of the 
guidance shifts during this cycle.

While environmental conditions are somewhat favorable for gradual 
strengthening, with low-moderate vertical wind shear and 
marginally warm SSTs, intensity guidance is even lower than the 
last cycle.  Slight strengthening seems most probable within the 
marginal environment, and the forecast continues to show a 45-kt 
peak in 5 days.  There is also the potential for greater 
strengthening beyond what is shown early next week as the cyclone 
will be in an environment characterized by lower shear, warmer SSTs 
around 28C, slightly more instability, but plentiful dry air aloft. 
The latest intensity forecast is very similar to the previous 
one, on the high side of the guidance envelope.



FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 18.3N  35.9W   30 KT  35 MPH
 12H  13/0600Z 18.9N  37.6W   35 KT  40 MPH
 24H  13/1800Z 19.4N  39.8W   35 KT  40 MPH
 36H  14/0600Z 19.7N  41.5W   35 KT  40 MPH
 48H  14/1800Z 19.8N  43.1W   40 KT  45 MPH
 60H  15/0600Z 19.9N  44.5W   40 KT  45 MPH
 72H  15/1800Z 19.8N  46.1W   40 KT  45 MPH
 96H  16/1800Z 19.8N  48.4W   40 KT  45 MPH
120H  17/1800Z 20.3N  50.0W   45 KT  50 MPH

$$
Forecaster Hurley/Blake