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Tropical Depression Four-E Discussion Number   2
NWS National Hurricane Center Miami FL       EP042023
800 AM PDT Fri Jul 21 2023
 
Convection associated with Tropical Depression Four-E has persisted 
overnight and into this morning. However, the convective pattern is 
one of a strongly sheared system, with cold echo tops only over the 
eastern side of the system. In the last few hours, Proxy-vis 
satellite imagery shows that the low-level center has become exposed 
near the western edge of the convection. Subjective Dvorak satellite 
estimates from TAFB and SAB were T2.5 and T2.0, respectively. Given 
the current structure with the low-level center becoming exposed, 
and the subjective satellite estimates, the initial intensity for 
this advisory remains at 30 kt.
 
The depression continues to be in an environment of strong 
upper-level westerly wind shear of 25 to 30 knots, which has exposed 
the low-level center, and displaced the convection to the east. The 
system will be crossing the 25 degree C isotherm later today, with 
cooler SSTs remaining along the forecast track. Given these marginal 
conditions, it is likely the depression will be short-lived, with 
the system becoming a remnant low later this weekend, and 
dissipating by 60 hours. However, some models suggest it could 
weaken and dissipate sooner.
 
The system is moving west-northwestward at 11 kt.  A ridge centered 
over the southwestern United States should continue to steer the 
depression on this general heading and speed for the next day or 
so. Afterward, the shallow remnant low is expected to turn more 
westward in the low-level flow.  The NHC track forecast lies near 
the previous forecast, which is near the center of the consensus 
aids.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/1500Z 15.2N 123.6W   30 KT  35 MPH
 12H  22/0000Z 15.9N 125.4W   30 KT  35 MPH
 24H  22/1200Z 16.5N 127.6W   30 KT  35 MPH
 36H  23/0000Z 16.8N 129.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  23/1200Z 17.0N 131.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  24/0000Z...DISSIPATED
 
$$
Forecaster Kelly/Brown
 
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