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Tropical Depression Four-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP042023
200 AM PDT Fri Jul 21 2023
 
Convection associated with an area of low pressure located nearly
1000 miles southwest of the southern tip of the Baja California 
peninsula has noticeably increased since last night.  Earlier 
last-light visible satellite imagery showed a well-defined 
low-level circulation before deep convection formed and persisted 
directly over it.  The system therefore meets the criteria for a 
tropical cyclone, and advisories have been initiated on Tropical 
Depression Four-E. The initial intensity is a conservative 30 kt, 
based on the satellite trends and a subjective satellite intensity 
estimate from TAFB of T2.5.
 
The depression is being sheared by strong upper-level westerly winds 
which are forecast to increase during the next few days.  The system 
is also crossing over a gradient of sea surface temperatures towards 
cooler waters. Given these marginal conditions and global model 
guidance it is likely the depression will be short-lived.  The 
official intensity forecast shows the cyclone gradually weakening, 
becoming a remnant low by 48 h, and dissipating by 60 h.  However, 
some models suggest it could weaken and dissipate sooner.
 
The system is moving west-northwestward at 9 kt.  A ridge centered 
over the southwestern United States should continue to steer the 
depression with this general motion for the next day or so. 
Afterward, the shallow vortex is expected to turn westward in the 
low-level flow.  The NHC track forecast lies near the center of the 
model guidance, which is generally in good agreement, and closest to 
the simple consensus aid, TVCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0900Z 14.5N 122.2W   30 KT  35 MPH
 12H  21/1800Z 15.3N 123.9W   30 KT  35 MPH
 24H  22/0600Z 16.1N 126.3W   30 KT  35 MPH
 36H  22/1800Z 16.4N 128.5W   25 KT  30 MPH
 48H  23/0600Z 16.7N 130.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  23/1800Z...DISSIPATED
 
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Forecaster Bucci
 
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