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Tropical Depression ONE-E

Tropical Depression One-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP012021
300 AM MDT Sun May 09 2021

Satellite images and scatterometer surface wind data indicate that 
the low pressure area southwest of Mexico that the NHC has been 
monitoring for the past few days has acquired sufficient organized 
deep convection and has developed a well-defined inner-core wind 
field for the system to be designated as the first tropical 
depression of the 2021 Eastern North Pacific hurricane season... 
albeit six days early. The initial intensity of 30 kt is based on 
30-kt surface winds noted in 0359 UTC and 0453 UTC ASCAT-B and 
ASCAT-C, respectively, scatterometer satellite data. There were some 
35-kt wind vectors present east of the center, but those appeared to 
be rain-contaminated at that time. The 30-kt initial intensity is 
also supported by a 0600 UTC TAFB satellite intensity estimate of 
T2.0/30 kt using a curved-band feature.

The initial motion estimate is 325/04 kt. For the next day or two, 
the tropical cyclone is forecast to move northwestward to 
north-northwestward around the western periphery of a weak 
subtropical ridge that extends westward from the southwestern Gulf 
of Mexico across central Mexico to just north of the system. The 
ridge is expected to build steadily westward over the next few 
days, resulting in the cyclone turning westward on Tuesday and then 
moving west-southwestward on Wednesday and Thursday. The HHC track 
forecast follows the overall trend of the consensus models TVCE 
and HCCA, but lies along the southern edge of the guidance envelope 
in anticipation of the system weakening and becoming a shallow 
cyclone by early Tuesday, after which it should be steered more by 
the low-level easterly to northeasterly trade-wind flow

Recent satellite trends suggest that the depression currently is not 
far from tropical storm status, and SHIPS intensity data indicate 
that the deep-layer shear is favorable for some additional 
strengthening. However, shear analyses from UW-CIMSS reveal that 
moderate southwesterly to westerly mid-level shear is currently 
displacing the convection to the northeast and east of the  
low-level center, and this unfavorable pattern is expected to hinder 
overall development. As a result, the cyclone is only forecast to 
become a low-end tropical storm before significant deep-layer shear 
begins to adversely affect the system by late Monday. During the 
period Tuesday through Thursday, very hostile wind shear in 
conjunction with sea-surface temperatures cooling to near 26-deg C 
beneath the cyclone should result in the system degenerating into a 
remnant low, with dissipation expected by early Friday, if not 
sooner. The official intensity forecast is similar to but slightly 
higher than the consensus models IVCN and HCCA for the next 24 
hours, and then closely follows those models thereafter.
INIT  09/0900Z 13.8N 107.7W   30 KT  35 MPH
 12H  09/1800Z 14.5N 108.1W   35 KT  40 MPH
 24H  10/0600Z 15.3N 108.6W   35 KT  40 MPH
 36H  10/1800Z 15.8N 109.2W   30 KT  35 MPH
 48H  11/0600Z 16.1N 110.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  11/1800Z 16.2N 110.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  12/0600Z 16.2N 112.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  13/0600Z 15.8N 115.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/0600Z...DISSIPATED
Forecaster Stewart