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Tropical Depression Twenty-One-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP212020
300 PM MDT Tue Nov 17 2020
 
Visible satellite imagery and recent ASCAT data indicate that the 
circulation of the area of low pressure located well south-southwest 
of Baja California has become better defined today. The associated 
convective activity has also become organized in a band around the 
western and southwestern portions of the circulation. Therefore, 
the system is being classified as a tropical depression with winds 
of 30 kt, as indicated by the scatterometer data and a T2.0 (30 kt) 
Dvorak classification from TAFB.

The depression is currently located over SSTs of around 28 deg C, 
and within a low shear environment.  These conditions are conducive 
for strengthening, but the surrounding mid-level environment is 
fairly dry which is likely to limit intensification.  Most of the 
intensity guidance calls for the system to become a short-lived 
tropical storm, and so does the official forecast.  After 24 hours, 
increasing upper-level westerly winds, cooler SSTs, and even less 
favorable thermodynamic conditions should cause the cyclone to 
weaken.  The system is likely to become a remnant low in about 48 
hours, and the global models show it degenerating into a trough of 
low pressure in 60-72 hours, which is also indicated in the NHC 
forecast. 

The initial motion estimate is 285/11 kt.  A mid-level ridge that 
extends westward from northern Mexico over the eastern Pacific 
should steer the system west-northwestward for the next couple of 
days.  After that time, the cyclone is likely to turn more westward 
as it weakens and is steered by the low-level trade wind flow.  The 
track guidance is in good agreement, and the NHC forecast is near 
the middle of the guidance envelope. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/2100Z 15.2N 113.3W   30 KT  35 MPH
 12H  18/0600Z 15.6N 114.9W   35 KT  40 MPH
 24H  18/1800Z 16.2N 117.0W   35 KT  40 MPH
 36H  19/0600Z 16.7N 119.1W   30 KT  35 MPH
 48H  19/1800Z 17.1N 121.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  20/0600Z 17.2N 123.3W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  20/1800Z...DISSIPATED
 
$$
Forecaster Brown
 
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