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Tropical Depression Twenty-One-E Discussion Number   2
NWS National Hurricane Center Miami FL       EP212020
800 PM MST Tue Nov 17 2020
 
Conventional satellite imagery and an earlier AMSR2 microwave pass 
showed curved bands developing over the western portion of the 
cyclone, although deep convection remains rather limited near the 
depression's surface center.  Subjective satellite intensity 
estimate T-numbers haven't changed during the past 6 hours and the 
initial intensity is held at 30 kt for this advisory. 
 
The HCCA and IVCN multi-model intensity aids along with the LGEM 
model indicate that the depression will strengthen to a low-end 
tropical storm during the next 12-24 hrs and the NHC forecast 
continues to show this trend.  Afterward, modest west-southwesterly 
shear, cooler oceanic temperatures, and the presence of a very dry 
and stable air mass should cause the cyclone to weaken and 
degenerate to a remnant low in 2 days.  The deterministic guidance 
agrees that the depression will open up into a trough of low 
pressure in 4 days, or less.  This is also reflected in the 
official intensity forecast.

The initial motion is estimated to be west-northwestward, or 285/10 
kt in the mid-tropospheric steering current provided by high 
pressure anchored to the north of the cyclone.  The depression is 
expected to continue in this general motion through Thursday.  
Through the remaining forecast period, the depression is forecast 
to turn westward in the low-level easterly flow as a shallow, or 
vertically limited cyclone.  The track forecast is basically an 
update of the previous one and is close to the HCCA and TVCE 
consensus models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  18/0300Z 15.5N 114.3W   30 KT  35 MPH
 12H  18/1200Z 15.9N 115.9W   35 KT  40 MPH
 24H  19/0000Z 16.5N 118.0W   35 KT  40 MPH
 36H  19/1200Z 16.9N 120.0W   30 KT  35 MPH
 48H  20/0000Z 17.3N 122.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  20/1200Z 17.3N 124.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  21/0000Z...DISSIPATED
 
$$
Forecaster Roberts
 
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