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Tropical Depression Sixteen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP162020
900 PM MDT Sat Sep 12 2020

The last few visible satellite images indicated convection growing 
closer to the center of a low pressure area that NHC has been 
tracking for the past few days.  Since the low was already 
well-defined this afternoon, the development of organized deep 
convection means that a tropical depression has formed.  The initial 
wind speed is set to 30 kt, which is a blend of the TAFB/SAB fixes 
and earlier ASCAT data.  The depression is embedded within a 
moderate easterly wind-shear environment, partially related to its 
position in the larger ITCZ/monsoon trough structure.  Global model 
guidance is in reasonable agreement on the large-scale circulation 
becoming focused on the new tropical cyclone and a slight relaxation 
of the shear during the next couple of days.  This change should 
lead to gradual intensification, and the new forecast is between the 
model consensus and the corrected-consensus aids.  Beyond 2-3 days, 
decreasing SSTs and increasing dry air entrainment should promote 
weakening, and that is reflected below.

The initial motion estimate is an uncertain northwestward or 315/08 
kt.  A mid-level ridge is forecast to build westward, causing the 
cyclone to move west-northwestward for a few days after the weekend. 
 A westward turn is forecast at long range due to the shallow 
cyclone feeling the low-level ridge.  One big uncertainty with this 
forecast is how it interacts with the larger ITCZ/monsoon trough 
circulation, including the remnants of Invest 91E.  For now, it is 
assumed that only a slight slow down occurs as the depression 
becomes the dominant circulation in the area, and the forecast is 
more consistent with the GFS- or UKMET-based guidance.  However, a 
slower ECMWF-like solution is also possible, but is being given less 
weight at this time.

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 16.7N 112.9W   30 KT  35 MPH
 12H  13/1200Z 17.5N 113.8W   35 KT  40 MPH
 24H  14/0000Z 18.3N 115.4W   40 KT  45 MPH
 36H  14/1200Z 18.9N 116.9W   45 KT  50 MPH
 48H  15/0000Z 19.5N 118.5W   50 KT  60 MPH
 60H  15/1200Z 20.0N 119.9W   55 KT  65 MPH
 72H  16/0000Z 20.5N 121.0W   55 KT  65 MPH
 96H  17/0000Z 21.5N 123.5W   45 KT  50 MPH
120H  18/0000Z 21.5N 126.0W   30 KT  35 MPH
 
$$
Forecaster Blake
 
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