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Tropical Depression Seventeen-E Discussion Number 4
NWS National Hurricane Center Miami FL EP172020
900 AM MDT Mon Sep 21 2020
Although the circulation still appears to be elongated, the
depression has become a little better organized during the past
several hours, with the low-level center closer to the large mass
of convection in the southwestern semicircle. Satellite intensity
estimates from TAFB and SAB are 30 kt, so the initial intensity is
nudged upward to 30 kt.
The initial motion is now 290/12. The depression is being steered
by a large low- to mid-level ridge to the north and northwest, and
this ridge is forecast to persist through the forecast period. The
track guidance shows that the system should continue west-
northwestward for about 36 h, followed by a westward motion through
120 h. The track guidance is very tightly clustered, and the new
forecast track is near the various consensus models.
Current indications are that the current easterly shear should
subside a little during the next 24-36 h, and this should allow the
system to become a tropical storm. As noted in the previous
advisory, the intensity after 36 h will be strongly dependent on
where the center is in relation to the strong sea surface
temperature gradient. The new intensity forecast is similar to the
previous forecast based on the forecast track keeping the
system over 25-26C water temperatures through 120 h. However, any
motion north of the forecast track would bring the center over
colder water and lead to a system weaker than forecast, while any
motion south of the track would keep it over warmer water and
possibly allow the cyclone to become a hurricane. As might have
guessed, this is a low confidence intensity forecast.
FORECAST POSITIONS AND MAX WINDS
INIT 21/1500Z 17.0N 112.0W 30 KT 35 MPH
12H 22/0000Z 17.8N 113.7W 35 KT 40 MPH
24H 22/1200Z 18.8N 115.9W 40 KT 45 MPH
36H 23/0000Z 19.5N 118.0W 45 KT 50 MPH
48H 23/1200Z 20.0N 119.9W 50 KT 60 MPH
60H 24/0000Z 20.3N 121.7W 55 KT 65 MPH
72H 24/1200Z 20.5N 123.4W 60 KT 70 MPH
96H 25/1200Z 20.5N 126.5W 60 KT 70 MPH
120H 26/1200Z 20.5N 130.5W 50 KT 60 MPH
$$
Forecaster Beven
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