[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 060254
TCDAT4

Tropical Depression Eta Discussion Number  22
NWS National Hurricane Center Miami FL       AL292020
900 PM CST Thu Nov 05 2020

Eta has not become any better organized during the past several
hours, and a specific center is hard to locate.  It is estimated
that the center is near a growing area of deep convection located
east of the Belize. While it is possible the system has degenerated
into a broad low or trough, there isn't enough evidence to break
continuity, so Eta remains a 30-kt tropical depression on this
advisory.  Scatterometer data will probably come in overnight to
provide a better look at the low-level circulation.

The initial motion is an uncertain 360/7 kt.  Eta should move
northeastward on Friday around a developing mid- to upper-level
trough over the Gulf of Mexico, then turn northward on Sunday and
west-northwestward early next week as the trough cuts off into a
closed low.  The details of this sinuous path, however, are pretty
fuzzy and small differences in the tropical cyclone position could
lead to large errors down the line. The most notable change tonight
is that the GFS-based guidance (including HWRF and HMON) have
generally shifted northward and faster.  The new forecast is moved
eastward near Cuba, and then northward near the Florida Keys in
response to this guidance and the 18Z ECMWF. It should be stressed
this is a fairly uncertain forecast due to the strong trough
interaction.

Eta should begin to strengthen on Friday due to the low-level
circulation forecast to become better defined in a fairly conducive
environment.  While vertical wind shear could increase this weekend,
it is expected that upper-level divergence and trough dynamics will
overwhelm the negative factors and cause continued intensification
until the system reaches Cuba. The new forecast is raised from the
previous one, but still lies below the NOAA corrected-consensus
model HCCA. There isn't a lot of agreement on the intensity after
Cuba, however, and the forecast hinges on how tropical it will
remain after the trough interaction.  The new forecast flattens out
the intensity near Florida as a compromise between the various
solutions, but I don't have much confidence in the forecast at that
range.

Key Messages:

1. Through Monday morning, heavy rainfall from Eta will lead to
catastrophic, life-threatening flash flooding and river flooding
across portions of Central America, along with landslides in areas
of higher terrain.  Flash and river flooding is also possible across
Jamaica, southeast Mexico, the Cayman Islands and western Cuba.

2. Eta is forecast to regain tropical storm strength over the
northwestern Caribbean Sea on Friday. Although the details of
the future track and intensity of Eta are uncertain, there is an
increasing risk of impacts from wind and rainfall in portions of the
Cayman Islands, Cuba, southern Florida and the Florida Keys and the
northwestern Bahamas this weekend and early next week.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 16.6N  87.8W   30 KT  35 MPH
 12H  06/1200Z 17.5N  87.2W   35 KT  40 MPH
 24H  07/0000Z 18.8N  85.4W   40 KT  45 MPH
 36H  07/1200Z 19.7N  83.2W   45 KT  50 MPH
 48H  08/0000Z 20.8N  81.0W   55 KT  65 MPH
 60H  08/1200Z 22.6N  79.8W   50 KT  60 MPH...INLAND
 72H  09/0000Z 24.2N  80.4W   55 KT  65 MPH...OVER WATER
 96H  10/0000Z 25.0N  83.0W   55 KT  65 MPH
120H  11/0000Z 25.5N  85.0W   55 KT  65 MPH

$$
Forecaster Blake
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