[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 032045
TCDAT4

Hurricane Eta Discussion Number  13
NWS National Hurricane Center Miami FL       AL292020
400 PM EST Tue Nov 03 2020

After meandering just offshore of the coast of northeastern
Nicaragua this morning, the eye of Eta began moving westward and is
currently making landfall along the coast of Nicaragua about 15 n
mi south of Puerto Cabezas.  Visible satellite imagery has shown
that the eye of Eta became larger as the hurricane completed an
eyewall replacement.  A blend of the earlier aircraft data and
recent subjective and objective satellite intensity estimates
yields an initial intensity of 120 kt. Eta remains an extremely
dangerous category 4 hurricane, and is likely producing a very high
storm surge and catastrophic damage.  In addition, the slow-moving
system is likely to produce torrential rains and inland flooding
that will continue to be an extremely serious threat over the next
couple of days.

Once the eyewall is fully onshore, rapid weakening should begin,
and Eta is forecast to weaken to a tropical storm by early
Wednesday, and become a tropical depression Wednesday night.
Although it appears unlikely that the surface circulation will
remain intact while Eta moves over Central America, most of the
global model guidance indicates that the low-level vorticity center
will emerge over the northwestern Caribbean Sea within 60-72 hours.
At that time, the system is forecast to interact with an
upper-level trough over the northern Gulf of Mexico, and
re-development later in the period appears likely with some
strengthening by days 4 and 5.  Due the interaction with the
upper-level trough, the system is likely to have a more hybrid or
subtropical structure late in the period.

Eta appears to be moving westward at about 4 kt.  A ridge to the
north of the hurricane should steer the system westward to west-
northwestward at a faster forward speed over the next couple of
days.  By late in the week, Eta or its remnants should turn
northward, and then northeastward around the southeastern portion
of the aforementioned trough.  Although the 12z GFS and ECMWF
models are in general agreement on the overall forecast scenario,
there are large differences in how fast Eta accelerates
northeastward.  The NHC track forecast is near the HFIP corrected
consensus model which lies between the faster GFS and slower ECMWF
solutions. There is still significant spread among the various
global models and the ensembles, which results in a higher than
normal level of uncertainty regarding the details of the track and
intensity forecast later in the period.

Key Messages:

1. Catastrophic wind damage is expected during the next few hours
as Eta's eyewall moves onshore along the northeastern coast of
Nicaragua.

2. A catastrophic and life-threatening storm surge, along with
destructive waves, are expected along portions of the northeastern
coast of Nicaragua near and to the north of where the center has
crossed the coast.  Water levels could reach as high as 14 to 21
feet above normal tide levels in some parts of the hurricane
warning area.

3. Through Friday evening, 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, El Salvador, southern Haiti, and the
Cayman Islands.

4. Eta is forecast to regain tropical storm strength as it moves
across portions of Cuba and approaches southern Florida this
weekend.  While it is too soon to determine the exact timing,
magnitude, and location of possible impacts from wind and rainfall,
interests in Cuba, southern Florida and the Florida Keys should
monitor the progress of Eta through the week.


FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 13.8N  83.5W  120 KT 140 MPH
 12H  04/0600Z 13.8N  84.2W   75 KT  85 MPH...INLAND
 24H  04/1800Z 14.1N  85.5W   40 KT  45 MPH...INLAND
 36H  05/0600Z 14.7N  87.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  05/1800Z 15.4N  88.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  06/0600Z 16.3N  88.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  06/1800Z 17.0N  87.7W   30 KT  35 MPH...OVER WATER
 96H  07/1800Z 20.0N  83.5W   40 KT  45 MPH
120H  08/1800Z 24.0N  80.5W   45 KT  50 MPH

$$
Forecaster Brown
This weather bulletin was brought to you by:
www.nashvilleweather.net