[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 090254
TCDAT4

Tropical Storm Eta Discussion Number  35
NWS National Hurricane Center Miami FL       AL292020
1000 PM EST Sun Nov 08 2020

Although deep convection has waned near the center of Eta since
this afternoon, radar imagery continues to show a ring of
low-topped convection around the center, with some deep convection
returning over the northeastern portion of the circulation. Doppler
radar velocities of 64-68 kt around 5000 ft, and recent NOAA
reconnaissance aircraft observations support maintaining the 55 kt
initial intensity.  The aircraft reported a minimum pressure of
around 993 mb.

Since Eta has a fairly large radius of maximum winds and a dry slot
that has wrapped into the inner core, it appears that any short-term
strengthening should be slow to occur.  As a result, the new NHC
intensity forecast calls for a little less strengthening until Eta
moves into the southeastern Gulf of Mexico in about 24 hours.
Regardless of whether Eta becomes a hurricane near the Florida Keys,
there is little difference in impacts between a 55-to-60-kt
tropical storm and a 65-kt hurricane.  After 24 hours, Eta is
forecast to move over warmer sea surface temperatures in the
southeastern Gulf of Mexico and the vertical shear is forecast to
decrease.  This is expected to allow for some strengthening and Eta
is forecast re-gain hurricane strengthen by Tuesday. Gradual
weakening is predicted between 72-120 hours due to increasing
southwesterly shear and the entrainment of dry mid-level air.  The
updated NHC intensity forecast is near the SHIPS/LGEM models during
the first couple of days, and in good agreement with the HFIP
corrected consensus model thereafter.

Eta has turned northwestward this evening around the north side
of a cut-off low located just south of western Cuba.  The tropical
cyclone should turn west-northwestward to westward overnight, and
a southwestward motion is expected on Tuesday as Eta pivots
around the upper-low. In 36-48 h, Eta is expected to slow down and
possibly stall over the southeastern Gulf of Mexico as the steering
currents weakening. In about 3 days, Eta should begin moving
northward between a mid-level ridge over the western Atlantic and a
broad trough over the central United States.  The models that
maintain Eta has a deeper system show a faster northeastward motion
late in the period, whereas models that weaken  Eta slow its
northward progression by day 5.  The NHC track forecast lies near
the model consensus at 96 and 120 h, and is similar to the previous
advisory.

Key Messages:

1. Heavy rainfall from Eta will continue across portions of Cuba,
Jamaica, the Bahamas, and southern Florida and spread north into
central Florida. Life-threatening flash flooding is possible
across the urban areas of southeast Florida.  Significant,
life-threatening flash flooding and river flooding is possible in
Cuba, and significant flash and urban flooding are possible
for Jamaica, the Bahamas and the remainder of southern Florida,
along with potential minor river flooding in central Florida.

2. Hurricane conditions are expected tonight and early Monday
across portions of the Florida Keys, and are possible across
portions of southern Florida. Tropical storm conditions will extend
well away from Eta's center across the southern and central
portions of the Florida peninsula.

3. There is a danger of life-threatening storm surge in portions of
the Florida Keys.  Life-threatening storm surge is possible along
portions of the southern coast of the Florida peninsula.  Residents
in these areas should follow any advice given by local officials.

4. Eta is forecast to approach the Florida Gulf Coast later this
week as a tropical storm, and could bring impacts from rain, wind,
and storm surge. Interests in this area should monitor the progress
of Eta and updates to the forecast this week.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0300Z 24.6N  80.5W   55 KT  65 MPH
 12H  09/1200Z 24.9N  82.6W   60 KT  70 MPH
 24H  10/0000Z 24.2N  84.3W   60 KT  70 MPH
 36H  10/1200Z 23.6N  85.1W   65 KT  75 MPH
 48H  11/0000Z 24.2N  85.1W   65 KT  75 MPH
 60H  11/1200Z 25.5N  84.9W   65 KT  75 MPH
 72H  12/0000Z 26.6N  84.6W   60 KT  70 MPH
 96H  13/0000Z 28.2N  83.6W   55 KT  65 MPH
120H  14/0000Z 30.0N  82.0W   45 KT  50 MPH...INLAND

$$
Forecaster Brown
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