[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 112057
TCDAT4

Tropical Storm Eta Discussion Number  46
NWS National Hurricane Center Miami FL       AL292020
400 PM EST Wed Nov 11 2020

Almost as quickly as Eta regained hurricane status, it then lost it
shortly thereafter.  Dry air entrainment eroded most of the
significant convection around the center this afternoon until a
slight resurgence recently developed. However, the overall
convective pattern has changed little with the bulk of the
convection located primarily northeast through southeast of the
center.  The last recon pass through Eta showed that the central
pressure had increased to 990 mb.  Recent Doppler velocities of
around 70 kt between 5000-6000 ft east of the center supports
surface winds of about 56-58 kt, so the 1800Z intensity of 60 kt
will also be kept for the 21Z advisory intensity.

The initial motion estimate is northward, or 010/10 kt.  Eta is
expected to move between north and north-northeastward tonight as
the cyclone rounds the western periphery of a deep-layer ridge to
the east.  The new NHC model guidance remains in excellent
agreement on Eta turning northeastward after 12 hours, with the
cyclone making landfall along the western coast of the northern
Florida peninsula in the region from Cedar Key to Crystal River.
Eta is then expected to accelerate northeastward across northern
Florida as a weakening tropical cyclone, and emerge over the western
Atlantic by late Thursday morning or early afternoon.  By 72 hours,
if not sooner, Eta is forecast to merge with a frontal system off of
the southeastern United States.  The new official track forecast is
similar to the previous advisory track, and lies close to a blend of
the consensus models TVCN, NOAA-HCCA, and FSSE.

Eta will be moving over progressively cooler waters during the next
12 hours, with SSTs decreasing to less than 25 deg C just before the
cyclone makes landfall along the Florida coast.  The cooler waters,
in conjunction with continued dry air entrainment and increasing
westerly vertical wind shear, should result in at least gradual
weakening until landfall occurs, followed by more rapid weakening as
Eta moves over the northern Florida peninsula.  Although the
official forecast calls for Eta to be a tropical storm as it nears
the northeast coast of Florida, a Tropical Watch or Warning are not
required at this time since any tropical-storm-force will likely be
occurring over water and not inland or along the coast due to Eta's
poor convective structure that is expected at that time. Eta is
forecast to degenerate into a remnant low by 60 hours due to even
stronger wind shear, and dissipate by 72 hours due to frontal
interaction.

Key Messages:

1. There is a danger of life-threatening storm surge along portions
of the Florida Gulf Coast from Bonita Beach to Suwannee River,
including Tampa Bay and Charlotte Harbor.  Residents in this area
should follow any advice given by local officials.

2. Tropical-storm-force winds are expected this evening and tonight
along portions of the Florida Gulf Coast from Bonita Beach to
Suwanee River, and are possible tonight and early Thursday from
Suwannee River to Aucilla River.  Interests elsewhere along the
Florida Gulf Coast should monitor the progress of Eta.

3. Heavy rainfall from Eta will continue to spread northward across
west and central Florida through Thursday.  Additional flash and
urban flooding will be possible in south Florida through Thursday,
especially across previously inundated areas.  Flash, urban, and
isolated minor river flooding are expected across portions of west
and north Florida through Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  11/2100Z 27.3N  83.6W   60 KT  70 MPH
 12H  12/0600Z 28.6N  83.1W   55 KT  65 MPH
 24H  12/1800Z 30.4N  81.5W   35 KT  40 MPH...INLAND
 36H  13/0600Z 32.0N  78.9W   30 KT  35 MPH...OVER WATER
 48H  13/1800Z 33.8N  75.2W   25 KT  30 MPH
 60H  14/0600Z 36.0N  69.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  14/1800Z...POST-TROP/EXTRATROP

$$
Forecaster Stewart
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