[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 110254
TCDAT4

Tropical Storm Eta Discussion Number  43
NWS National Hurricane Center Miami FL       AL292020
1000 PM EST Tue Nov 10 2020

Eta has been maintaining a large cluster of deep convection over the
northeastern portion of its circulation this evening. NWS Doppler
radar data from Key West is showing a well-defined mid-level
circulation in that area, but NOAA reconnaissance aircraft data so
far still indicates that the low-level center is located near the
southwestern portion of the convective mass.  However, it is
possible that the center will re-form closer to the mid-level
center overnight.  The plane has measured peak 850-mb flight-level
winds of 67 kt, and SFMR winds of 52 kt.  Based on these data the
initial intensity has been raised to 55 kt.

Eta's initial motion is a somewhat uncertain 015/8 kt. There has
once again been a significant eastward shift in the 18Z dynamical
model guidance, with the GFS, HWRF, and UKMET models all showing a
faster north-northeastward motion toward the Florida west coast.  As
a result, the NHC forecast has again been shifted eastward and lies
near the TVCA multi-model consensus through 36 h.  After that time,
the NHC track is slower and west of the bulk of the consensus aids
as the ECMWF still shows Eta weakening and lingering near the
Florida Big Bend.  While the new track has been shifted
significantly eastward after 36 h or so, some continuity with the
previous forecast is maintained with a slower northward motion
between the two model camps. While there is increasing confidence in
the faster north-northeastward motion in the short-term, there is
still considerable uncertainty by 48 hours and beyond, and further
adjustments to the track forecast could be required overnight.

Some additional strengthening is likely overnight and Wednesday
while Eta remains over warm water and within an area of
low-to-moderate vertical wind shear.  If the center re-forms closer
to the deep convection, Eta could re-gain hurricane status within
the next 12-24 hours.  After that time, increasing southwesterly
shear and cooler SSTs are likely to result in some weakening.  The
updated NHC intensity forecast is close to the SHIPS and HCCA model
guidance.

Given the eastward shift in the track and the expected faster motion
of Eta, a Tropical Storm Warning and Storm Surge Watch are being
issued for a portion of the west coast of Florida.  Additional
warnings could be required early Wednesday.

Key Messages:

1. Life-threatening storm surge is possible Thursday along portions
of the Florida Gulf Coast from Bonita Beach to Steinhatchee 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 by late Wednesday along
portions of the Florida Gulf Coast from Bonita Beach to Suwanee
River, and are possible Thursday from Suwannee River to Aucilla
River. Interests elsewhere along the Florida Gulf Coast should
monitor the progress of Eta, as additional watches and warnings may
be needed overnight.

3. Heavy rainfall from Eta will continue across western Cuba and
south Florida through tonight, and spread northward across portions
of west Florida, the eastern Florida Panhandle, and north Florida
Wednesday through Friday. Additional flash and urban flooding is
possible in south Florida tonight, especially across previously
inundated areas, and eventually across portions of west Florida, the
eastern Florida Panhandle, and north Florida Wednesday through
Friday.

FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 23.8N  84.5W   55 KT  65 MPH
 12H  11/1200Z 25.0N  84.3W   60 KT  70 MPH
 24H  12/0000Z 26.5N  84.0W   60 KT  70 MPH
 36H  12/1200Z 27.7N  83.7W   55 KT  65 MPH
 48H  13/0000Z 28.8N  83.1W   45 KT  50 MPH
 60H  13/1200Z 29.7N  82.5W   35 KT  40 MPH...INLAND
 72H  14/0000Z 30.3N  82.3W   30 KT  35 MPH...INLAND
 96H  15/0000Z 30.8N  82.3W   30 KT  35 MPH...INLAND
120H  16/0000Z...DISSIPATED

$$
Forecaster Brown
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