[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 100839
TCDAT4

Tropical Storm Eta Discussion Number  40
NWS National Hurricane Center Miami FL       AL292020
300 AM CST Tue Nov 10 2020

There hasn't been a lot of change to the cloud pattern of Eta
overnight, with the center apparently located on the northwestern
side of a small central dense overcast.  Scatterometer data from
earlier indicated 35-40 kt winds, and with the typical undersampling
from that instrument, along with consensus 45-kt estimates from
TAFB/SAB, so Eta's initial wind speed is kept at 45 kt.  A NOAA
Hurricane Hunter aircraft should be in the storm this morning.

Eta is forecast to be in a low-to-moderate shear environment over
warm SSTs for the next couple of days.  Gradual strengthening is
expected through early Thursday, with the main restrictive factor
being nearby dry air. After that time, increasing shear and
drier mid-level air are likely to cause Eta to weaken. The rate
of this weakening is pretty uncertain, and a lot depends on how
much Eta can re-intensify over the next couple of days. The new
forecast is similar to the previous one, which is quite close to
the consensus guidance.

The storm has basically become stationary overnight.  Eta should
drift to north today due to steering flow changes with a nearby
upper-level low losing influence while ridging east of Florida
builds southward.  A slow northward track is then anticipated for a
couple of days over the east-central Gulf of Mexico in this flow
pattern.  Beyond that time, model guidance is in rather poor
agreement, ranging from a stronger system moving faster to the
northeast due to broad troughing over the south-central United
States, to a weaker tropical cyclone getting caught under a narrow
ridge over the Gulf of Mexico and turning west-southwestward.  Since
the new forecast expects Eta to be weakening, the NHC forecast will
be west of the consensus and west of the previous track.  I have
little confidence in the long-range track forecast due to its
seeming dependence on the intensity, and the wide spread in the
guidance.

Key Messages:

1. Heavy rainfall from Eta will continue across western Cuba and
South Florida today and tonight.  Additional flash and urban
flooding, especially across previously inundated areas, will be
possible in South Florida. Flash and urban flooding will also be
possible for western Cuba.

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


FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 22.9N  85.5W   45 KT  50 MPH
 12H  10/1800Z 23.1N  85.6W   50 KT  60 MPH
 24H  11/0600Z 24.0N  85.6W   55 KT  65 MPH
 36H  11/1800Z 25.0N  85.4W   60 KT  70 MPH
 48H  12/0600Z 26.0N  85.3W   60 KT  70 MPH
 60H  12/1800Z 26.8N  85.3W   50 KT  60 MPH
 72H  13/0600Z 27.3N  85.4W   40 KT  45 MPH
 96H  14/0600Z 28.8N  86.5W   35 KT  40 MPH
120H  15/0600Z 30.0N  87.0W   30 KT  35 MPH

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