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Tropical Depression ETA

Tropical Depression Eta Discussion Number  23
NWS National Hurricane Center Miami FL       AL292020
300 AM CST Fri Nov 06 2020
Although satellite images and surface observations suggest that the
circulation of Eta is elongated, deep convection has been increasing
near and over the center during the past several hours.
Unfortunately, the ASCAT scatterometer missed the region where Eta
is located, so there has not been much additional data to analyze
the structure and intensity of the cyclone.  The initial wind speed
is held at 30 kt based on a 2.0/30 kt Dvorak classification from
TAFB. The NOAA and Air Force Hurricane Hunters are scheduled to
investigate Eta later today, and that data will be helpful in
analyzing the cyclone.
The depression is moving northward at 7 kt.  Eta is forecast to turn 
northeastward later today, and accelerate slightly in that direction 
through Saturday in response to a mid- to upper-level trough that is 
expected to slide southeastward across the Gulf of Mexico.  This 
motion should take Eta to the west of the Cayman Islands on Saturday 
and then across Cuba Saturday night or Sunday.  Around the time Eta 
is forecast to be near Cuba, the models show the storm slowing down 
and turning northwestward or westward as the trough cuts off, and 
Eta pivots around the north side of that cut off low.  This change 
in the storm motion should bring Eta near or over the Florida Keys 
and south Florida late in the weekend and early next week.  The 
details in the location and timing of where Eta and the mid- to 
upper-level low interact will be very important to the exact track 
of Eta for south Florida and the Florida Keys. The new track 
forecast is a touch to the north of the previous one when Eta is 
expected to be near Florida, to be in better agreement with the 
latest consensus aids.
The cyclone is currently over warm water, in a moist environment,
and will be moving into a region of upper-level diffluence as it
tracks across the northwestern Caribbean Sea.  These conditions
should allow for thunderstorms to organize near the center and for
the cyclone to gradually intensify during the next couple of days.
However, rapid intensification seems unlikely given the broad
structure of Eta.  The models show an increase in shear and some
dry air entraining into the circulation around the time it nears
Cuba this weekend, which in combination with land interaction could
limit additional strengthening by then.  The intensity forecast for
the 72-120 hour period is more complicated as it will depend on the
trough interaction mentioned above.  Most of the intensity models
show Eta holding steady in strength after its passage over Cuba,
and the NHC forecast does the same.
The wind field of Eta is expected to increase in size during the
next few days, and the cyclone will likely produce a large area of
tropical-storm-force winds on its north side when it is near Cuba,
the Florida Keys, and southern Florida.
Key Messages:
1. Through Monday morning, 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, the Cayman Islands and western Cuba.
2. Eta is forecast to regain tropical storm strength over the
northwestern Caribbean Sea later today. Although the details of
the future track and intensity of Eta are still uncertain, there is
an increasing risk of impacts from wind and rainfall in portions of
the Cayman Islands, Cuba, southern Florida and the Florida Keys and
the northwestern Bahamas this weekend and early next week.
INIT  06/0900Z 17.3N  87.4W   30 KT  35 MPH
 12H  06/1800Z 18.0N  86.6W   35 KT  40 MPH
 24H  07/0600Z 19.1N  84.5W   40 KT  45 MPH
 36H  07/1800Z 20.2N  82.2W   45 KT  50 MPH
 48H  08/0600Z 21.8N  80.3W   50 KT  60 MPH
 60H  08/1800Z 23.5N  79.9W   55 KT  65 MPH
 72H  09/0600Z 24.6N  80.7W   55 KT  65 MPH
 96H  10/0600Z 25.1N  83.7W   55 KT  65 MPH
120H  11/0600Z 25.9N  85.0W   55 KT  65 MPH
Forecaster Cangialosi