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Tropical Depression Eta Discussion Number  24
NWS National Hurricane Center Miami FL       AL292020
900 AM CST Fri Nov 06 2020
 
Satellite imagery indicates that Eta is producing organized
convection in a large band over its northern and eastern
quadrants, with the center located just off the coast of Belize
near the western end of the band.  These data, along with surface
observations, also show that the circulation is elongated.  The
initial intensity remains 30 kt in agreement with a satellite
intensity estimate from TAFB.  An Air Force Reserve Hurricane
Hunter aircraft is scheduled to investigate Eta this afternoon,
and a NOAA flight is scheduled for this evening. 
 
The initial motion is a somewhat uncertain 025/6 kt.  A developing 
mid- to upper-level trough over the Gulf of Mexico is expected to 
steer Eta northeastward for the next 48 h or so with an increase in 
forward speed. Between 48-72 h, the trough is forecast to become a 
closed low near south Florida and western Cuba, with Eta expected 
to turn northwestward around and into the low.  After 72 h, the 
merged system is likely to move slowly west-northwestward.  While 
the guidance is in good agreement on the synoptic evolution, there 
are a lot of differences in the track forecast details in terms of 
both the heading and the forward speed, with the GFS-based guidance 
tending to be to the east and north of the UKMET/ECMWF/Canadian.  
Overall, the consensus models have shifted a little to the east and 
north since the last advisory, and the new forecast track is also 
nudged in those directions.

Eta will move over the warm waters of the northwestern Caribbean 
during the next 48 h or so, and the upper-level divergence is 
forecast to be quite strong.  This should allow some strengthening, 
although this is likely to be slowed by 20-30 kt of southwesterly 
vertical wind shear.  The intensity forecast for this part of the 
cyclone's life is similar to the previous forecast and lies a bit 
below the bulk of the intensity guidance.  Between 48-72 h , Eta may 
take on at least some subtropical cyclone characteristics as it 
merges with the mid- to upper-level low.  During this process, some 
of the guidance suggests the possibility that a tight inner wind 
core may develop.   There is a chance that during this time that Eta 
could regain hurricane strength, although this would be an intensity 
above the current guidance.  After 72 h, dry air entrainment is 
expected to cause the cyclone to weaken.
 
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.

The new forecast track requires a Tropical Storm Warning for the 
Cayman Islands at this time, and a Tropical Storm Watch for 
portions of Cuba.  Watches may be required for portions of south 
Florida and the Florida Keys later today or tonight.
 
 
Key Messages:

1. Rainfall associated with Eta will continue to result in 
catastrophic, life-threatening flash flooding and river flooding 
across portions of Central America, along with landslides in areas 
of higher terrain.  Significant, life-threatening flash flooding and 
river flooding is possible in the Cayman Islands and Cuba.  Flash 
flooding and urban flooding is also possible for Jamaica and 
southeast Mexico.

2. This weekend Eta is expected to bring tropical storm conditions 
to portions of the Cayman Islands, where a Tropical Storm Warning is 
in effect. Tropical storm conditions possible in portions of western 
and central Cuba, where a Tropical Storm Watch is in effect. 

3. There is an increasing risk of impacts from wind and flash and 
urban flooding due to heavy rainfall in portions of southern 
Florida, the Florida Keys and portions of the Bahamas this weekend 
and early next week. Tropical Storm or Hurricane Watches will likely 
be issued later today or tonight for a portion of this area.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/1500Z 17.8N  87.0W   30 KT  35 MPH
 12H  07/0000Z 18.6N  85.7W   35 KT  40 MPH
 24H  07/1200Z 19.7N  83.5W   40 KT  45 MPH
 36H  08/0000Z 21.0N  81.4W   45 KT  50 MPH
 48H  08/1200Z 22.7N  79.9W   50 KT  60 MPH...INLAND
 60H  09/0000Z 24.1N  80.0W   55 KT  65 MPH...OVER WATER
 72H  09/1200Z 25.0N  81.2W   55 KT  65 MPH
 96H  10/1200Z 25.5N  84.0W   50 KT  60 MPH
120H  11/1200Z 26.5N  85.0W   50 KT  60 MPH
 
$$
Forecaster Beven
 
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