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Tropical Depression ETA

Tropical Depression Eta Discussion Number  21
NWS National Hurricane Center Miami FL       AL292020
300 PM CST Thu Nov 05 2020

The low-level circulation of Eta has become disorganized to the 
point that the system more resembles a remnant low than a tropical 
cyclone.  However, the system continues to produce convection in an 
area just north and northwest of the estimated center position, as 
well as in a cluster well to the northeast.  Based on this, and the 
expectation that the system will start re-developing during the next 
several hours as it moves back over water, Eta is maintained as a 
tropical depression for this advisory.  The initial intensity is 
increased to 30 kt based on scatterometer data, with those winds 
occuring well to the northeast of the center.

The center appears to be just south of the northwestern coast of 
Honduras, and the initial motion is an uncertain 330/7.  During the 
next 24 h, Eta should recurve northeastward in southwesterly flow 
between a ridge over the central Caribbean and a developing mid- to 
upper-level trough over the central Gulf of Mexico.  This motion 
should persist through about 72 h.  After that, the trough is 
forecast to become a closed low in the vicinity of western Cuba, 
with Eta turning to the west-northwest as it interacts or merges 
with the low.  While the models are in good agreement with the 
synoptic pattern, they are in poor agreement on the details of the 
track.  The forecast tracks show possible landfalls in Cuba 
anywhere between 77W-83W, and after the turn some of the tracks are 
as far north as southern Florida while other stay over Cuba.  In 
addition, there is a significant speed difference between the 
faster GFS/HWRF/HMON and the slower Canadian/ECMWF/UKMET.  The 
low-confidence official forecast compromises between these various 
extremes and is not changed much from the previous forecast.

Little change in strength is expected during the next 12 h or so as 
Eta starts to re-organized over water.  After that, gradual 
strengthening is expected until the system reaches Cuba in about  
72 h, with the main limiting factor being increasing southwesterly 
shear during that time.  From 72-120 h, there is a possibility that 
Eta will take on subtropical or hybrid characteristics as it 
interacts with the developing upper-level low.  The intensity 
forecast will be held at 50 kt during that time due to this 
interaction.  The new intensity forecast has only minor tweaks from 
the previous forecast.  However, it lies below the bulk of the 
intensity guidance for the first 60 h and above the bulk of the 
guidance from 72-120 h.

The new forecast track, intensity, and wind radii require a 
Tropical Storm Watch for the Cayman Islands at this time.  A 
Tropical Storm Watch will likely be required for portions of Cuba 
later tonight or on Friday.
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 in a day or so. Although the details of 
the future track and intensity of Eta are 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 this 
weekend and early next week.
INIT  05/2100Z 15.7N  87.7W   30 KT  35 MPH...INLAND
 12H  06/0600Z 16.4N  87.8W   30 KT  35 MPH...OVER WATER
 24H  06/1800Z 18.1N  86.3W   35 KT  40 MPH
 36H  07/0600Z 19.1N  84.8W   40 KT  45 MPH
 48H  07/1800Z 20.1N  83.1W   45 KT  50 MPH
 60H  08/0600Z 21.3N  81.5W   45 KT  50 MPH
 72H  08/1800Z 22.4N  80.1W   50 KT  60 MPH...INLAND
 96H  09/1800Z 23.5N  82.0W   50 KT  60 MPH...OVER WATER
120H  10/1800Z 24.5N  84.5W   55 KT  65 MPH
Forecaster Beven