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Tropical Depression Eta Discussion Number  20
NWS National Hurricane Center Miami FL       AL292020
900 AM CST Thu Nov 05 2020

Eta remains disorganized this morning, as visible imagery suggests 
that the circulation has become elongated and that multiple 
vorticity centers may be present inside the larger cyclonic 
envelope.  The center position for this advisory, which is over 
northwestern Honduras, is closer to convection in the northwestern 
semicircle than was the case 6 h ago, so the cyclone is being 
maintained as a tropical depression at this time.
 
The initial motion is a somewhat uncertain 305/8 kt.  Eta or its 
remnants should move generally northwestward today, then turn 
northward tonight. From 24-72 h, the system should move 
northeastward in response to a developing mid- to upper-level 
trough over the central and eastern Gulf of Mexico.  From 72-120 h, 
the trough is forecast to become a closed mid- to upper-level low 
in the vicinity of western Cuba, with the center of Eta likely to 
turn west-northwestward on the north side of the low.  While the 
global models are in good agreement with this synoptic evolution, 
there is a significant spread in the forecast tracks between the 
fastest and farthest east GFS and the slowest and farthest west 
UKMET.  The new forecast track lies between these extremes in best 
overall agreement with the ECMWF and Canadian models, and it calls 
for the system to be near western Cuba and the Cayman Islands in 
60-72 h, and then be over the southeastern Gulf of Mexico by the 
end of the forecast period.

Little change in strength is expected before the center moves back 
over the Caribbean, but there is still a chance that Eta could 
degenerate to a remnant low pressure area later today if the 
convection does not persist.  Intensification is expected over the 
warm waters of the Caribbean Sea from 24-72 h, although this may be 
slowed by southwesterly shear caused by the aforementioned trough.  
As the trough cuts off near or over Eta between 72-120 h, the 
global models suggest that the system could strengthen while 
acquiring at least some subtropical or hybrid characteristics due 
to upper-level cold air entrainment.  The new intensity forecast is 
little changed from the previous forecast, and in the latter part of 
the forecast period it lies near the intensity consensus.  It should 
be noted that while Eta regaining hurricane strength cannot be ruled 
out, there is little support for that in the current guidance.
 
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 late this week. 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.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/1500Z 15.1N  87.8W   25 KT  30 MPH...INLAND
 12H  06/0000Z 15.7N  88.0W   25 KT  30 MPH...INLAND
 24H  06/1200Z 16.8N  87.6W   25 KT  30 MPH...OVER WATER
 36H  07/0000Z 17.8N  86.2W   30 KT  35 MPH
 48H  07/1200Z 19.0N  84.5W   35 KT  40 MPH
 60H  08/0000Z 20.1N  83.0W   45 KT  50 MPH
 72H  08/1200Z 21.3N  81.2W   50 KT  60 MPH
 96H  09/1200Z 23.0N  80.0W   50 KT  60 MPH
120H  10/1200Z 24.0N  83.0W   55 KT  65 MPH
 
$$
Forecaster Beven
 
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