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Tropical Depression Eta Discussion Number  27
NWS National Hurricane Center Miami FL       AL292020
400 AM EST Sat Nov 07 2020
 
Satellite images show a large area of deep convection associated 
with Eta, but there is not much organization to the thunderstorm 
activity. An ASCAT-A pass from several hours ago showed that the 
circulation of Eta has become a little better defined, and the 
center was located a fair distance to the west-southwest of what was 
previously analyzed.  The pass also showed that Eta has not 
strengthened to a tropical storm yet, with the maximum winds in the 
25-30 kt range.  Based on that data, and a blend of the latest 
Dvorak classifications, the initial intensity is held at 30 kt.
 
After adjusting the initial position, the estimated motion is a 
little slower to the east-northeast than before, 060/9 kt.  It 
should be noted that some of the models show the center re-forming 
to the northeast later today, which is possible given the 
depression's convective asymmetry.  Regardless of these details, 
the large scale track forecast reasoning is unchanged.  A continued 
east-northeast to northeast motion is expected during the next 
day or two as Eta moves in the flow on the east side of a mid- to 
upper-level trough over the Gulf of Mexico.  This motion should take 
Eta near or to the west of the Cayman Islands later today and over 
central Cuba tonight and Sunday. After that time, the mid- to 
upper-level low is expected to cut off over the eastern Gulf of 
Mexico or the Florida Straits. As a result, Eta will pivot around 
the low, which should cause a slow down and a turn to the north and 
then the northwest toward the Florida Keys and south Florida Sunday 
night and Monday.  As Eta merges with the upper low, a slower motion 
to the northwest or north is forecast across the eastern Gulf of 
Mexico by the middle of next week.  The NHC track forecast lies 
between the GFS and ECMWF models, and is quite similar to the 
previous one.
 
Eta is expected to gradually strengthen on its approach to Cuba as
it remains over warm waters and in an region of upper-level
diffluence.  However, by the time Eta reaches Cuba, the models show
an increase in southwesterly wind shear and drier air being drawn
into the circulation.  These factors should cause Eta to level off
in strength, and likely become asymmetric.  When Eta interacts and
merges with the upper low, it will likely take on a subtropical
appearance and develop a large wind field near southern Florida.
The storm is forecast to slowly weaken when it passes to the west
of Florida as it moves in a drier environment.  The NHC intensity 
forecast is largely an update of the previous one and lies near the 
high end of the model guidance.
 
Based on the new forecast, the government of the Bahamas has issued 
a Tropical Storm Warning for the northwestern Bahamas.  In 
addition, the Tropical Storm Watch along the east coast of Florida 
has been extended northward.
 
Key Messages:
 
1. Heavy rainfall is diminishing across portions of Central America, 
although the threat of life-threatening flooding may continue, along 
with landslides in areas of higher terrain. Heavy rainfall from Eta 
will continue across the Cayman Islands and portions of Cuba, 
resulting in significant, life-threatening flash flooding and river 
flooding in Cuba. Flash and urban flooding will also be possible for 
the Cayman Islands, Jamaica, the Bahamas and southern Florida.
 
2. Tropical storm conditions are expected later today and Sunday in
portions of the Cayman Islands, Cuba, and the northwestern 
Bahamas, where a Tropical Storm Warning is in effect.
 
3. Tropical storm conditions are possible in the Florida Keys and 
portions of south and central Florida beginning late Sunday, where 
a Tropical Storm Watch is in effect.  Tropical Storm Warnings could 
be required for these areas later today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 18.3N  84.9W   30 KT  35 MPH
 12H  07/1800Z 19.3N  82.9W   40 KT  45 MPH
 24H  08/0600Z 20.7N  80.9W   45 KT  50 MPH
 36H  08/1800Z 22.6N  80.2W   50 KT  60 MPH...INLAND
 48H  09/0600Z 23.8N  80.2W   55 KT  65 MPH...OVER WATER
 60H  09/1800Z 24.9N  81.2W   55 KT  65 MPH
 72H  10/0600Z 25.5N  83.7W   50 KT  60 MPH
 96H  11/0600Z 26.0N  84.7W   45 KT  50 MPH
120H  12/0600Z 27.3N  85.0W   40 KT  45 MPH
 
$$
Forecaster Cangialosi
 
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