Tropical Depression ETA (Text)

Tropical Depression Eta Discussion Number  25
NWS National Hurricane Center Miami FL       AL292020
300 PM CST Fri Nov 06 2020

Reports from an Air Force Reserve Hurricane Hunter aircraft 
indicate that the center of Eta is elongated east-to-west with 
multiple vorticity centers present.  The central pressure is near 
1002 mb, and the maximum flight-level winds were 30-35 kt at 1500 
ft.  There were a few spot reports of 35-45 kt winds from the 
Stepped Frequency Microwave Radiometer, but these were in areas of 
heavy rain and their reliability is suspect.  Based on these data, 
the initial intensity is kept at 30 kt.

The aircraft data shows that the center is farther south than 
previously thought, and the initial motion is an uncertain 040/6 kt. 
There is no change to the previous track forecast philosophy.  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, causing 
Eta to turn northwestward around and into the low.  After 72 h, the 
merged system is likely to move slowly westward to northwestward.  
While the guidance is in good agreement on the synoptic evolution, 
there remain 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.  In 
addition, the HWRF/HMON/Canadian are faster than the other guidance. 
The new forecast track overall is a little slower than the previous 
track, and due to the initial position the first 36 h have been 
shifted southward.
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 again similar to the previous forecast and lies 
near 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.  The HWRF and HMON models 
still suggest the possibility that a tight inner wind core may 
develop, however, the guidance has trended weaker since this 
morning, and the new intensity forecast is above the bulk of the 
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 
portions of Cuba at this time.  Watches may be required for 
portions of south Florida and the Florida Keys tonight.
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 move into the Cayman islands and portions of Cuba, resulting in 
significant, life-threatening flash flooding and river flooding. 
Flash flooding and urban flooding is also possible for Jamaica and 
southeast Mexico.

2. Tropical storm conditions are expected this weekend in portions 
of the Cayman Islands and Cuba, where a Tropical Storm Warning is in 

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 for a portion of this area tonight. 
INIT  06/2100Z 17.3N  86.5W   30 KT  35 MPH
 12H  07/0600Z 18.2N  84.8W   35 KT  40 MPH
 24H  07/1800Z 19.4N  82.5W   40 KT  45 MPH
 36H  08/0600Z 20.8N  80.7W   45 KT  50 MPH
 48H  08/1800Z 22.5N  80.0W   50 KT  60 MPH...INLAND
 60H  09/0600Z 24.2N  80.6W   55 KT  65 MPH...OVER WATER
 72H  09/1800Z 24.9N  81.8W   55 KT  65 MPH
 96H  10/1800Z 25.0N  84.0W   50 KT  60 MPH
120H  11/1800Z 26.5N  85.5W   50 KT  60 MPH
Forecaster Beven

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Page last modified: Thursday, 31-Dec-2020 12:10:45 UTC