[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 040856
TCDAT4

Tropical Storm Eta Discussion Number  15
NWS National Hurricane Center Miami FL       AL292020
400 AM EST Wed Nov 04 2020

Eta still has a well-organized cloud pattern while it moves over
northern Nicaragua, but there has been a considerable decrease in
deep convection as evidenced by the warming cloud tops.  Assuming an
inland weakening rate as given by the Decay-SHIPS model, the current
intensity is reduced to 60 kt.  Continued weakening will occur over
the next 48 hours or so, and the system should degenerate into
remnant low tomorrow.  In fact, the surface circulation could lose
its identity in a day or two.  However, the upper-level circulation
is likely to remain intact, and a surface cyclone is predicted to
regenerate once the system moves into the northwestern Caribbean Sea
on Friday.  Some strengthening is forecast thereafter, in line with
the intensity model consensus.  However, the global models show the
system interacting with a strong upper-level trough in 3-5 days, so
the cyclone may have some hybrid or subtropical characteristics by
that time.

Eta continues westward, or at about 270/7 kt.  A mid-level ridge to
the north of the cyclone should steer it on a generally
west-northwestward track during the next 48 hours.  Thereafter, a
500-mb trough/low dropping into the Gulf of Mexico is expected to
cause the cyclone to move northeastward in 3-4 days.  By the end of
the forecast period, the system is expected to rotate cyclonically
around the eastern side of the low.  The official track forecast is
quite close to the latest corrected consensus, HCCA, prediction
which is usually a good performer.  There is still significant
uncertainty as to the details of the track in the 3- to 5-day time
frame.

Of more immediate concern are the torrential rains that Eta will
continue to produce over portions of Central America.


Key Messages:

1. Through Friday evening, 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, El Salvador, southern Haiti, and the
Cayman Islands.

2. Eta is forecast to regain tropical storm strength before it
moves across portions of Cuba and approaches southern Florida this
weekend.  While it is too soon to determine the exact timing,
magnitude, and location of possible impacts from wind and rainfall,
interests in Cuba, southern Florida and the Florida Keys should
monitor the progress of Eta through the week.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 13.8N  84.7W   60 KT  70 MPH
 12H  04/1800Z 14.0N  85.5W   40 KT  45 MPH...INLAND
 24H  05/0600Z 14.6N  87.0W   30 KT  35 MPH...INLAND
 36H  05/1800Z 15.5N  88.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  06/0600Z 16.5N  88.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  06/1800Z 17.6N  87.6W   30 KT  35 MPH...OVER WATER
 72H  07/0600Z 19.0N  85.5W   35 KT  40 MPH
 96H  08/0600Z 22.6N  81.8W   45 KT  50 MPH
120H  09/0600Z 25.0N  81.5W   50 KT  60 MPH

$$
Forecaster Pasch
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