[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 240257
TCDAT3

Tropical Storm Hanna Discussion Number   5
NWS National Hurricane Center Miami FL       AL082020
1000 PM CDT Thu Jul 23 2020

The system continues to organize with curved bands becoming
better established around the center.  The cyclone certainly has
the appearance of a tropical storm, and just minutes ago the NOAA
Hurricane Hunters found winds to support upgrading the system to a
35-kt tropical storm.  Data from the aircraft also show that the
minimum pressure has dropped to 1002 mb, indicating that the system
is on a developing trend.

Hanna is moving fairly slowly to the west-northwest, with
the latest initial motion estimated to be 285/6 kt.  This
west-northwest motion should continue on Friday, but a turn to the
west is expected by Friday night as a subtropical ridge strengthens
to the north of the cyclone.  This steering flow should take the
center of the storm across the southern Texas coast in 36 to 48
hours. After landfall, the storm is forecast to turn south of west
across extreme southern Texas and northern Mexico.  The models have
shifted southward again this cycle, and the NHC track forecast has
been adjusted in that direction.

Additional strengthening seems quite likely until the storm makes
landfall since it is expected to remain over the very warm Gulf of
Mexico waters and in generally low wind shear conditions.  After
landfall, steady weakening should commence, and the cyclone should
dissipate over the rugged terrain of northern Mexico in about 4
days.  The NHC intensity forecast is a little above the previous one
and at the high end of the guidance given the system's well
organized structure and favorable environment.

Due to the southward shift in the track forecast, the tropical
storm warning has been extended southward from Port Mansfield to
the Mouth of the Rio Grande.

Tropical Storm Hanna is the earliest 8th storm on record.  The
previous record was in 2005 when Harvey formed on August 3rd.


Key Messages

1. Hanna is forecast to strengthen and it is expected to
bring tropical-storm-force winds to portions of the Texas coast,
where a tropical storm warning is in effect.

2. Hanna is expected to produce heavy rains across portions of
Louisiana, southern Texas, and northern Mexico.  These rains could
result in flash flooding and isolated minor-to-moderate
river flooding.


FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z 26.2N  91.4W   35 KT  40 MPH
 12H  24/1200Z 26.6N  92.8W   40 KT  45 MPH
 24H  25/0000Z 27.1N  94.5W   45 KT  50 MPH
 36H  25/1200Z 27.2N  96.3W   55 KT  65 MPH
 48H  26/0000Z 27.2N  97.8W   45 KT  50 MPH...INLAND
 60H  26/1200Z 27.0N  99.3W   30 KT  35 MPH...INLAND
 72H  27/0000Z 26.5N 100.5W   25 KT  30 MPH...INLAND
 96H  28/0000Z...DISSIPATED

$$
Forecaster Cangialosi
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