Tropical Storm HANNA Advisory 7月24日

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Tropical Depression Eight Discussion Number   4
NWS National Hurricane Center Miami FL       AL082020
400 PM CDT Thu Jul 23 2020

Satellite imagery indicates that the depression continues to become
better organized, with the center near the eastern edge of a large
and broadly curved convective area, with a second curved band to
the east.  Several subjective and objective satellite intensity
estimates have increased to 35 kt since the last advisory.
However, surface observations, scatterometer data, and data from an
earlier Air Force Reserve Hurricane Hunter mission show a large
area of 25-30 kt winds south and east of the center, and no 35-kt
winds to justify an upgrade at this time.  Thus, the initial
intensity remains 30 kt.  A NOAA Hurricane Hunter aircraft is
scheduled to investigate the depression this evening, and the
current expectation is that they will find it is a tropical storm.

The center meandered a bit today, possibly due to reformation.
However, the system now seems to have resumed a west-northwestward
motion of 285/7 kt.  A mid-level ridge over the central United
States is the predominant steering influence, and the global models
forecast this ridge to build somewhat during the next several days.
This should cause the depression to turn westward by 36-48 h
and south of west after about 60 h.  The track guidance remains in
good agreement with that scenario, although there has been a
slight southward shift in the guidance envelope and the
consensus models.  The new NHC forecast track is also shifted
a little southward and has the center making landfall along the
Texas coast in about 48 h.

The depression is in an environment of light shear with good
anticyclonic outflow, and it will be over warm sea surface
temperatures until landfall.  This should allow steady
strengthening.  The new NHC intensity forecast has been increased
to show a peak intensity of 50 kt just before landfall, followed by
steady weakening and eventually dissipation after landfall.  The new
intensity forecast is close to the intensity consensus.

The aircraft and scatterometer data show that the strongest winds
in the cyclone are currently occurring about 70-90 n mi from the
center.  This has caused the forecast wind radii to be expanded,
and as a result a Tropical Storm Warning is needed for portions of
the Texas coast.


Key Messages

1. The depression is expected to strengthen and it is likely to
bring tropical-storm-force winds to portions of the Texas coast,
where a tropical storm warning has been issued.

2. The tropical cyclone 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  23/2100Z 26.1N  90.7W   30 KT  35 MPH
 12H  24/0600Z 26.5N  91.9W   35 KT  40 MPH
 24H  24/1800Z 27.1N  93.6W   45 KT  50 MPH
 36H  25/0600Z 27.5N  95.3W   50 KT  60 MPH
 48H  25/1800Z 27.6N  97.0W   50 KT  60 MPH
 60H  26/0600Z 27.5N  98.5W   40 KT  45 MPH...INLAND
 72H  26/1800Z 27.3N 100.0W   30 KT  35 MPH...INLAND
 96H  27/1800Z 27.0N 102.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  28/1800Z...DISSIPATED

$$
Forecaster Beven