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Tropical Storm HARVEY


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Tropical Storm Harvey Discussion Number  34...Corrected
NWS National Hurricane Center Miami FL       AL092017
400 PM CDT Mon Aug 28 2017

Corrected initial intensity in first paragraph

Radar and surface data show that the center of Harvey remains near
or just off the Texas coast south of Matagorda.  The associated
convection has increased in intensity and coverage in a cluster
extending from just north of the center northeastward into the
Houston metropolitan area.  Surface observations indicate that the
central pressure is around 997 mb, and there are recent reports of
sustained tropical-storm-force winds about 50-60 n mi southwest of
the center.  Based on these, the initial intensity is increased to
40 kt.

Very heavy rains and life-threatening flash flooding continue over
southeastern Texas and southwestern Louisiana.  There have been
reports of 2-day rainfall totals of close to 35 inches in the
Greater Houston area.  With the additional rains that are expected
over the next several days, rainfall totals could reach 50 inches in
some locations, which would be historic for the area.

While Harvey continues to produce widespread heavy rain, the
convective structure is not well organized in terms of being a
tropical cyclone.  In addition, a dry slot is seen in water vapor
imagery over the southern and southeastern parts of the circulation,
and the intensity guidance is not showing much additional
development as Harvey crosses the northwestern Gulf of Mexico.  The
intensity forecast reflects these issues by showing little change
in strength before landfall.  Weakening and eventual decay into a
remnant low are expected after landfall.

The center has drifted erratically eastward since the last
advisory, although a longer-term motion is 110/3.  Harvey is
currently between the subtropical ridge over the Gulf of Mexico and
a large deep-layer ridge over the western United States, with a
large trough in the westerlies weakening the Gulf ridge just enough
to allow an east-southeastward motion.  The large-scale models
suggest that the westerlies should erode the western ridge to some
extent during the forecast period, which should allow Harvey to
turn north-northeastward under the greater influence of the Gulf
ridge.  The track guidance has changed little since the previous
advisory except to show a faster motion from 96-120 h.  The new
forecast track remains close to that of the previous track, except
for an increased forward speed by 120 h.


Key Messages:

1. Ongoing catastrophic and life-threatening flooding will continue
across southeastern Texas.  Additional rainfall accumulations of 15
to 25 inches are expected across the upper Texas coast, with
isolated storm totals as high as 50 inches.  Please heed the advice
of local officials.  Do not attempt to travel if you are in a safe
place, and do not drive into flooded roadways.  Refer to products
from your local National Weather Service office and the NOAA Weather
Prediction Center for more information on the flooding hazard.  A
summary of rainfall totals compiled by the Weather Prediction Center
can be found at: www.wpc.ncep.noaa.gov/discussions/nfdscc1.html

2. The flood threat is spreading farther east into Louisiana.
Additional rainfall amounts of 15 to 25 inches are expected in
southwestern Louisiana, with rainfall amounts of 5 to 15 inches
expected in south-central Louisiana and 5 to 10 inches in
southeastern Louisiana. Please heed the advice of local officials
and refer to products from your local National Weather Service
office and the NOAA Weather Prediction Center for more information
on the flooding hazard in these areas.

3. While Tropical Storm Warnings have been extended eastward along
the coast of Louisiana and a Storm Surge Watch has been issued, the
impacts of winds and storm surge are expected to be secondary
compared to that of the rains.


FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 28.5N  95.7W   40 KT  45 MPH
 12H  29/0600Z 28.4N  95.5W   40 KT  45 MPH
 24H  29/1800Z 28.6N  95.0W   40 KT  45 MPH
 36H  30/0600Z 29.2N  94.5W   40 KT  45 MPH
 48H  30/1800Z 30.3N  94.1W   35 KT  40 MPH...INLAND
 72H  31/1800Z 32.5N  93.0W   30 KT  35 MPH...INLAND
 96H  01/1800Z 34.5N  91.5W   25 KT  30 MPH...INLAND
120H  02/1800Z 37.0N  89.0W   20 KT  25 MPH...POST-TROP/INLAND

$$
Forecaster Beven

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