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Tropical Depression HARVEY


Tropical Depression Harvey Discussion Number  12
NWS National Hurricane Center Miami FL       AL092017
1000 AM CDT Wed Aug 23 2017

Air Force Reserve Hurricane Hunter data indicate that Harvey has
regenerated in the Bay of Campeche, with a closed circulation
noted and a central pressure of about 1006 mb.  The initial wind
speed is 30 kt based on SFMR data from the aircraft.

Harvey is not well organized at the moment, with an asymmetric cloud
pattern and a large radius of maximum wind.  The environment,
however, is conducive for intensification while Harvey moves over
the very warm Gulf of Mexico waters in light-to-moderate shear.  The
biggest hindrance to intensification in the short term is the poor
structure.  Thus the NHC forecast will only show a gradual increase
in wind speed during the first day, with a more significant
intensification after that time.  Although not explicitly forecast
below, we are anticipating Harvey being a hurricane at landfall
after the 48 hour forecast point.  This forecast agrees well with
the guidance, almost all of which shows a quickly intensifying
cyclone approaching the Texas coast.

Since the center has just recently formed, the initial motion is
difficult to estimate, but the long-term motion is 310/8.  Harvey is
expected to move more slowly toward the northwest or north-
northwest as it enters a weakness in the Atlantic subtropical ridge
during the next day or so.  The ridge slightly strengthens by late
Thursday, which should cause a faster northwestward motion by then.
Around the time of landfall, however, Harvey should enter an area of
weaker steering currents near the upper Texas coast as high pressure
rebuilds over the southwestern United States.  The storm should slow
down markedly over southeast Texas, and there is considerable
uncertainty on exactly how fast Harvey moves out of that state ahead
of the next mid-latitude trough.  For now the NHC forecast will just
drift Harvey generally toward the east at days 4 and 5, on
the slow side of the model consensus. Hopefully later G-IV flights
and special soundings over the southern United States will help
clarify the long range forecast.

Key Messages:

1. Harvey is likely to bring multiple hazards to portions of the
Texas coast beginning on Friday.

2. Several days of heavy rainfall are likely across portions of
eastern Texas, Louisiana, and the lower Mississippi Valley from
Friday through early next week. This rainfall could cause life-
threatening flooding. Please refer to products from your local
National Weather Service office ( and the NOAA
Weather Prediction Center ( for more
information on the flooding hazard.

3. The National Weather Service has issued a Storm Surge Watch
from Port Mansfield to High Island, Texas. There is the possibility
of life-threatening inundation from rising water moving inland from
the coastline during the next 48 hours in these areas. For a
depiction of areas at risk, please see the National Weather Service
Storm Surge Watch/Warning Graphic, available at

4. The Potential Storm Surge Flooding Map will also be available on
the NHC website by 1200 PM CDT. Remember that the Potential Storm
Surge Flooding Map does not represent a forecast of expected
inundation, but rather depicts a reasonable worst-case scenario -
the amount of inundation that has a 10 percent chance of being
exceeded at each individual location. Because the Flooding Map is
based on inputs that extend out only to about 72 hours, it best
represents the flooding potential in those locations within the
watch area.

5. Hurricane conditions are possible along the Texas coast from
Port Mansfield to San Luis Pass.


INIT  23/1500Z 21.5N  92.5W   30 KT  35 MPH
 12H  24/0000Z 22.3N  93.2W   35 KT  40 MPH
 24H  24/1200Z 23.8N  93.9W   40 KT  45 MPH
 36H  25/0000Z 25.2N  94.9W   50 KT  60 MPH
 48H  25/1200Z 26.7N  96.3W   60 KT  70 MPH
 72H  26/1200Z 29.0N  97.3W   40 KT  45 MPH...INLAND
 96H  27/1200Z 29.8N  96.9W   35 KT  40 MPH...INLAND
120H  28/1200Z 30.0N  95.0W   35 KT  40 MPH...INLAND

Forecaster Blake