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Tropical Depression NINE Forecast Discussion


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000
WTNT44 KNHC 302103
TCDAT4

TROPICAL DEPRESSION NINE DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016
400 PM CDT TUE AUG 30 2016

The system has still not become better organized on satellite
imagery, with limited evidence of banding features.  There is an
apparent mid-level center of circulation located south of the
low-level center.  The highest flight-level wind reported by a
NOAA Hurricane Hunter aircraft was 34 kt and the highest
SFMR-observed surface winds were 30 kt, which continues to be used
for the advisory intensity.  There is some evidence of increasing
upper-level outflow to the north.  The latest intensity
guidance is a little more aggressive than before, with a little less
shear forecast over the northern Gulf coast region.  The official
intensity forecast has been increased slightly in comparison to the
previous one, and is a little below the latest model consensus.
Given that a couple of the models show the system becoming a
hurricane, and the 48-hour forecast point implies
tropical-storm-force winds near the coast, it is prudent to issue a
hurricane watch for a portion of the northeast Gulf of Mexico coast
at this time.

Fixes from the NOAA aircraft show that the initial motion is
northwestward, or 320/4 kt.  The global models continue to show a
mid-tropospheric trough developing over the southeastern United
States during the next couple of days.  This should cause the
tropical cyclone to turn toward the north and north-northeast in
24-48 hours.  The dynamical track guidance models have shifted a
bit to the west compared to their earlier runs, as has the
multi-model consensus.  Therefore the official track forecast is
also west of the previous one.

It is important not to focus on the forecast landfall point of this
system.  Among other reasons, dangerous storm surge flooding is
likely along the coast well to the east and south of the path of the
center.

FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 24.4N  87.3W   30 KT  35 MPH
 12H  31/0600Z 24.9N  87.5W   35 KT  40 MPH
 24H  31/1800Z 26.0N  87.0W   40 KT  45 MPH
 36H  01/0600Z 27.5N  86.0W   45 KT  50 MPH
 48H  01/1800Z 29.0N  84.8W   55 KT  65 MPH
 72H  02/1800Z 32.9N  79.2W   60 KT  70 MPH
 96H  03/1800Z 36.5N  71.0W   60 KT  70 MPH
120H  04/1800Z 39.0N  68.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch