[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 160210
TCDAT2

TROPICAL STORM BILL DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL022015
1000 PM CDT MON JUN 15 2015

Data from an Air Force Reserve Hurricane Hunter aircraft and
surface observations indicate that the circulation associated with
the low located in the northwestern Gulf of Mexico has become better
defined since earlier today.  While the circulation still appears to
be somewhat elongated, the center is defined enough to consider the
system a tropical cyclone, and advisories are being initiated on
Tropical Storm Bill at this time.

The aircraft data indicate an area of 40-45 kt winds north and
east of the center, and the initial intensity is set to 45 kt for
this advisory.  Given the relatively broad nature of the system, the
large radius of maximum winds, and the somewhat ragged convective
pattern, only a little strengthening is expected before the center
reaches the coast tomorrow, and the NHC intensity forecast is close
to the latest SHIPS and LGEM guidance.  After landfall Bill is
expected to weaken to a depression after 24 hours, and the low-level
circulation is forecast to dissipate by 48 hours following the GFS
and ECMWF solutions.  Note that the global models subsequently show
the low- to mid-level remnants of Bill moving northward and then
northeastward ahead of an upper trough into the southern Plains and
mid-Mississippi Valley.

The initial motion estimate is a relatively uncertain 320/10 given
the recent formation of the center.  The primary steering mechanism
is a mid-level anticyclone centered over the southeastern United
States, which should result in Bill moving northwestward toward the
Texas coast in the next 12 hours and then inland over south-central
Texas.  The track model guidance is in generally good agreement
through landfall.  The NHC track forecast is close to a blend of the
latest model fields from the UKMET, ECMWF, and GFS models and is a
little to the left of the multi-model consensus.  It is important
not to focus on the exact track of the center, given the large area
across which heavy rains and tropical storm conditions are expected
to occur.

Given this forecast, a tropical storm warning has been issued for
much of the middle and upper Texas coast.  However, the main hazard
associated with Bill and its remnants will be heavy rainfall and
flooding across portions of eastern Texas.  Please see products from
your local National Weather Service office for more information on
the flooding hazard.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0300Z 27.1N  94.2W   45 KT  50 MPH
 12H  16/1200Z 28.3N  95.8W   50 KT  60 MPH
 24H  17/0000Z 29.7N  97.3W   35 KT  40 MPH...INLAND
 36H  17/1200Z 31.5N  98.3W   25 KT  30 MPH...INLAND
 48H  18/0000Z...DISSIPATED

$$
Forecaster Brennan
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