[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 130841
TCDAT2

Tropical Storm Barry Discussion Number  12
NWS National Hurricane Center Miami FL       AL022019
400 AM CDT Sat Jul 13 2019

Barry continues to inch its way toward the Louisiana coast with some
of the northern bands now moving across southeastern Louisiana.
Satellite and radar imagery still indicate that the storm has an
asymmetric structure with most of its deep convection located to
the south and east of the center due to ongoing north-northwesterly
shear.  The convection has been expanding though, and some bands are
starting to wrap around the northeastern side, which could indicate
some decrease in shear.  The initial intensity for this advisory is
held at 55 kt, which is in agreement with recent ASCAT passes and a
Dvorak classification from TAFB.  Doppler radar velocities between
10000 and 12000 feet show winds of 60-67 kt, but based on
surface observations and the ASCAT data these might not be mixing
down to the surface.  The Air Force Hurricane Hunters are scheduled
to investigate Barry in a few hours and the data they collect should
provide a better assessment of the storm's intensity.

Barry continues its erratic motion toward the west-northwest.
Smoothing through the wobbles yields an initial motion of 300/4 kt.
A northwestward turn should occur soon, and the center is expected
to cross the coast of south-central Louisiana within the next 6 to
12 hours.  After that time, a turn toward the north-northwest and
north is forecast as the cyclone moves inland over the Mississippi
Valley toward a weakness in the ridge.  The NHC track forecast is
nudged a little to the west of the previous one, but it remains on
the eastern side of the guidance envelope in best agreement with the
GFS and ECMWF models.

Although not explicitly shown in the forecast below, Barry is
still expected to be a hurricane before it makes landfall later
today.  After landfall, steady weakening is expected and
Barry is forecast to become a tropical depression in about 36 hours
and degenerate into a remnant low in two to three days.  The global
models show the remnant low dissipating over the Ohio Valley in 3
or 4 days.  The NHC intensity forecast is a little above the
guidance in the short term, but in line with the consensus models
after that.

Key Messages:

1. There is a danger of life-threatening storm surge inundation
along the coast of southern and southeastern Louisiana, portions of
Lake Pontchartrain, and portions of coastal Mississippi where a
Storm Surge Warning is in effect. Water levels have already begun
to rise in these areas, with peak inundation expected to occur
later today. The highest storm surge inundation is expected between
Intracoastal City and Shell Beach.

2. The slow movement of Barry will result in a long duration heavy
rainfall and flood threat along the central Gulf Coast, across
portions of the Lower Mississippi Valley and north into the
Tennessee Valley through the weekend into early next week. Flash
flooding and river flooding will become increasingly likely, some of
which may be life-threatening, especially across portions of
southeast Louisiana into Mississippi.

3. Hurricane conditions are expected along a portion of the coast of
Louisiana, where a Hurricane Warning is in effect. Tropical storm
conditions are expected elsewhere along much of the Louisiana coast
and inland across portions of the lower Mississippi Valley where
tropical storm warnings are in effect.


FORECAST POSITIONS AND MAX WINDS

INIT  13/0900Z 29.1N  91.8W   55 KT  65 MPH
 12H  13/1800Z 29.8N  92.1W   60 KT  70 MPH...INLAND
 24H  14/0600Z 30.9N  92.6W   45 KT  50 MPH...INLAND
 36H  14/1800Z 32.3N  92.9W   30 KT  35 MPH...INLAND
 48H  15/0600Z 33.8N  93.0W   25 KT  30 MPH...INLAND
 72H  16/0600Z 36.5N  92.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  17/0600Z...DISSIPATED

$$
Forecaster Cangialosi
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