[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 111453
TCDAT2

Tropical Storm Barry Discussion Number   5
NWS National Hurricane Center Miami FL       AL022019
1000 AM CDT Thu Jul 11 2019

The low pressure area over the northern Gulf of Mexico has become
better organized during the past several hours, with a large
convective band in the southern semicircle.  The circulation
center has also become better defined, although it is still
elongated and multiple cloud swirls are seen rotating around the
mean center.  In addition, Air Force Reserve and NOAA Hurricane
Hunter aircraft report flight-level and SFMR winds high enough for
an initial intensity of 35 kt.  Based on these developments, the
system is upgraded to Tropical Storm Barry.

The initial motion is a rather uncertain 270/4.  Barry is being
steered by a weak low- to mid-level ridge to the north, and a
weakness in the ridge is forecast to develop during the next
24-48 h.  This should allow the cyclone to turn northwestward and
eventually northward.  However, there is a large spread in the track
guidance.  The HWRF and HMON forecast Barry to move almost due
north from its current position with a landfall in Mississippi,
while the UKMET takes the cyclone to the upper Texas coast.  The
GFS, ECMWF, and Canadian models lie between these extremes.
Overall, there has been a slight eastward shift of the guidance
envelope, so the new forecast track is also adjusted slightly to
the east.  It should be noted, though, that the new track is west
of the consensus models.

Barry is being affected by northerly shear, and water vapor imagery
indicates mid- to upper-level dry air moving into the cyclone from
the northeast.  Some moderate shear is now expected to persist until
the cyclone makes landfall.  Despite this less than ideal
environment, the guidance forecasts slow but steady intensification,
so the NHC forecast follows this trend.  The new intensity forecast
is similar to the previous one in calling for Barry to become a
hurricane just before landfall in Louisiana, and it lies between the
HCCA and ICON consensus models.

Key Messages:

1. Barry is expected to bring storm surge, rainfall, and wind
hazards to the central Gulf Coast during the next several days.

2. There is a danger of life-threatening storm surge inundation
along the coast of southern and southeastern Louisiana where a Storm
Surge Warning has been issued. The highest storm surge inundation is
expected between the Mouth of the Atchafalaya River and Shell Beach.
Residents in these areas should listen to any advice given by local
officials.

3. A Tropical Storm Warning and Hurricane Watch are in effect for
much of the Louisiana coast and additional watches and warnings
could be required later today. Residents in these areas should
ensure they have their hurricane plan in place.

4. The slow movement of this system will result in a long duration
heavy rainfall threat along the central Gulf Coast and inland
through the lower Mississippi Valley through the weekend and
potentially into early next week. Flash flooding and river flooding
will become increasingly likely, some of which may be significant,
especially along and east of the track of the system.

FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 27.8N  88.7W   35 KT  40 MPH
 12H  12/0000Z 27.8N  89.3W   35 KT  40 MPH
 24H  12/1200Z 28.1N  90.0W   45 KT  50 MPH
 36H  13/0000Z 28.6N  90.8W   55 KT  65 MPH
 48H  13/1200Z 29.4N  91.4W   65 KT  75 MPH
 72H  14/1200Z 32.0N  91.8W   30 KT  35 MPH...INLAND
 96H  15/1200Z 34.5N  91.5W   25 KT  30 MPH...INLAND
120H  16/1200Z 37.0N  89.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven
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