[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 121448
TCDAT2

Tropical Storm Barry Discussion Number   9
NWS National Hurricane Center Miami FL       AL022019
1000 AM CDT Fri Jul 12 2019

Reports from Air Force Reserve and NOAA Hurricane Hunter aircraft
indicate that Barry has strengthened during the past several hours.
The Air Force plane reported maximum 850-mb flight-level winds of 62
kt and reliable-looking SFMR winds of 50-55 kt in the strong
convection that has developed in the southern quadrant.  In
addition, the data from both planes indicate the central pressure
has fallen to near 998 mb.  Based on these data, the initial
intensity is increased to 55 kt.  Data from the NOAA plane, which is
flying near 460 mb, shows that the center at that level is south of
the low-level center, likely due to ongoing northerly shear.

The initial motion is an erratic 290/4.  While there is still a
larger than normal spread between the UKMET on the left side and the
HWRF on the right side, the track guidance has come into better
agreement that Barry will turn northwestward later today or tonight,
with this motion continuing until the center makes landfall along
the Louisiana coast in 24-30 h.  After landfall, the system should
move northward through a break in the ridge of high pressure over
the United States until the 72 h point, after which it should
recurve northeastward into the westerlies.  The new track forecast
has only minor tweaks from the previous forecast, and it lies near
the various consensus models.

Barry has been strengthening despite an asymmetric convective
structure, ongoing northerly shear, and the presence of mid- to
upper-level dry air over the northern semicircle.  The intensity
guidance suggests that, while the environment will be at best
marginally favorable, the cyclone will continue to intensify until
landfall.  Based on this, the new intensity forecast calls for Barry
to become a hurricane in 24 h, just before landfall, with this
forecast being slightly above the guidance.  After landfall, the
cyclone should steadily weaken, with decay to a remnant low
forecast to occur in about 72 h.

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 are already beginning
to rise in these areas, with the peak inundation expected on
Saturday. 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 south-central Louisiana where tropical
storm warnings are in effect.

FORECAST POSITIONS AND MAX WINDS

INIT  12/1500Z 28.2N  90.4W   55 KT  65 MPH
 12H  13/0000Z 28.6N  90.9W   60 KT  70 MPH
 24H  13/1200Z 29.4N  91.5W   65 KT  75 MPH
 36H  14/0000Z 30.5N  92.0W   45 KT  50 MPH...INLAND
 48H  14/1200Z 31.8N  92.4W   30 KT  35 MPH...INLAND
 72H  15/1200Z 34.4N  92.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  16/1200Z 37.0N  90.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  17/1200Z 39.5N  87.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven
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