Potential Tropical Cyclone THREE (Text)

Potential Tropical Cyclone Three Discussion Number   5
NWS National Hurricane Center Miami FL       AL032021
400 PM CDT Fri Jun 18 2021
A few hours ago, an ASCAT-A pass indicated that maximum winds were
about 40 kt well east of the ill-defined center of circulation, and
the initial wind speed was increased to that value at the
intermediate advisory at 18Z.  Recent surface observations just
offshore of southeastern Louisiana have been reporting maximum winds
between 30 and 40 kt.  Based on a combination of these data, and
since the structure of the system has not changed much during the
past few hours, the initial intensity is held at 40 kt for this
advisory.  Although the disturbance has wind speeds of tropical
storm intensity, it has not been named a tropical storm yet since
its center is ill defined and broad as evident in the Air Force
Hurricane Hunter data and surface observations.  Regardless of its
status, heavy rains and tropical-storm-force winds are spreading
across portions of the northern Gulf coast, and these conditions
will spread inland through tonight.
There has not been much change to the track forecast reasoning. The
cyclone is moving northward at about 14 kt, and a general north to
north-northeast motion is expected through landfall, which is likely
to occur overnight or early Saturday morning.  After the system
moves inland, a turn to the northeast and then east-northeast
across the southeast U.S. is predicted when the cyclone becomes
embedded in the westerlies on the north side of the subtropical
ridge.  The models remain in relatively good agreement, and only
small changes were made to the previous track forecast.
There is some opportunity for a little strengthening during the next
6 to 12 hours before the system makes landfall.  However,
significant intensification is not expected due to the cyclone's
broad and asymmetric structure, and ongoing west-southwesterly
vertical wind shear.  After landfall, weakening is forecast, and
dissipation is still predicted to occur by 72 hours. However, it
should be noted that the ECMWF and UKMET models hold onto the
vortex for a while longer.
Given the current and anticipated structure of this system, users
should not focus on the exact track of the center, as rainfall and
wind hazards are likely to extend well east of the center.
Key Messages:
1. The system is expected to produce heavy rainfall and considerable
flash, urban and small stream flooding tonight and through the
weekend along the Central Gulf coast.  Flood impacts will spread
northeastward into the Southern Appalachians.
2. Tropical storm conditions have begun along portions of the
central Gulf Coast from east of Morgan City, Louisiana, to the
Okaloosa/Walton County line, Florida, including New Orleans.  These
winds will spread inland and continue into Saturday.
INIT  18/2100Z 27.9N  91.2W   40 KT  45 MPH...POTENTIAL TROP CYCLONE
 12H  19/0600Z 29.5N  90.8W   40 KT  45 MPH...INLAND
 24H  19/1800Z 31.4N  89.4W   35 KT  40 MPH...INLAND
 36H  20/0600Z 32.8N  87.4W   30 KT  35 MPH...INLAND
 48H  20/1800Z 33.8N  84.9W   25 KT  30 MPH...INLAND
 60H  21/0600Z 34.7N  81.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  21/1800Z...DISSIPATED
Forecaster Cangialosi

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Page last modified: Tuesday, 26-Oct-2021 12:09:05 UTC