Tropical Storm NICHOLAS Advisory 9月15日

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Tropical Storm Nicholas Discussion Number  11
NWS National Hurricane Center Miami FL       AL142021
400 PM CDT Tue Sep 14 2021

Doppler weather radar data from Houston and Lake Charles, along with
surface observations, indicate that the intensity of Nicholas has
remained steady over the past several hours despite having moved a
little farther inland over the upper Texas coastal plain. Both
satellite and radar data also indicate that the overall circulation
has tightened up somewhat, although a large swath of stable low
clouds have advected into most of the southern semicircle of
Nicholas' circulation. The highest sustained wind speeds of 34-36
kt have occurred in a narrow band of fragmented, shallow convection
between Sabine Pass, Texas, and Cameron, Louisiana, during the past
couple of hours. Doppler radar velocity data from Lake Charles has
also indicated wind speeds of 40-45 at 3,000 ft altitude just
offshore the southwestern coast of Louisiana. Based on these wind
data, the initial intensity is set at 35 kt. The estimated central
pressure of 1003 mb is based on nearby surface observations,
especially the reports from the Eagle Point, Texas, C-MAN station,
which indicate that the center of Nicholas passed over or near that
station between 1800-1900 UTC. As Nicholas moves farther inland,
gradual weakening is forecast due to land interaction, entrainment
of drier and more stable low- and mid-level air, and strong
westerly vertical wind shear in excess of 30 kt. Nicholas is
forecast to become a tropical depression later this evening and
degenerate into a remnant low by late Wednesday or early Thursday.

The initial motion estimate is east-northeastward or 070 degrees at
5 kt. Nicholas is forecast by most of the global and regional models
continue its east-east-northeastward motion through tonight,
followed by an eastward motion at a slower forward speed on
Wednesday and Thursday. Nicholas could still stall over southwestern
or central Louisiana as the low-level steering flow collapses on
Thursday.  The new NHC track forecast is similar to the previous
advisory track, and lies near the consensus track models TCVA and
NOAA-HCCA.

Although the winds associated with Nicholas will gradually subside,
heavy rainfall and a significant flash flood risk will continue
along the Gulf Coast for the next couple of days.


Key Messages:

1. Heavy rainfall will impact areas across southern and central
Louisiana, southern Mississippi, far southern Alabama, and the
western Florida Panhandle through early Friday. Significant rainfall
amounts are expected, potentially resulting in areas of
life-threatening flash and urban flooding across these areas.
Widespread minor to isolated moderate river flooding is also
possible.

2. Storm surge inundation along the coasts of upper Texas and
southwestern Louisiana will gradually diminish into tonight.

3. Tropical storm conditions in the warning area long portions of
the upper Texas and southwestern Louisiana coasts will gradually
subside by this evening.


FORECAST POSITIONS AND MAX WINDS

INIT  14/2100Z 29.6N  94.6W   35 KT  40 MPH...INLAND
 12H  15/0600Z 29.8N  94.0W   25 KT  30 MPH...INLAND
 24H  15/1800Z 30.0N  93.2W   25 KT  30 MPH...INLAND
 36H  16/0600Z 30.1N  92.8W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  16/1800Z 30.5N  92.4W   15 KT  15 MPH...POST-TROP/REMNT LOW
 60H  17/0600Z 30.9N  92.4W   15 KT  15 MPH...POST-TROP/REMNT LOW
 72H  17/1800Z...DISSIPATED

$$
Forecaster Stewart