Tropical Storm HENRI Advisory 8月23日

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Tropical Storm Henri Discussion Number  28
NWS National Hurricane Center Miami FL       AL082021
500 PM EDT Sun Aug 22 2021

Henri's satellite and radar signatures have continued to erode
during the day today owing to moderate southeasterly vertical wind
shear and entrainment of drier and more stable air off of the cooler
Atlantic waters. The primary rain shield has shifted into the
western semicircle, which is typical for tropical cyclones that are
in the early stages of undergoing extratropical transition. Doppler
radar velocity data from Upton, New York, and Boston, Massachusetts,
along with surface observations indicate that Henri's peak winds
have continued to decrease, with any tropical-storm-force winds now
confined to the offshore waters of Long Island Sound. Additional
spin down of the vortex and weakening of the low-level wind field
are anticipated due to land interaction and entrainment of
additional stable air. As a result of these unfavorable conditions,
Henri should weaken to a tropical depression this evening, and
become a post-tropical remnant low by Monday afternoon or evening.

Henri is now moving west-northwestward or 290/06 kt. The tropical
storm has finally made the much anticipated sharp turn toward the
west-northwest around the northeastern periphery of a mid- to
upper-level low currently located over southern New Jersey. These
two weather systems are forecast to slowly dumbbell in a counter-
clockwise motion, with Henri's circulation absorbing the other low
by Monday morning, possibly resulting in Henri stalling near the
New York-Connecticut border. By early Monday afternoon, a weak
mid-tropospheric shortwave currently moving across the Great Lakes
region is expected to eject the cyclone or its remnants eastward
to east-northeastward across southern New England and into the Gulf
of Maine by Monday night, before dissipating near or over Nova
Scotia on Tuesday. The new NHC track forecast is similar to the
previous advisory track, and remains close to the tightly packed
simple- and corrected-consensus track models TVCA, HCCA, and FSSE.

Although Henri's winds will be weakening, the cyclone will still
continue to be a prolific rain producer, resulting in significant
flooding across southern New England and portions of the
northern mid-Atlantic states for the next day or two.

Key Messages:

1. Heavy rainfall will continue to lead to considerable flash,
urban, and small stream flooding, along with the potential for
additional minor to isolated moderate river flooding over portions
of Long Island, New England, eastern New York, New Jersey and
northeast Pennsylvania.

FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z 41.6N  72.4W   35 KT  40 MPH...INLAND
 12H  23/0600Z 42.0N  73.5W   30 KT  35 MPH...INLAND
 24H  23/1800Z 42.6N  73.0W   25 KT  30 MPH...INLAND
 36H  24/0600Z 43.0N  70.4W   25 KT  30 MPH...POST-TROP/INLAND
 48H  24/1800Z 43.6N  66.5W   25 KT  30 MPH...POST-TROP/INLAND
 60H  25/0600Z...DISSIPATED

$$
Forecaster Stewart