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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
 
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