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Tropical Storm Henri Forecast Discussion Number 28
2021-08-22 22:53:32| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Sun Aug 22 2021 000 WTNT43 KNHC 222053 TCDAT3 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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