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Tropical Storm Henri Discussion Number  21
NWS National Hurricane Center Miami FL       AL082021
1100 PM EDT Fri Aug 20 2021

Satellite imagery shows that Henri is becoming better organized 
this evening, with the low-level center becoming more embedded in 
the convective overcast and an increase in convective banding.  
There has also been an increase in the anticyclonic outflow.  
However, reports from Air Force Reserve and NOAA Hurricane Hunter 
aircraft show that this has not yet resulted in strengthening, as 
the maximum winds remain about 60 kt to the southeast of the 
elongated center and the central pressure is in the 994-996 mb 
range.  

Henri has turned northward, and the initial motion is now 010/8.  
A deep-layer mid-latitude trough over the Appalachians and the Ohio 
Valley will cut off into a closed low during the next 12-24 h, 
while a ridge builds northward to the east and northeast of Henri.  
This evolution should cause the storm to move north-northeastward 
for 12-24 h, followed by a turn toward the north-northwest from 
24-48 h.  This motion should bring the center of Henri over the 
mid-Atlantic states or southern New England between 36-48 h.  After 
48 h, the cyclone should get caught up in the southern edge of the 
westerlies and turn generally eastward across southern New England 
and the Gulf of Maine.  There has been little change in the 
direction of the forecast guidance since the last advisory, but the 
guidance is faster on this cycle through 48 h.  Thus, the new track 
forecast, which lies close to the consensus models, is faster than 
the previous forecast through the 48 h point.

A combination of decreasing shear, improved organization, and 
upper-level divergence associated with the trough to the west 
should allow Henri to strengthen for the next 24 h or so, and the 
new intensity forecast calls for a peak intensity of 75 kt.  After 
24 h, the center should move over cooler water, and weakening 
should start before landfall in the northeastern United States.  
However, the cyclone is still expected to be at or near hurricane 
intensity at landfall.  After landfall, Henri should weaken quickly 
and become post-tropical by the 72 h time.  Dissipation is forecast 
between 96-120 h.  The new intensity forecast follows the overall 
trend of the intensity guidance.
 
Users are reminded to not focus on the exact forecast of the
center of Henri since impacts will extend far from the center.
 
Key Messages:
 
1. Dangerous storm surge inundation is expected to begin late 
Saturday night or Sunday in portions of Long Island, Connecticut, 
Rhode Island, and southeastern Massachusetts, where a Storm Surge 
Warning has been issued. Dangerous storm surge is possible 
beginning late Saturday night or Sunday in western portions of Long 
Island and Connecticut in the Storm Surge Watch area.  Residents in 
these areas should follow any advice given by local officials.
 
2. Hurricane conditions are expected to begin late Saturday night 
or Sunday in portions of Long Island and Connecticut, where a 
Hurricane Warning has been issued.  Hurricane conditions are 
possible late Saturday night or Sunday across portions of Rhode 
Island and southeastern Massachusetts.
 
3. Heavy rainfall may lead to considerable flash, urban, and small 
stream flooding, along with the potential for widespread minor and 
isolated moderate river flooding, over portions of Long Island and 
New England Sunday into Monday.
 
4. Swells from Henri will continue to affect much of the east coast
of the U.S. through the weekend. These swells could cause
life-threatening surf and rip currents.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 32.3N  73.5W   60 KT  70 MPH
 12H  21/1200Z 34.3N  72.8W   65 KT  75 MPH
 24H  22/0000Z 37.7N  72.1W   75 KT  85 MPH
 36H  22/1200Z 40.2N  72.6W   70 KT  80 MPH
 48H  23/0000Z 41.4N  73.4W   50 KT  60 MPH...INLAND
 60H  23/1200Z 42.2N  73.2W   35 KT  40 MPH...INLAND
 72H  24/0000Z 42.7N  72.3W   30 KT  35 MPH...POST-TROP/INLAND
 96H  25/0000Z 43.5N  67.0W   25 KT  30 MPH...POST-TROPICAL
120H  26/0000Z...DISSIPATED
 
$$
Forecaster Beven
 
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