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Hurricane Henri Discussion Number  24
NWS National Hurricane Center Miami FL       AL082021
500 PM EDT Sat Aug 21 2021
 
Visible satellite images and microwave data indicate that a tight 
inner core has formed in association with Henri, but the convective 
pattern appears ragged in infrared images.  An ASCAT pass from 
earlier today indicated that the 34- and 50-kt winds continue to 
expand in the southeastern quadrant, and that data was used to 
update the initial wind radii.  The latest Dvorak estimates range 
from 55 to 77 kt, and based on that data, the initial intensity is 
held at 65 kt.  The NOAA Hurricane Hunters will be investigating 
Henri this evening.
 
Henri is moving faster to the north-northeast, or 020 degrees, at 16 
kt.  There continues to be little change to the forecast track 
philosophy.  A cut-off low located over the central Appalachians and 
a ridge building to the east and northeast of Henri should cause the 
storm to continue moving north-northeastward through tonight. A 
decresae in forward speed and a slight bend to the left is then 
forecast to occur on Sunday.  The latest model guidance has shifted 
slightly to the right, and the NHC official track forecast has been 
nudged in that direction.  This forecast shows landfall over eastern 
Long Island and southern Connecticut in about 24 hours. Users are 
reminded to not focus on the exact forecast track, as the average 
24-hour track uncertainty is around 40 miles and impacts will extend 
well away from the center.  
 
The environment looks favorable for Henri to strengthen through 
tonight with low shear, upper-level divergence associated with the 
upper-level trough, and warm SSTs.  In fact, SST analyses indicate 
that Henri will be passing over a patch of very warm 30 deg C waters 
this evening.  By early Sunday Henri is predicted to cross the 
north wall of the Gulf Stream.  That should result in some 
weakening, but Henri is forecast to be at or near hurricane strength 
at landfall.  Once the center moves inland over the northeast 
United States, rapid weakening is expected.  Henri is forecast to 
become post-tropical in about 48 hours and dissipate in 3 to 4 days.
 
Key Messages:
 
1. Dangerous storm surge inundation is expected to begin late 
tonight or Sunday in portions of Long Island, Connecticut, Rhode 
Island, and southeastern Massachusetts, where a Storm Surge Warning 
has been issued. Residents in these areas should follow any advice 
given by local officials.
 
2. Hurricane conditions are expected to begin late tonight or
Sunday in portions of Long Island, Connecticut, and Rhode Island,
where a Hurricane Warning is in effect. Tropical storm conditions
will begin in these areas tonight.
 
3. Heavy rainfall may lead to considerable flash, urban, and small 
stream flooding, along with the potential for widespread minor to 
isolated moderate river flooding over portions of Long Island, New 
England, eastern New York and New Jersey.
 
4. Swells from Henri will continue to affect much of the east coast
of the U.S. during the next day or two. These swells could cause
life-threatening surf and rip currents.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/2100Z 36.3N  71.4W   65 KT  75 MPH
 12H  22/0600Z 38.8N  71.4W   70 KT  80 MPH
 24H  22/1800Z 40.8N  72.1W   60 KT  70 MPH
 36H  23/0600Z 42.1N  72.4W   40 KT  45 MPH...INLAND
 48H  23/1800Z 43.3N  71.9W   25 KT  30 MPH...INLAND
 60H  24/0600Z 43.6N  69.9W   25 KT  30 MPH...POST-TROP/INLAND
 72H  24/1800Z 44.3N  68.1W   25 KT  30 MPH...POST-TROP/INLAND
 96H  25/1800Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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