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Hurricane Henri Discussion Number  25
NWS National Hurricane Center Miami FL       AL082021
1100 PM EDT Sat Aug 21 2021
 
The convective pattern associated with Henri is less ragged than it
was 6 h ago, as the convection has increased near the center and a
NOAA Hurricane Hunter aircraft reported a 25 n mi wide eye has
formed  However, the hurricane has not yet strengthened
significantly, as the maximum winds remain about 65 kt in the
southeastern eyewall and the central pressure is near 987 mb.
 
Henri has moved a little to the right of the previous track at
18-20 kt during the past several hours.  However, the cyclone now
seems to be moving northward with an initial motion of 355/18 kt.
There is no 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 move
generally northward tonight.  A turn toward the north-northwest and
a slower forward speed are expected on Sunday, which should bring
the center near or over southern New England or Long Island between
18-24 h.  With the more eastward initial position, the forecast
track is shifted a bit to the east of the previous forecast.
However, there is still some uncertainty of the landfall point, as
several of the guidance models are to the left of the official
forecast.  After landfall, Henri should slow its forward speed and
turn eastward as it become steered by the mid-latitude westerlies.
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.
 
Henri is almost out of time to strengthen, as the center will be
moving north of the north wall of the Gulf Stream during the next
several hours.  The intensity forecast will call for modest
strengthening during the first 12 h based on the premise that
strengthening will occur before Henri reaches the cooler waters.
After that, while the cyclone should start to weaken before
landfall, it should still be near or at hurricane strength when it
reaches southern New England.  Rapid weakening is expected after
landfall, and Henri is again 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 late 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  22/0300Z 38.6N  71.0W   65 KT  75 MPH
 12H  22/1200Z 40.3N  71.2W   70 KT  80 MPH
 24H  23/0000Z 41.9N  71.8W   55 KT  65 MPH...INLAND
 36H  23/1200Z 43.1N  71.7W   30 KT  35 MPH...INLAND
 48H  24/0000Z 43.9N  70.5W   25 KT  30 MPH...POST-TROP/INLAND
 60H  24/1200Z 44.4N  68.3W   25 KT  30 MPH...POST-TROPICAL
 72H  25/0000Z 44.8N  63.5W   25 KT  30 MPH...POST-TROP/INLAND
 96H  26/0000Z...DISSIPATED
 
$$
Forecaster Beven
 
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