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Hurricane Henri Discussion Number  23
NWS National Hurricane Center Miami FL       AL082021
1100 AM EDT Sat Aug 21 2021
 
The Air Force Reserve and NOAA Hurricane Hunters have been
investigating Henri this morning and continue to provide very
valuable data.  The Air Force aircraft measured a peak flight-level
wind of 82 kt at 700 mb, which easily supports hurricane strength,
but the initial intensity is set at 65 kt as a blend of these data
and somewhat lower SFMR winds.  In addition, aircraft data indicate
that the minimum pressure has fallen to 991 mb.  The NOAA tail
Doppler radar data indicate that the storm is becoming more
vertically aligned and that a more symmetric eyewall appears to be
forming.  In addition, dropsonde data from the NOAA Gulfstream IV
aircraft flying around Henri indicate that the 34- and 50-kt wind
radii are a little larger than previously estimated in the
southeastern quadrant.  NOAA buoy 41001 located in the northeastern
quadrant of the hurricane has recently reported 18 ft. seas.
 
Henri is moving north-northeastward, or 020 degrees, at 12 kt.  The
steering pattern appears fairly well established now with a cut off
low located over the central Appalachians and a ridge building to
the east and northeast of Henri.  This pattern should cause the
storm to accelerate to the north or north-northeast today followed
by a slight bend to the left on Sunday.  The latest run of the GFS
has shifted to the east, but overall the models are focused in on
landfall being between central Long Island and Rhode Island on
Sunday.  However, users are reminded to not focus on the center
itself, as impacts will extend well away from the center, especially
to the east.  The new NHC track forecast is a little to the east of
the previous one and very near the best-performing models, the
consensus aids.
 
The environment looks favorable for Henri to continue to gain
strength through tonight with low shear, upper-level divergence
associated with the upper-level trough, and warm SSTs.  In fact,
the GFS and HWRF models show the minimum pressure dropping by 15 mb
or more during that time period.  By early Sunday, Henri is
predicted to cross the north wall of the Gulf Stream and that should
cause 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 48-60 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. Dangerous storm surge is possible
beginning late tonight 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 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 and
isolated moderate river flooding, over portions of Long Island, New
England, southeast New York and northern 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  21/1500Z 34.4N  72.5W   65 KT  75 MPH
 12H  22/0000Z 36.9N  71.9W   75 KT  85 MPH
 24H  22/1200Z 39.7N  71.9W   70 KT  80 MPH
 36H  23/0000Z 41.3N  72.6W   60 KT  70 MPH...INLAND
 48H  23/1200Z 42.4N  72.9W   35 KT  40 MPH...INLAND
 60H  24/0000Z 43.1N  71.9W   25 KT  30 MPH...POST-TROP/INLAND
 72H  24/1200Z 43.8N  69.2W   25 KT  30 MPH...POST-TROP/INLAND
 96H  25/1200Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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