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Tropical Storm Henriette Discussion Number  18
NWS Central Pacific Hurricane Center Honolulu HI   EP082025
Issued by NWS National Hurricane Center Miami FL
500 AM HST Fri Aug 08 2025

Henriette has failed to produce deep convection for about 12 hours 
now. The latest subjective Dvorak estimates are 25 kt from JTWC and 
too weak to classify from SAB and PHFO.  Recent objective intensity 
estimates range from 25 to 40 kt.  An earlier ASCAT pass from 0535 
UTC showed a large area of 30-33 kt vectors on the north side of 
Henriette.  Henriette will be maintained as a 35-kt tropical storm 
for this advisory, but it could degenerate to a post-tropical 
remnant low at any time today.

The cyclone is moving just north of due west at 280/15 kt. A turn to 
the west-northwest is expected soon as the cyclone tracks along the 
southwestern periphery of a subtropical ridge to its northeast. A 
turn toward the northwest is forecast late this weekend into early 
next week as Henriette becomes steered between an amplifying 
longwave trough northwest of Hawaii and the subtropical ridge to its 
northeast.  The NHC track forecast is nearly identical to the 
previous one and is in good agreement with the tightly clustered 
consensus aids.  Confidence remains high that Henriette will remain 
far to the north of Hawaii.

Henriette is over 24C sea-surface temperatures (SSTs) and is 
embedded within a dry airmass.  These cold SSTs are expected to 
persist along the cyclone's track for another 12 to 24 h.  If 
Henriette doesn't generate organized convection soon, it could 
degenerate to a remnant low today, and this is explicitly shown in 
the NHC forecast Beyond 24 h, Henriette (or its remnants) will 
encounter progressively warmer water temperatures over the weekend, 
peaking around 26-27C in about 3 days.  Upper-level temperatures are 
also expected to decrease in a couple of days as the aforementioned 
trough approaches Henriette, which would increase instability. These 
factors, along with relatively low shear, will likely allow 
Henriette to restrengthen later this weekend into early next week, 
as depicted by most of the models.  The NHC intensity forecast is at 
the low end of the guidance envelope through 36 h, and at the high 
end of the guidance at 72-96 h.  Beyond day 4, wind shear from the 
longwave trough and cooling SSTs should lead to steady weakening as 
Henriette moves farther into the mid-latitudes.

Even if Henriette becomes post-tropical today, given the high 
likelihood of regeneration back into a tropical cyclone and 
subsequent restrengthening, NHC plans on maintaining advisories 
during the post-tropical phase.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 19.7N 141.5W   35 KT  40 MPH
 12H  09/0000Z 20.3N 143.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  09/1200Z 21.3N 146.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  10/0000Z 22.6N 148.7W   35 KT  40 MPH...TROPICAL CYCLONE
 48H  10/1200Z 24.1N 150.9W   45 KT  50 MPH
 60H  11/0000Z 25.9N 153.2W   55 KT  65 MPH
 72H  11/1200Z 27.9N 155.7W   65 KT  75 MPH
 96H  12/1200Z 32.3N 160.4W   65 KT  75 MPH
120H  13/1200Z 37.1N 165.1W   50 KT  60 MPH
 
$$
Forecaster Hagen
 
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