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Tropical Depression Henriette Discussion Number  22
NWS Central Pacific Hurricane Center Honolulu HI   EP082025
Issued by NWS National Hurricane Center Miami FL
500 AM HST Sat Aug 09 2025

Convection has persisted and perhaps increased slightly in areal 
coverage and organization over the last 6 hours.  A recent AMSR2 
microwave pass paints a similar picture to the GOES-18 imagery, with 
the convection confined to the northwest quadrant and the center 
located near the edge of the convection.  The latest subjective 
Dvorak classifications are 1.5/25 kt from JTWC and PHFO, and 1.0 
from SAB.  The UW-CIMSS objective intensity estimates are higher 
than the subjective estimates, mostly in the 30-35 kt range.  An 
earlier ASCAT-B pass from 0655 UTC indicates that peak winds were at 
least 30 kt.  The initial intensity is held at 30 kt for this 
advisory, but Henriette is close to regaining tropical storm 
strength.

The initial motion is toward the west-northwest, or 300 degrees at 
12 kt.  The global models show that Henriette will round the 
southwestern periphery of the subtropical ridge tonight, which will 
cause the cyclone to turn toward the northwest, in between the ridge 
and an approaching large deep-layer trough to the west.  In a couple 
days, the trough will become stationary or even retrograde westward. 
This steering pattern favors a continued northwestward motion 
through the forecast period.  The NHC track forecast is very similar 
to the previous one and lies near the middle of the tightly 
clustered consensus aids.

Henriette will move over gradually warming sea-surface temperatures 
(SSTs) and through gradually cooling upper-level temperatures now 
through the next 72 h.  SSTs currently near 24.5 to 25C are forecast 
to warm to the 26.5 to 27C range along the cyclone's path.  There is 
some uncertainty as to how the expected moderate wind shear may 
affect the cyclone, especially given how dry the mid-troposphere 
will continue to be along Henriette's path.  The shear direction 
could be close to the direction of the cyclone's motion, so the 
shear shouldn't be as much of a negative factor as the dry air.  
Given all the competing factors mentioned above, slow strengthening 
seems likely over the next few days.  The latest NHC intensity 
forecast is similar to the previous one and is near the middle of 
the guidance envelope.  Beyond day 3, wind shear should increase, 
and Henriette will likely reach cooler water again by day 4.  These 
factors should cause the system to lose its convection and become 
post-tropical in 4 to 5 days.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/1500Z 21.4N 146.8W   30 KT  35 MPH
 12H  10/0000Z 22.3N 148.5W   35 KT  40 MPH
 24H  10/1200Z 23.9N 150.6W   40 KT  45 MPH
 36H  11/0000Z 25.8N 152.8W   45 KT  50 MPH
 48H  11/1200Z 27.9N 155.3W   50 KT  60 MPH
 60H  12/0000Z 29.9N 157.9W   55 KT  65 MPH
 72H  12/1200Z 32.0N 160.4W   55 KT  65 MPH
 96H  13/1200Z 36.1N 165.0W   40 KT  45 MPH
120H  14/1200Z 40.3N 168.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Hagen
 
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