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Tropical Storm Henriette Discussion Number  15
NWS National Hurricane Center Miami FL       EP082025
1100 AM HST Thu Aug 07 2025
 
Henriette has been producing a smaller area of deep convection than
earlier, as it seems to be struggling a bit with dry air and
sea-surface temperatures near 24 C.  The latest subjective Dvorak
current intensity estimates are 2.5/35 kt from TAFB and 1.5/25 kt
from SAB.  The latest objective estimates from UW-CIMMS range from
about 30 to 40 kt.  A recent 1914 UTC ASCAT-C pass suggests that 
Henriette has likely weakened a bit from earlier.  Based on the 
above data, the initial intensity is lowered to 40 kt for this 
advisory.
 
The motion of 280/14 kt is unchanged from the previous advisory.
This motion will continue through today as Henriette is steered by
mid-level ridging well to its north.  The cyclone will then round
the southwestern periphery of the mid-level ridge as a large
deep-layer trough approaches from the west.  These features will
cause Henriette to gradually turn toward the northwest in a couple
of days.  Very little change has been made to the NHC track
forecast, which lies near the tightly clustered consensus aids.
Confidence in the track forecast is high through the weekend, and
Henriette will not directly impact the Hawaiian Islands.
 
Henriette is expected to continue moving over cool ocean waters near 
24C for another 36 h before it begins to gradually move over 
increasing water temperatures.  The tropical storm will also 
continue moving through a very dry environment.  Most of the 
guidance shows the storm maintaining a 35-40 kt intensity during 
this time. Henriette is also expected to encounter colder than 
normal mid- and upper-level temperatures in a couple of days.  If 
Henriette survives the next 48 h or so, then strengthening would 
appear likely later in the forecast period due to increasing 
sea-surface temperatures, very low vertical wind shear, and 
decreasing mid- to upper-level temperatures as the aforementioned 
deep-layer trough approaches. The official forecast shows some 
slight weakening in the short term, followed by strengthening to a 
hurricane by day 4 well to the north of Hawaii.  The latest NHC 
forecast is near the intensity consensus and close to the higher end 
of the guidance at day 4 and 5.  It should be noted that the HAFS 
models are showing a slightly higher intensity than the NHC 
forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/2100Z 18.9N 136.8W   40 KT  45 MPH
 12H  08/0600Z 19.3N 139.2W   40 KT  45 MPH
 24H  08/1800Z 19.9N 142.2W   40 KT  45 MPH
 36H  09/0600Z 20.9N 145.0W   40 KT  45 MPH
 48H  09/1800Z 22.1N 147.5W   40 KT  45 MPH
 60H  10/0600Z 23.5N 150.0W   45 KT  50 MPH
 72H  10/1800Z 25.2N 152.3W   55 KT  65 MPH
 96H  11/1800Z 28.9N 156.7W   70 KT  80 MPH
120H  12/1800Z 32.6N 160.6W   65 KT  75 MPH
 
$$
Forecaster Hagen
 
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