Tropical Storm Henriette Discussion Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Sat Aug 09 2025
Satellite imagery shows that Henriette retains a well-organized
low-level structure, with a curved band wrapping around the west
side of the circulation. However, convection within the band has
struggled to persist due to surrounding dry mid- to upper-level air.
Subjective Dvorak current intensity estimates from SAB, JTWC, and
HFO, along with objective estimates from UW-CIMSS, support holding
the initial intensity at 35 kt for this advisory.
The initial motion is toward the northwest at 13 kt, steered by a
subtropical ridge to the northeast and an amplifying mid-latitude
trough to the northwest. Henriette’s forward speed is expected to
increase through 36 hours, level off near 60 hours, and then slow
through 96 hours as the steering flow weakens. This motion will keep
Henriette well northeast of the Hawaiian Islands. Guidance indicates
the sharp upper trough will cut off into an upper low on Monday and
retrograde westward, a pattern that should maintain Henriette’s
northwestward motion. The track forecast is very similar to the
previous one but is slightly left of the earlier forecast from days
3 to 4, and lies near the middle of the tightly clustered consensus
aids.
Sea-surface temperatures along Henriette’s forecast track should
gradually warm from near 25 degrees C to around 26–27 degrees C
through about 60 h. Despite surrounding dry mid- to upper-level air,
a combination of warmer waters and increasing upper-level divergence
associated with an upper trough to the northwest should enhance
outflow and support gradual strengthening. The NHC forecast
continues to show a peak near 55 kt in the 36–48 h period, nearly
identical to the previous forecast and within the middle to upper
end of the guidance envelope. Thereafter, cooler waters, increasing
shear, and diminishing upper-level outflow should result in steady
weakening, with Henriette expected to become a post-tropical remnant
low by 96 h and dissipate by 120 h as it is absorbed into the
mid-latitude flow.
FORECAST POSITIONS AND MAX WINDS
INIT 10/0900Z 23.8N 150.3W 35 KT 40 MPH
12H 10/1800Z 25.1N 151.9W 40 KT 45 MPH
24H 11/0600Z 27.2N 154.2W 50 KT 60 MPH
36H 11/1800Z 29.3N 156.8W 55 KT 65 MPH
48H 12/0600Z 31.4N 159.4W 55 KT 65 MPH
60H 12/1800Z 33.7N 161.8W 50 KT 60 MPH
72H 13/0600Z 35.4N 164.1W 45 KT 50 MPH
96H 14/0600Z 38.7N 168.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 15/0600Z...DISSIPATED
$$
Forecaster Gibbs (CPHC)
NWS Central Pacific Hurricane Center Honolulu HI EP082025
Issued by NWS National Hurricane Center Miami FL
1100 PM HST Sat Aug 09 2025
Satellite imagery shows that Henriette retains a well-organized
low-level structure, with a curved band wrapping around the west
side of the circulation. However, convection within the band has
struggled to persist due to surrounding dry mid- to upper-level air.
Subjective Dvorak current intensity estimates from SAB, JTWC, and
HFO, along with objective estimates from UW-CIMSS, support holding
the initial intensity at 35 kt for this advisory.
The initial motion is toward the northwest at 13 kt, steered by a
subtropical ridge to the northeast and an amplifying mid-latitude
trough to the northwest. Henriette’s forward speed is expected to
increase through 36 hours, level off near 60 hours, and then slow
through 96 hours as the steering flow weakens. This motion will keep
Henriette well northeast of the Hawaiian Islands. Guidance indicates
the sharp upper trough will cut off into an upper low on Monday and
retrograde westward, a pattern that should maintain Henriette’s
northwestward motion. The track forecast is very similar to the
previous one but is slightly left of the earlier forecast from days
3 to 4, and lies near the middle of the tightly clustered consensus
aids.
Sea-surface temperatures along Henriette’s forecast track should
gradually warm from near 25 degrees C to around 26–27 degrees C
through about 60 h. Despite surrounding dry mid- to upper-level air,
a combination of warmer waters and increasing upper-level divergence
associated with an upper trough to the northwest should enhance
outflow and support gradual strengthening. The NHC forecast
continues to show a peak near 55 kt in the 36–48 h period, nearly
identical to the previous forecast and within the middle to upper
end of the guidance envelope. Thereafter, cooler waters, increasing
shear, and diminishing upper-level outflow should result in steady
weakening, with Henriette expected to become a post-tropical remnant
low by 96 h and dissipate by 120 h as it is absorbed into the
mid-latitude flow.
FORECAST POSITIONS AND MAX WINDS
INIT 10/0900Z 23.8N 150.3W 35 KT 40 MPH
12H 10/1800Z 25.1N 151.9W 40 KT 45 MPH
24H 11/0600Z 27.2N 154.2W 50 KT 60 MPH
36H 11/1800Z 29.3N 156.8W 55 KT 65 MPH
48H 12/0600Z 31.4N 159.4W 55 KT 65 MPH
60H 12/1800Z 33.7N 161.8W 50 KT 60 MPH
72H 13/0600Z 35.4N 164.1W 45 KT 50 MPH
96H 14/0600Z 38.7N 168.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 15/0600Z...DISSIPATED
$$
Forecaster Gibbs (CPHC)
