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Post-Tropical Cyclone Henriette Discussion Number  20
NWS Central Pacific Hurricane Center Honolulu HI   EP082025
Issued by NWS National Hurricane Center Miami FL
500 PM HST Fri Aug 08 2025
 
Henriette remains a post-tropical remnant low, consisting of a 
well-defined low-level swirl with a recent burst of deep convection 
that has persisted north of the center for the past few hours. This 
convective pulse has not persisted long enough, nor organized 
sufficiently, to justify reclassifying the system as a tropical 
cyclone at this time. Given the marginal environment and a recent 
ASCAT pass, the initial intensity is held at 30 kt for this 
advisory.

The remnant low is moving west-northwestward at 290/14 kt, steered 
by a low- to mid-level ridge to its north. This general motion is 
expected to continue through tonight. From 24 to 72 hours, Henriette 
should gradually turn toward the northwest as it approaches a 
weakness in the ridge caused by an amplifying upper-level trough 
well northwest of Hawaii. Between 72 and 96 hours, the system is 
forecast to turn toward the north-northwest as the trough becomes 
the primary steering feature. The updated track forecast is very 
similar to the previous advisory and lies close to the consensus 
aids, which remain tightly clustered through the forecast period.

The system is currently located over sea-surface temperatures near 
24 degrees C and within a stable, dry mid- to upper-level 
environment, which should limit convective coverage in the short 
term. However, global model guidance continues to indicate that the 
system will traverse a tongue of slightly warmer waters over the 
weekend. At the same time, increasing upper-level divergence 
associated with the approaching trough should enhance instability 
and favor the redevelopment of persistent deep convection. This is 
expected to allow the system to regenerate into a tropical cyclone 
over the weekend, with gradual strengthening into early next week. 
Model phase-space diagrams indicate it will likely maintain a 
shallow warm-core structure during its peak. Thereafter, increasing 
shear and diminishing outflow should support a transition to steady 
weakening as it becomes absorbed into the mid-latitudes. The new 
intensity forecast is very similar to the previous NHC forecast and 
lies near the middle- to upper-end of the guidance envelope.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 20.2N 144.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 12H  09/1200Z 21.1N 146.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  10/0000Z 22.3N 148.7W   35 KT  40 MPH...TROPICAL CYCLONE
 36H  10/1200Z 23.9N 151.0W   40 KT  45 MPH
 48H  11/0000Z 25.8N 153.2W   50 KT  60 MPH
 60H  11/1200Z 27.8N 155.6W   55 KT  65 MPH
 72H  12/0000Z 29.9N 158.1W   55 KT  65 MPH
 96H  13/0000Z 34.5N 162.6W   50 KT  60 MPH
120H  14/0000Z 39.7N 166.1W   40 KT  45 MPH
 
$$
Forecaster Gibbs (CPHC)
 
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