451 WTPA43 PHFO 090239 TCDCP3 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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