000 WTPA43 PHFO 090835 TCDCP3 Tropical Depression Henriette Discussion Number 21 NWS Central Pacific Hurricane Center Honolulu HI EP082025 Issued by NWS National Hurricane Center Miami FL 1100 PM HST Fri Aug 08 2025 Deep convection that developed north of Henriette’s well-defined low-level circulation earlier today has persisted during the past several hours. Given this sustained convective activity and the presence of a closed surface circulation, Henriette is being reclassified as a tropical depression. A Metop-B ASCAT pass at 0655 UTC indicated peak winds up to 30 kt in the northern semicircle, supporting the initial intensity estimate of 30 kt. The initial motion is toward the west-northwest at about 13 kt, steered by a low- to mid-level ridge to its north. This general motion is expected to continue through the next 24 hours. From 24 to 72 hours, the cyclone 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, Henriette is forecast to turn toward the north-northwest as the trough becomes the primary steering feature. The updated track forecast remains very similar to the previous advisory and is near the middle of the tightly clustered consensus aids. 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 near term. However, global model guidance indicates that the cyclone will traverse an area of slightly warmer water between 24 and 72 hours. At the same time, upper-level divergence is forecast to increase in association with the approaching trough, which should enhance instability and support gradual strengthening beginning late Saturday and continuing into early next week. After that time, upper-level divergence is forecast to diminish, vertical shear will increase, and water temperatures will cool sharply. This loss of outflow support and more hostile environment should result in steady weakening, with Henriette expected to become a post-tropical remnant low by 120 h and dissipate soon thereafter as it is absorbed by a larger mid-latitude system. The new intensity forecast is nearly unchanged from the previous NHC forecast and lies near the middle- to upper-end of the guidance envelope. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 20.7N 145.7W 30 KT 35 MPH 12H 09/1800Z 21.6N 147.4W 30 KT 35 MPH 24H 10/0600Z 23.0N 149.6W 35 KT 40 MPH 36H 10/1800Z 24.8N 151.6W 45 KT 50 MPH 48H 11/0600Z 26.8N 154.2W 50 KT 60 MPH 60H 11/1800Z 28.7N 156.7W 55 KT 65 MPH 72H 12/0600Z 30.8N 159.2W 55 KT 65 MPH 96H 13/0600Z 35.2N 163.7W 45 KT 50 MPH 120H 14/0600Z 39.0N 167.0W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Gibbs (CPHC)
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