002 WTPA41 PHFO 310234 TCDCP1 Tropical Storm Iona Discussion Number 16 NWS Central Pacific Hurricane Center Honolulu HI CP012025 Issued by NWS National Hurricane Center Miami FL 500 PM HST Wed Jul 30 2025 Iona continues to weaken, with the low-level circulation center remaining mostly exposed. Recent satellite imagery showed a convective burst on the north side of the center, with cloud tops reaching as cold as -75°C. However, this burst has not been sustained, and convection remains generally disorganized. An earlier ASCAT pass sampled peak winds of around 40 kt in the northern semicircle of the circulation. Subjective and objective satellite intensity estimates remain in the 40–65 kt range. Taking into account the degraded satellite presentation, ASCAT data, and the blend of available intensity estimates, the initial intensity is set at 45 kt. The initial motion is 275/20 kt. There is little change in the forecast philosophy from the past couple of forecasts, as a general westward motion is expected to continue during the next day or so while Iona moves along the southern periphery of a low- to mid-level subtropical ridge to the north. A turn toward the west-northwest and a gradual decrease in forward speed are expected after 36 h as the system is steered into a weakness in the ridge. There has been little change in the forecast guidance since the last advisory, and the new forecast track is similar to the previous track. The weakening trend appears to have stabilized, with only slight additional weakening expected tonight. By Thursday, Iona's intensity is forecast to level off as it moves over warmer sea surface temperatures and into a marginally more favorable atmospheric environment. The system is expected to resume weakening by early next week as it encounters mid-level dry air and increasing vertical shear. The intensity forecast has been adjusted slightly downward to reflect the recent trends. This forecast assumes that Iona will maintain enough convection to remain a tropical cyclone. Should convection fail to persist, the system could degenerate into a remnant low or trough before day five. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 11.8N 164.8W 45 KT 50 MPH 12H 31/1200Z 12.2N 167.7W 40 KT 45 MPH 24H 01/0000Z 12.8N 171.3W 35 KT 40 MPH 36H 01/1200Z 13.4N 174.8W 35 KT 40 MPH 48H 02/0000Z 14.2N 177.7W 35 KT 40 MPH 60H 02/1200Z 15.0N 179.6E 35 KT 40 MPH 72H 03/0000Z 16.0N 177.3E 35 KT 40 MPH 96H 04/0000Z 18.2N 172.6E 35 KT 40 MPH 120H 05/0000Z 20.6N 168.1E 30 KT 35 MPH $$ Forecaster Gibbs (CPHC)
Source link