325 WTPA41 PHFO 282037 TCDCP1 Hurricane Iona Discussion Number 7 NWS Central Pacific Hurricane Center Honolulu HI CP012025 Issued by NWS National Hurricane Center Miami FL 1100 AM HST Mon Jul 28 2025 After rapidly strengthening overnight, the cloud pattern and overall structure of Iona has changed little during the past 6 hours. A fairly symmetric Central Dense Overcast is seen over the center in geostationary satellite imagery, but there has been no recent microwave data to examine the inner core structure. The latest subjective satellite intensity estimates are T4.0/65 kt from SAB, and T3.5/55 kt from both PHFO and JTWC. Objective estimates remain lower, although it is possible that the small size of the cyclone is making it difficult for those techniques to capture the true intensity. The initial intensity for this advisory will remain 65 kt, in line with the higher subjective estimate from SAB. Iona is located within a low-shear environment and over sea surface temperatures of around 28C. Those conditions favor strengthening, however some nearby dry mid-level air may have been entrained in the circulation which likely caused the recent pause in intensification. Given the favorable upper-air pattern and warm sea surface temperatures, additional strengthening appears likely. The regional hurricane models are more aggressive this cycle and indicate that Iona could be near or at major hurricane strength in a day or so. As a result, the lastest official forecast calls for rapid strengthening during the next 24 hours and the peak intensity is raised slightly from the previous advisory. Around midweek, slightly lower SSTs and an increase in vertical wind shear are expected to cause gradual weakening through the remainder of the forecast period. The updated NHC intensity forecast is close to the regional models through 24 hours, and then follows the latest multi-model (IVCN) consensus aid after that time. Iona is moving westward or 270 degrees at 9 kt. The storm is forecast to move along the southern portion of a subtropical ridge that is well established over the central Pacific. This steering pattern should take the storm westward during the next day or so, followed by a faster west-northwestward motion after midweek. The updated track forecast is once again near the center of the model envelope, close to the various consensus aids. Confidence remains high that Iona will stay well south of the Hawaiian Islands. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 10.6N 151.0W 65 KT 75 MPH 12H 29/0600Z 10.6N 152.6W 80 KT 90 MPH 24H 29/1800Z 10.6N 155.0W 95 KT 110 MPH 36H 30/0600Z 10.7N 157.7W 90 KT 105 MPH 48H 30/1800Z 10.9N 161.0W 80 KT 90 MPH 60H 31/0600Z 11.2N 164.5W 65 KT 75 MPH 72H 31/1800Z 11.7N 168.1W 55 KT 65 MPH 96H 01/1800Z 12.9N 175.2W 45 KT 50 MPH 120H 02/1800Z 14.7N 178.5E 40 KT 45 MPH $$ Forecaster Brown
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