Tropical Cyclone Discussion
909 WTPZ42 KNHC 242051 TCDEP2 Hurricane Polo Discussion Number 17 NWS National Hurricane Center Miami FL EP172026 300 PM CST Thu Sep 24 2026 A NOAA Hurricane Hunter aircraft has investigated Polo during the past few hours, and its data indicates that the eyewall replacement cycle mentioned in the previous advisory is almost complete. The first aircraft pass reported concentric eyewalls of 15 and 30 n mi diameters. Subsequent passes reported that the inner eyewall dissipated, while the remaining outer eyewall contracted to 25 n mi diameter. In addition, 700-mb flight level winds in the northeast eyewall increased by about 15 kt during the mission, with the maximum winds of 147 kt. The central pressure also started to fall during the mission, and the estimated value from data on the last pass is near 935 mb. Based on these data, the initial intensity is set at 130 kt. It should be noted that the strengthening observed by the aircraft has not yet been fully reflected in satellite imagery. Polo is now moving west-northwestward or 285/9 kt. There is little change to the track forecast reasoning from the previous advisory. A mid-level ridge building westward from northern Mexico should steer the hurricane generally westward for the next 24-36 h or so. After that, a mid-latitude trough moving eastward across the northeastern Pacific should prevent the ridge from building farther west, with Polo likely to recurve northward and northeastward around the western end of the ridge. The track guidance is generally in good agreement with this scenario, although there remains some spread in the forward speed between the slower HAFS models and the faster GFS and HCCA models. The new track, which is an update of the previous forecast, takes the center away from the southwestern coast of Mexico this evening and then has it moving across Baja California into northwestern mainland Mexico in 96-120 h. The new intensity forecast now calls for Polo to strengthen for the next 12 h or so after the end of the eyewall replacement, and Polo is expected to regain Category 5 strength tonight or Friday morning. After that, a slow weakening is expected through 96 h as Polo encounters somewhat increased shear, with the caveat that there could be some fluctuations due to additional eyewall replacement cycles. Rapid weakening is expected when the cyclone crosses Baja California and moves into mainland Mexico. The new forecast again lies near the upper edge of the intensity guidance. It should be noted that moisture from Hurricane Polo and Odalys will be carried a long distance into the southwestern United States this weekend and early next week, and may indirectly contribute to a heavy rainfall and flash flood threat in the region. See products issued by the Weather Prediction Center for more information. Key Messages: 1. Heavy rainfall associated with Polo will impact coastal portions of southwest Mexico today. This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain. 2. Wind gusts to tropical storm force may occur along portions of the southwestern coast of Mexico this evening. 3. Polo is forecast to approach the Baja California Peninsula early next week as a hurricane. Interests there should closely monitor the latest updates and ensure that they have their preparedness plan in place. FORECAST POSITIONS AND MAX WINDS INIT 24/2100Z 17.1N 105.5W 130 KT 150 MPH 12H 25/0600Z 17.2N 106.8W 140 KT 160 MPH 24H 25/1800Z 17.4N 108.8W 135 KT 155 MPH 36H 26/0600Z 17.8N 110.5W 130 KT 150 MPH 48H 26/1800Z 18.7N 112.0W 125 KT 145 MPH 60H 27/0600Z 20.3N 113.1W 120 KT 140 MPH 72H 27/1800Z 22.0N 113.4W 110 KT 125 MPH 96H 28/1800Z 25.2N 112.8W 95 KT 110 MPH 120H 29/1800Z 27.9N 109.9W 60 KT 70 MPH...INLAND