Tropical Cyclone Discussion
700 WTPZ42 KNHC 211453 TCDEP2 Tropical Storm Polo Discussion Number 4 NWS National Hurricane Center Miami FL EP172026 900 AM CST Mon Sep 21 2026 Polo is in the midst of a significant rapid intensification episode. Satellite images indicate a developing central dense overcast with very deep convection in the core. Additionally, microwave images indicate that a small eye has formed beneath the overcast with hints of a banded eyewall. The initial intensity is set to 55 kt, consistent with the latest TAFB classification, and a NOAA Hurricane Hunter aircraft is enroute to provide a better look at the intensity. Conditions look ideal for explosive intensification during the next day or two, with Polo's small inner core over very warm and untapped waters above 30.5C, within light shear and plentiful mid-level moisture. Every model responds to these conditions by showing rapid intensification, and the SHIPS rapid intensification index is showing percentages as high as I have ever seen them. The new forecast is raised from the previous one and is very aggressive, but still below the latest HCCA corrected-consensus aid, which verbatim would be at least a 99th percentile event for intensification. Polo is expected to be a small but very dangerous hurricane by tomorrow and beyond. The storm is drifting eastward, and still caught in weak steering currents. A mid-level ridge is expected to develop over Mexico by late Tuesday, causing Polo to move towards the west-northwest or northwest by Wednesday into late week. This could bring the core of the storm near or south of the coast of southwestern Mexico on Thursday, and then south of the Baja California Peninsula on Saturday. There is a large north-south spread in the guidance, which has both short and long-range implications. Generally, the guidance has nudged southward again, and the NHC forecast is adjusted in that direction. Given the spread in the track guidance, this is a low-confidence forecast. Key Messages: 1. Heavy rainfall associated with Polo will impact coastal portions of southwest Mexico through Thursday. This rainfall may produce life-threatening flooding and mudslides, especially in areas of steep terrain. 2. Polo is forecast to strengthen to a major hurricane while it moves closer to the coast of southwestern Mexico during the next few days. Although the core of the hurricane is forecast to stay offshore, it is too soon to determine the exact location or magnitude of impacts. Residents in southwestern Mexico should closely monitor its progress and updates to the forecast. A Tropical Storm Watch is in effect for portions of southwestern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 15.4N 103.4W 55 KT 65 MPH 12H 22/0000Z 15.2N 102.8W 85 KT 100 MPH 24H 22/1200Z 15.1N 102.3W 105 KT 120 MPH 36H 23/0000Z 15.4N 102.3W 125 KT 145 MPH 48H 23/1200Z 16.0N 102.8W 135 KT 155 MPH 60H 24/0000Z 16.8N 103.6W 140 KT 160 MPH 72H 24/1200Z 17.6N 104.8W 140 KT 160 MPH 96H 25/1200Z 18.6N 107.8W 130 KT 150 MPH 120H 26/1200Z 20.3N 110.4W 120 KT 140 MPH