Tropical Cyclone Discussion
893 WTPZ42 KNHC 220247 TCDEP2 Hurricane Polo Discussion Number 6 NWS National Hurricane Center Miami FL EP172026 900 PM CST Mon Sep 21 2026 Polo continues to rapidly intensify (RI) this evening. On geostationary satellite, the hurricane's structure is becoming increasingly impressive, with the earlier ragged eye clearing out as very cold cloud tops (-80 C and below) wrap around. In addition, an F17 SSMIS microwave pass at 0105 UTC suggests the earlier eyewall replacement cycle (ERC) observed from the NOAA-P3 aircraft has completed. Not surprisingly, satellite intensity estimates are quickly rising, with the latest subjective Dvorak estimate from TAFB up to T5.0/90 kt, with the DMINT estimate associated with that recent SSMIS pass at 96 kt. Given the continued improvement of Polo on satellite, the initial intensity is being increased to 95 kt for this advisory. The intensifying hurricane continues to move a little south of due east, with its estimated motion at 105 degrees at 4 kt. This short-term motion is expected to continue for the next 12-18 h before mid- to upper-level ridging over Mexico intensifies. The net result of this synoptic pattern change is that the primary steering should flip in about 24 h, causing Polo to make a sharp turn to the northwest and then west-northwest in the 36-60 h time frame, bringing the core of the hurricane near, but just offshore of, the coast of southwestern Mexico. Finally, toward the end of the forecast period, Polo will likely be reaching the westward extent of the deep-layer ridge. In addition, Polo may also be approaching Tropical Storm Odalys that is forecast to be positioned west of Polo, and much of the track guidance responds to this evolution by showing the hurricane turning more northward by 120 h. There continues to be quite a bit of cross-track uncertainty, both in terms of how sharp Polo's turn to the northwest will be in the next 48 h, and also toward the end of the forecast when Polo could experience binary interaction with Odalys. The NHC track forecast continues to favor a blend of the HFIP Corrected Consensus Approach (HCCA) and Google DeepMind ensemble mean (GDMI) aids, but the track uncertainly remains high in the 3-5 day period. Now that it appears the earlier ERC has completed, it is hard to see what could prevent Polo from continuing to RI for the next day or so. Shear remains low, analyzed at 6 kt by UW-CIMSS, and there is ample deep-layer moisture. Sea-surface temperatures are also very warm (31 C) and extend vertically down 50-100 meters along the short-term track of Polo per a ARGO profiler, which should limit cooler ocean upwelling despite the slow motion of the hurricane. SHIPS RI indices continue to be very high, with DTOPS showing an 81 percent chance of at least a 40 kt increase in intensity over the next 24 h. Thus, the NHC intensity forecast will continue to show RI, and now shows a 140-kt peak in 24 h. This intensity forecast agrees with the HCCA intensity aid, and is also close to the 18z HAFS-B forecast which also shows a 140-kt peak in its raw output in 24 h. Beyond that time, inner-core fluctuations related to additional ERCs will likely lead to intensity oscillations, and both the GFS- and EC-SHIPS guidance does show a marked increase in easterly shear beyond 48 h. Therefore, slow weakening is shown in the day 3-5 period, though it still remains a bit higher than the intensity guidance consensus aside from HCCA. Regardless, Polo is expected to remain a major hurricane through the entire forecast period. 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 and has been extended to Manzanillo. FORECAST POSITIONS AND MAX WINDS INIT 22/0300Z 15.0N 102.3W 95 KT 110 MPH 12H 22/1200Z 14.9N 101.8W 115 KT 130 MPH 24H 23/0000Z 15.1N 101.7W 140 KT 160 MPH 36H 23/1200Z 15.6N 102.2W 140 KT 160 MPH 48H 24/0000Z 16.5N 103.2W 135 KT 155 MPH 60H 24/1200Z 17.3N 104.5W 130 KT 150 MPH 72H 25/0000Z 17.7N 106.0W 125 KT 145 MPH 96H 26/0000Z 18.6N 109.2W 115 KT 130 MPH 120H 27/0000Z 20.1N 111.7W 105 KT 120 MPH