{"id": "1213675820928368647", "title": "Tropical Cyclone Discussion", "adv_date": "2026-09-26T21:00:00Z", "msg": "317\nWTPZ42 KNHC 262034\nTCDEP2\n \nHurricane Polo Discussion Number  25\nNWS National Hurricane Center Miami FL       EP172026\n200 PM MST Sat Sep 26 2026\n \nSAR data valid this morning that arrived after the issuance of the \nlast advisory indicated that Polo's inner-core has expanded, \npossibly due to an eyewall replacement cycle. A combination of a \nslight increase in easterly wind shear over the past 12 hours  \n(10-15 kt according to both SHIPS diagnostics and UW-CIMSS \nanalysis) and the likely eyewall replacement cycle are likely \ncausing Polo to weaken. Intensity estimates vary greatly, from a 105 \nkt estimate with that SAR pass to over 140 kt from the ADT. Taking \nthe available data as a whole, the intensity is set at 125 kt for \nthis advisory, which is also fairly close to recent estimates from \nof the newer techniques from UW-CIMSS: AiDT, DPRINT and DMINT. A \nNOAA Hurricane Hunter aircraft is scheduled to investigate Polo \nlater today, which should provide more information about the \nstructure and intensity of the hurricane.\n \nThe hurricane has turned northwestward as it moves around the\nwestern end of a mid-level ridge centered over northern Mexico.\nPolo will gradually turn northward, and then northeastward over\nthe next two days as it continues to move around the ridge and is\nsteered increasingly by a mid- to upper-level trough approaching\nfrom the northwest. There is an unusually large spread in the track\nmodels, primarily associated with Polo's forward speed. The AI\nguidance, including GDM, show a notably faster forward motion than\nmany of the dynamical models, with some of the hurricane regional\nmodels even forecasting the hurricane to stall offshore of the west\ncoast of the Baja California peninsula. No changes of note were made\nto the track forecast with this advisory and the NHC forecast still\nleans toward the AI models and HCCA, but confidence in that forecast\nis not particularly high due to the high model spread.\n \nThe models have better agreement on the intensity forecast and \nnearly unanimously depict Polo steadily weakening over the next 48 \nhours. Some short-term intensity fluctuations will be possible \nduring that period, but a combination of moderate shear and a drier \nenvironment along the forecast track should prevent it from \nsignificantly restrengthening. It is worth noting that Polo is still \nexpected to be a strong hurricane when it approaches Baja California \nSur. More rapid weakening is likely beyond 60 hours, as the shear is \nexpected to increase substantially and Polo is forecast to begin \ninteracting with land.\n \nPolo is expected to become a remnant low and then dissipate before\nit reaches the southern U.S., but distant moisture associated with\nit and Odalys will be transported into the southwestern United\nStates late this weekend and early next week, and may indirectly\ncontribute to a heavy rainfall and flash flood threat in the region.\nSee products issued by the Weather Prediction Center for more\ninformation.\n \n \nKey Messages:\n \n1. Polo is forecast to approach the west coast of the Baja\nCalifornia peninsula on Monday as a hurricane, and a Hurricane\nWatch is in effect for that region. Tropical storm conditions\ncould reach portions of the coast as soon as Sunday night or early\nMonday, making further preparations difficult. A storm surge will\nbe possible, especially in areas of onshore winds.\n \n2. Heavy rainfall associated with Polo may begin to impact Baja \nCalifornia Sur Sunday night into Tuesday. This rainfall may produce \nlife-threatening flooding and mudslides, especially in areas of \nsteep terrain.\n \n3. Dangerous surf and rip currents are likely along portions of\nthe northwest coast of Mexico and Baja California for the next\nseveral days.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  26/2100Z 18.7N 112.5W  125 KT 145 MPH\n 12H  27/0600Z 19.8N 113.4W  115 KT 130 MPH\n 24H  27/1800Z 21.4N 114.0W  105 KT 120 MPH\n 36H  28/0600Z 23.2N 114.0W   95 KT 110 MPH\n 48H  28/1800Z 24.8N 113.3W   85 KT 100 MPH\n 60H  29/0600Z 26.4N 111.9W   70 KT  80 MPH...INLAND\n 72H  29/1800Z 28.0N 110.2W   50 KT  60 MPH...INLAND\n 96H  30/1800Z 31.2N 105.7W   20 KT  25 MPH...POST-TROP/INLAND\n120H  01/1800Z...DISSIPATED\n \n"}