{"id": "1217644455192133639", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-10T21:00:00Z", "msg": "162\nWTPZ45 KNHC 102059\nTCDEP5\n \nHurricane Simon Discussion Number  14\nNWS National Hurricane Center Miami FL       EP202026\n300 PM CST Sat Oct 10 2026\n\nAir Force Reserve Hurricane Hunters have been investigating Simon \nthis afternoon, finding that the hurricane is indeed a Category 4 \nstorm. The minimum pressure is estimated to be down to 932 mb, and \nthe peak 700 mb flight level winds were 134 kt in the eastern \nquadrant of the hurricane. While a standard 0.9 reduction would \ntypically support a 10 meter sustained wind of 120-125 kt, the \nentire wind field of Simon was not fully sampled. In addition, there \nwas an earlier partial Synthetic Aperture Radar (SAR) RCM-1 pass \nwhich had a peak wind of 138 kt. Satellite intensity estimates, \nwhich have been lagging behind the estimated intensity of Simon, \nhave also risen somewhat today. Taking all these data points \ntogether, the initial intensity is held at 130 kt this advisory. The \naircraft also reported concentric eyewalls, with the inner eyewall \n12 n mi and outer wall at 36 n mi. Some concentric bands were also \npicked up by a recent AMSR-3 microwave pass. \n \nAfter slowing down to a crawl earlier, aircraft fixes indicate that \nSimon starting to move due north again, with an estimated motion at \n360/4 kt. As previously discussed, the hurricane is being primarily \nsteered by a weak mid-level ridge to the east, providing deep-layer \nsoutherly flow. A subtle narrow mid-level ridge to the northwest is \nalso imparting a slight amount of northerly flow. Once again, the \ntrack guidance this afternoon has made a slower adjustment. In \naddition, there is a bit of an eastward shift in the guidance \nenvelope. One notable change from this morning, now all the \nhurricane-regional model runs (HWRF, HMON, HAFS-A, HAFS-B) all show \nSimon making landfall in Jalisco in 24-36 h. In addition, both the \nGoogle DeepMind ensemble mean (GDMI) and its upgraded Weather Next \nmodel (WN3I) also nudged their tracks eastward. Thus, the NHC track \nforecast has shifted a bit to the east, but still lies on the \neastern end of the guidance. Part of the reason for favoring the \neastern edge of the guidance is that there is a pretty well-known \nbias that tropical cyclones in this area tend to track east of the \nforecast track due to interaction with the high topography of \ncoastal Mexico.\n\nAs mentioned this morning, the future intensity forecast of Simon is \nheavily influenced by Simon's ultimate track. Because large-scale \nenvironmental conditions remain favorable, Simon's short-term \nintensity forecast will likely be controlled by inner-core \nfluctuations, like eyewall replacement cycles. This is pertinent \ngiven the concentric eyewalls noted by the aircraft mission. \nHowever, as Simon nears the Mexican coast, the high topography will \ninteract with the hurricane's outer circulation, and spot soundings \nin the HAFS-A/B runs show evidence of downslope subsidence occurring \nas Simon nears landfall. This effect will both cause the hurricane's \nwind field to shrink in size, and will likely result in weakening \neven before the hurricane makes landfall in Mexico. Weakening is \nexpected to begin between 12-24 h, with more substantial weakening \noccurring when Simon moves fully onshore. Once again, this intensity \nforecast is quite uncertain. If Simon remains offshore, like the \nECMWF and a decent chunk of GDM ensemble members show, it may remain \nmuch stronger than the latest NHC intensity forecast. The latest \nforecast is a bit lower than the prior one, with a bit more \nconfidence that Simon will move inland, though the latest forecast \nstill shows Simon dissipating over Mexico after 60 h.\n \nKey Messages:\n \n1. Catastrophic wind and life-threatening storm surge impacts are \nlikely along a portion of the west-central coast of Mexico, and a \nHurricane Warning is in effect from Punta San Telmo to El Roblito. \nPreparations to protect life and property should be completed this \nafternoon.\n \n2. Heavy rainfall associated with Simon will impact portions of \nsouthwestern Mexico through this weekend. This rainfall will produce \nlife-threatening flooding and mudslides, especially in areas of \nsteep terrain.\n \n3. Swells will affect portions of the southwestern and west-central\ncoast of Mexico through the weekend. These swells are likely to\ncause life-threatening surf and rip current conditions. Please\nconsult products from your local weather office.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  10/2100Z 17.6N 104.8W  130 KT 150 MPH\n 12H  11/0600Z 18.3N 104.9W  130 KT 150 MPH\n 24H  11/1800Z 19.4N 105.1W  110 KT 125 MPH\n 36H  12/0600Z 20.8N 105.2W   70 KT  80 MPH...INLAND\n 48H  12/1800Z 21.9N 105.2W   45 KT  50 MPH...INLAND\n 60H  13/0600Z 22.8N 105.1W   15 KT  15 MPH...POST-TROP/INLAND\n 72H  13/1800Z...DISSIPATED\n \n"}