{"id": "1218348819870187523", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-13T09:00:00Z", "msg": "394\nWTPZ45 KNHC 130842\nTCDEP5\n \nHurricane Simon Discussion Number  24\nNWS National Hurricane Center Miami FL       EP202026\n200 AM MST Tue Oct 13 2026\n \nSimon remains a very small hurricane. Synthetic aperture radar (SAR) \ndata from around 01 UTC showed its compact wind field, with a 5-n-mi \nradius of maximum wind and tropical-storm-force winds that extended \nonly 30-40 n mi from the center. Satellite images reveal Simon has \nmaintained a small central dense overcast tonight, with a sharper \nedge to the cloud tops on the northeastern side, perhaps the result \nof some vertical wind shear. Given the small size of Simon, it is \npossible that conventional satellite estimates are struggling to \nrepresent its true intensity. The initial intensity is set at 80 kt, \nwhich lies in between the latest Dvorak CI number from TAFB (4.5/77 \nkt) and the earlier SAR data. \n \nThe hurricane is moving slowly northwestward (310/3 kt) around a \nsubtropical ridge over the southern United States. During the next \ncouple of days, Simon is forecast to become caught in weak steering \ncurrents between this ridge and another ridge that should build to \nthe northwest over the eastern Pacific. As a result, most of the \ntrack guidance now shows little net motion of the storm through 60 \nh, although Simon meanders in several different directions in the \nvarious global models and ensembles. Given the lack of a clear model \nsignal, the new NHC forecast attempts to maintain some continuity by \nusing a blend of the latest Google DeepMind, AI-GFS, and ECMWF track \naids through 72 h. Once again, the trend is slower and farther west \nthan the previous prediction. A general northward motion is shown at \n96-120 h as the system (if it survives that long) should become \nsteered by a cutoff upper low to its northwest. Needless to say, the \nlack of model agreement makes this a very low confidence forecast.\n\nSimon's intensity forecast is also very challenging and highly \nsensitive to its uncertain track. The small system is forecast to be \nwithin a generally low shear environment over very warm SSTs for the \nnext couple of days. However, the slow forward speed of Simon could \nlead to upwelling of cooler waters, and its proximity to land could \nmake it susceptible to intrusions of drier air from mainland Mexico. \nMuch of the guidance shows little intensity change or even some \nweakening through midweek, and the NHC forecast remains on the \nhigher end of the intensity guidance. By Thursday, the model \nconsensus favors more steady weakening through the rest of the \nperiod due to increased vertical wind shear, and the latter half of \nthe NHC forecast has been lowered notably from the previous one.\n\nIt is worth emphasizing that this is a very low confidence forecast, \nand interests in west-central Mexico should continue to closely \nmonitor the latest updates. Changes to watches and warnings may \nbe required later today based on the latest forecast trends.\n\n \nKey Messages:\n \n1. Hurricane conditions are likely on Las Islas Marias over the\nnext day or so, where a Hurricane Warning remains in effect.\n \n2. Simon could approach the coast of western Mexico later this \nweek at or near hurricane strength, and a Hurricane Watch remains \nin effect for a portion of the area.\n \n3. Heavy rainfall associated with Simon will impact portions of \nwest-central Mexico over the next few days. This rainfall will \nproduce life-threatening flooding and mudslides, especially in areas \nof steep terrain.\n \n4. Large swells will affect portions of the southwestern and\nwest-central coasts of Mexico over the next several days. These\nswells are likely to cause life-threatening surf and rip current\nconditions.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  13/0900Z 20.6N 107.2W   80 KT  90 MPH\n 12H  13/1800Z 20.7N 107.4W   75 KT  85 MPH\n 24H  14/0600Z 20.9N 107.7W   75 KT  85 MPH\n 36H  14/1800Z 21.0N 107.8W   75 KT  85 MPH\n 48H  15/0600Z 21.2N 107.9W   75 KT  85 MPH\n 60H  15/1800Z 21.8N 108.0W   70 KT  80 MPH\n 72H  16/0600Z 23.0N 108.1W   65 KT  75 MPH\n 96H  17/0600Z 24.2N 108.1W   55 KT  65 MPH\n120H  18/0600Z 25.4N 108.2W   30 KT  35 MPH...POST-TROP/INLAND\n \n"}