{"id": "1222169332724269063", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-26T21:00:00Z", "msg": "374\nWTPZ42 KNHC 262034\nTCDEP2\n \nTropical Storm Vance Discussion Number  22\nNWS National Hurricane Center Miami FL       EP222026\n200 PM MST Mon Oct 26 2026\n \nThe structure of Vance hasn't changed much since the previous \nadvisory.  Visible satellite imagery is consistent with recent \nmicrowave fixes that the center is near the western edge of the main \nconvective area.  The initial intensity will again be held at 55 kt, \nwhich is supported by the latest TAFB current intensity estimate and \nrecent DMINT intensity estimates.\n\nVance has been jogging toward the west today, with the current \nmotion estimated at 280/5 kt.  A slow west-northwestward track is \nexpected over the next 24 hours or so due to a weak mid-level ridge \nto the north of the system.  By Wednesday, a broad mid-level trough \nnear the Baja California peninsula should induce a turn toward the \nnorth.  The NHC track forecast has again been shifted slightly to \nthe west of the previous one, and is in between the latest GDMI and \nHCCA forecasts.  It should be noted that there is considerable \nspread/uncertainty in the timing/forward speed of Vance after it \nmakes the northward turn, with the HAFS and ECMWF faster to the \nnorth, while the GFS and GDMI show a slower northward motion.  The \nNHC forecast is a little on the slower side compared to some of the \nguidance but is faster than the GDMI.\n \nAlthough Vance remains in a favorable thermodynamic environment with \nwarm water and enough atmospheric moisture, the cyclone is \nexperiencing moderate to strong west-southwesterly wind shear.  The \nwind shear is forecast to increase a bit more (to near 25 kt) by \nhour 12, and this should be enough to cause gradual to steady \nweakening over the next day or so.  On Wednesday, as Vance turns \nnorthward and gets closer to the broad trough over Baja California \nand the subtropical jet, the west-southwesterly vertical wind shear \nincreases to over 35 kt, and is forecast to increase further on \nThursday.  Surprisingly, most of the models hold onto this system as \na tropical storm for a couple more days.  The NHC intensity forecast \nis similar to the previous one, and lies in the middle to lower \nportion of the guidance envelope.  It is likely that Vance's \nconvection will be sheared off by 72 hours, and the NHC forecast \nshows Vance degenerating to a post-tropical remnant low around that \ntime.  All of the models show the low-level circulation of Vance \ndissipating before day 4, so the timing of dissipation has been \nmoved up to day 4 in the official forecast, which is before the \ncirculation reaches the coast of Mexico.\n\nKey Messages:\n \n1. Periods of heavy rainfall associated with Vance will impact\nportions of western Mexico during much of this week. This rainfall\nmay produce flooding and mudslides across southern Sinaloa,\nsouthwest Durango and coastal sections of Nayarit, Jalisco, Colima\nand Michoacan, especially in areas along steep terrain.\n \n2. Although the wind threat to southwest Mexico is decreasing as the\nforecast track shifts westward away from the coast, interests there\nshould continue to monitor Vance's progress.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  26/2100Z 15.4N 106.1W   55 KT  65 MPH\n 12H  27/0600Z 15.6N 106.9W   50 KT  60 MPH\n 24H  27/1800Z 16.7N 107.9W   45 KT  50 MPH\n 36H  28/0600Z 18.1N 108.4W   40 KT  45 MPH\n 48H  28/1800Z 19.8N 108.6W   40 KT  45 MPH\n 60H  29/0600Z 21.3N 108.4W   35 KT  40 MPH\n 72H  29/1800Z 22.6N 108.2W   30 KT  35 MPH...POST-TROP/REMNT LOW\n 96H  30/1800Z...DISSIPATED\n \n"}