{"id": "1218422859727405059", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-13T15:00:00Z", "msg": "807\nWTPZ45 KNHC 131459\nTCDEP5\n \nHurricane Simon Discussion Number  25\nNWS National Hurricane Center Miami FL       EP202026\n800 AM MST Tue Oct 13 2026\n \nSmall stubborn Simon continues to defy expectations this morning. \nFirst light visible satellite imagery shows the hurricane still has \na small eye, and is also located farther south than was analyzed by \nsatellite imagery last night. This is further supported by microwave \nimages from AMSR-3 at 09 UTC and SSMIS at 1125 UTC which both show \nan eyewall that is little better organized, though it remains open \non the west side. This structure could be due to some residual shear \nor dry air that was ingested into the circulation. Satellite \nintensity estimates are all over the place this morning, ranging \nfrom as low as 47 kt from UW-CIMSS ADT, and as high as 95 kt by \nSATCON. Given the small eye signature surrounded by -65 to -70 C \ncold cloud tops, the initial intensity will be held at 80 kt, on the \nupper side of these estimates, but should be considered more \nuncertain than usual. \n \nSimon continues to move south of the previous forecast track, and \nthe initial motion is a slow westward drift at 270/2 kt. The farther \nsouth initial position and current motion necessitates some pretty \nsignificant changes to the short-term track forecast. As mentioned \nyesterday, Simon is very close to a saddle point, or col, in the \ndeep-layer steering flow. This feature means that Simon's future \ntrack is very sensitive to which side of the saddle point the storm \nis located. Yesterday, a plurality of the guidance was maintaining \nSimon on a northwestward to northward track, causing it to be on the \nnorth side of the saddle point, resulting in continued poleward \nmotion. However, Simon has gained very little latitude over the past \n24 h, and thus now finds itself on the south side of the saddle \npoint. Consequently, the track guidance over the past few cycles has \nshifted substantially southward. The NHC track forecast is now \nshifted in a similar fashion, showing a very slow motion over the \nnext 36-48 h as Simon makes a small cyclonic loop. The first part of \nthe track forecast is substantially farther south than the prior \none, but still not as far south as the HFIP Corrected Consensus \nApproach (HCCA), or any of the latest hurricane-regional models. \nAfter 48 h, deep-layer steering finally begins to shift out of the \nsouth as a deep-layer cutoff low digs into southern California, and \nSimon will finally start moving northward in earnest during the \n48-72 h time frame. Towards the end of the forecast, Simon could \nbend back more north-northwestward, potentially entering the Gulf of \nCalifornia and finally making landfall in Mexico between 96-120 h. \nHowever, this forecast should be considered very low confidence at \nthat time frame, as there are a host of solutions from landfall in \nmainland Mexico even before reaching the Gulf of California, direct \nimpacts to Baja California Sur, or solutions that stay south of \nMexico entirely over the next 5 days.\n \nThe intensity forecast is not much easier either. Simon has managed \nto maintain a small inner-core and hurricanes of this size are known \nto be sensitive to small changes in their environmental conditions \nthat could result in rapid changes in intensity, either up or down. \nThis is also exhibited in the intensity guidance this morning, which \nranges from Simon weakening to a tropical depression all the way to \nit regaining major hurricane intensity over the next 48-60 h. While \nshear over Simon is expected to remain low for the next 48 h and \nsea-surface temperatures (SSTs) are in the 29-30 C range, one wild \ncard is how Simon's slow motion might cause some cool ocean \nupwelling. There is one ocean glider providing subsurface ocean \ntemperature data near Simon, and it depicts 28 C waters down to \nabout 80 m below the ocean surface. Assuming Simon does not \ncompletely stall, this is likely to support it maintaining hurricane \nintensity for the next 48-72 h. Given all this information, the NHC \nintensity forecast will show Simon maintaining its intensity as an \n80 kt hurricane for the next 48 h. Afterwards, southwesterly \nvertical wind shear is forecast to increase in earnest, and the \nsmall Simon is forecast to quickly weaken even as it moves over \nwarmer SSTs. This latest forecast is initially on the high side of \nthe guidance above HCCA, but not as high as the latest HAFS-A, \nCOAMPS-TC, or HMON runs. After 48 h this forecast falls back to the \nmiddle of the guidance envelope. \n \nIt is worth stressing that this is a very low confidence forecast \nfor both track and intensity, and interests in west-central Mexico \nand Baja California Sur should continue to closely monitor the \nlatest updates. Changes to watches and warnings could be required \nlater today based on the latest forecast trends.\n \n \nKey Messages:\n \n1. Simon could approach Las Islas Marias on Wednesday and the coast \nof western Mexico later this week at or near hurricane strength, and \na Hurricane Watch is in effect for a portion of these areas. \nInterests in west-central Mexico and Baja California Sur should \ncontinue to closely monitor the latest updates to Simon's forecast. \nChanges to watches and warnings could be required later today based \non the latest forecast trends.\n\n2. 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  13/1500Z 20.3N 107.3W   80 KT  90 MPH\n 12H  14/0000Z 20.3N 107.6W   80 KT  90 MPH\n 24H  14/1200Z 20.3N 107.8W   80 KT  90 MPH\n 36H  15/0000Z 20.1N 107.9W   80 KT  90 MPH\n 48H  15/1200Z 20.1N 107.7W   80 KT  90 MPH\n 60H  16/0000Z 21.0N 107.8W   75 KT  85 MPH\n 72H  16/1200Z 22.8N 108.2W   70 KT  80 MPH\n 96H  17/1200Z 25.2N 109.6W   55 KT  65 MPH\n120H  18/1200Z 28.5N 110.5W   30 KT  35 MPH...POST-TROP/INLAND\n \n"}