{"id": "1218209408904167427", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-12T21:00:00Z", "msg": "653\nWTPZ45 KNHC 122053\nTCDEP5\n \nHurricane Simon Discussion Number  22\nNWS National Hurricane Center Miami FL       EP202026\n200 PM MST Mon Oct 12 2026\n \nThis afternoon, Simon is a small hurricane that is dealing with some\neasterly vertical wind shear. The inner-core continues to produce a\nlot of lightning but mostly in the eastern semicircle. The most\nrecent microwave image was a 1718 UTC AWS pass that also showed this\ncore asymmetry with the eyewall open on the northwest side on the\n180 GHz channel. While the latest 18 UTC subjective Dvorak estimate\nremains at CI 5.5/102-kt, the objective intensity estimates from\nUW-CIMSS continue to gradually decrease. Thus, the initial intensity\nis being reduced to a somewhat uncertain 85 kt this advisory, which\nalso matches the D-MINT mean estimate from the AWS microwave pass\nabove. A helpful 1712 UTC Metop-C scatterometer pass was useful to\nhelp adjust Simon's radii and also to indicate its wind field has\nbecome quite small, with 34-kt winds only extending out about     \n40 n mi.\n\nSimon's track has thrown us a few curve balls over the past 24-36 h, \nand this afternoon is no exception as the hurricane made a brief \nwestward jog, with the longer-term motion estimated at 290/3 kt. The \ntrack forecast remains problematic. Part of the slow motion Simon is \nexhibiting today is related to competing steering synoptic features, \nprimarily a mid-level ridge centered near the Texas Coast versus \nanother mid-level ridge located southwest of the hurricane. The \ninfluence of the northeastern ridge has been a little stronger, but \nsteering diagnostics suggest that Simon may be soon reaching a \nbifurcation or COL point in the flow. This feature indicates the \narea where the net steering flow collapses and helps explain why \nboth the deterministic and ensemble track guidance spread increases \nquite dramatically in 24 to 48 h. For example, the HAFS-A/B models, \nwhich earlier this morning were showing a faster northeastward turn \nback into Mexico, now show Simon stalling and executing a slow \ncyclonic loop in the waters between mainland Mexico and the southern \ntip of the Baja California Peninsula. The European ensemble spread \nsuggests that these individual solutions are likely just different \nflavors of the overall distribution, which is spread out in a \nsouthwest to northeast fashion. While the overall track guidance \ncontinues to have large spread, there has been a northward and \nfaster shift this cycle. This shift is a bit odd given the current \nstorm motion, so the NHC track forecast is initially on the left \nside of the guidance over the first 12-24 h, but falls back closer \nto the middle of the guidance envelope, and attempts to blend the \nlatest HFIP Corrected Consensus Approach (HCCA), Google Deepmind \nensemble mean (GDMI), and their latest Weather Next model (WN3I). \nUltimately the latest track forecast converges close to the prior \none near landfall in Mexico in 72-96 h, but this remains a low \nconfidence track forecast.\n \nThe intensity forecast for Simon is also challenging. The current\nmid-level easterly shear affecting Simon's inner core structure has\nnot been well anticipated by the model guidance. Small tropical\ncyclones like Simon are often more sensitive to negative\nenvironmental factors, and even 15-20 kt of easterly shear could be\nenough to disrupt the core structure, especially with nearby\nenvironmental dry air. The factors may result in additional\nweakening in the short-term. However, EC-SHIPS guidance shows the\nshear lowering below 5 kt in 24-48 h. Assuming Simon is able to\nmaintain an inner core structure and take advantage of the more\nfavorable conditions, restrengthening is still forecast, especially\nas the hurricane is expected to track over the warmest sea-surface\ntemperatures in the Eastern Pacific basin (31-32 C). The intensity\nguidance shows more short-term weakening compared to the previous\ncycle, and the NHC intensity forecast is lower early on, but still\nshows restrengthening as Simon encounters those more favorable\nconditions, and ends up on the high end of the intensity guidance in\n60-72 h. Small storms like Simon can also be prone to rapid changes\nin intensity, which continues to make this intensity forecast also\nmore uncertain than usual. Rapid weakening is still anticipated when\nSimon eventually makes landfall in the latter part of this week\nbetween 72-96 h.\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 is expected to approach the coast of western Mexico later\nthis week, where hurricane conditions are possible. A Hurricane\nWatch is in effect from Cabo Corrientes to Bahia Tempehuaya.\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 few days. These swells\nare likely to cause life-threatening surf and rip current\nconditions. Please consult products from your local weather office.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  12/2100Z 20.2N 106.8W   85 KT 100 MPH\n 12H  13/0600Z 20.5N 107.0W   75 KT  85 MPH\n 24H  13/1800Z 20.9N 107.5W   65 KT  75 MPH\n 36H  14/0600Z 21.2N 107.7W   70 KT  80 MPH\n 48H  14/1800Z 21.5N 107.7W   75 KT  85 MPH\n 60H  15/0600Z 22.2N 107.4W   80 KT  90 MPH\n 72H  15/1800Z 23.0N 107.0W   85 KT 100 MPH\n 96H  16/1800Z 24.2N 106.6W   30 KT  35 MPH...POST-TROP/INLAND\n120H  17/1800Z...DISSIPATED\n \n"}