{"id": "1214528006177554439", "title": "Tropical Cyclone Discussion", "adv_date": "2026-09-29T21:00:00Z", "msg": "715\nWTPZ43 KNHC 292048\nTCDEP3\n \nTropical Storm Rachel Discussion Number  11\nNWS National Hurricane Center Miami FL       EP182026\n300 PM CST Tue Sep 29 2026\n \nThere has been a wealth of data to parse through this afternoon with \nRachel. On satellite imagery, Rachel is exhibiting a large \nconvective burst with cloud tops below -85 C, though this burst is \nstill centered a little south of the center fixes provided by the \nNOAA P-3 aircraft that conducted a research mission into the storm. \nThe peak 700-mb flight level winds from the mission were 66 kt. In \naddition, there was a dropsonde launched in the radius of maximum \nwind on its east side that had 500 m average of 75 kt, which using  \na typical reduction factor yields 60 kt. Furthermore, there was a \nuncrewed aircraft system (UAS) that was launched in the same area in \nthe boundary layer, finding 975-mb winds also up to 75 kt. An \nexperimental reduction factor developed by CIRA indicated this value \ntranslates to a 10-meter sustained wind of 63 kt. All of the above \ndata suggests that Rachel is nearly a hurricane, and the initial \nintensity is set at 60 kt this advisory. A 1620 UTC ASCAT-B pass, in \naddition to the aircraft data, were both useful to adjust the 34- \nand 50-kt radii this afternoon. \n\nRachel continues to move off to the northwest, with aircraft fixes \nindicating a motion of 305 degrees at 12 kt. A mid-level ridge \nlocated over central Mexico is expected to steer the tropical \ncyclone in that same direction over the next 12-24 h. However, an \nupper-level cutoff low moving across the four corners region of the \nsouthwestern United States will soon erode this ridge, leading to a \nsignificant slowdown in Rachel's motion. After 48 h, another \nmid-level ridge begins to build in over California and Nevada behind \nthis cutoff low as it ejects into the central Plains. The net effect \nof this synoptic pattern is Rachel should then turn more westward, \nbut still at a slow forward motion. Some of the reliable track aids \nhave made a southward shift in Rachel's track this afternoon, and \nthe latest NHC track forecast has been shifted in that direction, \nblending the HFIP Corrected Consensus Approach (HCCA), the Google \nDeepMind ensemble mean (GDMI), and their new experimental model \n(WN3I). \n\nShear analysis from UW-CIMSS indicates that the northeasterly shear \nthat had been affecting Rachel is starting to decrease, and both the \nEC- and GFS-based SHIPS guidance show this lowering below 15 kt in \n24 h. In addition, the latest forecast track brings Rachel initially \nto the north of the cool wake left behind by Polo, with nearby ocean \ndrifters still showing sea-surface temperatures (SSTs) in the 29-30 \nC range still. Thus as the shear decreases, and assuming Rachel's \ncore is becoming more vertically aligned, the short-term intensity \nhas been raised and now shows a period of rapid intensification from \n24-48 h, making it a 105 kt major hurricane at the end of that time \nframe. After that time, as Rachel turns westward, it will finally \npass over Polo's cool wake, where another drifter in that vicinity \nshowing SSTs much lower, in the 26-27 C range, and that combined \nwith Rachel's slow motion will likely lead to weakening in 60-96 h. \nThe latest NHC intensity forecast remains on the upper-end of the \nguidance, closest to HCCA through 48 h, but then falls back closer \nto the guidance mean in 72-120 h.  \n \nKey Messages:\n \n1. Although the core of Rachel is forecast to remain offshore of\nMexico, tropical-storm-force winds are expected along a portion of\nthe coast of southwestern Mexico in the Tropical Storm Warning area\ntoday or tonight. Tropical storm conditions are possible in the\nwatch area tonight or on Wednesday.\n \n2. Outer bands from Rachel will bring locally heavy rainfall to \nportions of coastal southwest Mexico through Thursday. This rainfall \nmay produce life-threatening flooding and mudslides, especially in \nareas of steep terrain.\n \n3. Large waves could produce life-threatening surf and rip current\nconditions along portions of the southwestern coast of Mexico during\nthe next several days.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  29/2100Z 16.0N 105.7W   60 KT  70 MPH\n 12H  30/0600Z 17.3N 107.0W   70 KT  80 MPH\n 24H  30/1800Z 18.2N 108.0W   85 KT 100 MPH\n 36H  01/0600Z 19.0N 108.9W  100 KT 115 MPH\n 48H  01/1800Z 19.4N 109.5W  105 KT 120 MPH\n 60H  02/0600Z 19.6N 110.3W  100 KT 115 MPH\n 72H  02/1800Z 19.8N 111.1W   90 KT 105 MPH\n 96H  03/1800Z 20.2N 112.9W   80 KT  90 MPH\n120H  04/1800Z 20.5N 115.0W   85 KT 100 MPH\n \n"}