{"id": "1216083594537205767", "title": "Tropical Cyclone Discussion", "adv_date": "2026-10-05T09:00:00Z", "msg": "630\nWTPZ43 KNHC 050840\nTCDEP3\n \nHurricane Rachel Discussion Number  33\nNWS National Hurricane Center Miami FL       EP182026\n200 AM PDT Mon Oct 05 2026\n \nRachel has the satellite appearance of a hurricane that recently\nunderwent an eyewall replacement cycle (ERC), with a broad ring of\nouter convection while the smaller core it had yesterday is decaying\nwithin. On microwave imagery, a 0302 UTC GMI pass also showed a more\nprominent outer eyewall that was open on the northwest side on the\n89 GHz channel. This structure suggests some dry air is also being\nentrained into the circulation, likely due to 15-20 kt of\nnortheasterly vertical wind shear diagnosed by UW-CIMSS. The D-MINT\nintensity estimate associated with that GMI microwave pass was     \n83 kt, but other subjective and objective satellite estimates \ncontinue to gradually decrease, so the initial intensity is being \nlowered to 80 kt for this advisory.\n \nThe hurricane continues to move north of due west, estimated at\n280/7 kt. A mid-level ridge over the southwestern United States\nextends into the east Pacific and is expected to continue steering\nRachel off in a general westward to west-northwestward motion over\nthe next 2-4 days. Near the end of the forecast period, a mid- to\nupper-level trough is forecast to dig in to the northwest of Rachel,\nwith the guidance showing the tropical cyclone's motion coming to a\nhalt and potentially turning northeastward by 120 h. While both the\ndeterministic and ensemble track guidance are tightly clustered over\nthe first 3-4 days, the possible trough interaction results in a\nlarge increase in track spread by 120 h. The latest NHC track\nforecast is just a touch north of the previous one, following the\nblend in the latest HFIP Corrected Consensus Approach (HCCA), Google\nDeepMind ensemble mean (GDMI), and its newer version (WN3I).\n \nThe intensity forecast for Rachel is a little interesting. Part of\nthe recent weakening is likely due to the combination of the\nhurricane undergoing an ERC while there was a subtle increase in\nnortheasterly shear over the past day. Both the GFS and EC-SHIPS\nguidance show this shear persisting for the next 12-24 h before\ndiminishing below 10 kt as the hurricane continues to traverse\nsea-surface temperatures (SSTs) in the 26-27 C range. Thus, while a\nlittle additional weakening is shown in the short-term, the\nhurricane might stabilize for a bit if the shear decreases, and I\ncan't rule out the possibility it might still develop annular\ncharacteristics in the 36-48 h time frame. Thereafter, while shear\nwill likely remain low, SSTs decrease to around 25 C, and most of\nthe guidance responds by showing slow weakening resuming. Rachel may\nstart to struggle to produce organized convection by 120 h. However,\nthis is a trickier-than-usual forecast, because during that time it\nmay also interact with an upper-level trough which could provide\nsome baroclinic support to help maintain convection. In fact, this\npossibility is shown in the simulated infrared imagery from the 00\nUTC GFS and ECMWF runs. Thus, post-tropical status is not shown at\n120 h quite yet. The latest NHC intensity forecast lies closest to\nthe HCCA intensity aid.\n \n \nFORECAST POSITIONS AND MAX WINDS\n \nINIT  05/0900Z 20.4N 115.6W   80 KT  90 MPH\n 12H  05/1800Z 20.5N 116.7W   75 KT  85 MPH\n 24H  06/0600Z 20.6N 118.2W   75 KT  85 MPH\n 36H  06/1800Z 20.7N 119.7W   75 KT  85 MPH\n 48H  07/0600Z 21.0N 121.0W   75 KT  85 MPH\n 60H  07/1800Z 21.5N 122.5W   65 KT  75 MPH\n 72H  08/0600Z 22.0N 124.1W   60 KT  70 MPH\n 96H  09/0600Z 22.4N 126.7W   50 KT  60 MPH\n120H  10/0600Z 22.6N 126.5W   40 KT  45 MPH\n \n"}