Tropical Cyclone Discussion
908 WTPZ43 KNHC 280842 TCDEP3 Tropical Storm Rachel Discussion Number 5 NWS National Hurricane Center Miami FL EP182026 300 AM CST Mon Sep 28 2026 Rachel has intensified since the previous advisory. The METOP-C Advanced Scatterometer sampled the center and western half of the system around 0431z, and found reliable winds to 40 kt. This is in agreement with the objective satellite intensity estimates from UW-CIMMS and a subjective Dvorak of T3.0/45 kt from TAFB. Therefore, the initial intensity is set at 40 kt for this advisory, and there is more confidence in the initial position of the cyclone. The cyclone is now moving toward the west-northwest at 290/7 kt, and it appears Rachel is starting to move a bit faster. A deep-layer ridge building over north-central Mexico is forecast to steer the cyclone west-northwestward, with some acceleration in forward motion through early next week. On Thursday, a trough over the southwestern United States will weaken the ridge somewhat, leading to diminished steering flow near Rachel and a deceleration in the cyclone's west-northwestward motion. The new initial position, informed by the aforementioned scatterometer pass, lies to the right of the previous official forecast track. As a result, the new forecast is adjusted to the right of the previous one, and blends toward the most recent Google DeepMind (GDM) and HFIP Corrected Consensus Approach (HCCA) guidance. Rachel is apparently less-than-hindered by the northeasterly vertical wind shear diagnosed near the tropical storm. All other environmental parameters support intensification, and the new intensity forecast is largely an update of the previous one. The intensity forecast is again on the higher end of the guidance envelope, and blends the GDM and HCCA solutions. Rachel is forecast to become a hurricane on Tuesday. There is some uncertainty beyond 72 hr, with some of the guidance showing weakening during that time. It is not entirely clear to me why weakening would occur during this time-frame, given favorable dynamics and thermodynamics indicated across the deterministic global model fields. Rachel could track over some of the cool wake from Hurricane Polo, though recent drifter data captured vertical profiles that show high ocean heat content (OHC) persists in the region. Given the uncertainty, and the shift in track more east of the cool wake, I show Rachel maintaining its intensity from 72 through 120 hr. Key Messages: 1. Although the core of Rachel is forecast to remain offshore of Mexico, tropical storm force winds are possible along a portion of the coast of southwestern Mexico in the Tropical Storm Watch area on Tuesday. 2. Large waves could produce life-threatening surf and rip current conditions along portions of the southwestern coast of Mexico during the next several days. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 13.4N 100.4W 40 KT 45 MPH 12H 28/1800Z 13.9N 101.7W 50 KT 60 MPH 24H 29/0600Z 14.9N 103.5W 55 KT 65 MPH 36H 29/1800Z 16.1N 105.3W 60 KT 70 MPH 48H 30/0600Z 17.3N 106.6W 70 KT 80 MPH 60H 30/1800Z 18.2N 107.6W 80 KT 90 MPH 72H 01/0600Z 19.0N 108.5W 85 KT 100 MPH 96H 02/0600Z 19.6N 109.2W 85 KT 100 MPH 120H 03/0600Z 20.4N 110.0W 85 KT 100 MPH