954
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

$$
Forecaster Mahoney