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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
 
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