Advisories

000
WTPZ43 KNHC 292048
TCDEP3
 
Tropical Storm Rachel Discussion Number  11
NWS National Hurricane Center Miami FL       EP182026
300 PM CST Tue Sep 29 2026
 
There has been a wealth of data to parse through this afternoon with 
Rachel. On satellite imagery, Rachel is exhibiting a large 
convective burst with cloud tops below -85 C, though this burst is 
still centered a little south of the center fixes provided by the 
NOAA P-3 aircraft that conducted a research mission into the storm. 
The peak 700-mb flight level winds from the mission were 66 kt. In 
addition, there was a dropsonde launched in the radius of maximum 
wind on its east side that had 500 m average of 75 kt, which using  
a typical reduction factor yields 60 kt. Furthermore, there was a 
uncrewed aircraft system (UAS) that was launched in the same area in 
the boundary layer, finding 975-mb winds also up to 75 kt. An 
experimental reduction factor developed by CIRA indicated this value 
translates to a 10-meter sustained wind of 63 kt. All of the above 
data suggests that Rachel is nearly a hurricane, and the initial 
intensity is set at 60 kt this advisory. A 1620 UTC ASCAT-B pass, in 
addition to the aircraft data, were both useful to adjust the 34- 
and 50-kt radii this afternoon. 

Rachel continues to move off to the northwest, with aircraft fixes 
indicating a motion of 305 degrees at 12 kt. A mid-level ridge 
located over central Mexico is expected to steer the tropical 
cyclone in that same direction over the next 12-24 h. However, an 
upper-level cutoff low moving across the four corners region of the 
southwestern United States will soon erode this ridge, leading to a 
significant slowdown in Rachel's motion. After 48 h, another 
mid-level ridge begins to build in over California and Nevada behind 
this cutoff low as it ejects into the central Plains. The net effect 
of this synoptic pattern is Rachel should then turn more westward, 
but still at a slow forward motion. Some of the reliable track aids 
have made a southward shift in Rachel's track this afternoon, and 
the latest NHC track forecast has been shifted in that direction, 
blending the HFIP Corrected Consensus Approach (HCCA), the Google 
DeepMind ensemble mean (GDMI), and their new experimental model 
(WN3I). 

Shear analysis from UW-CIMSS indicates that the northeasterly shear 
that had been affecting Rachel is starting to decrease, and both the 
EC- and GFS-based SHIPS guidance show this lowering below 15 kt in 
24 h. In addition, the latest forecast track brings Rachel initially 
to the north of the cool wake left behind by Polo, with nearby ocean 
drifters still showing sea-surface temperatures (SSTs) in the 29-30 
C range still. Thus as the shear decreases, and assuming Rachel's 
core is becoming more vertically aligned, the short-term intensity 
has been raised and now shows a period of rapid intensification from 
24-48 h, making it a 105 kt major hurricane at the end of that time 
frame. After that time, as Rachel turns westward, it will finally 
pass over Polo's cool wake, where another drifter in that vicinity 
showing SSTs much lower, in the 26-27 C range, and that combined 
with Rachel's slow motion will likely lead to weakening in 60-96 h. 
The latest NHC intensity forecast remains on the upper-end of the 
guidance, closest to HCCA through 48 h, but then falls back closer 
to the guidance mean in 72-120 h.  
 
Key Messages:
 
1. Although the core of Rachel is forecast to remain offshore of
Mexico, tropical-storm-force winds are expected along a portion of
the coast of southwestern Mexico in the Tropical Storm Warning area
today or tonight. Tropical storm conditions are possible in the
watch area tonight or on Wednesday.
 
2. Outer bands from Rachel will bring locally heavy rainfall to 
portions of coastal southwest Mexico through Thursday. This rainfall 
may produce life-threatening flooding and mudslides, especially in 
areas of steep terrain.
 
3. 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  29/2100Z 16.0N 105.7W   60 KT  70 MPH
 12H  30/0600Z 17.3N 107.0W   70 KT  80 MPH
 24H  30/1800Z 18.2N 108.0W   85 KT 100 MPH
 36H  01/0600Z 19.0N 108.9W  100 KT 115 MPH
 48H  01/1800Z 19.4N 109.5W  105 KT 120 MPH
 60H  02/0600Z 19.6N 110.3W  100 KT 115 MPH
 72H  02/1800Z 19.8N 111.1W   90 KT 105 MPH
 96H  03/1800Z 20.2N 112.9W   80 KT  90 MPH
120H  04/1800Z 20.5N 115.0W   85 KT 100 MPH
 
$$
Forecaster Papin