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Tropical Depression Thirteen-E Discussion Number   2
NWS National Hurricane Center Miami FL       EP132025
900 PM CST Thu Sep 11 2025
 
The satellite appearance of Thirteen-E has improved some since the 
previous advisory, with deep convection continuing to burst over or 
near the estimated low-level center.  The latest subjective Dvorak 
current intensity estimates from TAFB and SAB were 2.5/35 kt and 
2.0/30 kt.  Meanwhile the objective estimates from UW-CIMSS have 
ranged from 28 to 35 kt since the previous advisory.  Based on a 
blend of these data, the initial intensity has been held, perhaps 
conservatively, at 30 kt for this advisory package. 

The depression is moving to the west-northwest, or 290 degrees, at 
10 kt.  This general motion is expected to continue for the next 
couple days, as the cyclone is steered by a mid-level ridge over 
northern Mexico and Texas.  A turn toward the northwest along with a 
decrease in forward speed is expected over the weekend, as the 
system moves along the southwestern periphery of the mid-level 
ridge, with that motion continuing through day 5.  The official 
track forecast lies is very close to the previous advisory, roughly 
between the corrected consensus HCCA and AI-Driven GDMI track aids.

The circulation of Thirteen-E remains very small, with an estimated 
radius of the outermost closed isobar only 80 n mi, and this may be 
generous.  In the next couple of days, the global models suggest 
that moderate northeasterly vertical wind shear, along with the 
proximity to land, should limit the system's ability to intensify 
significantly, and the intensity forecast only calls for some slow 
strengthening.  Over the weekend, environmental conditions should 
become more favorable for intensification, as the system will be 
farther offshore, over very warm water and surrounded by moist 
mid-level air, while vertical wind shear will drop off to light 
levels and become aligned with the motion of the cyclone.  This 
should lead to steady strengthening, with the system forecast to 
become a hurricane by 72 hours.  By day 5, cooler sea surface 
temperatures and drier more stable environment should lead to a 
weakening trend.  The official intensity forecast lies on the higher 
end of the intensity guidance envelope and closest to the AI-Driven 
GDMI intensity aid.


Key Messages: 
1. Heavy rainfall associated with Tropical Depression Thirteen-E 
will impact southern and southwestern Mexico through Sunday, which 
could result in flash flooding, particularly in areas of higher 
terrain.

2. The depression is forecast to become a tropical storm later 
tonight, while moving parallel to the southern and southwestern 
coasts of Mexico.  While the strongest winds are expected to remain 
offshore, gusty winds are possible along portions of the southern 
and southwestern coast of Mexico from Punta Maldonado through 
Manzanillo during the next day or so. Interests in these areas 
should monitor the progress of this system.  
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0300Z 16.0N  99.6W   30 KT  35 MPH
 12H  12/1200Z 16.5N 101.3W   35 KT  40 MPH
 24H  13/0000Z 17.1N 103.5W   40 KT  45 MPH
 36H  13/1200Z 17.6N 105.5W   45 KT  50 MPH
 48H  14/0000Z 18.0N 107.1W   50 KT  60 MPH
 60H  14/1200Z 18.4N 108.6W   60 KT  70 MPH
 72H  15/0000Z 18.9N 109.9W   70 KT  80 MPH
 96H  16/0000Z 20.7N 112.6W   70 KT  80 MPH
120H  17/0000Z 23.0N 114.7W   55 KT  65 MPH
 
$$
Forecaster Jelsema (CPHC)
 
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