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Tropical Depression Eighteen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP182026
300 AM CST Sun Sep 27 2026

The tropical disturbance located south of Mexico, formerly Invest 
90E, has become better organized based on satellite imagery over the 
last several hours. Scatterometry data from around 0300 UTC depicts 
a closed circulation, with the system moving into a favorable 
environment for further development. Subjective Dvorak 
intensity analysis from TAFB also rated the system at 2.0/30 kt.  
Therefore, advisories have begun for Tropical Depression 
Eighteen-E. 

The initial motion is somewhat uncertain since the cyclone has only 
recently formed, but the motion estimate is around 285/9 kt. Track 
guidance is in good agreement on steering this system generally to 
the west-northwest over the next several days, with an increase in 
forward speed as it runs south of a mid-level high over Mexico. The 
current NHC track forecast generally falls within the middle of the 
guidance envelope, favoring HCCA in particular. 

SHIPS guidance suggests that vertical wind shear may be an 
inhibiting factor for development for the first 24 h, before the 
Depression is expected to gradually strengthen as SSTs remain warm 
and mid-level moisture appears favorable. There is some uncertainty 
with regards to SSTs due to colder waters potentially being churned 
up in the wake of Hurricane Polo, so the current intensity forecast 
is a little conservative at first, before depicting gradual 
strengthening through the late weekend onward. This still falls 
around the median of the guidance envelope. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  27/0900Z 12.2N  99.1W   30 KT  35 MPH
 12H  27/1800Z 12.7N  99.6W   30 KT  35 MPH
 24H  28/0600Z 13.2N 100.8W   35 KT  40 MPH
 36H  28/1800Z 13.8N 102.2W   45 KT  50 MPH
 48H  29/0600Z 14.7N 104.1W   55 KT  65 MPH
 60H  29/1800Z 15.7N 105.9W   65 KT  75 MPH
 72H  30/0600Z 16.9N 107.7W   75 KT  85 MPH
 96H  01/0600Z 18.7N 109.6W   80 KT  90 MPH
120H  02/0600Z 19.7N 110.3W   75 KT  85 MPH
 
$$
Forecaster Evans/Pasch
 
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