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Tropical Storm Otis Discussion Number   8
NWS National Hurricane Center Miami FL       EP182023
400 AM CDT Tue Oct 24 2023
 
Otis has strengthened overnight.  There has been a significant 
increase in banding and the center is now well embedded within the 
deep convection.  While there has been no recent microwave imagery 
to evaluate the inner core structure, a couple of earlier ASCAT 
overpass indicated that the center had become embedded within the 
cold cloud tops.  The initial intensity has been increased to 55 kt 
for this advisory, and that is in agreement with subjective Dvorak 
data T-numbers of 3.5 from both SAB and TAFB.  

It appears that the vertical shear over Otis has decreased as there 
has been an expansion of the cirrus outflow over the eastern portion 
of the storm.  The shear is expected to remain light to moderate 
while Otis moves over SSTs of 29-30 degrees C during the next day or 
so.  These conditions should allow for continued strengthening as 
Otis approaches the southern coast of Mexico.  The latest NHC 
intensity forecast calls for Otis to become a hurricane today, and 
it shows additional strengthening before Otis reaches southern 
Mexico in a day or so. By 36 hours, Otis is forecast to be inland, 
and rapid weakening should occur as the cyclone moves over 
mountainous terrain.  The NHC intensity forecast is at the high end 
of the guidance in best agreement with the HWRF and HAFS-B models.  
The SHIPS Rapid Intensification Index now shows about a 1 in 4 
chance of rapid strengthening during the next 24 hours, which 
supports being on the higher side of the guidance. 

Otis is moving north-northwestward at about 7 kt. A north-northwest 
motion is expected to continue during the next couple of days 
between a mid- to upper-level trough to the cyclone's northwest and 
a ridge to its east.  The GFS has finally come onboard with this 
scenario and the track guidance is much more tightly clustered than 
before.  The main difference is in the forward speed with the ECMWF 
being on the faster side of the guidance envelope.  The NHC 
forecast is near a blend of the latest GFS and ECMWF models, which 
is a little faster than the simple consensus aids. 

Based on the updated track and intensity forecast, the government 
of Mexico has issued a Hurricane Warning for a portion of the 
southern coast of Mexico. 

 
Key Messages:
 
1. Otis is forecast to become a hurricane before it reaches the 
southern coast of Mexico late tonight or Wednesday, and hurricane 
and tropical storm conditions are expected along portions of the 
southern coast of Mexico where hurricane and tropical storm 
warnings are in effect. 

2. Heavy rains from Otis will begin to impact areas of southern and 
southwestern Mexico later today.  This rainfall will produce flash 
and urban flooding, along with mudslides in areas of higher terrain.

3. A dangerous storm surge is expected to produce significant 
coastal flooding near and to the east of where the center makes 
landfall.  Near the coast, the surge will be accompanied by large 
and destructive waves.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 14.2N  98.5W   55 KT  65 MPH
 12H  24/1800Z 15.0N  99.0W   65 KT  75 MPH
 24H  25/0600Z 16.1N  99.7W   75 KT  85 MPH
 36H  25/1800Z 17.1N 100.3W   70 KT  80 MPH...INLAND
 48H  26/0600Z 17.9N 100.9W   35 KT  40 MPH...INLAND
 60H  26/1800Z 18.6N 101.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  27/0600Z...DISSIPATED
 
$$
Forecaster Brown
 
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