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Tropical Storm Otis Discussion Number   4
NWS National Hurricane Center Miami FL       EP182023
400 AM CDT Mon Oct 23 2023
 
Deep convection has continued to pulse over the northwestern portion 
of Otis overnight.  The center was noted near the southeastern edge 
of the deep convection in shortwave infrared satellite imagery 
earlier in the night.  Since that time, the center has become a 
little more embedded within the cold cloud tops. As a result, the 
initial intensity has been increased to 40 kt for this advisory.  
This intensity is a blend of the most recent Dvorak T- and CI- 
numbers from TAFB and SAB, and close to the latest SATCON and 
D-PRINT objective estimates from UW/CIMSS.
 
Otis has been moving northward or 360/4 kt.  The storm is expected 
to move northward to north-northwestward between a ridge over the 
northwestern Caribbean Sea and a trough over northwestern Mexico.   
The ECMWF, UKMET, and Canadian models all take Otis near the coast 
of southern Mexico by midweek, with the ECMWF being the fastest.  
That model shows the storm making landfall in southern Mexico in 
just over 48 hours.  Meanwhile, the GFS continues to depict a weaker 
system that stays embedded within the Intertropical Convergence Zone 
and meanders well south of Mexico for several days.  Since the 
majority of the guidance has a track closer or inland over Mexico, 
the NHC forecast continues to lean toward that scenario and takes 
Otis inland in a few days, but this could occur much sooner.  The 
NHC track is a blend of the ECMWF, UKMET, Canadian, HMON, and the 
HFIP corrected consensus aid. 

The storm is over very warm waters and within an environment of 
light to moderate shear.  These conditions should allow for gradual 
strengthening while the system remains over water.  Some increase 
in shear and the possibility of land interaction could cause the 
intensity to level off in a couple of days.  The NHC intensity 
forecast is again near the higher end of the guidance, close to the 
statistical guidance and the HCCA model. 

Based on this latest forecast, the government of Mexico has issued a 
Tropical Storm Watch for a portion of the coast of southern Mexico. 

Key Messages:

1. Heavy rains from Otis will begin to impact areas of southwest 
Mexico early this week.  This rainfall will produce flash and urban 
flooding, along with mudslides in areas of higher terrain.
 
2. Tropical storm conditions are possible by Tuesday night or early 
Wednesday along portions of the southern coast of Mexico where a 
Tropical Storm Watch is now in effect. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/0900Z 11.4N  97.1W   40 KT  45 MPH
 12H  23/1800Z 12.1N  97.3W   45 KT  50 MPH
 24H  24/0600Z 13.0N  97.5W   45 KT  50 MPH
 36H  24/1800Z 14.0N  97.9W   50 KT  60 MPH
 48H  25/0600Z 15.0N  98.4W   50 KT  60 MPH
 60H  25/1800Z 15.6N  98.8W   50 KT  60 MPH
 72H  26/0600Z 16.4N  99.4W   50 KT  60 MPH
 96H  27/0600Z 17.9N 100.7W   30 KT  35 MPH...INLAND
120H  28/0600Z...DISSIPATED
 
$$
Forecaster Brown
 
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