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Tropical Storm OTIS

Tropical Storm Otis Discussion Number   7
NWS National Hurricane Center Miami FL       EP182023
1000 PM CDT Mon Oct 23 2023

Otis has the appearance of a sheared tropical storm this evening, 
with the center on the eastern edge of a relatively new burst of 
deep convection.  The overall satellite intensity estimates still 
support an initial wind speed of 45 kt for this advisory.  Despite 
the shear, recent microwave data indicate that Otis has notable 
low-level structure, with a ring observed in 37 GHz microwave data. 
While this can be associated with rapid intensification, none of 
the models show that intensity change occurring, seemingly due to 
persistent moderate shear and some dry air in the mid-levels.  
Still, it makes sense to stay on the high side of the guidance given 
the structure and very warm SSTs in the path.  Thus, the new NHC 
forecast track is similar to the previous one, showing Otis near 
hurricane strength at landfall between 36-48 hours. 

Otis continues moving slowly north-northwestward at 6 kt in the flow
between a mid- to upper-level trough to its northwest and a ridge to
its east.   This flow will likely cause the storm to move to the 
north-northwest or northwest through landfall.  While most of the 
models respond by bringing Otis to the coast of southern Mexico on 
Wednesday, the GFS model remains an outlier and keeps Otis weaker 
and offshore.  The GFS solution seems very unlikely given the 
overall synoptic pattern, so the NHC track forecast will put little 
weight on its solution, keeping the official forecast about the same 
as the previous one, on the eastern side of the guidance envelope.
Key Messages:
1. Heavy rains from Otis will begin to impact areas of southwest
Mexico on Tuesday.  This rainfall will produce flash and urban
flooding, along with mudslides in areas of higher terrain.
2. Tropical storm conditions are expected and hurricane conditions
are possible beginning late Tuesday along portions of the southern
coast of Mexico, where a Tropical Storm Warning and Hurricane Watch
remain in effect.
INIT  24/0300Z 13.6N  97.9W   45 KT  50 MPH
 12H  24/1200Z 14.4N  98.3W   50 KT  60 MPH
 24H  25/0000Z 15.5N  98.9W   55 KT  65 MPH
 36H  25/1200Z 16.4N  99.5W   60 KT  70 MPH
 48H  26/0000Z 17.3N 100.3W   50 KT  60 MPH...INLAND
 60H  26/1200Z 18.0N 101.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  27/0000Z...DISSIPATED
Forecaster Blake