000 WTPZ43 KNHC 240239 TCDEP3 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. FORECAST POSITIONS AND MAX WINDS 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