UPDATE 3-Hurricane Otis barrels toward Mexico's Acapulco as Category 5 storm

(Adds strengthening to Category 5, detail from advisory, paragraphs 3, 5-6)

By Javier Verdin

ACAPULCO, Mexico, Oct 24 (Reuters) - Hurricane Otis barreled toward Mexico's beach resort of Acapulco as a Category 5 storm on Tuesday and was poised to make landfall on its Pacific coast early on Wednesday.

Otis was blowing maximum sustained winds of 160 mph (257 kph) and was expected to bring heavy rain capable of "catastrophic damage," the U.S. National Hurricane Center said.

By 9 p.m. time (0300 GMT on Wednesday) Otis was about 55 miles south-southeast of Acapulco, the Miami-based NHC added.

Once Otis comes ashore, it should weaken rapidly, it said.

Hurricane conditions were expected within 12 hours for the stretch of coast between the beach towns of Zihuatanejo and Punta Maldonado in the state of Guerrero, which is home to Acapulco, the NHC said.

The storm could bring up to 20 inches (51 cm) of rain in parts of Guerrero and neighboring Oaxaca state, possibly causing flash flooding and mudslides, a "potentially catastrophic" storm surge, and surf and rip currents, the center added.

Schools across Guerrero canceled classes for Wednesday ahead of Otis' arrival, Governor Evelyn Salgado said on social media.

Over the weekend, Hurricane Norma killed at least three people as it passed along the northwest coast of Mexico. Days before, the powerful Hurricane Lidia left one person dead and several injured after battering Mexico's Pacific coast. (Reporting by Brendan O'Boyle, Diego Ore and Natalia Siniawski; Editing by Alison Williams and Sandra Maler)