Timeline of the 2015 Pacific hurricane season
The 2015 Pacific hurricane season was the second-most active Pacific hurricane season on record, and featured the strongest tropical cyclone ever observed in the Western Hemisphere: Hurricane Patricia. The season officially started on May 15 in the Eastern Pacific—east of 140°W—and on June 1 in the Central Pacific—between the International Date Line and 140°W—and ended on November 30. These dates typically cover the period of each year when most tropical cyclones form in the Northeastern Pacific tropical cyclone basin. The season's first storm , Hurricane Andres, developed on May 28; the season's final storm, Tropical Depression Nine-C, dissipated on December 31, well after the official end of the season. Throughout the season, 31 tropical depressions developed, 26 of which became tropical storms, a record-tying 16 of them reached hurricane strength, and a record-breaking 11 achieved major hurricane intensity. Activity in the Central Pacific shattered records, with 16 tropical cyclones forming in or entering the basin; the previous highest was 11 during the 1992 and 1994 seasons. On August 30, three hurricanes at Category 4 strength—Ignacio, Jimena, and Kilo—existed  simultaneously in the Northeastern Pacific, which was a first for the basin. On October 23, Hurricane Patricia became the strongest hurricane ever recorded in the Western Hemisphere, with a minimum atmospheric pressure of 872 mbar (hPa; 25.75 inHg) and maximum sustained winds of . Activity in the basin was boosted by the strong 2014–16 El Niño event, which brought anomalously high sea surface temperatures and low vertical wind shear that helped the numerous systems form and intensify. Four time zones are utilized in the basin: Central for storms east of 106.0°W, Mountain from 106.0°W to 114.9° W, Pacific from 115.0°W to 140.0°W, and Hawaii–Aleutian for storms between the International Date Line and 140°W. However, for convenience, all information is listed by Coordinated Universal Time (UTC) first with the respective local time included in parentheses. This timeline includes information that was not operationally released, meaning that data from post-storm reviews by the National Hurricane Center and Central Pacific Hurricane Center are included. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.