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.

This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season. It includes information that was not released throughout the season, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not initially warned upon, has been included.

The time stamp for each event is first stated using Coordinated Universal Time (UTC), the 24-hour clock where 00:00 = midnight UTC. The NHC uses both UTC and the time zone where the center of the tropical cyclone is currently located. The time zones utilized (east to west) are: Central, Mountain, Pacific and Hawaii. In this timeline, the respective area time is included in parentheses. Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (miles, or kilometers), following National Hurricane Center practice. Direct wind observations are rounded to the nearest whole number. Atmospheric pressures are listed to the nearest millibar and nearest hundredth of an inch of mercury. __TOC__

Timeline

May May 15 The 2015 Pacific hurricane season officially begins.

May 28 06:00 UTC (12:00 a.m. MDT) at – Tropical Depression One-E develops from an area of disturbed weather about 830 mi (1,335 km) south of the southern tip of the Baja California Peninsula. 12:00 UTC (6:00 a.m. MDT) at – Tropical Depression One-E intensifies into a tropical storm and is named Andres while located 815 mi (1,310 km) south of the southern tip of the Baja California Peninsula.

May 29 18:00 UTC (12:00 p.m. MDT) at – Tropical Storm Andres intensifies to a Category 1 hurricane approximately southwest of Socorro Island.

May 30 12:00 UTC (5:00 a.m. PDT) at – Hurricane Andres strengthens into a Category 2 hurricane about southwest of Socorro Island.

May 31 00:00 UTC (5:00 p.m. PDT, May 30) at – Hurricane Andres intensifies to a Category 3 hurricane roughly southwest of Socorro Island. This marks only the fifth such storm since 1971 to develop during May. 12:00 UTC (7:00 a.m. CDT) at – Tropical Depression Two-E develops from an area of disturbed weather approximately south-southwest of Acapulco, Mexico.

June June 1

00:00 UTC (5:00 p.m. PDT, May 31) at – Hurricane Andres strengthens into a Category 4 hurricane about west-southwest of Socorro Island. 06:00 UTC (11:00 p.m. PDT, May 31) at – Hurricane Andres achieves its peak intensity with maximum sustained winds of and a barometric pressure of 937 mbar (hPa; ) while situated west-southwest of Socorro Island. 12:00 UTC (7:00 a.m. CDT) at – Tropical Depression Two-E intensifies into Tropical Storm Blanca roughly southwest of Acapulco, Mexico.

June 2 00:00 UTC (5:00 p.m. PDT, June 1) at – Hurricane Andres weakens to a Category 3 hurricane roughly 695 mi (1,120 km) west-southwest of Socorro Island. 06:00 UTC (11:00 p.m. PDT, June 1) at – Hurricane Andres weakens to a Category 2 hurricane approximately 730 mi (1,175 km) west-southwest of Socorro Island. 12:00 UTC (5:00 a.m. PDT) at – Hurricane Andres weakens to a Category 1 hurricane about 775 mi (1,245 km) west of Socorro Island. 18:00 UTC (1:00 p.m. CDT) at – Tropical Storm Blanca intensifies into a Category 1 hurricane roughly south-southwest of Zihuatanejo, Mexico.

June 3

06:00 UTC (11:00 p.m. PDT, June 2) at – Hurricane Andres weakens to a tropical storm about 895 mi (1,440 km) west of Socorro Island. 06:00 UTC (1:00 a.m. CDT) at – Hurricane Blanca strengthens into a Category 2 hurricane about southwest of Acapulco, Mexico. 12:00 UTC (7:00 a.m. CDT) at – Hurricane Blanca rapidly intensifies to Category 4 intensity about southwest of Acapulco, Mexico. This marks the earliest occurrence of a season's second major hurricane since reliable records began in 1971. 18:00 UTC (1:00 p.m. CDT) at – Hurricane Blanca achieves its peak intensity with winds of and a barometric pressure of 936 mbar (hPa; ) while located about south-southwest of Lázaro Cárdenas, Mexico.

June 4 06:00 UTC (1:00 a.m. CDT) at – Tremendous upwelling of cooler waters underneath Hurricane Blanca results in the storm degrading to Category 3 status about south-southwest of Lázaro Cárdenas, Mexico. 12:00 UTC (5:00 a.m. PDT) at – Tropical Storm Andres degenerates to a remnant low roughly 905 mi (1,455 km) west-northwest of Socorro Island. 12:00 UTC (7:00 a.m. CDT) at – Hurricane Blanca rapidly weakens to Category 2 intensity about south-southwest of Lázaro Cárdenas, Mexico.

June 5 12:00 UTC (6:00 p.m. MDT) at – Hurricane Blanca further weakens to a Category 1 strength about southwest of Manzanillo, Mexico.

June 6 00:00 UTC (6:00 p.m. MDT, June 5) at – Hurricane Blanca re-intensifies to Category 2 status about southwest of Manzanillo, Mexico. 06:00 UTC (12:00 a.m. MDT) at – Hurricane Blanca regains Category 3 intensity about southwest of Puerto Vallarta, Mexico. 12:00 UTC (6:00 a.m. MDT) at – Hurricane Blanca reaches its secondary peak as a Category 4 hurricane with winds of about southwest of Puerto Vallarta, Mexico. 18:00 UTC (12:00 p.m. MDT) at – Hurricane Blanca weakens back to Category 3 status about southwest of Puerto Vallarta, Mexico.

June 7 Around 03:30 UTC (9:30 p.m. MDT, June 6) – Hurricane Blanca makes its closest approach to Socorro Island, passing roughly to the northeast. An automated weather station there records sustained winds of , with a peak gust of , before it ceases reporting. 06:00 UTC (12:00 a.m. MDT) at – Hurricane Blanca weakens to a Category 2 hurricane again about south-southwest of Cabo San Lucas, Mexico. 18:00 UTC (12:00 p.m. MDT) at – Hurricane Blanca degrades to a tropical storm about south-southwest of Cabo San Lucas, Mexico.

June 8

10:00 UTC (4:00 a.m. MDT) at – Tropical Storm Blanca makes landfall over Isla Santa Margarita, Mexico, with winds of . This marks the earliest instance of a tropical cyclone making landfall along the Baja California Peninsula since reliable records began in 1971, and occurred a month earlier than the previous record. 11:15 UTC (5:15 a.m. MDT) at – Tropical Storm Blanca traverses Magdalena Bay and makes a second landfall along the Baja California Peninsula, this time near Puerto Argudin with winds of . 20:00 UTC (2:00 p.m. MDT) at – Tropical Storm Blanca briefly emerges back over the Pacific Ocean, weakening to a tropical depression in the process. It subsequently makes its third and final landfall about south-southwest of El Patrocinio, Mexico, with winds of .

June 9 06:00 UTC (12:00 a.m. MDT) at – Tropical Depression Blanca degenerates to a non-convective remnant low about northwest of Santa Rosalía, Mexico.

June 10 18:00 UTC (1:00 p.m. CDT) at – Tropical Depression Three-E develops from a large area of low pressure approximately south-southwest of Puerto Escondido, Mexico.

June 11 12:00 UTC (7:00 a.m. CDT) at – Tropical Depression Three-E intensifies into Tropical Storm Carlos about south of Acapulco, Mexico.

June 13

12:00 UTC (7:00 a.m. CDT) at – Tropical Storm Carlos intensifies into a Category 1 hurricane about south of Acapulco, Mexico. 18:00 UTC (1:00 p.m. CDT) at – Hurricane Carlos attains its lowest barometric pressure of 978 mbar (hPa; ) approximately south of Acapulco, Mexico.

June 15 00:00 UTC (7:00 p.m. CDT, June 14) at – Hurricane Carlos degrades into a tropical storm, possibly due to upwelling of cooler waters from its slow motion, while situated west-southwest of Acapulco, Mexico. 18:00 UTC (1:00 p.m. CDT) at – Tropical Storm Carlos regains hurricane status about southwest of Lázaro Cárdenas, Mexico.

June 16 18:00 UTC (1:00 p.m. CDT) at – The unusually small Hurricane Carlos, with tropical-storm-force winds extending just from its center, attains its peak winds of roughly south of Manzanillo, Mexico.

June 17 06:00 UTC (1:00 a.m. CDT) at – Hurricane Carlos quickly degrades to a tropical storm about southwest of Manzanillo, Mexico. 09:00 UTC (4:00 a.m. CDT) at – Tropical Storm Carlos makes landfall near Tenacatita, Mexico, with winds of . 18:00 UTC (12:00 p.m. MDT) at – Tropical Storm Carlos degenerates into a remnant low, with winds falling below gale-force, approximately southwest of Puerto Vallarta, Mexico.

July July 8

00:00 UTC (5:00 p.m. PDT, July 7) at – Tropical Depression Four-E forms about 1,025 mi (1,650 km) east-southeast of Hilo, Hawaii, quickly crossing west of 140°W and entering the Central Pacific basin. 12:00 UTC (2:00 a.m. HST) at – Tropical Depression Four-E intensifies into Tropical Storm Ela about 885 mi (1,425 km) east-southeast of Hilo, Hawaii. 18:00 UTC (8:00 a.m. HST) at – Tropical Storm Ela reaches its peak strength with winds of and a pressure of 1002 mbar (hPa; ), while located approximately 785 mi (1,265 km) east-southeast of Hilo, Hawaii.

July 10 00:00 UTC (2:00 p.m. HST, July 9) at – Tropical Storm Ela weakens to a tropical depression about east of Hilo, Hawaii. 06:00 UTC (8:00 p.m. HST, July 9) at – Tropical Depression One-C develops from an area of low pressure about 1,025 mi (1,650 km) southwest of Honolulu, Hawaii. 06:00 UTC (8:00 p.m. HST, July 9) at – Tropical Depression Two-C develops from an area of low pressure about 750 mi (1,205 km) southeast of Honolulu, Hawaii. 12:00 UTC (2:00 a.m. HST) at – Tropical Depression Ela degenerates into a post-tropical low about east-northeast of Hilo, Hawaii.

July 11 00:00 UTC (2:00 p.m. HST, July 10) at – Tropical Depression One-C strengthens into Tropical Storm Halola about 1,200 mi (1,930 km) southwest of Honolulu, Hawaii. 12:00 UTC (7:00 a.m. CDT) at – Tropical Depression Five-E develops from an area of low pressure about south-southeast of Acapulco, Mexico. 18:00 UTC (8:00 a.m. HST) at – Tropical Depression Two-C intensifies into Tropical Storm Iune about south of Honolulu, Hawaii. Iune simultaneously reaches its peak strength with winds of and a pressure of 1004 mbar (hPa; ). 18:00 UTC (1:00 p.m. CDT) at – Tropical Depression Five-E intensifies into Tropical Storm Dolores about south of Acapulco, Mexico.

July 12

06:00 UTC (8:00 p.m. HST, July 11) at – Tropical Storm Halola attains winds of and a pressure of 999 mbar (hPa; ), its maximum strength while within the Central Pacific basin.