The 2013 Pacific hurricane season was an above average Pacific hurricane season with 21 tropical cyclones forming. Of these, 20 became named storms18 in the Eastern Pacific basin (east of 140°W), and 2 in the Central Pacific basin (between 140°W and the International Date Line). Of the 18 named storms in the east, 9 became hurricanes, with one, Raymond, becoming the season's only major hurricane (category three or higher on the Saffir–Simpson hurricane wind scale). In the central, neither named storm became a hurricane. It was also a below-normal season in terms of Accumulated cyclone energy (ACE), as many of its systems were weak and short-lived. The season officially began on May 15 in the Eastern Pacific and started on June 1 in the Central Pacific; both ended on November 30. These dates conventionally delimit the period of each year when most tropical development occurs in these North Pacific basins. The first cyclone, Tropical Storm Alvin, formed on May 15, and the last, Tropical Storm Sonia, dissipated on November 4.

Several systems directly affected Mexico this season. Hurricane Barbara brought widespread heavy rains to much of Southwestern Mexico and Central America in late May. Damage estimates from the storm range from $50 to $356 million (2013 USD). Hurricane Erick, and Tropical Storms Ivo and Juliette threatened Baja California Sur; Ivo also triggered flash floods across the Southwestern United States. In mid-September, Hurricane Manuel killed at least 169 people in Mexico, and was responsible for significant damage to the western coast and the area around Acapulco. Tropical Storms Juliette, Octave, and Sonia also made landfall in Baja California or northwestern Mexico, bringing with them heavy rains and strong winds. Additionally, Hurricane Raymond, which remained offshore, was the only major hurricane of the year.

Seasonal forecasts +Predictions of tropical activity in the 2013 seasonSourceDateNamedstormsHurricanesMajorhurricanesRefAverage (1981 – 2010)15.48.43.9Record high activity2716 (tie)11Record low activity8 (tie)30 (tie)CPCMay 23, 201311–165–81–4Actual activity2091

On May 21, the Central Pacific Hurricane Center (CPHC) released its forecast for tropical activity across the Central Pacific during 2013. In its report, the organization predicted a 70 percent chance of a below-average season, a 25 percent chance of a near-average season, and a 5 percent chance of an above-average season, equating to 1–3 tropical cyclones across the basin. An average season yields 4–5 tropical cyclones. This forecast was based primarily on the expectation of Neutral El Niño–Southern Oscillation conditions and a continuation of the positive Atlantic multidecadal oscillation.

Two days later, the Climate Prediction Center (CPC) issued its forecast for tropical activity across the East Pacific during 2013. With near or below average sea surface temperatures in the eastern equatorial Pacific and a continuation of the climate pattern responsible for the ongoing era of low Pacific hurricane activity that began in 1995, the organization called for a 55 percent chance of a below-average season, a 35 percent chance of a near-average season, and a 10 percent chance of an above-average season. In total, the CPC predicted 11–16 named storms, 5–8 hurricanes, and 1–4 major hurricanes; an average season yields 15.4 named storms, 8.4 hurricanes, and 3.9 major hurricanes. Both the CPHC and CPC stressed the importance of being prepared prior to the start of the season, noting that significant tropical cyclones can occur even in below-average seasons.

Seasonal summary

The Accumulated Cyclone Energy (ACE) index for the 2013 Pacific hurricane season (Eastern Pacific and Central Pacific combined) as calculated by Colorado State University using data from the National Hurricane Center was 74.8 units. Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of .

The season's first tropical storm formed on May 15, coinciding with the official start of the Pacific hurricane season. On average, a tropical cyclone develops in May in the eastern Pacific every other year. The formation of Barbara in late May marked only the fifth time since 1949 that two tropical storms formed during the month, with the other seasons being 1956, 1984, 2007, 2012, and 2021.

Systems

Tropical Storm Alvin

A tropical wave was first observed over the southeastern Caribbean Sea on May 4. The wave entered the East Pacific a few days later, where atmospheric conditions allowed for gradual development. Curved bands of convection developed around a defined center early on May 15, leading to the formation of a tropical depression around 06:00 UTC that day; at 7.8°N, the depression tied 1976's Hurricane Annette as the second-lowest-latitude tropical cyclone to form in the East Pacific. Twelve hours later, the depression intensified into Tropical Storm Alvin. Influenced by a subtropical ridge over central Mexico, Alvin steadily strengthened and reached peak winds of early on May 16. Thereafter, increasing wind shear and the introduction of mid-level dry air caused the cyclone to begin a quick weakening trend. The low-level circulation became increasingly elongated and opened up into a trough at 00:00 UTC on May 17. Six hours later, Alvin dissipated while located about southwest of Manzanillo, Mexico.

Hurricane Barbara

A tropical wave emerged off the western coast of Africa on May 16, entering the East Pacific on May 24. Following the passage of an atmospheric kelvin wave, a broad area of low pressure formed and gradually organized as convection simultaneously increased. At 12:00 UTC on May 28, the wave was declared a tropical depression; six hours later, the depression intensified into Tropical Storm Barbara. Steered northeastward amid favorable atmospheric conditions, a period of rapid deepening ensued, and the system was upgraded to a Category 1 hurricane at 18:00 UTC on May 29. At 19:50 UTC that day, Barbara attained peak winds of as it moved ashore west-southwest of Tonalá, Chiapas. The cyclone quickly weakened thereafter as it passed over the Sierra Madre mountain range. At 00:00 UTC on May 30, Barbara weakened to a tropical storm, and by six hours later, it further weakened to a tropical depression. After losing its deep convection, the depression degenerated into a remnant low at 12:00 UTC, while located over the Bay of Campeche. The remnant low opened into a trough at 00:00 UTC on May 31.

The precursor disturbance brought rainfall to El Salvador, where one person was killed. In Mexico, rainfall peaked at . Even though Hurricane Barbara struck a largely undeveloped stretch of coastal lagoons, containing small fishing villages, two elderly people were killed in Oaxaca. Furthermore, 14 fishermen were left missing off the coast of Tapanatepec; eight of which were found alive. The towns of Tonala and Arriaga were the worst affected by the hurricane. Although damage was minor, 50 people were evacuated and 2,000 homes were damaged. Throughout the region, 57,000 people were homeless and 10,000 hectares of crops were destroyed. Total losses were estimated at 1.89 billion pesos (US$148 million).

Hurricane Cosme

A tropical wave, the same responsible for Tropical Storm Barry in the Atlantic, moved across the eastern Pacific in late June, yielding a broad area of low pressure by June 21. Northwesterly shear initially hindered development of the system, but a subsequent decrease in upper-level winds, as well as the passage of an eastward-moving kelvin wave, led to the formation of a tropical depression by 12:00 UTC on June 23; twelve hours later, the depression intensified into Tropical Storm Cosme. Steered northwest and eventually west-northwest, the cyclone intensified amid favorable atmospheric dynamics, becoming a minimal hurricane by 12:00 UTC on June 25 and attaining peak winds of twelve hours later. A track over cooler waters and into an increasingly stable environment caused Cosme to weaken to a tropical storm by 18:00 UTC on June 26 and further degenerate into a remnant low by 12:00 UTC the next day while located about west-southwest of Cabo San Lucas, Mexico. The remnant low tracked westward prior to dissipating well east-southeast of the Hawaiian Islands on July 1.

Due to the storm's large size, a "green" alert (low risk) was issued for the states of Colima, Jalisco and Michoacán while a "blue" alert (minimum risk) was placed into effect for the states of Nayarit, Guerrero, and Baja California Sur. As the system passed through the Revillagigedo Islands, winds reached on Socorro Island. The outer rainbands brought moderate rains to Guerrero, causing minor flooding in Acapulco. Across the state, the storm generated 24 landslides, which blocked highways. Two people were killed in the Guerrero, one a tourist that drowned in Zihuatanejo and the other a police officer in an airplane crash that injured 19 others. High seas flooded numerous buildings across coastal towns in Colima, damaging 34 tourist facilities and killing one person. Additionally, many restaurants built of wood and coconut were damaged. In Manzanillo, the port was closed to small craft, as was the port of Mazatlán. Overall, 50 homes were damaged by the storm.

Hurricane Dalila

A tropical wave was first observed over the central Atlantic on June 17. It entered the East Pacific on June 24 and steadily organized, acquiring enough organization to be declared a tropical depression by 18:00 UTC on June 29. Twelve hours later, it was upgraded to Tropical Storm Dalila. Steered northwest parallel to the coastline of Mexico, the cyclone only slowly organized despite favorable conditions, becoming a Category 1 hurricane by 12:00 UTC on July 2. After attaining peak winds of six hours later, the influence of drier air and increasing shear caused the storm to begin a weakening trend. At 18:00 UTC on July 3, Dalila was downgraded to a tropical storm, and by 00:00 UTC on July 5, the system further weakened to a tropical depression. After becoming devoid of convection, Dalila degenerated into a remnant low at 06:00 UTC on July 7 while located roughly south-southwest of Cabo San Lucas, Mexico. The low turned east-northeastward into the circulation of Tropical Storm Erick thereafter, dissipating late on July 8.

When Dalila threatened Western Mexico, the states of Colima, Michoacán, and Jalisco went under a yellow alert; Nayarit was placed on a green alert. Blue alerts were issued for Baja California Sur, Sinaloa, Guerrero, and Oaxaca. The port of Manzanillo was closed as a precaution, where the storm brought rain and storm surge. The outer rainbands of the storm also brought moderate to heavy rainfall along coastal areas of Colima and Jalisco. A total of 49 structures were damaged due to the storm.

Hurricane Erick