The 2018 Pacific hurricane season was one of the most active Pacific hurricane seasons on record, producing the highest accumulated cyclone energy value in the basin at the time until it was surpassed in 2026. It also had the fourth-highest number of named storms – 23, tied with 1982. The season also featured eight landfalls, six of which occurred in Mexico. The season officially began on May 15 in the Eastern Pacific, and on June 1 in the Central Pacific; they both ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Pacific basin. However, tropical cyclone formation is possible at any time of the year, as illustrated when the first tropical depression formed on May 10, five days prior to the official start of the season.
The second named storm of the season, Hurricane Bud, struck Baja California Sur in mid-June, causing minor damage. Tropical Storm Carlotta stalled offshore of the Mexican coastline, where it also caused minor damage. In early August, Hurricane Hector became one of the few tropical cyclones to cross into the Western Pacific from the Eastern Pacific, while also affecting Hawaii. Tropical Storm Ileana brought torrential rainfall to southwestern Mexico during early August, causing relatively minor damage. A few weeks later, Hurricane Lane obtained Category 5 intensity while also becoming Hawaii's wettest tropical cyclone on record and the second wettest tropical cyclone in United States history, only behind Hurricane Harvey of the previous year. Hurricane Olivia also struck Hawaii, resulting in relatively minor damage.
In late September, hurricanes Rosa and Sergio formed, both of which eventually brought thunderstorms and flash flooding to the Baja California Peninsula and the Southwestern United States. Tropical Depression Nineteen-E became the first tropical cyclone to form in the Gulf of California before it brought severe flooding to Sinaloa, Mexico, causing significant damage. Meanwhile, Hurricane Walaka attained Category 5 intensity before causing disruptions in the Northwestern Hawaiian Islands. In late October, Hurricane Willa became the record-tying third Category 5 hurricane of the season (tied with the 1994, 2002 and 2026 seasons ) before striking Sinaloa as a major hurricane, causing severe damage. Tropical Storm Vicente simultaneously affected the region just south of where Willa made landfall, causing severe flooding and dozens of landslides. Altogether, six systems made landfall this season. Damage across the basin reached $1.64 billion (2018 USD), while 57 people were killed by the various storms.
Seasonal forecasts
The National Oceanic and Atmospheric Administration (NOAA) released its annual forecast on May 24, 2018, predicting an 80% chance of a near- to above-average season in both the Eastern and Central Pacific basins, with a total of 14–20 named storms, 7–12 hurricanes, and 3–7 major hurricanes. The reason for their outlook was the possible development of an El Niño, which reduces vertical wind shear across the basin and increases sea surface temperatures. In addition, many global computer models expected a positive Pacific decadal oscillation (PDO) that had been ongoing since 2014 to continue. PDO is a phase of a multi-decade cycle that favors much warmer than average sea surface temperatures, which is in contrast to the 1995–2013 period, which featured below-normal activity. The Servicio Meteorológico Nacional (SMN) issued its first forecast for the season on May 25, predicting a total of 18 named storms, 6 hurricanes, and 4 major hurricanes to develop.
Seasonal summary
The accumulated cyclone energy (ACE) index for the 2018 Pacific hurricane season as calculated by the National Hurricane Center was 318.1 units, the second-highest total ACE of any Pacific hurricane season on record. Broadly speaking, ACE is a measure of the power of a tropical storm multiplied by the length of time it existed. Therefore, a stronger storm with a longer duration contributes more to the seasonal total than several short-lived, weaker storms combined.
Overall, 26 tropical depressions formed, with 23 reaching tropical storm intensity. Thirteen of the tropical storms became hurricanes, with 10 reaching major hurricane intensity. El Niño-like conditions prevailed across much of the basin, leading to elevated activity. Sea surface temperatures were above average for much of the season, stretching from the coast of North America to near the 150th meridian east. A subpolar gyre located in the Northern Atlantic increased atmospheric convection and reduced vertical wind shear across the Eastern Pacific. Wind shear near Hawaii's Big Island decreased even more after the subtropical jet pushed northward in September. Higher levels of humidity were present between 10°N–20°N at a height of 4,781–9,882 ft (1,457–3,012 m). Storms were also kept in more favorable environments by stronger easterlies as a result of an above-normal subtropical ridge.
The season started with the formation of Tropical Depression One-E on May 10, which was five days before the official start of hurricane season in the Eastern Pacific. There were five named storms in June, tied with 1985 for the most during the month. Aletta and Bud both intensified into Category 4 major hurricanes, marking the first time since 2010 that two occurred in June. After a below-normal July, August had above-normal activity. Hurricane Hector spent more days as a major hurricane than any other storm in the basin. In mid-August, Hurricane Lane became a Category 5 hurricane before it brought record rainfall to Hawaii's Big Island, becoming the wettest tropical cyclone for that state and the second wettest in the United States. September saw the formation of five tropical cyclones – Olivia, Paul, Nineteen-E, Rosa, and Sergio. Hurricane Olivia became the first tropical cyclone in recorded history to make landfall on the islands of Maui and Lanai on September 12. Tropical Depression Nineteen-E formed in the Gulf of California on September 19, the first such instance in recorded history. In October, both hurricanes Walaka and Willa became Category 5 hurricanes, the latter of which hit Sinaloa as a weakened hurricane. After Tropical Storm Xavier dissipated on November 6, the season ended on November 30.
Systems
Tropical Depression One-E
In early May, a disturbance formed within the Intertropical Convergence Zone (ITCZ), south of the Gulf of Tehuantepec. The system propagated westward over the next several days, spawning an area of low pressure on May 8. Convection or thunderstorm activity initially decreased, before steadily increasing and organizing around the system's center on May 10. A tropical depression formed at 12:00 UTC on the same day, while located approximately 1,265 mi (2,036 km) west-southwest of the southern tip of the Baja California Peninsula. Moderate-to-high wind shear produced by an upper-level trough located to the west prevented the depression from strengthening any further as it continued westward. By 18:00 UTC on May 11, the depression had weakened into a remnant low after losing all of its convection as a result of the increasing shear. The depression's remnants dissipated one day later while about 1,495 mi (2,406 km) west-southwest of the southern tip of Baja California.
Hurricane Aletta
A tropical wave departed from the western coast of Africa on May 22. The wave traversed the Atlantic Ocean and Caribbean, before later crossing over Central America and entering the Pacific Ocean. Convection associated with the system increased on June 3 while it was located south of the Gulf of Tehuantepec. Over the next couple of days, the system continued to organize, with banding features becoming established. After the storm's center became demarcated, a tropical depression formed at 00:00 UTC on June 6, while located approximately 345 mi (555 km) south-southwest of Manzanillo, Mexico. At that time, the system was located within favorable environmental conditions of near 86 °F (30 °C) sea surface temperatures and very low wind shear.
The depression intensified into Tropical Storm Aletta at 06:00 on June 6, and gradually strengthened over the next day before rapid intensification ensued. Aletta peaked as a Category 4 hurricane with maximum sustained winds of 140 mph (220 km/h) and a minimum central pressure of 943 mbar (27.85 inHg) at 12:00 UTC on June 8, while located about 575 mi (925 km) south-southwest of Manzanillo. Meanwhile, the hurricane was traveling north of west by the flow of a subtropical ridge, which was located over the southwestern United States. Aletta began to rapidly weaken on June 9 after it moved into a region of cooler sea surface temperatures and stable air. The system was downgraded to a remnant low at 12:00 UTC on June 11 after it lost all of its convection. Aletta's remnants were influenced by a surface flow for several days before they dissipated.
Hurricane Bud
A tropical wave departed from the western coast of Africa on May 29 and propagated westward across the Atlantic Ocean, eventually entering the Eastern Pacific on June 6. Associated convective activity increased considerably on June 8 as the result of a nearby Kelvin wave. A low-pressure area formed the next day and continued to increase in organization, spawning a tropical depression at 18:00 UTC on June 9, about 330 mi (530 km) south of Acapulco, Mexico. At that time, the storm was moving in a west-northwest to northwest direction around a mid-level ridge that was located over Mexico. The depression quickly strengthened into Tropical Storm Bud and rapidly intensified thereafter due to warm sea surface temperatures and abundant mid-level moisture. Bud became a hurricane at 18:00 UTC on June 10 and a Category 3 major hurricane by 12:00 UTC on June 11. The cyclone ultimately peaked as a Category 4 hurricane with winds of 140 mph (220 km/h) and a pressure of 943 mbar (27.85 inHg) around 00:00 UTC on June 12, while located approximately 200 mi (320 km) southwest of Manzanillo, Mexico. After Bud's peak intensity, the hurricane rapidly weakened back to a tropical storm. Moderately warm sea surface temperatures allowed Bud to maintain some of its strength, although its structure degraded as it approached Baja California Sur. Bud made landfall near San José del Cabo around 02:00 UTC on June 15, with winds of 45 miles per hour (75 km/h). Increasing wind shear and the mountainous terrain of Baja California Sur caused Bud to weaken into a post-tropical cyclone by 12:00 UTC. The circulation opened up into a trough about 12 hours later, located around 35 mi (55 km) southwest of Huatabampito, Mexico.
Hurricane Bud prompted the issuance of tropical cyclone watches and warnings along Baja California Sur and the northwestern coast of Mexico. Strong wind gusts were recorded in Baja California, causing minimal damage. Despite remaining offshore for most of its track, the hurricane caused torrential rainfall and severe flooding in several regions. A peak rainfall total of 6.50 in (165 mm) was recorded in San Lorenzo, Sinaloa. In Guadalajara, Jalisco, hundreds of vehicles were inundated and swept away. A canal overflowed in Guadalajara, causing damage to multiple stores in a mall. At least 100 additional structures were damaged in the city. In Guerrero, hundreds of businesses and homes were flooded. Over 100 businesses in Pie de la Cuesta were damaged by strong waves. More than 60 homes in Maruata, Michoacán, experienced flood or wind damage. Heavy rainfall from Bud generated currents that swept away a child who was crossing a road in Mexico City. The remnants of Bud brought moisture to drought-stricken regions of the Southwestern United States, and slowed the advance of wildfires in Colorado and Wyoming.
Tropical Storm Carlotta
A low-pressure area developed on June 12 south of the Gulf of Tehuantepec. Two days later, the system's convection organized enough for the low to be classified as a tropical depression approximately 140 mi (225 km) south of Acapulco, Mexico. The nascent depression tracked north-northeastward toward the Mexican coast. Wind shear prevented strengthening initially, but the depression became Tropical Storm Carlotta around 18:00 UTC on June 15. The storm temporarily stalled on June 16 just off the coast of Acapulco. At 00:00 UTC on June 17, Carlotta reached its peak intensity with winds of 65 mph (100 km/h) and a pressure of 997 mbar (29.44 inHg). Land interaction, dry air, and increasing wind shear caused the storm to weaken as it progressed to the west-northwest. Carlotta weakened to a tropical depression late on June 17, and deteriorated into a remnant low by early on June 19. The system dissipated offshore between
Manzanillo and Zihuatanejo, Mexico shortly after.
Tropical Storm Carlotta warranted the issuance of tropical storm watches and warnings along the southern coast of Mexico. Carlotta caused severe flooding in the states of Aguascalientes, Guerrero, Michoacán, Oaxaca, and Puebla, as well as the Yucatán Peninsula; the storm also killed a total of three people. A peak rainfall total of 11.2 in (285 mm) was recorded in Melchor Ocampo, Michoacán. Carlotta and two other systems dropped 3–20 in (70–400 mm) of rain across the Yucatán Peninsula, resulting in severe flooding. In Oaxaca, dwellings, a hospital, utilities, and roads and bridges sustained wind and flood damage. Multiple rivers overflowed their banks in Michoacán, flooding several homes and damaging water pumps. Carlotta also caused several landslides throughout the state. Insurance claims related to the storm reached US$7.6 million (MX$156 million) statewide. Another 12 houses were flooded in Aguascalientes.