2018 Pacific hurricane season
The 2018 Pacific hurricane season produced the highest accumulated cyclone energy value on record in the basin. With 23 named storms, it was the fourth-most active season on record, tied with 1982. The season also featured seven landfalls  (Bud, Olivia, Nineteen-E, Rosa, Sergio, Vicente, and Willa), 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. 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 US history, only behind Hurricane Harvey of the previous year. Hurricane Olivia also struck Hawaii, resulting in slight 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. 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 and 2002 seasons) before striking Sinaloa as a major hurricane. Damage across the basin reached $1.25 billion (2018 USD), while 52 people were killed by the various storms.

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Seasonal forecasts

On May 24, 2018, the National Oceanic and Atmospheric Administration released its annual forecast, 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), a phase of a multi-decade cycle that favored much warmer than average sea surface temperatures that had been ongoing since 2014 to continue, in contrast to the 1995–2013 period, which featured below normal activity. On May 25, the Servicio Meteorológico Nacional (SMN) issued its first forecast for the season, predicting a total of 18 named storms, 6 hurricanes, and 4 major hurricanes to develop.

Seasonal summary

The season began early with the formation of Tropical Depression One-E on May 10, which formed five days prior to the official start of the season. June was an extraordinarily active month throughout the basin, breaking the record for number of tropical cyclones (six), as well as tying the records for the number of named storms (five) and major hurricanes (two). Fabio's intensification into a tropical storm on July 1 marked the earliest date of a season's sixth named storm, beating the previous record of July 3 set in both 1984 and 1985. Activity abruptly slowed thereafter, with only three tropical cyclones forming during the month of July. One of those cyclones continued to intensify into Hurricane Hector in August, which became the third major hurricane of the season. In August, activity increased dramatically, with Tropical Storm Ileana and Hurricane John forming just a day apart on August 4 and August 5, respectively, followed by Tropical Storm Kristy two days later. Hurricane Lane formed in mid-August and became the first Category 5 storm of the season as well as the wettest tropical cyclone on record in Hawaii. 

Hurricanes Miriam and Norman soon followed, forming in late August, becoming the seventh and eighth hurricanes of the season, respectively, while Norman became the fifth major hurricane of the season. Hurricane Olivia formed soon after in early September, and became the sixth major hurricane of the season. Short-lived Tropical Storm Paul followed, forming on September 8 and dissipating three days later far from land. The short-lived Tropical Depression Nineteen-E brought destructive floods to western Mexico from September 19 to September 20. During the last days of the month, Hurricane Rosa became the seventh major hurricane of the season, striking Baja California before dissipating on October 2. 

On October 4, Hurricane Sergio became the eighth Category 4 hurricane of the season in the eastern Pacific region, breaking the previous record of seven, which was set in 2015. Activity resumed on October 14 when Tropical Storm Tara formed and hugged the Mexican coast. After a few days of inactivity, two tropical storms developed, named Vicente and Willa. Willa later rapidly intensified and became the thirteenth hurricane of the season. On the next day, Willa strengthened further into a Category 4 hurricane, becoming the season's tenth major hurricane. A day later, Willa strengthened to Category 5 status, making 2018 the third Pacific hurricane season on record to feature three Category 5 hurricanes, after 1994 and 2002. The season concluded with Tropical Storm Xavier, which developed on November 2 and hugged the southwest coast of Mexico before rapidly degenerating into a remnant low on November 6.

The Accumulated Cyclone Energy index for the 2018 Pacific hurricane season is 316.565 units (201.9725 units for the Eastern Pacific and 114.5925 units for the Central Pacific). Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. Therefore, a stronger storm with a longer duration, such as Hurricane Hector, contributes more to the seasonal total than several short-lived, weaker storms combined. 2018 has the highest total ACE of any Pacific hurricane season on record, having surpassed the 1992 Pacific hurricane season.

Systems

Tropical Depression One-E

In early May, a westward-tracking trough or tropical wave embedded in the monsoon trough interacted with a convectively-coupled Kelvin wave. This interaction led to a large area of shower and thunderstorm activity well southwest of Mexico, which the National Hurricane Center began monitoring for tropical cyclone formation on May 7. The disturbance organized over the next 48 hours but lacked a well-defined center needed for classification; by late on May 9, environmental conditions were becoming less favorable for development. In spite of this, an increase in convection and formation of a well-defined circulation led to the designation of the season's first tropical depression at 21:00 UTC on May 10. The system failed to intensify after formation and, owing to strong westerly wind shear, ultimately degenerated into a remnant low by 18:00 UTC on May 11.

Unrelated to One-E, Subtropical Storm Alberto developed in the Atlantic Ocean on May 25th, marking the third year in a row that the first tropical cyclones of the Atlantic and Eastern Pacific hurricane center developed before their official beginning dates.

Hurricane Aletta

A tropical wave departed western Africa on May 22, moving inconspicuously across the Atlantic and failing to develop convection until it was south of the Gulf of Tehuantepec on June 3. Following the formation of a well-defined center, the system was upgraded to a tropical depression around 00:00 UTC on June 6. It intensified into Tropical Storm Aletta six hours later. Subtropical ridging over the United States directed the system west-northwest, while ideal environmental conditions allowed Aletta to reach hurricane strength around 18:00 UTC on June 7. A period of rapid deepening ensued shortly thereafter, with maximum winds increasing from 75 mph (120 km/h) to 140 mph (220 km/h) within an 18-hour period. At peak, the hurricane was characterized by a distinct eye embedded within cloud tops colder than -70 °C (-94 °F). A track into cooler waters and a more stable air mass caused Aletta to weaken as quickly as it intensified, falling from Category 4 strength to a tropical storm within 30 hours. After losing its associated deep convection, the system degenerated to a remnant low around 12:00 UTC on June 11. The low meandered for several days, before dissipating early on June 16.

Hurricane Bud

A broad area of disturbed weather formed west of Costa Rica on June 5 in association with a westward-moving tropical wave. Gradual organization occurred as the wave tracked generally westward across the eastern Pacific Ocean. On June 9, the disturbance developed a well-defined surface circulation, leading to the classification of a tropical depression at 21:00 UTC. Six hours later, the depression strengthened into Tropical Storm Bud. A mid-level ridge to the storm's north directed it on a northwest heading for several days, while favorable environmental conditions led to rapid intensification. Bud attained hurricane strength by 21:00 UTC on June 10, and continued intensification up to its peak as a Category 4 hurricane with winds of 140 mph (220 km/h) around 00:00 UTC on June 12. The effects of cold water upwelling prompted a rapid weakening trend shortly after peak, with Bud falling to a tropical storm by 12:00 UTC on June 13. The system made landfall near Cabo San Lucas with winds of 45 mph (75 km/h), shortly after 00:00 UTC on June 15, before progressing into the Gulf of California, where it ultimately degenerated to a remnant low around 21:00 UTC that day.

Tropical Storm Carlotta

A broad area of low pressure formed south of Mexico on June 12, organizing into the season's fourth tropical depression by 21:00 UTC on June 14 and further into Tropical Storm Carlotta around 18:00 UTC on June 15. Initial forecasts showed the storm only slightly intensifying before moving ashore the coastline of Mexico; instead, Carlotta stalled just offshore and strengthened to attain peak winds of 65 mph (100 km/h) as it established an inner core and eye. Interaction between the system's eyewall and land prompted a swift weakening trend as it paralleled the Mexican shoreline, and Carlotta fell to tropical depression intensity by 18:00 UTC on June 17, before degenerating to a remnant low at 00:00 UTC on June 19.

Tropical Storm Daniel

Late on June 21, the NHC began monitoring a surface trough and its associated disorganized convection several hundred miles southwest of Baja California. Environmental conditions were expected to be marginally conducive for development as it moved north-northwestward. Convection began to show signs of organization early on June 23, and this process led to the formation of a tropical depression by 03:00 UTC on the next morning, as spiral bands wrapped into the storm's well-defined center. At 15:00 UTC on June 24, the depression was upgraded to a tropical storm and was assigned the name Daniel. At 18:00 UTC on June 24, Tropical Storm Daniel reached peak intensity with sustained winds of 45 mph (75 km/h). At 15:00 UTC on June 25, Daniel began to weaken as it moved over seas cooler than 25 °C (77 °F). The system weakened to a tropical depression at 18:00 UTC that day. At 15:00 UTC on June 26, Daniel degenerated into a remnant low, as it lost all convection and was reduced to a swirl of low-level clouds. The remnants of Daniel dissipated completely on June 28.

Tropical Storm Emilia

On June 23, the NHC noted the potential for tropical cyclogenesis from a tropical wave crossing over Costa Rica. Environmental conditions were expected to be conducive for development as it moved westward. The system then steadily organized over warm waters, developing into Tropical Depression Six-E at 18:00 UTC June 27, about 480 miles (770 km) southwest of Manzanillo, Mexico. It gradually strengthened into Tropical Storm Emilia at 12:00 UTC on June 28. At 12:00 UTC on June 29, Emilia reached its peak intensity with maximum sustained winds of 60 mph (95 km/h); however, it was then subject to strong wind shear. The shear took its toll on Emilia, and by 12:00 UTC the next day, it weakened into a tropical depression. Finally, at 00:00 UTC on July 2, Emilia degenerated into a remnant low, as it lost its convection and was reduced to a swirl of clouds.

Hurricane Fabio

The NHC first noted the potential for tropical cyclogenesis from a tropical wave crossing over Honduras and Nicaragua at 18:00 UTC on June 24.  Subsequent development was expected of the system as it moved westward. It steadily organized over warm waters and transitioned into Tropical Depression Seven-E at 21:00 UTC June 30, 490 miles (790 km) southwest of Acapulco, Mexico. The system gradually strengthened into Tropical Storm Fabio at 09:00 UTC on July 1. With SSTs of 30 °C (86 °F) and almost no wind shear, Fabio began to intensify, quickly strengthening into a hurricane by 15:00 UTC on July 2. Initially, forecasters at the NHC predicted that Fabio would intensify further and become a major hurricane, although it failed to do so and peaked with maximum sustained winds of 110 mph (175 km/h), just shy of major hurricane status. Afterward, Fabio began to rapidly weaken as it moved over cooler waters. At 15:00 UTC on July 6, Fabio degenerated into a remnant low as it lost its convection while located 1,285 miles (2,065 km) off the coast of the Baja Peninsula.

Tropical Storm Gilma

On July 18, the NHC forecast the development of an area of low pressure over the east Pacific Ocean within the next few days. A weak area of low pressure developed several hundred miles south-southeast of the Gulf of Tehuantepec on July 22. Little development occurred over the next few days as the low moved northwestward across the Pacific Ocean. However, shower and thunderstorm activity associated with the low began to quickly organize on July 26, leading to the formation of a tropical depression at 12:00 UTC on July 26. Six hours later, the depression strengthened into Tropical Storm Gilma. However, northwesterly wind shear soon exposed the center of circulation, causing Gilma to weaken to a tropical depression at 18:00 UTC the following day. At 12:00 UTC on July 29, the system degenerated into a remnant low shortly before entering the Central Pacific basin.

Tropical Depression Nine-E

The NHC began monitoring a disorganized area of low pressure in the deep tropical Pacific Ocean on July 24 for tropical cyclone development. Gradual organization ensued as the low moved westward, and by July 26, it had organized sufficiently to be classified as a tropical depression. The tropical depression failed to organize, however, and the center soon became difficult to locate on satellite imagery. After having lasted less than a day as a tropical cyclone, the depression opened up into a trough, as it became embedded within the Intertropical Convergence Zone at 12:00 UTC on July 27. Although Nine-E's remnants produced intermittent convection; high wind shear and dry air prevented it from regenerating back into a tropical cyclone, and the storm's remnants dissipated a few days later.

Hurricane Hector

Late on July 26, the NHC noted the development of an area of low pressure that was forecast to form a couple hundred miles west-southwest of Mexico. A broad area of low pressure formed several hundred miles south-southeast of Acapulco, Mexico, at 12:00 UTC on July 28. The system gradually developed into a tropical depression at 21:00 UTC on July 31. The depression quickly organized, developing a more defined center and spiral banding, and at 03:00 UTC on August 1, it strengthened into Tropical Storm Hector. Hector further strengthened and became a hurricane at 14:00 UTC on August 2. Afterward, the small hurricane rapidly strengthened, becoming a strong Category 2 hurricane just six hours later. However, the eye became clouded and ill-defined shortly afterward, while the storm underwent an eyewall replacement cycle, and Hector's intensification halted momentarily, as northeasterly shear and dry air impinged on the system, weakening the system back to a Category 1 hurricane. Yet, the hurricane quickly intensified yet again, and restrengthened back into a Category 2 hurricane, and later to a Category 3 hurricane, making it the third major hurricane of the season. A strong convective band soon wrapped into Hector's central dense overcast (CDO), strengthening it to a Category 4 major hurricane. On the next morning, a shrinking CDO weakened Hector back into a Category 3 storm. In the following hours, Hector underwent another eyewall replacement cycle and was set to weaken thereafter. After the completion of the eyewall replacement cycle, Hector rapidly intensified back to a high-end Category 4 storm on August 6. At 09:00 UTC on August 8, Hector weakened to a Category 3 hurricane. At 21:00 UTC, the CPHC reported that Hector was passing about 200 miles (320 km) south of the Big Island with winds of 115 mph. At the same time, Hector began a third eyewall replacement cycle. By 09:00 UTC on August 9, Hector completed the eyewall replacement cycle.

By 15:00 UTC on the same day, Hector began to intensify once again, as it moved due west. At 21:00 UTC on August 10, Hector reached its secondary peak intensity with winds of 140 mph (220 km/h) as it began to turn west-northwest. On August 11, Hector began another weakening trend as increasing wind shear began to take a toll on the system. By this time, the hurricane set a record for the longest consecutive duration as a major hurricane in the northeastern Pacific. Late on August 11, Hector weakened below major hurricane strength due to increasing wind shear, a status it had held for nearly eight days. Hector weakened to Category 1 status on August 12. On August 13 at 15:00 UTC, Hector crossed the International Date Line as a tropical storm.

Tropical Storm Ileana

A tropical wave entered the eastern Pacific Ocean on August 3, where the NHC began to monitor the system for tropical development. Although the system was initially disorganized, it rapidly organized over the next two days, and on August 4, the system developed into a tropical depression while located south of the Gulf of Tehuantepec. The depression continued to organize that night through the next day, and at 21:00 UTC on August 5, the system strengthened into Tropical Storm Ileana. After strengthening to peak winds of 65 mph (100 km/h), Ileana weakened as it began to feel the influence of the much larger Hurricane John, with the two systems experiencing the Fujiwhara effect. On August 7, the small circulation of Ileana dissipated, as the storm was absorbed by John.

Heavy rain in Guerrero resulted in three deaths, while rip currents caused an additional fatality along the coast of Chilpancingo. The storm ultimately resulted in $737,000 in damages in Mexico.

Hurricane John

On July 29, the NHC began forecasting the development of an area of low pressure that was expected to form several hundred miles off the Mexican coast. A broad area of low pressure formed several hundred miles south of the Gulf of Tehuantepec on August 2. Gradual organization occurred as the low moved slowly west-northwestward, and at 21:00 UTC on August 5, the low had organized sufficiently to be classified as the season's twelfth tropical depression. The depression quickly strengthened into Tropical Storm John six hours later. Amid very favorable environmental conditions, John rapidly intensified, and by 21:00 UTC on August 6, John had become the fifth hurricane of the season, and soon began to interact with Tropical Storm Ileana to the east, due to the Fujiwhara effect. On August 7, Hurricane John absorbed the smaller Tropical Storm Ileana, while continuing to strengthen. At 15:00 UTC August 7, John reached peak intensity with winds of 105 mph (165 km/h). However, John began to move over cooler waters and began to weaken. The cyclone weakened to a Category 1 hurricane by 15:00 UTC on August 8, and to tropical storm status by 09:00 UTC on August 9, until it finally degenerated into a remnant low at 15:00 UTC on August 10.

Although John never made landfall, it produced high surf along the coastlines of Baja California and Southern California.

Tropical Storm Kristy

On August 2, an area of disturbed weather associated with a tropical wave formed south of Mexico, the NHC began monitoring the disturbance for potential tropical development. The system lingered for days without developing as it tracked generally towards the west, finally at 05:00 UTC August 7, the well-defined low was embedded within a developing area of convection, along with tight banding near the center and was classified as Tropical Depression Thirteen-E accordingly. The depression developed into Tropical Storm Kristy by 09:00 UTC the same day. Kristy gradually strengthened over the next few days, and at 03:00 UTC on August 10, it attained its peak intensity with maximum sustained winds of 70 mph (110 km/h), just short of hurricane status. However, as Kristy moved over progressively cooler waters, it gradually weakened. By 15:00 UTC August 11, Kristy degenerated into a remnant low as cooler waters and wind shear had taken its toll on Kristy's cloud structure which consisted of a swirl of low clouds with some mid and high-level clouds. Despite degenerating into a remnant low, showers and thunderstorms redeveloped in association with Post-Tropical Cyclone Kristy by 00:00 UTC August 12 and the disturbance was monitored, however cold waters prevented the system from regenerating back into a tropical cyclone.

Hurricane Lane

A tropical depression formed well southwest of Baja California around 03:00 UTC on August 15, from an area of disturbed weather the NHC had been monitoring for days. Steered due west amid favorable environmental conditions, the system intensified into Tropical Storm Lane by 15:00 UTC on the next day, and further strengthened to a hurricane around 03:00 UTC on August 17 as an eye became apparent. Following the formation of an inner core, Lane began a period of rapid intensification that brought the system to its initial peak intensity as a Category 4 hurricane with winds of 140 mph (220 km/h) and a pressure of 950 mbar (hPa; 28.05 inHg) early on August 18. It crossed into the Central Pacific thereafter, where strong westerly wind shear caused a substantial degradation in satellite presentation. Upper-level winds gradually slackened, allowing Lane to regain Category 4 intensity late on August 20. Despite forecasts calling for the storm to weaken, Lane continued to strengthen. By 04:30 UTC on August 22, data from a reconnaissance aircraft measured maximum 1-minute sustained winds near 160 mph (260 km/h), and Lane was upgraded to a Category 5 hurricane as it maintained a distinct eye surrounded by deep convection. However, shear increased, weakening Lane to a Category 4 as it was guided towards Hawaii by a strengthening ridge. Rapid weakening ensued thereafter, weakening Lane from a Category 2 to a tropical storm in 6 hours due to 35 to 40 knots of wind shear impacting Lane's core convection. Early on August 26, Lane made the turn west that it had been predicted to make as it was embedded in the trade winds. At 15:00 UTC August 26, Lane weakened into a tropical depression as its low level center was nearly entirely exposed. However, at 15:00 UTC on August 27, Lane re-intensified into a tropical storm as a convective bursts partially covered the low level center. However, this re-intensification would be short lived, as 18 hours later, Lane weakened back into a tropical depression, as its low-level circulation center was once again exposed, due to constant wind shear. Finally, just before 00:00 UTC on August 29, Lane degenerated into a remnant low, as its circulation became elongated and cloud tops near the center warmed and were displaced from the center.

Hurricane Miriam

At 21:00 UTC on August 22, forecasters at the NHC forecasted that an area of low pressure could form several hundred miles southwest of the Baja California Sur. Shortly afterward, on August 24, a trough of low pressure formed where the NHC predicted where it would be, predictions said that gradual development would be possible of the system. Gradual development ensued and a tropical depression formed at 9:00 UTC on August 26. At 15:00 UTC on the same day, the depression intensified into a tropical storm, where it was given the name Miriam. The system gradually intensified and at 21:00 UTC on August 29, Miriam intensified into a hurricane. At 0:00 UTC on August 30, Miriam entered the Central Pacific where responsibility was handed over to the CPHC. At 12:00 UTC on August 31, Miriam intensified to attain its peak intensity as a Category 2 hurricane. Soon thereafter, Miriam began to be affected by wind shear, weakening into a Category 1 hurricane on August 31. Late on September 2, Miriam degenerated into a remnant low, due to strong wind shear.

Hurricane Norman

Hurricane Norman originated from a broad area of low pressure that formed several hundred miles south-southwest of Acapulco, Mexico on August 25. Traveling west-northwest, the system coalesced into a tropical depression by at 15:00 UTC on August 28 while situated approximately 420 miles (675 km) south-southwest of the southern tip of Baja California. A subtropical ridge steered the system west for several days. Early on August 29, the depression intensified into a tropical storm and received the name Norman. Favorable environmental conditions enabled quick intensification, and the system achieved hurricane strength early on August 30. Rapid intensification ensued throughout the day, culminating with Norman attaining its peak intensity at 15:00 UTC, with sustained winds of 150 mph (240 km/h) and a central pressure of 937 mbar (27.67 inHg). During a 24-hour period, the hurricane's winds increased by 80 mph (130 km/h), the largest such increase since Hurricane Patricia in 2015.

The combination of an eyewall replacement cycle and increasing wind shear induced weakening beginning on August 31. At 03:00 UTC on August 31, Norman turned to the west-southwest due to a deep-layer ridge to the north. Norman fell to Category 2 status for a period, before unexpectedly rapidly intensifying back to a Category 4 hurricane on September 2. The storm attained a secondary peak with winds of 140 mph (235 km/h) and a pressure of 947 mbar (28.00 inHg). Initially proving resilient to adverse conditions, Norman succumbed to increasing wind shear and lower sea surface temperatures on September 3. Its central dense overcast warmed and its eye filled. At the same time, Norman took a turn to a more westerly direction. On September 4, the hurricane crossed west of 140°W, and warning responsibility shifted to the Central Pacific Hurricane Center (CPHC). On the next day, another bout of unexpected intensification ensued and Norman regained major hurricane status. However, wind shear increased once again thereafter, and Norman weakened into a Category 1 hurricane on September 6. On September 7, Norman weakened further to a tropical storm as it began to lose its tropical characteristics. The CPHC issued its final advisory on Norman at 21:00 UTC on September 8, as it was rapidly becoming extratropical; Norman subsequently completed its extratropical transition on the next day.

Hurricane Olivia

Hurricane Olivia originated from a broad area of low pressure that formed several hundred miles southwest of Mexico on August 30. The National Hurricane Center (NHC) continued to monitor the disturbance as it moved west-northwest for the next couple of days. At 03:00 UTC on September 1, the NHC declared that a tropical depression had formed about 400 miles (645 km) southwest of Mexico. Due to unfavorable conditions, the depression slowly became more organized over the next day and half before strengthening into Tropical Storm Olivia at 09:00 UTC on September 2. At that time, wind shear from the north-northeast was continuing to prevent significant development of the system. Over the next day and a half, Olivia changed little in strength before beginning a period of rapid intensification on September 3. At 03:00 UTC on September 4, Olivia became a Category 1 hurricane. Olivia continued to rapidly intensify, becoming a Category 2 hurricane twelve hours later. At 21:00 UTC on September 4, Olivia became the sixth major hurricane of the season. Six hours later, Olivia reached its initial peak intensity, with maximum sustained winds of 125 mph (205 km/h) and a minimum central pressure of 955 mbar (28.20 inHg). Olivia then started weakening due to increasing wind shear and lower sea surface temperatures at 09:00 UTC on September 5. Olivia then weakened more and fell below major hurricane strength at 15:00 UTC on the same day. Unexpectedly, Olivia intensified into a Category 4 hurricane with a new peak intensity of 130 mph (215 km/h) and a minimum central pressure of 948 mbar (28.00 inHg). Olivia then headed into the Central Pacific Basin with maximum sustained winds of 85 mph (140 km/h). As Olivia got closer to the Hawaiian Islands, tropical storm watches were issued for Oahu, Maui, Molokai, Lanai, Kahoolawe, and The Big Island. At 21:00 UTC on September 12, Olivia made landfall in Northwest Maui and Lanai as a tropical storm. Olivia weakened into a tropical depression as wind shear affected the storm on September 13. Olivia then degenerated into a remnant low at 00:00 UTC on September 14 and dissipated on September 19, after crossing the International Date Line.

Tropical Storm Paul

A large area of disorganized thunderstorms and cloudiness formed several hundred miles off the southwest coast of Mexico on September 4. The disturbance gradually organized as it moved slowly west-northwestward, and by 15:00 UTC on September 8, it had acquired sufficient organized convection to be classified as a tropical depression. Although initial forecasts called for the depression to eventually strengthen into a hurricane, it remained a sheared tropical cyclone with its center of circulation exposed on the eastern side. At 09:00 UTC on September 9, the depression strengthened into Tropical Storm Paul. Despite a moderately favorable environment, Paul failed to strengthen significantly and remained a poorly organized system, eventually weakening to a tropical depression early on September 11. After lacking deep convection for over 12 hours, Paul degenerated into a remnant low at 00:00 UTC on September 12, marking the first time since August 14 that no tropical cyclones were active in the northeastern Pacific.

Tropical Depression Nineteen-E

At 0:00 UTC on September 11, forecasters at the NHC predicted that an area of low pressure would develop within a few days. At 12:00 UTC on September 14, a broad area of disturbed weather had developed, as expected. Some development followed, but the system began to approach the Baja California Peninsula, which was initially expected to cause the system to fail to develop due to land interaction. Despite land interaction, the system continued to organize, and at 15:00 UTC on September 19, Tropical Depression Nineteen-E formed within an inverted trough in the Gulf of California, with the NHC initiating advisories on the system. The storm dumped large amounts of rain on Baja California Sur and northwestern Mexico while it was still offshore. The depression turned out to be short-lived, as the storm dissipated after making landfall in northwestern Mexico, early on September 20.

Severe flooding affected much of Sinaloa and Sonora. Damage in the former state reached an estimated 800 million pesos (US$42.5 million).

Hurricane Rosa

At 18:00 UTC on September 19, the NHC forecasted an area of low pressure that would develop in a few days. At 00:00 UTC on September 23, a broad area of disturbed weather formed where the NHC predicted. Gradual development occurred and the system organized into a tropical depression at 09:00 UTC on September 25. The depression then developed into a tropical storm and was given the name, Rosa, at 15:00 UTC on the same day. Rosa gradually strengthened and at 03:00 UTC on September 26, Rosa intensified into a hurricane. At 21:00 UTC on September 27, Rosa then rapidly intensified and became the seventh Category 4 hurricane of the season. Late on September 28, Rosa started weakening due to an eyewall replacement cycle and rapidly lost structure, falling to Category 3 status. Early on September 29, Rosa weakened below major hurricane status. By the afternoon, Rosa started re-intensifying, with the eyewall replacement having been completed. Late on September 29, Rosa started to weaken yet again, as it was impacted by high amounts of wind shear and low sea surface temperatures. By September 30, Rosa had weakened to a tropical storm while approaching Baja California. The storm quickly weakened into a remnant low on October 2, as it passed over the peninsula, before dissipating on the next day.

Hurricane Sergio

Late on September 25, the NHC forecasted an area of low pressure to develop within the Gulf of Tehuantepec, south of Mexico within a couple of days. Early on September 26, an area of low pressure developed as expected, with the NHC initially giving the system a low chance of tropical development. Over the next few days, the disturbance gradually organized while slowly moving westward, and on September 29, the disturbance organized into Tropical Storm Sergio, while situated south-southwest of Acapulco, Mexico. As the system moved roughly to the west, Sergio quickly intensified, reaching Category 1 hurricane status early on October 1. On October 2, Sergio intensified to a Category 2 hurricane, before strengthening into a Category 3 major hurricane later that day. Late on October 3, Sergio intensified into a Category 4 hurricane, becoming the record-breaking eighth hurricane in the East Pacific basin of Category 4 or 5 intensity. Early on October 4, Sergio reached its peak intensity, with maximum sustained winds of 140 mph (220 km/h) and a minimum central pressure of . Afterward, Sergio began to weaken, dropping to Category 3 intensity by 03:00 UTC on the next day. Early on October 6, Sergio had restrengthened into a strong Category 3 hurricane, while continuing westward, and the storm held that intensity for another day before a weakening trend resumed, weakening Sergio into a Category 2 hurricane early on October 7. Sergio continued to weaken over cooler waters, and after stalling five days as a Category 1, it finally dropped to tropical storm strength late on October 9, before making landfall on Baja California early on October 12. Later on the same day, Sergio weakened into a tropical depression, after making a second landfall on the Mexican mainland. Soon afterward, Sergio degenerated into a remnant low.

Hurricane Walaka

On September 29, a tropical disturbance to the southwest of Hawaii organized into Tropical Storm Walaka, becoming the first named storm in the Central Pacific basin since Hurricane Ulika in 2016. Walaka organized into a hurricane on September 30 and began rapidly intensifying. Within 24 hours, Walaka had intensified into a major hurricane. Walaka continued to intensify, reaching Category 4 status at 8:00 HST (18:00 UTC) on October 1. Early on the next day, at 00:00 UTC, Walaka became the second Category 5 hurricane of the year east of the International Date Line. Later on October 2, however, the hurricane underwent an eyewall replacement cycle that caused it to weaken while passing close to Johnston Atoll. At 12:00 UTC on October 3, Walaka started to reintensify while moving away from Johnston Atoll and toward Papahānaumokuākea Marine National Monument. However, northwesterly wind shear began to adversely affect Walaka, causing it to weaken before crossing the archipelago. Walaka continued to weaken over cooler waters further north. At 15:00 UTC on October 6, Walaka transitioned into an extratropical cyclone 1,085 miles (1,740 km) north-northwest of Honolulu, Hawaii. Unrelated to Walaka, Typhoon Kong-rey developed and intensified into a Category 5-equivalent super typhoon around the same time Walaka reached its peak intensity, marking the first time since 2005 when two tropical cyclones of Category 5 strength existed simultaneously in the Northern Hemisphere.

Tropical Storm Tara

Early on October 11, the NHC began monitoring a large area of disturbed weather that had developed near the Gulf of Tehuantepec for possible tropical cyclone development. The disturbance gradually contracted and became better-defined as it moved west-northwestward paralleling the coast of Mexico. By 15:00 UTC on October 14, the low had finally acquired sufficiently organized convection to be classified as a tropical depression. The depression then strengthened into Tropical Storm Tara at 09:00 UTC on October 15. Amid favorable conditions, the tiny cyclone strengthened, reaching its peak intensity with maximum sustained winds of 65 mph (100 km/h). However, a burst of moderate to strong southeasterly shear caused the low-level and upper-level circulations of the cyclone to decouple as it crawled slowly northwestward, and rapid weakening ensued as Tara neared the Mexican coast. At 21:00 UTC on October 16, Tara weakened to a tropical depression while just south of Manzanillo, Mexico, before degenerating into an elongated trough with no discernible circulation six hours later.

Tropical Storm Vicente

On October 17, an elongated low-pressure system developed to the south of Guatemala. Although the system was given a high chance of tropical development, it remained disorganized while moving westward. Early on October 19, a new trough of low pressure developed to the south of Guatemala, within the broad area of disturbed weather, east of the original low of the larger disturbance. The new system quickly organized; consequently, and was designated as Tropical Depression Twenty-Three-E roughly 12 hours later on October 19. Just six hours later, Twenty-Three-E strengthened into a tropical storm, receiving the name Vicente, and also it soon developed an eye, which did not last long whatsoever. Thereafter, moderate northeasterly wind shear began to weaken the relatively small system. A burst of mild restrengthening followed on the next day; however, it was short-lived, and the storm resumed weakening six hours later. At 15:00 UTC on October 23, Vicente degenerated into a remnant low shortly after making landfall in Michoacán, before dissipating shortly afterward.

In Mexico, 16 people were killed, due to heavy rains and mudslides triggered by Vicente.

Hurricane Willa

On October 14, the NHC began monitoring an Atlantic tropical wave that had developed an area of low pressure in the southwestern Caribbean Sea. On the next day, the system became better organized southeast of the Yucatán Peninsula, and the storm encountered more favorable conditions as it neared land; a Hurricane Hunter aircraft was scheduled to survey the system for further development. However, organization was hindered as the system quickly made landfall in Belize on the next day. Early on October 17, the tropical wave moved into the East Pacific and quickly organized; however, the system failed to coalesce into a tropical cyclone and became increasingly disorganized on the next day. Early on October 19, a new low-pressure trough developed to the east of the original low, which organized into Tropical Storm Vicente later that day. The original low to the west gradually organized while moving westward, and early on October 20, the system developed into Tropical Depression Twenty-Four-E while situated off the coast of southwestern Mexico. Several hours later, the system strengthened into a tropical storm and was given the name Willa. Early on October 21, Willa underwent rapid intensification and became a Category 1 hurricane. Further rapid intensification ensued and Willa became a Category 3 hurricane at 21:00 UTC, just twelve hours after reaching hurricane status, becoming the tenth major hurricane of the season. Soon afterward, at 22:30 UTC, Willa intensified further into a Category 4 hurricane, becoming the ninth of the year in the East Pacific. At 6:00 UTC on October 22, Willa reached its peak intensity as the third Category 5 hurricane of the year, though operationally, Willa was assessed as reaching its peak at 15:00 UTC. Soon after reaching peak intensity, Willa began to weaken, due to the commencement of an eyewall replacement cycle, weakening to a high-end Category 4 hurricane six hours later. Willa encountered wind shear and weakened further into a Category 3 hurricane by the next day, before making landfall at Category 3 intensity at 1:00 UTC on October 24 (7:00 pm on October 23, local time), in Sinaloa, southwestern Mexico. Following landfall, Willa rapidly weakened, dissipating on October 24 over northeastern Mexico.

In Nayarit state, Willa killed four people – three drowned along the San Pedro River, and the other was discovered by fishermen. Heavy rainfall killed two people in Nogales, Sonora. There, floods swept away cars and entered homes and businesses.

Tropical Storm Xavier

Xavier originated from a trough of low pressure that the NHC began tracking on October 25. The NHC tracked the disturbance for the next several days as it slowly organized and turned from a more westerly direction to the northwest. However, the disturbance became less organized on October 30. Over the next several days, the NHC continued to track the disturbance as it re-organized and turned towards the northeast. At 21:00 UTC on November 2, the system organized into a tropical depression a few hundred miles southwest of Manzanillo, Mexico, which subsequently strengthened into Tropical Storm Xavier at 03:00 UTC on November 3. This made Xavier the first storm to reach the "X" name on the Eastern Pacific naming list since 1992. Throughout its lifespan, Xavier was buffeted by high wind shear, which prevented the system from strengthening. The system became sheared of all convection late on November 5, and degenerated into a post-tropical cyclone early on November 6.

Xavier brought tropical-storm-force winds and heavy rains to the coast of western Mexico.

Other systems

On August 29, an upper-level low absorbed the remnants of Hurricane Lane to the west-northwest of Hawaii. The storm was assigned the designation 96C by the United States Naval Research Laboratory (NRL). Traversing an area with sea surface temperatures 2 °C (3.6 °F) above-normal, the system coalesced into a subtropical storm by August 31. On September 2, the system reached its peak intensity and began to display an eye. Afterward, the system gradually began to weaken, while accelerating northward into colder waters. On September 3, the system weakened below tropical depression intensity, back into an extratropical low. On September 4, the system was absorbed by a larger extratropical storm in the Bering Sea.

Storm names

The following list of names was used for named storms that form in the northeastern Pacific Ocean during 2018. No names were retired, so this list will be used again in the 2024 season. This is the same list used in the 2012 season. The name Vicente was used for the first time this year, while the names Willa and Xavier were both used once in 1962 and 1992, respectively.

For storms that form in the Central Pacific Hurricane Center's area of responsibility, encompassing the area between 140 degrees west and the International Date Line, all names are used in a series of four rotating lists. The next four names that were slated for use in 2018 are shown below; however, only the name Walaka was used.

Season effects
This is a table of all the storms that have formed in the 2018 Pacific hurricane season. It includes their duration, names, affected areas, damages, and death totals. Deaths in parentheses are additional and indirect (an example of an indirect death would be a traffic accident), but were still related to that storm. Damage and deaths include totals while the storm was extratropical, a tropical wave, or a low, and all the damage figures are in USD. Potential tropical cyclones are not included in this table.