2018 Pacific hurricane season

Tropical depression (SSHWS)
Duration	May 10 – May 11
Peak intensity	35 mph (55 km/h) (1-min)  1007 mbar (hPa)

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,[18] which the National Hurricane Center began monitoring for tropical cyclone formation on May 7.[19] The disturbance organized over the next 48 hours but lacked a well-defined center needed for classification;[20] by late on May 9, environmental conditions were becoming less favorable for development.[21] 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.[22] 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.[23]

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

Category 4 hurricane (SSHWS)
Duration	June 6 – June 11
Peak intensity	140 mph (220 km/h) (1-min)  943 mbar (hPa)

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.[24] 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.[25] At peak, the hurricane was characterized by a distinct eye embedded within cloud tops colder than -70 °C (-94 °F).[26] 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.[25]

Category 4 hurricane (SSHWS)
Duration	June 9 – June 15
Peak intensity	140 mph (220 km/h) (1-min)  943 mbar (hPa)

A broad area of disturbed weather formed west of Costa Rica on June 5 in association with a westward-moving tropical wave.[27] 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.[28] Six hours later, the depression strengthened into Tropical Storm Bud.[29] A mid-level ridge to the storm's north directed it on a northwest heading for several days,[30] while favorable environmental conditions led to rapid intensification. Bud attained hurricane strength by 21:00 UTC on June 10,[31] 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.[32] 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.[33] 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,[34] where it ultimately degenerated to a remnant low around 21:00 UTC that day.[35]

Tropical storm (SSHWS)
Duration	June 14 – June 18
Peak intensity	65 mph (100 km/h) (1-min)  997 mbar (hPa)

A broad area of low pressure formed south of Mexico on June 12,[36] 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.[37][38] Initial forecasts showed the storm only slightly intensifying before moving ashore the coastline of Mexico;[39] 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.[40] 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.[41][42]

Tropical storm (SSHWS)
Duration	June 24 – June 26
Peak intensity	45 mph (75 km/h) (1-min)  1004 mbar (hPa)

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.[43] Convection began to show signs of organization early on June 23,[44] 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.[45] At 15:00 UTC on June 24, the depression was upgraded to a tropical storm and was assigned the name Daniel.[46] At 18:00 UTC on June 24, Tropical Storm Daniel reached peak intensity with sustained winds of 45 mph (75 km/h).[47] At 15:00 UTC on June 25, Daniel began to weaken as it moved over seas cooler than 25 °C (77 °F).[48] The system weakened to a tropical depression at 18:00 UTC that day.[49] 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.[50] The remnants of Daniel dissipated completely on June 28.[51]

Tropical storm (SSHWS)
Duration	June 27 – July 1
Peak intensity	60 mph (95 km/h) (1-min)  997 mbar (hPa)

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.[52] 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.[53] It gradually strengthened into Tropical Storm Emilia at 12:00 UTC on June 28.[53] 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.[53] The shear took its toll on Emilia, and by 12:00 UTC the next day, it weakened into a tropical depression.[53] 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.[53]

Category 2 hurricane (SSHWS)
Duration	June 30 – July 6
Peak intensity	110 mph (175 km/h) (1-min)  964 mbar (hPa)

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.[54] 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.[55] The system gradually strengthened into Tropical Storm Fabio at 09:00 UTC on July 1.[56] 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.[57] 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.[58] 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.[59]

Tropical storm (SSHWS)
Duration	July 26 – July 29
Peak intensity	45 mph (75 km/h) (1-min)  1005 mbar (hPa)

On July 18, the NHC forecast the development of an area of low pressure over the east Pacific Ocean within the next few days.[60] 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.[61] Six hours later, the depression strengthened into Tropical Storm Gilma.[61] 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.[61] At 12:00 UTC on July 29, the system degenerated into a remnant low shortly before entering the Central Pacific basin.[61]

Tropical depression (SSHWS)
Duration	July 26 – July 27
Peak intensity	35 mph (55 km/h) (1-min)  1007 mbar (hPa)

The NHC began monitoring a disorganized area of low pressure in the deep tropical Pacific Ocean on July 24 for tropical cyclone development.[62] Gradual organization ensued as the low moved westward, and by July 26, it had organized sufficiently to be classified as a tropical depression.[63] The tropical depression failed to organize, however, and the center soon became difficult to locate on satellite imagery.[64] 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.[65] 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.[66]

Category 4 hurricane (SSHWS)
Duration	July 31 – August 13 (Exited basin)
Peak intensity	155 mph (250 km/h) (1-min)  936 mbar (hPa)

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.[67] A broad area of low pressure formed several hundred miles south-southeast of Acapulco, Mexico, at 12:00 UTC on July 28.[68] The system gradually developed into a tropical depression at 21:00 UTC on July 31.[69] 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.[70] Hector further strengthened and became a hurricane at 14:00 UTC on August 2.[71] Afterward, the small hurricane rapidly strengthened, becoming a strong Category 2 hurricane just six hours later.[72] 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.[73] 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.[74] On the next morning, a shrinking CDO weakened Hector back into a Category 3 storm.[75] 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.[76]

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.[77]

Tropical storm (SSHWS)
Duration	August 4 – August 7
Peak intensity	65 mph (100 km/h) (1-min)  998 mbar (hPa)

A tropical wave entered the eastern Pacific Ocean on August 3, where the NHC began to monitor the system for tropical development.[78] 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.[79] 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.[80] 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.[81]

Heavy rain in Guerrero resulted in three deaths, while rip currents caused an additional fatality along the coast of Chilpancingo.[82] The storm ultimately resulted in $737,000 in damages in Mexico.

Category 2 hurricane (SSHWS)
Duration	August 5 – August 10
Peak intensity	110 mph (175 km/h) (1-min)  964 mbar (hPa)

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.[83] A broad area of low pressure formed several hundred miles south of the Gulf of Tehuantepec on August 2.[84] 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.[85] The depression quickly strengthened into Tropical Storm John six hours later.[86] 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.[87] On August 7, Hurricane John absorbed the smaller Tropical Storm Ileana, while continuing to strengthen.[81] At 15:00 UTC August 7, John reached peak intensity with winds of 105 mph (165 km/h).[88] 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.[89]

Although John never made landfall, it produced high surf along the coastlines of Baja California and Southern California.[90]

Tropical storm (SSHWS)
Duration	August 6 – August 12
Peak intensity	70 mph (110 km/h) (1-min)  991 mbar (hPa)

On August 2, an area of disturbed weather associated with a tropical wave formed south of Mexico,[91] 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.[92] The depression developed into Tropical Storm Kristy by 09:00 UTC the same day.[93] 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.[94] 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.[95] 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.[96]

Category 5 hurricane (SSHWS)
Duration	August 15 – August 28
Peak intensity	160 mph (260 km/h) (1-min)  926 mbar (hPa)

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.[97] Steered due west amid favorable environmental conditions, the system intensified into Tropical Storm Lane by 15:00 UTC on the next day,[98] and further strengthened to a hurricane around 03:00 UTC on August 17 as an eye became apparent.[99] 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.[100] It crossed into the Central Pacific thereafter, where strong westerly wind shear caused a substantial degradation in satellite presentation.[101] Upper-level winds gradually slackened, allowing Lane to regain Category 4 intensity late on August 20.[102] 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.[103][104][105] However, shear increased, weakening Lane to a Category 4 as it was guided towards Hawaii by a strengthening ridge.[106] 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.[107] Early on August 26, Lane made the turn west that it had been predicted to make as it was embedded in the trade winds.[108] At 15:00 UTC August 26, Lane weakened into a tropical depression as its low level center was nearly entirely exposed.[109] 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.[110] 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.[111] 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.[112]

Category 2 hurricane (SSHWS)
Duration	August 26 – September 2
Peak intensity	100 mph (155 km/h) (1-min)  974 mbar (hPa)

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.[113] 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.[114] Gradual development ensued and a tropical depression formed at 9:00 UTC on August 26.[115] At 15:00 UTC on the same day, the depression intensified into a tropical storm, where it was given the name Miriam.[116] The system gradually intensified and at 21:00 UTC on August 29, Miriam intensified into a hurricane.[117] 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.[118] Soon thereafter, Miriam began to be affected by wind shear, weakening into a Category 1 hurricane on August 31.[119][120] Late on September 2, Miriam degenerated into a remnant low, due to strong wind shear.

Category 4 hurricane (SSHWS)
Duration	August 28 – September 9
Peak intensity	150 mph (240 km/h) (1-min)  937 mbar (hPa)

Hurricane Norman originated from a broad area of low pressure that formed several hundred miles south-southwest of Acapulco, Mexico on August 25.[121] Traveling west-northwest,[122] 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.[123] A subtropical ridge steered the system west for several days.[124] Early on August 29, the depression intensified into a tropical storm and received the name Norman.[125] Favorable environmental conditions enabled quick intensification, and the system achieved hurricane strength early on August 30.[126] 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).[127][128][129] 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.[130]

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.[131][132][133] Norman fell to Category 2 status for a period,[134] 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).[135] 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.[136] At the same time, Norman took a turn to a more westerly direction.[137] On September 4, the hurricane crossed west of 140°W, and warning responsibility shifted to the Central Pacific Hurricane Center (CPHC).[138] On the next day, another bout of unexpected intensification ensued and Norman regained major hurricane status.[139] 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.[140]

Category 4 hurricane (SSHWS)
Duration	September 1 – September 14
Peak intensity	130 mph (215 km/h) (1-min)  951 mbar (hPa)

Hurricane Olivia originated from a broad area of low pressure that formed several hundred miles southwest of Mexico on August 30.[141] The National Hurricane Center (NHC) continued to monitor the disturbance as it moved west-northwest for the next couple of days.[142] At 03:00 UTC on September 1, the NHC declared that a tropical depression had formed about 400 miles (645 km) southwest of Mexico.[143] 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.[144] At that time, wind shear from the north-northeast was continuing to prevent significant development of the system.[145] Over the next day and a half, Olivia changed little in strength before beginning a period of rapid intensification on September 3.[146][147] At 03:00 UTC on September 4, Olivia became a Category 1 hurricane.[148] Olivia continued to rapidly intensify, becoming a Category 2 hurricane twelve hours later.[149] At 21:00 UTC on September 4, Olivia became the sixth major hurricane of the season.[150] 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).[151] 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.[152] 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).[153] Olivia then headed into the Central Pacific Basin with maximum sustained winds of 85 mph (140 km/h).[154] As Olivia got closer to the Hawaiian Islands, tropical storm watches were issued for Oahu, Maui, Molokai, Lanai, Kahoolawe, and The Big Island.[155] At 21:00 UTC on September 12, Olivia made landfall in Northwest Maui and Lanai as a tropical storm.[156] Olivia weakened into a tropical depression as wind shear affected the storm on September 13.[157] 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.[158]

Tropical storm (SSHWS)
Duration	September 8 – September 11
Peak intensity	45 mph (75 km/h) (1-min)  1002 mbar (hPa)

A large area of disorganized thunderstorms and cloudiness formed several hundred miles off the southwest coast of Mexico on September 4.[159] 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.[160] 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.[161] 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.[162] After lacking deep convection for over 12 hours, Paul degenerated into a remnant low at 00:00 UTC on September 12,[163] marking the first time since August 14 that no tropical cyclones were active in the northeastern Pacific.[164]

Tropical depression (SSHWS)
Duration	September 19 – September 20
Peak intensity	35 mph (55 km/h) (1-min)  1002 mbar (hPa)

At 0:00 UTC on September 11, forecasters at the NHC predicted that an area of low pressure would develop within a few days.[165] At 12:00 UTC on September 14, a broad area of disturbed weather had developed, as expected.[166] 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.[167] 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.[168] The storm dumped large amounts of rain on Baja California Sur and northwestern Mexico while it was still offshore.[169] The depression turned out to be short-lived, as the storm dissipated after making landfall in northwestern Mexico, early on September 20.[170]

Severe flooding affected much of Sinaloa and Sonora. Damage in the former state reached an estimated 800 million pesos (US$42.5 million).[171]

Category 4 hurricane (SSHWS)
Duration	September 25 – October 2
Peak intensity	150 mph (240 km/h) (1-min)  936 mbar (hPa)

At 18:00 UTC on September 19, the NHC forecasted an area of low pressure that would develop in a few days.[172] At 00:00 UTC on September 23, a broad area of disturbed weather formed where the NHC predicted.[173] Gradual development occurred and the system organized into a tropical depression at 09:00 UTC on September 25.[174] The depression then developed into a tropical storm and was given the name, Rosa, at 15:00 UTC on the same day.[175] Rosa gradually strengthened and at 03:00 UTC on September 26, Rosa intensified into a hurricane.[176] At 21:00 UTC on September 27, Rosa then rapidly intensified and became the seventh Category 4 hurricane of the season.[177] Late on September 28, Rosa started weakening due to an eyewall replacement cycle and rapidly lost structure, falling to Category 3 status.[178] Early on September 29, Rosa weakened below major hurricane status.[179] By the afternoon, Rosa started re-intensifying, with the eyewall replacement having been completed.[180] 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.[181] By September 30, Rosa had weakened to a tropical storm while approaching Baja California.[182] The storm quickly weakened into a remnant low on October 2, as it passed over the peninsula, before dissipating on the next day.[183]

Category 4 hurricane (SSHWS)
Duration	September 29 – October 13
Peak intensity	140 mph (220 km/h) (1-min)  942 mbar (hPa)

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.[184] 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.[185] 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.[186] As the system moved roughly to the west, Sergio quickly intensified, reaching Category 1 hurricane status early on October 1.[187] On October 2, Sergio intensified to a Category 2 hurricane,[188] before strengthening into a Category 3 major hurricane later that day.[189] 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.[190] 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 943 millibars (27.8 inHg).[191] Afterward, Sergio began to weaken, dropping to Category 3 intensity by 03:00 UTC on the next day.[192] Early on October 6, Sergio had restrengthened into a strong Category 3 hurricane, while continuing westward,[193] 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.[194] 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,[195] before making landfall on Baja California early on October 12.[196] Later on the same day, Sergio weakened into a tropical depression, after making a second landfall on the Mexican mainland.[197] Soon afterward, Sergio degenerated into a remnant low.[198]

Category 5 hurricane (SSHWS)
Duration	September 29 – October 6
Peak intensity	160 mph (260 km/h) (1-min)  921 mbar (hPa)

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.[199] Walaka organized into a hurricane on September 30 and began rapidly intensifying.[200] Within 24 hours, Walaka had intensified into a major hurricane.[201] 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.[202] Later on October 2, however, the hurricane underwent an eyewall replacement cycle that caused it to weaken while passing close to Johnston Atoll.[203] 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.[204] Walaka continued to weaken over cooler waters further north.[205] At 15:00 UTC on October 6, Walaka transitioned into an extratropical cyclone 1,085 miles (1,740 km) north-northwest of Honolulu, Hawaii.[206] 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.[207]

Tropical storm (SSHWS)
Duration	October 14 – October 17
Peak intensity	65 mph (100 km/h) (1-min)  995 mbar (hPa)

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.[208] 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.[209] The depression then strengthened into Tropical Storm Tara at 09:00 UTC on October 15.[210] Amid favorable conditions, the tiny cyclone strengthened, reaching its peak intensity with maximum sustained winds of 65 mph (100 km/h).[211] 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.[212] At 21:00 UTC on October 16, Tara weakened to a tropical depression while just south of Manzanillo, Mexico,[213] before degenerating into an elongated trough with no discernible circulation six hours later.[214]

Tropical storm (SSHWS)
Duration	October 19 – October 23
Peak intensity	50 mph (85 km/h) (1-min)  1002 mbar (hPa)

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.[215] 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.[216] The new system quickly organized; consequently, and was designated as Tropical Depression Twenty-Three-E roughly 12 hours later on October 19.[217] 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.[218] Thereafter, moderate northeasterly wind shear began to weaken the relatively small system.[219] A burst of mild restrengthening followed on the next day;[220] however, it was short-lived, and the storm resumed weakening six hours later.[221] At 15:00 UTC on October 23, Vicente degenerated into a remnant low shortly after making landfall in Michoacán, before dissipating shortly afterward.[222]

In Mexico, 16 people were killed, due to heavy rains and mudslides triggered by Vicente.[223][224][225]

Category 5 hurricane (SSHWS)
Duration	October 20 – October 24
Peak intensity	160 mph (260 km/h) (1-min)  925 mbar (hPa)

On October 14, the NHC began monitoring an Atlantic tropical wave that had developed an area of low pressure in the southwestern Caribbean Sea.[226] 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.[227] However, organization was hindered as the system quickly made landfall in Belize on the next day.[228] Early on October 17, the tropical wave moved into the East Pacific and quickly organized;[229] however, the system failed to coalesce into a tropical cyclone and became increasingly disorganized on the next day.[230] Early on October 19, a new low-pressure trough developed to the east of the original low,[216] which organized into Tropical Storm Vicente later that day.[218] 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.[231] Several hours later, the system strengthened into a tropical storm and was given the name Willa.[232] Early on October 21, Willa underwent rapid intensification and became a Category 1 hurricane.[233] 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.[234] Soon afterward, at 22:30 UTC, Willa intensified further into a Category 4 hurricane, becoming the ninth of the year in the East Pacific.[15] 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.[16] 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.[235] Willa encountered wind shear and weakened further into a Category 3 hurricane by the next day,[236] 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.[237] Following landfall, Willa rapidly weakened, dissipating on October 24 over northeastern Mexico.[238]

In Nayarit state, Willa killed four people – three drowned along the San Pedro River, and the other was discovered by fishermen.[239] Heavy rainfall killed two people in Nogales, Sonora. There, floods swept away cars and entered homes and businesses.[240]

Tropical storm (SSHWS)
Duration	November 2 – November 5
Peak intensity	65 mph (100 km/h) (1-min)  995 mbar (hPa)

Xavier originated from a trough of low pressure that the NHC began tracking on October 25.[241] The NHC tracked the disturbance for the next several days as it slowly organized and turned from a more westerly direction to the northwest.[242] However, the disturbance became less organized on October 30.[243] Over the next several days, the NHC continued to track the disturbance as it re-organized and turned towards the northeast.[244] At 21:00 UTC on November 2, the system organized into a tropical depression a few hundred miles southwest of Manzanillo, Mexico,[245] which subsequently strengthened into Tropical Storm Xavier at 03:00 UTC on November 3.[246] This made Xavier the first storm to reach the "X" name on the Eastern Pacific naming list since 1992.[247] Throughout its lifespan, Xavier was buffeted by high wind shear, which prevented the system from strengthening.[248][249] The system became sheared of all convection late on November 5,[250] and degenerated into a post-tropical cyclone early on November 6.[251]

Xavier brought tropical-storm-force winds and heavy rains to the coast of western Mexico.[252]

Invest 96C at peak intensity, as a subtropical storm, on September 2.

On August 29, an upper-level low absorbed the remnants of Hurricane Lane to the west-northwest of Hawaii.[253] The storm was assigned the designation 96C by the United States Naval Research Laboratory (NRL).[254] Traversing an area with sea surface temperatures 2 °C (3.6 °F) above-normal,[255] the system coalesced into a subtropical storm by August 31.[253] On September 2, the system reached its peak intensity and began to display an eye.[254] 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.[254]