A broad area of low pressure developed in association with the trough south of the Mexico–Guatemala border two days later, and the disturbance steadily organized with aid from an eastward-moving convectively-coupled kelvin wave.

After intensifying into a tropical storm at 12:00 UTC on June 3 and attaining peak winds of 45 mph (70 km/h) six hours later, increasing land interaction caused Boris to begin weakening.

[30] Most of the impacts associated with Boris were due to its developing precursor, whose heavy rainfalls caused 20 mudslides, killing five and resulting in extensive property damage.

The combination of an eyewall replacement cycle, cooler waters, and entrainment of dry air caused Cristina to begin weakening shortly after peak; it fell to tropical storm intensity early on June 14 and degenerated to a remnant low by 06:00 UTC the next morning.

On June 28, the disturbance became distinctively better defined with a well-defined center and spiral banding, signifying the formation of a tropical depression by 18:00 UTC while positioned about 345 mi (555 km) south-southwest of Manzanillo, Mexico.

Steered west-northwest and eventually northwest under the influence of a mid-level ridge, the broad cyclone slowly intensified into a tropical storm by 00:00 UTC on June 30, attaining peak winds of 50 mph (80 km/h) late the next day.

Thereafter, a track over cooler waters and into a drier environment caused the system to begin weakening; at 06:00 UTC on July 5, Douglas degenerated into a non-convective remnant low well west of Baja California.

Steered westward around a subtropical ridge, the depression intensified into Tropical Storm Fausto six hours later and simultaneously attained peak winds of 45 mph (70 km/h).

[41] On July 13, the NHC began to monitor a large area of disturbed weather centered about 1,500 mi (2,415 km) west-southwest of the southern tip of the Baja California peninsula associated with a tropical wave.

It attained major hurricane intensity before crossing the International Date Line into the western Pacific early on August 7, where the system further intensified into a Category 5-equivalent typhoon.

Initially devoid of convection, shower and thunderstorm activity increased significantly a few days later, possibly due to the passage of a convectively-coupled kelvin wave.

A mid-level ridge over Mexico directed the system west-northwest, while improving upper-level winds allowed Iselle to begin rapid intensification.

The high terrain of Hawaii contributed to the disruption of Iselle's cloud pattern, and it degenerated to a remnant low by 06:00 UTC on August 9 before dissipating west of the island late the next day.

Although the cyclone fell to a tropical storm early on August 12, an upper-level environment still favorable for strengthening allowed Julio to briefly regain hurricane strength the next day.

By August 19, as it remained disorganized, a large ridge to its north diminished and a sprawling tropical cyclone—Lowell—formed to its east, leading to weak steering currents that allowed Karina to meander.

It executed a three-day-long cyclonic loop, while environmental conditions began to improve, and became a hurricane again by 18:00 UTC on August 22; twelve hours later, Karina reached peak winds of 85 mph (135 km/h).

Lower ocean temperatures and increasing shear soon deteriorated the storm's cloud pattern, and it fell below hurricane strength early on August 24.

An eyewall replacement cycle later that day curbed the strengthening trend, and by August 26, a persistent ridge over the southern United States directed Marie into cooler ocean waters; both of these events caused steady to rapid weakening.

Departure from the ITCZ resulted in the system moving north initially, but a series of ridges over Mexico directed it on a west to northwest track for the remainder of its duration.

Over anomalously warm ocean waters, and part of an increasingly favorable shear regime, Norbert intensified into a hurricane by 00:00 UTC on September 4.

Situated between two mid-level ridges, the system moved northwest while steadily intensifying, becoming Tropical Storm Odile six hours after formation and further strengthening into a hurricane by 06:00 UTC on September 13.

The onset of an eyewall replacement cycle caused the hurricane to weaken slightly on September 14, but Odile still maintained winds of 125 mph (200 km/h) when it made landfall near Cabo San Lucas at 04:45 UTC.

It entered the East Pacific four days later, where an increase in organization led to the development of a tropical depression well southwest of Baja California around 06:00 UTC on September 11.

Tracking northwest within an environment conducive for strengthening, Polo intensified into a Category 1 hurricane and reached peak winds of 75 mph (120 km/h) by 00:00 UTC on September 18 as an eye became evident on satellite imagery.

[64] A tropical wave departed Africa on September 14 and continued into the eastern Pacific ten days later, where it interacted with the ITCZ and produced a large area of convection.

The system turned northwest around the periphery of a ridge, tracking into a region of low ocean heat content that prompted cold water upwelling.

The post-tropical cyclone turned east and moved ashore Baja California Sur several hours later before dissipating over rugged terrain by 06:00 UTC the next day.

Amid an exceptionally favorable environment, Trudy quickly intensified as it moved north-northwestward, with the formation of an inner core and eye evident on conventional and microwave satellite imagery.

[80][81] A trough that extended from the Atlantic's Tropical Storm Hanna into the eastern Pacific led to widespread convection south of the Gulf of Tehuantepec in late October.

Vance curved northeast into a higher shear environment by November 4, causing the system to weaken from a Category 2 hurricane to a tropical depression in an 18-hour period.