While both organizations cited an intensifying El Niño as a cause of increased activity, the CPC also highlighted the difference in global sea surface temperature patterns in 2015 versus the 1995–2014 period.

[12] The well-above-average activity levels were largely attributed to the strong 2014–16 El Niño event, which brought anomalously high sea surface temperatures and low vertical wind shear to western parts of the basin.

[44] Moisture extending from the remnants of Andres brought light rain to parts of the Southwest United States, with Phoenix, Arizona having measurable precipitation on June 5 for the first time since records began in 1896.

Wind shear and dry air afterwards caused Carlos to rapidly weaken, falling to tropical storm intensity on June 17 and degenerating into a remnant low-pressure area hours later.

Maintaining that intensity, Halola crossed the International Date Line into the Western Pacific basin late on July 12, and entered the area of responsibility of the Japan Meteorological Agency.

The small size of the cyclone made it especially susceptible to moderate upper-level winds, and it failed to intensify to Tropical Storm Iune until 18:00 UTC on July 11, when deep convection persisted near the center.

By the morning of July 17, Dolores had deteriorated to a tropical storm, and eventually degenerated into a post-tropical remnant low about 300 mi (485 km) west of the Baja California coast the next day.

The disturbance was initially disorganized, with a broad, elongated circulation and intermittent convection; by 06:00 UTC on July 23, however, it acquired sufficient organization to be declared a tropical depression about 430 mi (690 km) southwest of Baja California.

Located in an environment of low wind shear, high sea surface temperatures and abundant moisture, conditions were very favorable for strengthening, allowing Nine-E to intensify into Tropical Storm Guillermo just six hours later.

Continuing to rapidly intensify, Hilda eventually reached its peak intensity as a Category 4 hurricane late on August 8, possessing 145 mph (235 km/h) sustained winds and a minimum pressure of 937 mbar (hPa; 27.67 inHg).

A nearby upper-level trough restricted the outflow of the storm shortly after formation, causing it to briefly weaken to a tropical depression early on August 22 while it moved in an undulating fashion.

[15] Amid high sea surface temperatures and low vertical wind shear, Kilo began to quickly strengthen while being steered westwards by a mid-level ridge, attaining hurricane status on August 29.

[100] Ignacio continued to rapidly intensify as it turned to the northwest and away from Hawaii, attaining peak intensity at Category 4 status with winds of 145 mph (235 km/h) and a minimum central pressure of 942 mbar (hPa; 27.82 inHg) on August 30.

The system weakened to tropical storm strength at midnight on September 2 well north of Hawaii, but was soon able to reattain hurricane status while passing over anomalously warm waters and experiencing a brief respite in wind shear.

At 06:00 UTC on August 29, Jimena reached its peak intensity as a strong Category 4 hurricane, possessing winds of 155 mph (250 km/h) and a minimum barometric pressure of 932 mbar (hPa; 27.52 inHg).

However, upwelling of cooler waters beneath the hurricane and entrainment of mid-level dry air into the circulation, as well as a second eyewall replacement cycle, resulted in a steady weakening beginning late on August 31.

Jimena continued to weaken slowly amid cooling sea surface temperatures and increasing westerly wind shear, eventually degrading below hurricane status on September 5.

[101] Curving to the northwest, bursts of convection maintained Jimena as a tropical storm, in spite of westerly wind shear in excess of 25 mph (40 km/h) causing the low-level circulation center to be exposed.

[101] While passing north of the Hawaiian Islands on September 11, the remnants of Jimena diverted the winds to blow from the southeast, bringing humid air and atmospheric instability to the east-facing slopes of the Koʻolau Range on Oahu.

Although it initially only produced transient bursts of convection, slow organization of the feature led to the formation of a tropical depression by 18:00 UTC on August 31 while located well south of Baja California.

Despite moving over very warm waters, a mid- to upper-level low-pressure system well northeast of the Hawaiian islands inflicted moderate wind shear over Niala, causing it to struggle to intensify.

Steered steadily westward, the wave entered the East Pacific where deep convection coalesced around a well-defined center; this led to the formation of a tropical depression about 335 mi (540 km) southwest of Acapulco, Mexico by 18:00 UTC on September 26.

Wind shear abruptly increased following peak intensity, causing the cyclone to weaken quickly; it was downgraded to a tropical storm at 06:00 UTC on September 29 and degenerated into a remnant low a day later.

Moving along a west to west-northwest track, the cyclone entered the Central Pacific on October 11, where favorable environmental conditions allowed it to peak with winds of 70 mph (115 km/h) and a minimum pressure of 993 mbar (hPa; 29.32 inHg), just shy of hurricane strength.

Soon after, Olaf began to rapidly intensify amid very favorable environmental conditions and became a hurricane on October 18, with hints of an eye starting to appear within a small central dense overcast.

Although the eye reappeared on satellite as the eyewall cycle completed, another one began while northwesterly wind shear increased, causing Olaf to weaken below major hurricane status while being pulled to the north by a passing trough.

[140] In Emiliano Zapata and Chamela, the villages most badly affected by Patricia, violent winds tore off roofs, toppled concrete power poles and transmission lines, and defoliated trees.

The disturbance encountered a persistent area of convection in the Intertropical Convergence Zone, eventually coalescing into a tropical depression by 12:00 UTC on November 18 while located 715 mi (1,151 km) south-southeast of the southern tip of Baja California.

[39][149] Despite the official end of the hurricane season about a month prior, a westerly wind burst in the equatorial waters of the Central Pacific led to the development of a tropical disturbance on December 27.

[150] Moving slowly eastward, the disturbance stayed in an environment with anomalously high sea surface temperatures and ample ocean heat content associated with the ongoing El Niño event, allowing thunderstorms in the system to develop and persist.