Based on data from satellite imagery and weather reports from the cargo ships Hamburg Express and Aleksander Vermishev, the Eastern Pacific Hurricane Center (EPHC) upgraded a tropical disturbance into a tropical depression.
At this time, the depression was  located 390 mi (630 km) west of Clipperton Island, a small remote island in the Pacific Ocean, at 1200 UTC July 16.
Moving towards the west beneath a high pressure area, the depression intensified into Tropical Storm Estelle 12 hours after formation.
Upon being named sea surface temperatures along the storm's path were 84 °F (29 °C), and thus Estelle began to rapidly intensify.
The EPHC reported that Estelle had intensified a Category 1 hurricane on the Saffir-Simpson Hurricane Scale on 1200 UTC July 17, 24 hours after first forming.

Shortly after attaining hurricane intensity, an eye began to appear on weather satellite imagery.
Based on this, the EPHC re-assessed the intensity of the system at 85 mph (135 km/h).
Continuing to intensity, Hurricane Estelle became the first major hurricane of the 1986 Pacific hurricane season on 0000 UTC July 18.
As its motion accelerated, Estelle peaked intensity at 135 mph (215 km/h).
Moving west, Hurricane Estelle emerged into the Central Pacific Hurricane Center's area of responsibility while still a major hurricane.
Shortly thereafter, Estelle's forward motion increased to close to 25 mph (40 km/h).
As such, forecasters noted the path of a potential landfall on the Big Island.
Due to a shearing environment from a trough, Estelle weakened as it continued to approach Hawaii.
A possible re-curve towards the island never materialized, and the hurricane veered to west and passed south of the islands.
Estelle weakened to a tropical storm on July 23 while passing south of Hawaii, and two days later it weakened to a depression.
The tropical cyclone dissipated on July 27.
Based on data from satellite imagery and weather reports from the cargo ships Hamburg Express and Aleksander Vermishev, the Eastern Pacific Hurricane Center (EPHC) upgraded a tropical disturbance into a tropical depression. At this time, the depression was  located 390 mi (630 km) west of Clipperton Island, a small remote island in the Pacific Ocean, at 1200 UTC July 16. Moving towards the west beneath a high pressure area, the depression intensified into Tropical Storm Estelle 12 hours after formation. Upon being named sea surface temperatures along the storm's path were 84 °F (29 °C), and thus Estelle began to rapidly intensify. The EPHC reported that Estelle had intensified a Category 1 hurricane on the Saffir-Simpson Hurricane Scale on 1200 UTC July 17, 24 hours after first forming.
Shortly after attaining hurricane intensity, an eye began to appear on weather satellite imagery. Based on this, the EPHC re-assessed the intensity of the system at 85 mph (135 km/h). Continuing to intensity, Hurricane Estelle became the first major hurricane of the 1986 Pacific hurricane season on 0000 UTC July 18. As its motion accelerated, Estelle peaked intensity at 135 mph (215 km/h). Moving west, Hurricane Estelle emerged into the Central Pacific Hurricane Center's area of responsibility while still a major hurricane. Shortly thereafter, Estelle's forward motion increased to close to 25 mph (40 km/h). As such, forecasters noted the path of a potential landfall on the Big Island. Due to a shearing environment from a trough, Estelle weakened as it continued to approach Hawaii. A possible re-curve towards the island never materialized, and the hurricane veered to west and passed south of the islands. Estelle weakened to a tropical storm on July 23 while passing south of Hawaii, and two days later it weakened to a depression. The tropical cyclone dissipated on July 27.
Hurricane Estelle (1986)