The 1986 Pacific hurricane season featured several tropical cyclones that contributed to significant flooding to the Central United States. The hurricane season officially started May 15, 1986, in the eastern Pacific, and June 1, 1986 in the central Pacific, and lasted until November 30, 1986 in both regions. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean. A total of 17 named storms and 9 hurricanes developed during the season; this is slightly above the averages of 15 named storms and 8 hurricanes, respectively. In addition, 26 tropical depressions formed in the eastern Pacific during 1986, which, at the time, was the second most ever recorded; only the 1982 Pacific hurricane season saw a higher total.
Several storms throughout the season affected land. Hurricane Estelle passed south of Hawaii, resulting in $2 million in damage and two deaths. Hurricanes Newton, Paine and Roslyn each struck Northwestern Mexico. While damage was minimal from these three systems near their location of landfall, Paine brought considerable flooding to the Great Plains. The overall flooding event resulted in $350 million in damage, with the worst effects being recorded in Oklahoma. Hurricane Roslyn was the strongest storm of the season, attaining peak winds of .
Seasonal summary
Activity in the Eastern Pacific Hurricane Center's (EPHC) area of responsibility was above average. There were 25 tropical depressions, one short of the record set in 1982, which had 26. Only one system formed in the Central Pacific Hurricane Center's (CPHC) area of responsibility, and six others entered the CPHC area of responsibility from the EPHC area of responsibility. In all, 17 systems formed, which is two storms above normal. In addition, 9 hurricanes were reported during the season, one more than average. An average number (3) of major hurricanes – Category 3 or higher on the Saffir-Simpson hurricane wind scale—was also reported.
The season began with the formation of Hurricane Agatha on May 22 and ended with the dissipation of Tropical Depression Twenty-Five on October 25, spanning 147 days. Although it was nearly two weeks shorter than the 1985 Pacific hurricane season, the season was six days longer than average. The EPHC issued 406 tropical cyclone advisories, which were issued four times a day at 0000, 0600, 1200, and 1800 UTC. In 1986, hurricane hunters flew into three storms; Newton, Roslyn, and Estelle. In Newton, the National Oceanic and Atmospheric Administration (NOAA) conducted environmental research in the cyclone. In addition, the National Weather Service Field Service Station provided the East Pacific with excellent satellite coverage.
During the months of May and June, four named systems developed. In July, one tropical storm and two hurricanes formed. The following month, five tropical systems developed. Towards the end of the season, tropical cyclone activity declined somewhat. While five storms formed in September, only one formed in October and none during the month of November. A moderate El Niño was present throughout the season; water temperatures across the equatorial Central Pacific were above normal. In addition, the Pacific Decadal Oscillation (PDO) was in a warm phase during this time period.
Three tropical cyclones made landfall in 1986. The first, Hurricane Newton made landfall near Cabo San Lucas, bringing minor damage. Another storm, Hurricane Paine brushed Cabo San Lucas, and later moved inland over Sonora. Paine caused minimal impacts at landfall, but its remnants were described as one of the worst floods in Oklahoma history. Flooding affected 52 counties in Oklahoma, which resulted in a total of $350 million in damage. The final storm to make landfall during the hurricane season was Hurricane Roslyn. The hurricane produced some flooding, but no serious damage. In addition, Hurricane Estelle came close enough to Hawaii to require a hurricane watch. Two drownings were reported, and the total damage was around $2 million.
Systems
Hurricane Agatha
The 1986 Pacific hurricane season's first tropical disturbance formed from the tip of Baja California Sur on May 20. By 0000 UTC May 22, the circulation began to tighten and become more organized, and thus the EPHC upgraded the disturbance into Tropical Depression One-E that morning. Approximately 48 hours after becoming a tropical depression, the system was upgraded into Tropical Storm Agatha, the first storm of the season. After moving southeast, the cyclone made an abrupt change in direction, turning towards the north. Agatha strengthened into a hurricane on May 25 near the coast of Mexico, reaching its peak intensity of . Turning southeast, the system quickly weakened into a tropical depression, but regained tropical storm strength on May 28, only to dissipate that day. Rainfall spread around both the Atlantic and Pacific Mexican coasts, peaking at at Xicotepec de Juarez, Puebla.
Tropical Depression Two
A tropical disturbance formed on May 30 in the eastern Gulf of Tehuantepec. The disturbance was moving very slowly when it was upgraded to Tropical Depression Two-E on May 31. The depression began to weaken six hours later and the final advisory by the EPHC was released on June 1. Most of Mexico received rainfall, with over falling on Yucatán Peninsula. The worst rain occurred in Central Mexico, where over of precipitation fell, peaking at in Tenosique, Tabasco. The rest of the country was hit by of rainfall.
Tropical Storm Blas
A tropical disturbance originated from the Intertropical Convergence Zone (ITCZ) on June 16. The disturbance moved west-northwest at below a weak upper-level high, becoming the third tropical depression of the 1986 season on June 17. The depression intensified into Tropical Storm Blas the next day. It kept that strength for only six hours, weakening into a depression again as it moved into cooler waters. After Blas's convection dissipated, the EPHC ceased advisories on June 19 while situated roughly south of Cabo San Lucas.
Hurricane Celia
On June 24, five days after Tropical Storm Blas dissipated, a tropical disturbance developed south of the Gulf of Tehuantepec. Later that day, its circulation had become well-defined enough for the EPHC to upgrade the disturbance into Tropical Depression Four. Winds reached , enough to upgrade the system into Tropical Storm Celia on June 26. While located off the coast of Mexico, Celia strengthened into a hurricane at 1800 UTC June 27. An eye became evident on satellite imagery and the hurricane reached its peak intensity of on June 28 at 1600 UTC as it tracked near Socorro Island. Meanwhile, Celia moved into much cooler water, which resulted in rapid weakening. On June 30, Celia was downgraded into a tropical depression. The EPHC released its final advisory at 1800 UTC that day as the system had dissipated.
Tropical Storm Darby
The fifth tropical cyclone of the season originated from a tropical disturbance that was first noticed on July 2. Moving northwest at about , the disturbance entered warmer waters and began to develop rapidly. The disturbance was upgraded into Tropical Depression Five at 1800 UTC July 3. Turning west-northwest, the depression strengthened into Tropical Storm Darby on July 5. Darby peaked at , and after turning northwest, encountered waters. The storm began to weaken as thunderstorm activity became displaced from the center and spread northward over Arizona and California on July 6. The cyclone dissipated on July 7.
Hurricane Estelle
During the afternoon of July 16, a tropical depression formed thousands of miles west of Mexico, and within 12 hours it strengthened into a tropical storm. On July 18, Estelle intensified into a hurricane. Located in a favorable environment, Estelle continued strengthening to become the first major hurricane of the season on July 20. The hurricane entered the Central Pacific Hurricane Center's area of responsibility near its peak strength of , a Category 4 hurricane. The hurricane veered to the west and passed south of Hawaii. Estelle weakened to a tropical storm on July 23, and on July 25, it weakened to a depression. The storm dissipated two days later.
In advance of Hurricane Estelle, the National Weather Service issued a hurricane watch and high-surf advisory for the Island of Hawaii. More than 200 people evacuated from their homes. Huge waves crashed on the shores of the Big Island on the afternoon of July 22. The high waves washed away five beachfront homes and severely damaged dozens of others on the beach resort of Vacation Land. The total damage was around $2 million. However, only two deaths reported from the storm, both of whom drowned offshore Oahu.
Hurricane Frank
The EPHC began monitoring a tropical disturbance located southwest of San Salvador on 1800 UTC July 23. About 24 hours later, the disturbance was upgraded into a tropical depression. Initially moving towards the west-northwest due to an upper-level low and a ridge over Mexico, the storm then turned to the west as the upper-level low changed direction. By July 28, the depression was upgraded into Tropical Storm Frank. After turning back to the west-northwest, Frank reached hurricane intensity early on July 30. The storm quickly developed a well-defined eye and three hours later, Hurricane Frank reached its peak intensity as a moderate Category 1 hurricane, with winds of . Hurricane Frank maintained this intensity for 18 hours. Subsequently, the hurricane began to rapidly weaken over sea surface temperatures. Wind shear soon increased, thus accelerating the weakening process. On July 31, Frank was reduced to tropical storm intensity. Not long after weakening into a depression, the storm entered the CPHC's area of responsibility. Wind shear increased further, and upon entering the region, Frank moved over slightly cooler water. It transitioned into an extratropical cyclone on August 3.
Tropical Storm Georgette
On August 3, a tropical depression developed in the open ocean over west of the Mexican coastline. Twelve hours later, it strengthened into Tropical Storm Georgette before weakening to a depression on August 4. It then accelerated to a very rapid speed of . Due to its fast speed, Georgette could not maintain a closed circulation, and thus degenerated into a non-cyclonic disturbance on August 4. The disturbance kept up its rapid forward motion, crossed the dateline and entered the western Pacific, where it reformed and reached its peak intensity as Severe Tropical Storm Georgette. By August 16, the remnants of Georgette were absorbed by nearby Typhoon Tip.
Tropical Storm Howard
A tropical wave crossed Southwestern Mexico and Belize in mid-August. A tropical disturbance developed from this wave south of Acapulco on August 15, the same day that the system moved offshore. Moving west-northwest south of an upper-level high, the system was classified as a tropical depression the next day about south of Manzanillo. Several hours later, the depression reached tropical storm intensity. Turning towards the northwest due to a trough, it failed to intensify beyond minimal tropical storm strength. Passing south of the Baja California Peninsula, the storm rapidly moved over cooler waters. Howard weakened into a tropical depression at 0600 UTC August 18. Transversing water, Howard dissipated. Rainfall along the southern coast reached in some places, with totals in excess of in isolated locations. Further north, rainfall was more scattered. The maximum rainfall was in Reforma, near the southern part of the country.
Tropical Storm Isis