The 1981 Pacific hurricane season was a slightly below average Pacific hurricane season. The season officially started on May 15 in the eastern Pacific basin and June 1 in the central Pacific basin. Both basins' seasons ended on November 30; these dates conventionally delimit the period during which most tropical cyclones form in the northeastern Pacific Ocean. The first tropical cyclone of the season was designated on May 30, and the final storm of the season, Hurricane Otis, dissipated on October 30. The season produced fifteen named storms and a total of eight hurricanes, which was near normal. However, the total of one major hurricane was below the average of three.
The strongest tropical cyclone of the season was Hurricane Norma, which was a powerful Category 3 hurricane on the Saffir–Simpson Hurricane Scale. The storm caused six deaths – five in Texas, and one in Mexico, due to severe flooding. Additionally, the storm caused $74 million (equivalent to $ million in ) in damage, which is credited to significant crop damage and many tornadoes. However, the deadliest tropical cyclone of the season was Tropical Storm Lidia, which made two landfalls – one on the southern tip of the Baja California Peninsula and the other along the shores of Sinaloa in early October. As the result of its heavy rainfall in northwestern Mexico, seventy-three fatalities were reported, along with $80 million in damage.
Seasonal summary
There was an absence in storm activity across the Central Pacific Hurricane Center's area of responsibility, as no storms developed in the basin. However, two tropical cyclones from the eastern Pacific, Greg and Jova, entered the central Pacific, the latter entering as a hurricane. The season produced fifteen named storms and eight hurricanes; both of these numbers were equal to the average. The season's one major hurricane, a storm with winds of at least , was below the average of three. There are also at least two tropical depressions that did not strengthen into tropical storms. Six tropical cyclones made landfall in Mexico. First, Tropical Storm Adrian made landfall east-southeast of Acapulco, but did not cause any damage. Afterwards, Tropical Storm Irwin made landfall in Baja California Sur, but similarly to Adrian, did not cause any damage. Tropical Storm Knut later made landfall near Mazatlán with winds equivalent to a minimal tropical storm, but no deaths or damage was reported. Tropical Storm Lidia struck about south of Los Mochis on October 8, with winds of 45 mph (75 km/h). Heavy rainfall associated with the cyclone caused moderate damage in northwestern Mexico, and at least seventy-three deaths can be attributed to the storm. On May 30, an area of intense shower and thunderstorm activity located 270 mi (430 km) south of the Mexican coastline. The second to strike the area in 10 days, Norma was absorbed by a frontal system on October 14. The combined entity produced heavy rainfall and severe weather across Texas, which subsequently led to severe crop damage. The final storm to make landfall on Mexico during the 1981 season was Hurricane Otis. Intensifying into a hurricane by October 26, the hurricane brushed the coast of Jalisco before making landfall near Mazatlán at hurricane intensity on October 30. Otis was the second of two hurricanes to make landfall in the country this season.
Systems
Tropical Storm Adrian
On May 30, an area of intense shower and thunderstorm activity located to the south of the Mexican coastline intensified into a tropical depression. Drifting towards the north and then east-northeast around an area of high pressure centered off the southern coast of Mexico, the depression began to strengthen over water. Twelve hours after formation, the depression strengthened into Tropical Storm Adrian. Reaching a peak intensity of 45 mph (75 km/h), Adrian began to move over slightly cooler ocean temperatures of and subsequently began to weaken. After being downgraded to a tropical depression by June 2, data from two cargo ships, the Androemda and Santa Maria, were helpful in locating Adrian's center of circulation as it moved towards the Mexican coastline. On June 4, the system made landfall east-southeast of Acapulco; however, no damage associated with the tropical cyclone was reported, and Adrian dissipated later that same day.
Hurricane Beatriz
On June 28, the season's second tropical depression formed approximately east of Clipperton Island. Moving quickly towards the west over warm sea-surface temperatures, the depression strengthened into Tropical Storm Beatriz just twelve hours after formation. Embedded within an area of favorable atmospheric conditions, Beatriz attained hurricane status at 1800 UTC on June 30, and intensified further to attain its first brief peak at by early on June 1. Fluctuating in intensity, Hurricane Beatriz attained its peak intensity for a second time on June 2, only to enter an area of higher wind shear and cooler sea-surface temperatures. Far away from land, Beatriz was downgraded to a tropical storm on June 3, and then further into a tropical depression the following day. The tropical cyclone dissipated on July 4 while located several hundred miles to the west of Baja California Sur.
Since Beatriz briefly posed a threat to Mexico and California, the Hurricane Hunters were put on standby, but no flights were made into the storm. The system did produce wave heights as high as to Southern California; however, impact from the storm was less than anticipated.
Tropical Storm Calvin
An area of disturbed weather located several hundred miles to the south of Acapulco organized into a tropical depression on July 4. Moving towards the west-northwest over warm sea-surface temperatures, the depression intensified into a tropical storm on July 5, receiving the name Calvin. Reaching a peak intensity of 50 mph (85 km/h) later that day, Calvin began to move north-northwest around the western periphery of a high pressure system located over extreme northern Mexico. Calvin then moved over cooler water and subsequently weakened to a minimal tropical storm. Located 98 mi (158 km) south-southeast of Cabo San Lucas on July 8, Calvin further weakened to a tropical depression and turned to the west. The system dissipated the following day. As a dying system, Calvin produced high clouds over California and Arizona.
Hurricane Dora
Based on satellite imagery and data from a nearby ship, Yamazuru, a tropical depression formed far away from land on July 10. Passing north of Clipperton Island, the depression began to strengthen under favorable atmospheric conditions, and was designated Tropical Storm Dora twelve hours after formation. Moving towards the west-northwest, Dora attained hurricane status on July 13; subsequently, the ship Amestelmolen reported seas of , a minimum barometric pressure of , and winds as it passed north of the storm's center. As Dora reached its peak intensity of 90 mph (150 km/h) on July 14, a well-defined eye became apparent on satellite imagery, and the storm turned more towards the west. Cooler ocean temperatures below 74 °F (23 °C) subsequently caused the hurricane to weaken, and it was downgraded to a tropical storm on July 15. The storm's structure further deteriorated the following day, and Dora dissipated over southwest of Cabo San Lucas.
Tropical Storm Eugene
Following Dora's dissipation, another tropical depression formed west of the Mexican coastline. While retaining its intensity, the depression moved west-northwest before bending towards the southwest as it intensified into Tropical Storm Eugene on July 18. Above exceptionally warm sea surface temperatures of , Eugene slowly intensified. After passing south of Socorro Island, the storm accelerated west-northwest, reaching a peak intensity of early on June 19. Shortly thereafter, the system began to meander over cooler ocean temperatures, and weakened to a tropical depression on July 20. After changing little in intensity for nearly 24 hours, Eugene dissipated on July 21 while located west of the Baja California Peninsula, over water temperatures of . There were no reports of any effects attributed to the storm.
Hurricane Fernanda
Fernanda originated from an area of showers and thunderstorms that gained sufficient organization to be designated a tropical depression on August 6. Moving rapidly towards the west, the system passed north of Clipperton Island. Above warm ocean temperatures, the depression strengthened to become a tropical storm twenty-one hours after formation, and after briefly turning towards the west-northwest, Fernanda attained hurricane status on August 9. A well-defined eye associated with the hurricane became visible, and the system reached its peak intensity as a 105 mph (165 km/h) Category 2 hurricane on the Saffir–Simpson Hurricane Scale on August 10. Turning towards the northwest, Fernanda began to enter an area of cooler ocean temperatures and higher wind shear, subsequently weakening. On August 11, Fernanda was downgraded to a Category 1 hurricane, and then further to a tropical storm later that evening. By midday the following day, Fernanda had become a tropical depression, and dissipated early on August 13.
Hurricane Greg
An area of intense thunderstorm activity left the southern coast of Mexico in mid-August. About south of Socorro Island, it formed on August 13. Over warm sea surface temperatures, the depression steadily intensified; it was upgraded to Tropical Storm Greg at 1800 UTC. As the storm was moving on the southwest periphery of an area of high pressure, it curved west-northwest. Meanwhile, the storm passed south of Clarion Island at 2100 UTC on August 14. After turning toward the west, the storm's motion slowed. After maintaining its intensity while still a minimal tropical storm, Greg turned to the west-southwest for a day, only to resume its westerly course. As its speed increased a little, Greg gradually strengthened. Based on data from the ship Chapa, Greg was upgraded into a hurricane early on August 20. However, increased wind shear caused the storm to rapidly weaken back into a tropical storm. At this time, the tropical storm was located over water. Shortly thereafter, Greg moved into the Central Pacific Hurricane Center (CPHC)'s area of responsibility. It continued to weaken, and was only a minimal tropical storm by the afternoon of August 21. Although Greg weakened into a depression, it maintained a well-defined center of circulation for an additional 24 hours until dissipating at 1800 UTC on August 22 over east-northeast of Hawaii.
Hurricane Hilary
Based on a report from a cargo ship, the Eastern Pacific Hurricane Center upgraded a tropical disturbance into a tropical depression roughly west of the Mexican coast at 2105 UTC on August 21. Four hours later, the system strengthened into Tropical Storm Hilary. After turning towards the west, it passed about south of Socorro Island. Even though Hilary developed a well-defined eye late on August 23, the cyclone was not upgraded into a hurricane until the next afternoon. Accelerating, Hilary reached its peak strength of 85 mph (140 km/h) while located west of Cabo San Lucas. Moving west, Hilary began to weaken over water. Late on August 28, nearly 24 hours following Hilary's downgrade into a tropical depression, the tropical cyclone dissipated far from land.
Tropical Storm Irwin
A tropical depression formed west of Acapulco on August 27. Over water, the depression intensified into Tropical Storm Irwin the next day. By August 25, Tropical Storm Irwin had peaked in intensity as a moderate tropical storm, then weakened as it moved over sea-surface temperatures. Less than southeast of Baja California, Irwin was downgraded into a depression. Turning west-northwest, Irwin made landfall about south of La Paz on August 30. After moving offshore the next day, Irwin dissipated. No damage was reported.
Hurricane Jova