The 1990 Pacific hurricane season was a very active season which observed 21 named storms within the basin. The season also produced the fifth highest ACE index value on record. The season was officially started on May 15 in the eastern Pacific, and on June 1 in the central Pacific, and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean. However, the formation of tropical cyclones is possible at any time of the year, as illustrated in 1990 by the formation of the season's first named storm, Hurricane Alma, on May 12. At the time, this was the earliest formation of a tropical storm on record in the eastern Pacific.
Overall, the impact of this season was minimal. Tropical Storm Rachel made two landfalls in Mexico and brought rain to the United States. Hurricane Boris brought light showers to California.
Systems
Hurricane Alma
A tropical wave emerged from Africa on April 29. It then moved across the Atlantic, crossed northern South America, and entered the Pacific Ocean on May 9. Convection started to increase with the wave just to the south of Panama. The wave moved westward and continued to become better organized over the next few days. On May 12, the wave had become organized enough and was designated Tropical Depression One-E.
Tropical Depression One-E moved slowly to the northwest while strengthening slowly due to easterly vertical wind shear. The depression was upgraded to Tropical Storm Alma on May 14. The storm quickly strengthened once the vertical wind shear relaxed and was near hurricane force by the morning of May 15. Hurricane Alma reached its peak intensity early on May 16 with maximum sustained winds of 85 mph (137 km/h). The hurricane entered an area of southwesterly wind shear caused by an upper-level ridge of high pressure. The increasing vertical wind shear and cooler water caused Alma to weaken to a tropical storm. On May 17, the storm continued to weaken and became a depression. The next day, the system dissipated as a tropical cyclone well west of mainland Mexico.
Hurricane Boris
A tropical wave came off the northwest coast of Africa on May 20. The wave did not significantly develop as it moved west across the Atlantic Ocean and Caribbean Sea. Once it crossed Central America into the eastern Pacific Ocean, cloudiness increased considerably with the system on May 31. It became well-enough organized to be upgraded to Tropical Depression Two-E on June 2. After becoming a depression, the system moved to the west-northwestward. Upper-level easterly vertical wind shear limited the amount of the initial strengthening. However, an increase in convective banding led to its upgrade to Tropical Storm Boris on June 4, 500 mi (800 km) southwest of Manzanillo. Further strengthening occurred due to an anticyclone aloft fostered additional development, and by June 5, Boris became a hurricane. The hurricane began to move to the north-northwest in response to a trough off of the West Coast of the United States. Strengthening continued, and the storm reached its peak strength with winds of 90 mph (140 km/h) and a minimum central pressure of 977 mb (28.9 inHg). The hurricane's cloud pattern became elongated along a southwest–northeast axis on June 6 due to an increased amount of vertical wind shear. Boris was downgraded to a tropical storm later in the day on June 6. The deep convection of the tropical storm decreased, as Boris moved over cooler waters. It was downgraded to a tropical depression on June 7 due to these factors. The depression dissipated as a tropical cyclone on June 8 as the system quickly lost its tropical characteristics. A small circulation remained in the cloud field offshore the northwest coast of Baja California for a few more days.
The winds in the eyewall of Boris ripped off the sails of the Azure Dream sailboat. Outer rainbands from the storm produced moderate rain in several Mexican states. In Mexico, rainfall peaked at 8.83 in (224 mm) near San Lucas, Michoacán. The remnants of Boris also brought sporadic rainfall over the western United States, with precipitation being reported in Arizona, California, Colorado, Nevada and Wyoming. The remnants of Boris were responsible for causing the wettest June in San Diego since records began in 1850; however, not even 1 in (25 mm) of rain fell at that location. Rainfall from the remnant system in the United States peaked at 3.28 in (83 mm) over the Santa Rita Mountains. No other direct damages or casualties were reported from Boris.
Tropical Storm Cristina
A tropical wave emerged into the Atlantic Ocean off the coast of Africa on May 28. The wave moved across Central America into the northeastern Pacific Ocean, where convection organized with the system on June 6. The system became well-enough organized to be upgraded to Tropical Depression Three-E on June 8, while 920 mi (1,480 km) south of the southern tip of Baja California. The depression continued to strengthen, and was upgraded to Tropical Storm Cristina on June 9.
Cristina initially had well-established upper-level outflow. It failed to reach hurricane status, peaking with maximum sustained winds of 65 mph (105 km/h) due to movement of its associated upper-level anticyclone to the north over Mexico which caused Cristina to be exposed to easterly vertical wind shear. Cristina moved generally northwestward, which eventually placed the storm in cooler waters, and caused the deep convection of the system to dissipate. On June 14, Cristina diminished to a tropical depression. Cristina moved west-northwestward with the low-level flow. The depression dissipated as a tropical cyclone on June 16, after a lack of deep convection for 48 hours.
Tropical Storm Douglas
A tropical wave moved off the northwest coast of Africa on June 5. It continued westward across the tropical North Atlantic and Caribbean Sea without significant development. The wave entered the northeastern Pacific Ocean on June 16, where it generated an area of increased cloudiness. Organization of thunderstorm activity increased late on June 18 and early on June 19. Tropical Depression Four-E formed on June 19, when it was 230 mi (370 km) south of Acapulco after evidence of low-level circulation for the past 24 hours. The depression moved in a west-northwest direction, due to a subtropical ridge north of the depression. Satellite analysis indicated that the depression had reached tropical storm force strength, and it was upgraded to Tropical Storm Douglas on June 19, while 230 mi (370 km) southwest of Acapulco. Douglas reached peak strength of 65 mph (105 km/h) on June 21
A tropical storm warning was issued on June 21, from Punta Tejupan to Cabo Corrientes before being discontinued on June 22. Tropical Storm Douglas brushed the western coast of Mexico. The center of circulation approached within 17 mi (27 km) of the coast of Mexico on June 22. Douglas then began to weaken because of interaction with the mountainous terrain of Mexico. The system continued to weaken despite warm water temperatures and favorable upper-level conditions. Douglas dissipated early on June 24, while 138 mi (222 km) south-southeast off the southern tip of Baja California Sur. The highest rainfall report from Mexico from Douglas totaled 11.07 in (281 mm) at La Huerta. No deaths or damage were reported.
Hurricane Elida
A tropical wave came off the coast of Africa into the eastern Atlantic Ocean on June 10 and 11. The system moved across the Atlantic and entered into the northeastern Pacific Ocean. The wave became a significant tropical system, with cyclonic turning in the lower and middle layers of the system's cloudiness on June 25. The center of circulation was located 345 mi (555 km) south of Acapulco, Mexico. The system exhibited sufficient organization to be considered Tropical Depression Five-E on June 26. The depression quickly strengthened and became Tropical Storm Elida later that day. The track of Elida was west-northwestward to northwestward from June 27 through June 28. Some rainbands moved over the mountainous region of southwestern Mexico, but no flooding, damage, or casualties were reported as a result. Elida continued strengthening and it was upgraded to a hurricane early on June 28 passing directly over Socorro Island later in the day, right as Elida reached peak strength of 80 mph (130 km/h), dropping 3.7 in (94 mm) of rain on the island. Some windows broke also as a result, and minor structural damage was reported as a result on the island.
A high-pressure area to the north forced Elida to move more westward on June 29. Convection began to decrease in the hurricane as it moved into cooler waters, and it weakened to a tropical storm later in the day. It then weakened to a tropical depression on July 1, and dissipated on July 2.
Tropical Depression Six-E
An area of disturbed weather south of Acapulco organized into Tropical Depression Six-E on June 29 and the system began to move northwest. Originally the system was expected to reach tropical storm strength and near hurricane intensity by late on July 2 or early on July 3, however persistent vertical wind shear over the system impeded its development. After convection began to merge into the Intertropical Convergence Zone (ITCZ), the National Hurricane Center discontinued advisories on Tropical Depression Six-E, stating that the depression dissipated, and regeneration seemed unlikely.
However, wind shear began to decrease, and convection associated with the remnants of Tropical Depression Six-E quickly began to increase. Although the low-level circulation was near the edge of the deep convection, the National Hurricane Center resumed advisories on Tropical Depression Six-E by July 1. Intensification into a tropical storm was again predicted, but Tropical Depression Six-E remained poorly defined, and eventually dissipated on July 4.
Hurricane Fausto
A tropical wave came off the northwest coast of Africa on June 19. The wave crossed the Atlantic Ocean and Caribbean Sea, into the warm waters of the northeastern Pacific Ocean, on July 2. An area of disturbed weather moved northwards towards the Gulf of Tehuantepec and became Tropical Depression Seven-E early on July 6. The depression moved northwest, and because of increased organization of deep convection, was designated Tropical Storm Fausto on July 7, 265 mi (426 km) south of Manzanillo, Mexico. A weakly defined eye formed on July 8, and the storm was upgraded to Hurricane Fausto, 310 mi (500 km) south of Cabo San Lucas.
Fausto peaked in strength with winds of 85 mph (137 km/h) and a central pressure of 979 mb (28.9 inHg) on July 9. Fausto passed 40 mi (64 km) north of Socorro Island causing a northwest wind of 40 mph (64 km/h), and 4.3 in (110 mm) of rain at that location. The hurricane fluctuated in intensity on July 10, before weakening into a tropical storm later that day, 403 mi (649 km) west of Cabo San Lucas. The weakening Fausto moved over continuing cooler waters, and was downgraded to a tropical depression on July 11, 690 mi (1,110 km) west of Cabo San Lucas. The depression dissipated as a tropical cyclone on July 13, and its low level circulation of clouds persisted for a few days.
Hurricane Genevieve
A tropical wave moved off the coast of Africa on June 25 and moved across the Atlantic Ocean and central Caribbean Sea with little development. Within the western Caribbean Sea, convection developed with the wave on July 7. The system became better organized as it moved into the northeastern Pacific Ocean. The system was upgraded to Tropical Depression Eight-E on July 11. The depression moved west-northwest, with a good outflow to the north, and gradually strengthened into Tropical Storm Genevieve later that day. Genevieve continued to strengthen, reaching hurricane strength on July 13. The storm approached within 23 mi (37 km) of Socorro Island where a sustained wind of 44 mph (71 km/h) and gust of 50 mph (80 km/h) were reported, before the weather equipment on the island failed.
The hurricane began to turn west because of the strengthening and growing ridge to its north. Increasing outflow aloft began to form, and the hurricane reached its peak strength of 105 mph (169 km/h) with a well-defined eye at its center of circulation. Genevieve turned northwest on July 16 into an area with strong vertical wind shear and low water temperatures. The hurricane quickly weakened into a tropical storm on July 17 and then into a tropical depression on July 18. Genevieve dissipated as a tropical cyclone later in the day, reduced to a circulation in the stratocumulus cloud field.