The 2001 Pacific hurricane season featured tropical cyclone activity in every month from May to November across the Pacific Ocean, north of the equator and east of the International Date Line. It was a near-average Pacific hurricane season, featuring 15 named storms across the Pacific basin, one fewer than the seasonal average at the time. Eight of the storms attained hurricane status, including two major hurricanes. There were also four tropical depressions that did not intensify into a named storm. The season officially began on May 15 in the Pacific Ocean east of 140°W, and on June 1 in the Central Pacific. The season ended on November 30.
The first storm of the season, Adolph, formed on May 25 offshore southwest Mexico. It became the strongest hurricane in the month of May at the time, attaining maximum sustained winds of 145 mph (230 km/h) on May 29, making it a Category 4 hurricane on the Saffir-Simpson scale. In June, Tropical Storm Barbara passed just north of Hawaii, bringing minimal impact. There were three storms in July, including Hurricane Dalila, which killed two people from lightning strikes. There was only one named storm in August, Hurricane Flossie. It was the first of five storms to originate from a tropical wave that earlier produced a tropical cyclone in the Atlantic. The remnants of Flossie produced thunderstorms in California that killed two people from lightning strikes.
September was much more active with six systems developing, of which three became hurricanes. Hurricane Gil and Tropical Storm Henriette interacted with each other until the latter was absorbed by the former. The most notable storm of the season, Hurricane Juliette, formed during the month; it killed 13 people and left $400 million in damage in Mexico. Juliette made the only landfall during the season, when it moved ashore Baja California Sur as a tropical storm. There were four named storms in October, including two hurricanes. The final storm of the season, Hurricane Octave, dissipated on November 3, 27 days before the official end of the season.
Seasonal summary
The basin experienced La Niña to neutral atmospheric conditions, which began in 1998 and continued through the year. The season officially began on May 15 in Eastern Pacific and on June 1 in Central Pacific; both ended on November 30. There were 15 tropical storms in the eastern Pacific basin during the 2001 season, one below-average. Seven of those became hurricanes, which have maximum sustained winds of at least 75 mph (120 km/h). This was two below-normal. Two hurricanes became major hurricanes, which reach Category 3 intensity or higher on the Saffir–Simpson hurricane scale (SSHS). This was below the normal of four major hurricanes. Four tropical depressions also formed and dissipated before reaching the intensity of a named storm. The four tropical cyclones in the Central Pacific was near the long-term average, although all were weak.
Hurricane Adolph, the first storm of the season, formed in late May, and became the strongest May hurricane on record at the time. It was later surpassed by Hurricane Amanda in 2014. This season featured one named storm in June, followed by three in July. There was only one named storm in August – Flossie; well below the average of four. Activity picked up in September, when five named storms were observed. These included Hurricane Gil and Tropical Storm Henriette, which interacted with each other, and Juliette, which had the season's only landfall in Mexico. There were three named storms in October. In addition to Juliette, several storms came close enough to land to require tropical cyclone warnings and watches, including Adolph, Dalila, Ivo, and Lorena.
Systems
Hurricane Adolph
On May 7, a tropical wave exited the west coast of Africa and moved across the Atlantic. A weak low pressure area began forming along the wave axis on May 18. The system crossed into the eastern Pacific on May 22. At first the system was disorganized, until convection, or thunderstorms, became more organized on May 24. On the next day, it developed into Tropical Depression One-E about 250 miles (400 km) south-southwest of Acapulco, Mexico. The nascent depression moved slowly eastward, steered by a ridge to the north. With low wind shear and warm water temperatures, the depression strengthened into Tropical Storm Adolph on May 26. A day later, the storm had developed an eye, as the storm turned northwestward. Late on May 27, Adolph attained hurricane status, and the next day it passed about 165 mi (265 km) southwest of Acapulco. Continuing to strengthen, Adolph reached peak winds of 145 mph (230 km/h) on May 29, making it a Category 4 hurricane. While it was rapidly intensifying, Adolph's pressure dropped 1.46 mbars per hour, falling to a minimum of 940 mbar (28 inHg). The hurricane underwent an eyewall replacement cycle and it subsequently weakened. Water and air temperatures cooled, and Adolph fell to tropical storm status on June 1 as the convection rapidly diminished. It quickly weakened into a tropical depression, and was no longer a tropical cyclone by June 2. The remaining clouds persisted for a few more days to the southwest of the Baja California peninsula.
Due to Adolph's threat, the government of Mexico issued a tropical storm warning and a hurricane watch from Acapulco to Lázaro Cárdenas. Ports in Acapulco were closed to small vessels. Adolph ultimately produced rainfall and heavy surf to the southwest Mexican coastline.
Tropical Storm Barbara
A tropical wave moved off the coast of Africa on June 1, which entered the eastern Pacific ten days later. Continuing to the west, the wave eventually developed a broad circulation on June 18. After further organization, the system developed into Tropical Depression Two-E on June 20, located about 1,325 mi (2,130 km) southwest of Cabo San Lucas, Mexico. Within 18 hours of forming, the depression strengthened into Tropical Storm Barbara. On June 21, Barbara attained peak winds of 60 mph (95 km/h). Around that time, the convection had become more organized, with banding features. Shortly thereafter, the storm encountered stronger wind shear and cooler water temperatures. On June 22, Barbara weakened into a tropical depression as it crossed into the central Pacific. It was the recorded first June tropical cyclone in the central Pacific. On June 23, the CPHC issued its final advisory on Barbara. The circulation continued to the west-northwest, passing north of the Hawaiian Islands on June 25. Across the state, the storm brought 5 to 8 ft (1.5 to 2.4 m) waves, along with unsettled weather. The circulation dissipated northwest of Kauai on June 26, and the remnants were absorbed by a frontal zone near Midway Island.
Tropical Storm Cosme
A tropical wave entered the eastern Pacific basin on July 6, and proceeded westward. A low pressure area formed on July 10, but it was halted by wind shear from an upper-level trough. The system gradually organized, developing into Tropical Depression Three-E on July 13, located about 330 mi (530 km) southwest of Manzanillo, Mexico. It quickly strengthened into Tropical Storm Cosme, and within 12 hours of forming, it attained peak winds of 45 mph (75 km/h). On July 14, the wind shear stripped the thunderstorms from the center, causing Cosme to weaken back into a tropical depression. Moving over cooler waters, Cosme degenerated into a remnant low on July 15, although the circulation lasted another three days before dissipating.
Tropical Storm Erick
A tropical wave reached the eastern Pacific on July 16. Continuing westward, it developed an area of thunderstorms on July 18 while the system was south of the Baja California peninsula. Following gradual organization, Tropical Depression Four-E developed late on July 20, located about 790 mi (1,275 km) southwest of the southern tip of the Baja California peninsula. The depression moved to the west-northwest, although it was large and disorganized, impacted by wind shear. Late on July 21, the depression intensified into Tropical Storm Erick, reaching peak winds of 40 mph (65 km/h) and a minimum pressure of 1,001 mbar (29.6 inHg). Erick soon encountered cooler waters, which prevented further strengthening. The storm fell to tropical depression status on July 23, and degenerated into a remnant low the next day, which produced intermittent thunderstorms before dissipating.
Hurricane Dalila
A tropical wave entered the eastern Pacific on July 18. Continuing westward, the system gradually organized. Early on July 21, it developed into Tropical Depression Five-E, located about 250 mi (400 km) south of the Gulf of Tehuantepec. A subtropical ridge the north steered the system to the west-northwest, parallel to the southern Mexican coastline. Within 12 hours of forming, the depression strengthened into Tropical Storm Dalila, aided by warm water temperatures and low wind shear. On July 22, the storm approached within 115 mi (185 km) of the southwest Mexican coast, between Acapulco and Manzanillo. Moving farther offshore, Dalila briefly reached hurricane status on July 24, with peak winds of 75 mph (120 km/h) and a minimum pressure of 987 mbar (987 hPa). The NHC assessed the estimated peak intensity based on the circulation embedded within the central dense overcast, and a warm spot in the center. Soon after peaking, Dalila began weakening due to increased wind shear. It passed directly over Socorro Island on July 25 as a tropical storm. Although the wind shear dropped, the water temperatures cooled, causing the thunderstorms to diminish. On July 28, Dalila fell to tropical depression status, and it dissipated soon after off the southwest coast of the Baja California peninsula.
The threat of the Dalila led to tropical storm warnings in southwestern Mexico from Punta Maldonado, Guerrero to Lázaro Cárdenas, Michoacán. This included a hurricane watch from Lázaro Cárdenas to Manzanillo. The storm produced heavy rainfall in southwest Mexico that led to flash flooding. In Chiapas, lightning strikes killed two people and injured eight others. Dozens of homes were damaged by the floods in the state, affecting about 1,000 people. In Guererro, rainfall reached 6.3 in (161 mm). In Acapulco, the floods damaged about 20 homes.
Hurricane Flossie
The origins of Flossie were from the same tropical wave that spawned Tropical Storm Chantal in the Atlantic. The southern portion of the wave crossed into the eastern Pacific on August 21, and continued westward without much organization at first. On August 25, the system passed near Manzanillo, producing wind gusts of 46 mph (74 km/h) there. The circulation was too broad for the system to be classifiable as a tropical cyclone at the time. As it moved away from the Mexican coast, the circulation became better defined. On August 26, the system developed into Tropical Depression Seven-E while located about 270 mi (435 km) southeast of the southern tip of the Baja California peninsula. It quickly strengthened into Tropical Storm Flossie. Steered by a ridge to its north, Flossie moved to the west-northwest, passing just north of Socorro Island. Late on August 27, Flossie attained hurricane status, despite wind shear from a nearby upper-level low. The two systems interacted, causing Flossie to slow, turn to the southwest, and execute a small loop. After the upper-level low moved northeastward away from the hurricane, Flossie strengthened further, as the eye became better defined. On August 29, the hurricane reached peak winds of 105 mph (165 km/h), and a minimum pressure of 972 mbar (28.7 inHg). Soon after, Flossie weakened due to wind shear from an approaching mid-level trough. It fell to tropical storm status on August 31 as water temperatures decreased. Flossie weakened further into a tropical depression on September 1 while curving to the northeast. It dissipated on September 2, although the circulation persisted for a few more days.
While Flossie was dissipating, its middle and upper-level circulation moved across Baja California and into the southwestern United States. The remnants of the storm generated thunderstorms across southern California, killing two people due to lightning strikes. The lightning injured two other people and also led to several small fires. The thunderstorms also produced flash flooding in San Diego and Riverside counties in California after dropping more than 2 in (51 mm) of rain in one hour. The floods caused mudslides that affected several roads. A strong downdraft knocked a tree onto a house. Damage in California reached $35,000.
Hurricane Gil
The same tropical wave that spawned Atlantic Tropical Storm Dean also entered the eastern Pacific on August 24. Continuing westward into a monsoon-like environment, the system slowly organized, developing into a tropical depression on September 4. At the time, it was located about 850 mi (1,370 km) southwest of the southern tip of the Baja California peninsula. The depression quickly intensified into Tropical Storm Gil. Developing a ragged eye, Gil attained hurricane status on September 6, and later that day reached peak winds of 100 mph (155 km/h), with a minimum pressure of 975 mbar (28.8 inHg). Around the time of Gil reaching peak intensity, it interacted with nearby Tropical Storm Henriette, and the two storms orbited around each other. Outflow from Henriette caused Gil to weaken as the hurricane accelerated northward, and Gil weakened to tropical storm status on September 8. On the next day, the track shifted to the southwest as Gil absorbed the remnants of Henriette and it fell to tropical depression status. Gil was no longer a tropical cyclone by September 10, although the circulation continued to the northwest over the next few days. On September 19, a cold front north of Hawaii absorbed the remnants of Gil.