Hurricane Felicia developed out of a broad area of low pressure, several that formed hundred miles southwest of Baja California Sur on August 3, developing into Tropical Depression Eight-E the next day, shortly after Tropical Depression Seven-E formed directly to the east. It strengthened into a tropical storm and was named Felicia early on August 4. It rapidly strengthened that morning as an eyewall quickly developed, the rapid intensification being attributed to warm water along the forecast track, which allowed for more rapid intensification. Felicia continued to intensify and became a hurricane that afternoon. Rapid intensification continued into that evening, and the NHC upgraded Felicia to a Category 2 hurricane. It continued to rapidly strengthen, becoming the first major hurricane of the season on the morning of August 5, when the NHC upgraded it to a Category 3 hurricane. Later that day, Felicia rapidly intensified to a Category 4 hurricane, with maximum winds increasing to 145 mph (230 km/h), making it the strongest storm in the Eastern Pacific since Daniel in 2006. The NHC predicted that Felicia would rapidly weaken during the next couple of days starting on August 6, but it was also noted by the NHC that Felicia was displaying annular hurricane characteristics, which would allow for it to maintain intensity for longer than expected over marginal SSTS. On August 8 it crossed into the Central Pacific basin, gradually weakening to a tropical storm and then a tropical depression as it approached the Hawaiian Islands. Tropical storm and flash flood watches were issued on August 7 for the Big Island of Hawaii and Maui County, and were extended to include Oahu on August 9. The watches for the Big Island were later canceled as the track for Felicia appeared to turn toward the north. All watches were canceled at 11 a.m. HST August 11 as Felicia dissipated to a remnant low.
Tropical Depression Nine-E developed out of a small area of low pressure west-southwest of Baja California on August 9. The NHC initially forecast Nine-E to strengthen to a tropical storm by August 10, but moderate shear inhibited development, and the depression was no longer forecast to strengthen to a tropical storm, as the shear inhibited deep convection within the depression's circulation. Shear continually inhibited development until the end, when Nine-E degenerated to a remnant low on August 12. The next day, the NHC noted the possibility for regeneration of the system, although, by late on the 14th, the disturbance had weakened, and was becoming embedded in the ITCZ, as a result, the probability for regeneration was low. Nine-E's remnants dissipated on August 15, while located just within the central Pacific.
Tropical Depression One-C developed out of an area of low pressure southwest of Kauai on August 11. Since it formed when Hurricane Felicia was still active, its formation made August 11, 2009 the first time since October 31, 2002 that two tropical cyclones were active in the central north Pacific at the same time. It was numbered One-C as it was the first system to develop in the Central Pacific region, even though Lana was named there. Late that day, the system strengthened to a tropical storm and was named Maka, the second named storm to form in the Central Pacific in 2009. The next afternoon, the final advisory on Maka was issued as it weakened, degenerating into a remnant low, likely caused by unexpected shear. The remnants of Tropical Storm Maka crossed the international dateline and moved into the Western Pacific and regenerated into a tropical depression.
Hurricane Guillermo formed on August 12 from a broad area of low pressure nearly 700 miles SW of Baja California. The system developed a good series of banding features and convection, and as a result, in the afternoon later that day, it strengthened into a tropical storm, the seventh in the eastern Pacific that year. On August 14, it strengthened to become the fourth hurricane of the season, concurrent to the development of a good, banding type eye. That afternoon, Guillermo strengthened to a Category 2 hurricane with maximum winds increasing to 100 mph (155 km/h). Early on August 15, Guillermo intensified to become the second major hurricane of the season, as it was upgraded by the NHC to a Category 3 hurricane, with maximum winds increasing to 115 mph (185 km/h). On August 16 it crossed into the Central Pacific basin as a Category 1 hurricane, and then quickly weakened to a tropical storm thereafter.