The 2005 Pacific hurricane season was a near-average season which produced fifteen named storms, only seven hurricanes formed and two major hurricanes. It was also the second consecutive season in which no tropical cyclone of at least tropical storm intensity made landfall. The season officially began on May 15 in the East Pacific Ocean, and on June 1 in the Central Pacific; they ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Pacific basin. However, the formation of tropical cyclones is possible at any time of the year.
Activity began with the formation of Hurricane Adrian, the fourth-earliest-forming tropical storm on record in the basin at the time. Adrian led to flash flooding and several landslides across Central America, resulting in five deaths and $12 million (2005 USD) in damage. Tropical storms Calvin and Dora caused minor damage along the coastline, while Tropical Storm Eugene led to one death in Acapulco. In early October, Otis produced tropical storm-force winds and minor flooding across the Baja California peninsula. The remnants of Tropical Depression One-C in the central Pacific, meanwhile, caused minor impacts in Hawaii. The strongest storm of the season was Hurricane Kenneth, which attained peak winds of 130 mph (215 km/h) over the open Pacific.
Pre-season forecasts
The first forecast for the 2005 season was produced by the Servicio Meteorológico Nacional (SMN) in the second month of the year. In their report, the organization cited a list of analog years – 1952, 1957, 1985, 1991, and 1993 – with similar oceanic and atmospheric patterns. An overall total of 17 tropical storms, 10 hurricanes, and 7 major hurricanes was forecast, above the average. The National Oceanic and Atmospheric Administration (NOAA), meanwhile, released their seasonal outlook on May 16, predicting 11 to 15 named storms, 6 to 8 hurricanes, and 2 to 4 major hurricanes. The organization noted that when the Atlantic basin was busier than average, as expected in 2005, the eastern Pacific generally saw lesser activity. That same day, NOAA issued a forecast for activity across the central Pacific, expecting 2 to 3 tropical cyclones to occur across the basin. A normal season averaged 4 to 5 tropical cyclones, including 1 hurricane. A near-normal El Niño–Southern Oscillation existed across the equatorial Pacific throughout 2005, which indicated conditions generally less conducive for activity there.
Seasonal summary
The Accumulated Cyclone Energy (ACE) index for the 2005 Pacific hurricane season as calculated by Colorado State University using data from the National Hurricane Center was 96.6 units. Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of 39 mph (63 km/h).
The season's first tropical cyclone, Adrian, developed on May 17 and reached its peak as a Category 1 hurricane. Named storms are infrequent in May, with one tropical storm every two years and a hurricane once every four years. At the time, Adrian was the fourth earliest tropical cyclone to form in the eastern Pacific since reliable record-keeping began in 1971. Activity throughout the remainder of the season was far less notable, with 16 tropical cyclones, 15 named storms, 7 hurricanes, and 2 major hurricanes. The long-term 1971–2004 average suggests an average season to feature 15 named storms, 9 hurricanes, and 4 major hurricanes. October in particular was notably quiet, with the formation of only one tropical depression; only three other seasons, 1989, 1995, and 1996, ended the month without the designation of a named storm.
Analysis of the environment suggested that most storms formed during the passage of the positive Madden–Julian oscillation and its associated upper-air divergence, which is favorable for tropical cyclone formation. Extended reprieves in tropical activity were connected to upper-level convergence. Another factor that led to a below-average season was the presence of cooler than average ocean temperatures during the peak months, helping to extend the period of lesser activity that began throughout the eastern Pacific around 1995. The 2005 became a record-tying most active in the month of September between 1966, 1992, 1994, 1997, later in 2019 forming six named storms in the basin