The 2007 Pacific hurricane season was a well below-average Pacific hurricane season, featuring only one major hurricane. The season officially started on May 15 in the eastern Pacific and on June 1 in the central Pacific, and ended on November 30; these dates conventionally delimit the period during which most tropical cyclones form in the region. The first tropical cyclone of the season, Alvin, developed on May 27, while the final system of the year, Kiko, dissipated on October 23. Due to unusually strong wind shear, activity fell short of the long-term average, with a total of 11 named storms, 4 hurricanes, and 1 major hurricane. At the time, 2007 featured the second-lowest value of the Accumulated cyclone energy (ACE) index since reliable records began in 1971. Two tropical cyclones – Cosme and Flossie – crossed into the central Pacific basin during the year, activity below the average of 4 to 5 systems.
Impact during the season was relatively minimal. In early June, Tropical Storm Barbara moved ashore just northwest of the Mexico–Guatemala border, causing $55 million (2007 USD) in damage and 4 deaths. In late July, Cosme passed south of the island of Hawaii as a weakening tropical depression; light rain and increased surf resulted. A few days later, Dalila passed offshore the coastline of southwestern Mexico, killing 11 and causing minimal damage. Hurricane Flossie followed a similar track to Cosme in mid-August, producing gusty winds and light precipitation in Hawaii. Hurricane Henriette in early September produced torrential rainfall in southwestern Mexico, killing 6 and causing $25 million in damage. Baja California received moderate rains from Hurricane Ivo in mid-September, though no damage nor fatalities were reported. In mid-October, Tropical Storm Kiko passed just offshore the coastline of southwestern Mexico. Though no deaths were reported on the Mexico mainland, the storm capsized a ship with 30 people on board, 15 of whom were recovered dead, and 9 of whom were reported missing. Overall, the season ended with $80 million in damage and 49 deaths.
Seasonal forecasts
On May 21, 2007, the National Oceanic and Atmospheric Administration's Central Pacific Hurricane Center released its outlook for the 2007 Central Pacific hurricane season, predicting a total of 2–3 tropical cyclones to form or cross into the basin; in a typical season, 4–5 systems cross or form in the Central Pacific. A day later, the National Oceanic and Atmospheric Administration's Climate Prediction Center released its seasonal prediction for the 2007 East Pacific hurricane season, predicting a total of 11–16 named storms, 6–9 hurricanes, and 2–4 major hurricanes. Below-average activity was expected as a result of either ENSO-Neutral or La Niña conditions, as well as the continuation of the reduction in activity beginning in 1995.
Seasonal summary
The Accumulated Cyclone Energy (ACE) index for the 2007 Pacific hurricane season (Eastern Pacific and Central Pacific combined) as calculated by Colorado State University using data from the National Hurricane Center was 51.6 units, which was a well below the 1981–2010 average of 113.3 units, and at the time the second-lowest value observed since reliable records began in 1971. 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).
Tropical cyclone activity totaled to eleven named storms, four hurricanes, and only major hurricane within the season; all three of these values fall below the 1971–2006 long-term average of 15 named storms, 9 hurricanes, and 4 major hurricanes. The main contributing factor to below-average activity was much above-average wind shear across the Pacific basin. In May 2007, two tropical storms – Alvin and Barbara – developed, marking at the time the third such instance of more than one tropical storm developing within the month since official records began in 1949. In June 2007, only one tropical depression developed in the East Pacific basin, making 2007 one of only four years in which a tropical storm did not form in the month. By the following month, in terms of ACE, 2007 was considered the third quietest year-to-date since the satellite era began in 1966; in September, the season fell to the second quietest year-to-date. Below-average activity continued for the remainder of the year.