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. Systems Tropical Storm Alvin The genesis of Alvin can be attributed to a tropical wave that crossed Dakar, Africa on May 9. The wave remained poorly organized as it moved across the Atlantic Ocean and Caribbean Sea through mid-May. On May 20, the disturbance crossed Central America and emerged into the eastern Pacific Ocean, where convection—shower and thunderstorm activity—gradually began to increase over the well-defined center; this led to the formation of a tropical depression by 0000 UTC on May 27, approximately