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ABSTRACT

The hurricane season of 2007 in the eastern North Pacific Ocean basin is summarized, individual tropical cyclones are described, and a forecast verification is presented. The 2007 eastern North Pacific season was not an active one. There were 11 tropical storms, of which only 4 became hurricanes. Only one cyclone became a major hurricane. One hurricane struck Mexico and one tropical storm made landfall near the Guatemala-Mexico border. The 2007 National Hurricane Center forecast track errors were lower than the previous 5-yr means at all forecast lead times, and especially so for the 72-, 96-, and 120-h periods when the errors were 16%, 22%, and 20% lower, respectively. The official intensity forecasts had only limited skill.

1. Overview

After a year of above-normal activity in 2006 (Pasch et al. 2009) tropical cyclone activity in the eastern North Pacific Ocean basin returned to the relative low levels that have prevailed in most of the years since 1995. Eleven tropical storms developed and only four of these strengthened into hurricanes. Furthermore, only one cyclone intensified into a major hurricane [category 3 or higher on the Saffir-Simpson Hurricane Scale (Saffir 1973; Simpson 1974)]. These totals are well below the 1971-2006 average of 15 tropical storms, 9 hurricanes, and 4 major hurricanes. Four additional tropical depressions formed during the 2007 season but failed to strengthen into tropical storms. Category 1 Hurricane Henriette was the only Pacific basin hurricane to hit Mexico, causing nine deaths. Barbara made landfall as a tropical storm near the Mexico-Guatemala border.

A useful measure of overall season activity is the accumulated cyclone energy (ACE) index, which reflects the combined intensity and duration of the entire season's storms. This index is calculated by summing the squares of the wind speeds (in knots) for all tropical cyclones while at or above tropical storm strength. The ACE for 2007 in the eastern North Pacific was 34 × 10^sup 4^ kt^sup 2^ or about 31% of the long-term (1971-2006) mean value of 113. This is the second lowest value since reliable records began in 1971. Only 1977 was less active by this measure.

The 2007 season began close to the average start date of the first tropical storm, with the formation of Tropical Storm Alvin on 27...

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