Every year, about 15 cyclones form off the southwest coast of Mexico or regenerate there from Caribbean storms that have crossed Central America; about half of these become hurricanes. Prior to the 1970s, these storms were thought to have no effect on weather in the United States. However, Court (1980)brought a new perspective to eastern Pacific cyclones when he showed that 40 storms occurring between 1904 and 1980 had affected the western United States.