Hurricane Tracking Activity Source: Developed from the National Hurricane Center Website. Background Hurricanes are tropical storms that have a sustained wind speed greater than 74 miles per hour. They can deliver intense rainfall and record flooding. An average of 10 tropical storms develop in the Atlantic Ocean, Caribbean Sea or Gulf of Mexico each year, and an average of six of these become hurricanes. In the western North Pacific, hurricanes are called typhoons, and similar storms in the Indian Ocean are called cyclones. [Read More]