Hurricanes generally have lifespans lasting 9 days, although some form and dissipate in 24 hours or less while others remain intact for up to a month. Regardless of lifespan, all hurricanes undergo a defined development process, called a life cycle. Several factors contribute to their longevity, such as air and ocean temperatures and other atmospheric conditions.
Hurricanes, like many weather elements, require specific conditions for formation. Hurricanes begin their lives as tropical depressions, taking the shape of low center regions forming over ocean waters. They develop strong rotational winds and a defined core, eventually moving in a circular pattern. Hurricanes gain in intensity with warm ocean waters and warm air. Tropical air masses become tropical depressions with sustained winds reaching 39 miles per hour, then upgrade to tropical storms when their winds reach 74 miles per hour. Having sustained wind speeds above 74 miles per hour makes storms qualify as hurricanes. Once formed, hurricanes fall into one of five categories of strength, based on the Saffir-Simpson Hurricane Wind Scale. Storms might reach diameters of 600 miles and have ceilings extending 8 miles into the atmosphere. Smaller storms reach land quickly, while larger storms progress slowly through the ocean. Regardless of size, hurricanes reach their maximal strengths just before making landfall, causing most destruction within 12 hours of arriving onshore.