A hurricane is a type of tropical cyclone that forms over tropical or subtropical waters and has a closed low-level circulation. These storms are characterized by organized thunderstorm activity and rotate counterclockwise in the Northern Hemisphere. When a tropical cyclone’s maximum sustained winds reach 74 mph (64 knots or 119 km/h) or higher, it is classified as a hurricane. In the western North Pacific, hurricanes are called typhoons, while similar storms in the Indian Ocean and South Pacific Ocean are called cyclones.
Here’s a breakdown of hurricane-related terms and some historical context:
Key Terms
- Tropical Cyclone: A general term for a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters.
- Tropical Depression: A tropical cyclone with maximum sustained winds of 38 mph (33 knots) or less.
- Tropical Storm: A tropical cyclone with maximum sustained winds between 39 and 73 mph (34 to 63 knots). Once a storm reaches this intensity, it is assigned a name.
- Hurricane/Typhoon/Cyclone: The same type of storm, but referred to by different names based on the region where they form.
- Major Hurricane: A hurricane with maximum sustained winds of 111 mph (96 knots) or higher, corresponding to Category 3, 4, or 5 on the Saffir-Simpson Hurricane Wind Scale.
- Eye: The relatively calm center of the hurricane.
- Eyewall: The band of strong thunderstorms immediately surrounding the eye, where the strongest winds occur.
- Storm Surge: An abnormal rise in sea level accompanying a hurricane or other intense storm.
- Saffir-Simpson Hurricane Wind Scale: A scale that classifies hurricanes based on their maximum sustained winds, ranging from Category 1 (weakest) to Category 5 (strongest).
Brief History
- Naming Conventions: Until the mid-1900s, storms were named arbitrarily. The practice of using predetermined lists began in 1953. Names of particularly deadly or costly storms may be retired.
- Deadliest Hurricane: The 1900 Galveston Hurricane in Texas is considered the deadliest natural disaster in U.S. history, causing at least 8,000 fatalities.
- Monitoring: The United States National Hurricane Center (NHC) monitors tropical weather systems in the North Atlantic basin and issues reports, watches, and warnings. Satellites, radar, and reconnaissance aircraft are all used to monitor these storms.
- Hurricane Season: The Atlantic hurricane season runs from June 1 to November 30. The Eastern Pacific hurricane season runs from May 15 to November 30.