A tropical cyclone in the Northern Hemisphere with sustained winds of at least 119 kph (74 mph) or greater in the North Atlantic Ocean, Caribbean Sea or Gulf of Mexico. These winds blow in a large spiral around a relatively calm center of extremely low pressure known as the eye. Around the rim of the eye, winds may gust to more than 200 miles per hour. The entire storm, which can be up to 550 kilometers (340 miles) in diameter, dominates the ocean surface and lower atmosphere over tens of thousands of square miles. Hurricanes draw their energy from the warm surface water of the tropics (usually above 27 Celsius) and latent heat of condensation, which explains why hurricanes dissipate rapidly once they move over cold water or large land masses.