Hurricanes are one of the most destructive weather hazards around. Most people know that hurricanes are dangerous, but do you know how they are made?
It’s hard to believe, but big and powerful hurricanes start off as just a few thunderstorms in the middle of the ocean! Hurricanes only need a few ingredients to grow from a group of thunderstorms into a hurricane.
The first ingredient is the warm ocean, at least 80°F. Vapor from the warm water rises into the atmosphere, which then condenses, causing heat to be released into the atmosphere and the air to be lighter. As the warm air continues to rise, more air moves in near the surface to take its place, which causes strong winds.
The next ingredient is local winds. They need to blow in the same direction and at the same speed from the ocean surface to the top of the atmosphere.
Finally, all this needs to happen away from the equator, due to a phenomenon called the Coriolis Effect, which describes how air moving toward the equator and the poles curves due to the Earth’s rotation. The Coriolis Effect is what makes hurricanes spin, and there is no Coriolis Effect near the equator.
If the thunderstorms over the ocean have these things, they can start to grow into a hurricane!
Those thunderstorms, called tropical disturbances, start to cluster together, drop in air pressure and become a tropical depression. Wind speeds in a tropical depression are only about 38 mph. As the Coriolis Effect makes the tropical depression spin, it becomes a tropical storm. This is like a mini hurricane, and its winds are 39-73 mph. As it continues to spin, it takes more energy from the warm ocean water below and grows stronger until it is a hurricane.
If it keeps growing and getting stronger, major hurricanes can reach wind speeds of 111 mph or faster. That’s as strong as a tornado.
The National Hurricane Center has said that it’s rare to get all the ingredients together. Lucky for us, not all thunderstorms or tropical storms become a hurricane. For more information on hurricanes, visit Tropics Intro and Hurricanes.
