How Warm Oceans Build Hurricanes

By the end of this lesson, you will be able to describe how ocean currents and air masses work together to create tropical cyclones like hurricanes and typhoons.

Think about a hot summer afternoon in Houston or Corpus Christi. The air feels thick and sticky because warm water from the Gulf of Mexico is evaporating and filling the air with moisture. That same steamy combination, spread across hundreds of miles of ocean, is the fuel for the biggest storms on Earth.

Ocean currents, which are rivers of water that move heat around inside the ocean, carry warm water from the tropics toward places like the Gulf. When ocean water is about 80 degrees Fahrenheit or warmer, it heats the air sitting on top of it. That heated, moist air becomes an air mass, a huge body of air that has nearly the same temperature and humidity throughout. Warm, moist air masses are lighter than cool air, so they rise.

As the air rises, it leaves behind an area of low pressure near the ocean surface, and more warm, moist air rushes in to take its place. Higher up, the rising water vapor cools and condenses into clouds, releasing heat that pushes the air even higher. This cycle feeds itself and can grow into a tropical cyclone, a spinning storm system with strong winds and heavy rain that forms over warm tropical oceans. Earth's rotation makes the storm spin, and the calm center becomes the eye.

The same kind of storm gets different names in different places. Over the Atlantic Ocean and the Gulf of Mexico, we call it a hurricane. Over the western Pacific Ocean, near Japan and the Philippines, it is called a typhoon. When one of these storms moves over land or cool water, it loses its warm, moist fuel and weakens.

Try it: if a hurricane crosses a patch of unusually cold ocean water, would it get stronger or weaker, and why?