Ask A Scientist

How do hurricanes form? 

Asked by: Kiera Stephens
School: Johnson City Intermediate School
Grade: 4
Teacher: Allison Gerber
Hobbies/Interests: Art, playing with her dog 
Career Interest: Veterinarian 

Answer from Colin Evans

Resident Director

About Scientist: Colin has a bachelor’s degree in environmental science and a master of science degree in atmospheric science Research area: Bio-diesel fuels, climate change, boundary layer weather modeling analysis Interests/hobbies: Baseball, reading, movies, writing  

Hurricanes are, without a doubt, the most destructive storms on Earth. Because they are so large and destructive, their formation is very complicated. Hurricanes are called different names in other parts of the world, too. So if you ever hear someone talk about a typhoon or tropical cyclone, they are talking about a hurricane.

The first thing you need to know about hurricanes is that they need two main things to form: wind and warm, wet air. The best place on the planet to find both of those things is in tropical regions, over oceans. Hurricanes develop in four distinct stages: tropical disturbance, tropical depression, tropical storm, and tropical cyclone (hurricane).

So how does it happen? When the warm, moist air over tropical oceans condenses, clouds form, and heat is released into the air. The warm air rises, creating a column of clouds. The cycle of evaporation and condensation continues, building up the cloud columns. With the right wind, it starts circling around these cloud columns. If enough of the columns form together, a cluster of thunderstorms is born. This is called a tropical disturbance.

If the columns of clouds get big enough, the tops of the clouds actually get so high that they begin to cool down, and they become really unstable. When the clouds cool, they release their heat to atmosphere, which actually causes the clouds to warm up again and the pressure of the air at the top of the clouds increases. This causes winds to move away from where the pressure is increasing and then causes the pressure at the surface to decrease. The air at the surface moves towards the low pressure areas and actually makes more thunderstorms. The winds that are created begin spinning faster and faster, and when they reach 25 miles an hour, a tropical depression is created.

Last Updated: 3/1/17