Cyclone, decoded. One storm, three names.

A cyclone is a giant wheel of wind spinning around a calm low-pressure center — and if you have ever watched a hurricane on the news, you have watched a cyclone. The storm is the same in every ocean; only the name changes with the water it spins over. This page is the short version of what a cyclone is, why it has three names, how the tropical kind forms over warm water, what its colder cousin does to your winter, and what to do when one is headed your way.

WHAT IT ACTUALLY IS.

A giant wheel of wind spinning around low pressure.

A cyclone is a large storm system that rotates around a center of low pressure, with winds spiraling inward — counterclockwise in the Northern Hemisphere, clockwise in the Southern, because the Earth itself is turning underneath it. The lower the pressure at the center, the faster the winds spin, which is why the middle of the storm is both the calmest place (the eye, if it has one) and the most violent ring around it. It is the same shape whether it forms over a warm tropical ocean or a cold winter coastline — what changes is what powers it.

THREE NAMES, ONE STORM.

Hurricane, typhoon, cyclone — the ocean decides.

A tropical cyclone starts over warm ocean water, generally 80°F or warmer, feeding on the heat rising off the sea. At 38 mph or less it is a tropical depression; from 39 to 73 mph it is a tropical storm; at 74 mph and up it earns the big name — hurricane in the Atlantic, Caribbean, and eastern Pacific, typhoon in the northwest Pacific, and cyclone in the Indian Ocean and South Pacific. Same storm, same Saffir-Simpson scale from Category 1 to 5, just a different name on the map depending on which ocean it is spinning over.

WHAT TO DO ABOUT IT.

Know your zone. Leave early. Never drive through water.

If you live near the coast, know your evacuation zone before the season starts — and when officials say leave, leave early, because the roads clog and the storm does not wait. The other kind of cyclone, the extratropical one, is the engine behind most winter storms and nor'easters: it runs on the clash between cold and warm air masses, and it is the reason a "regular" winter storm can still knock out power for days. Either way, never drive through flooded roads — six inches of water can knock you down, twelve inches can carry a car, and two feet can float most vehicles — and check Brzzy's forecast, live radar, and severe weather alerts before the sky makes the decision for you.

What is a cyclone?

What is the difference between a cyclone, a hurricane, and a typhoon?

They are the same kind of storm with different names by ocean: a tropical cyclone is called a hurricane in the Atlantic, Caribbean, and eastern Pacific, a typhoon in the northwest Pacific, and a cyclone in the Indian Ocean and South Pacific. All three use the same strength scale — tropical depression at 38 mph or less, tropical storm at 39–73 mph, hurricane/typhoon/cyclone at 74 mph and up.

How does a tropical cyclone form?

It starts over warm ocean water, generally 80°F or warmer, feeding on the heat rising off the sea. Warm, moist air rises, cools, and condenses into clouds, and the rotation of the Earth starts the whole system spinning — the warmer the water and the calmer the upper winds, the stronger it can grow.

What is an extratropical cyclone?

An extratropical cyclone is the colder cousin: instead of warm ocean water, it is powered by the temperature contrast between colliding air masses over land or cooler water. It drives most mid-latitude weather, including winter storms and nor'easters, and it is the reason a "regular" winter storm can still bring heavy snow, high winds, and days without power.

Does Brzzy tell me about cyclones?

Brzzy shows your local forecast with hourly updates, live radar, severe weather alerts, GIF forecasts, and activity ratings that weigh the sky for your plans. Brzzy is free to download on iPhone.

More from Brzzy: Full weather glossary, Hurricane, Tropical Storm