A typhoon is a tropical cyclone that occurs in the Northwest Pacific Ocean, explains the National Ocean Service. Typhoons, cyclones and hurricanes are all the same type of weather disturbance, but different names are used depending on the storm's location. Hurricanes occur in the Atlantic and Northeast Pacific Oceans, while cyclones occur in the South Pacific and Indian Oceans.
A typhoon begins when warm, moist air rises from the ocean's surface while surrounding air rushes into the low-pressure area it leaves behind. The new air in the low pressure area also becomes warm and moist, explains NASA. This pattern of rising warm air and low pressure continues, creating the distinctive swirling wind characteristic of tropical cyclones. The rising warm air cools as it reaches higher elevations, and its evaporated water vapor condenses to form clouds. This combined system of clouds and cyclical winds continues to spin and grow.
NASA describes tropical cyclones as giant engines that use the ocean's warm air as fuel. An eye of low air pressure forms at the center of the storm system as it rotates faster. When the swirling winds reach a speed of 39 miles per hour, the storm is called a "tropical storm." At 74 miles per hour, the storm is officially a typhoon.