The main ingredients in the recipe for the development of a hurricane are warm water, warm air and wind. As the warm water condenses in large gusts of wind, the water vapor rises and cools to form cumulonimbus clouds, the beginning stage of a hurricane.
Hurricanes generally form within 20 degrees either north or south of the equator, excluding the 5 degrees closest to the equator, because ocean temperatures less than 165 feet below the surface are at least 80 degrees Fahrenheit. When the water condenses and rises, it releases heat into the surrounding air. That air then also rises and is pulled into the cloud. As this process repeats, the air begins to pinwheel around, giving the hurricane its circular shape.
The first stage of a hurricane is called a tropical disturbance and occurs when this pinwheel joins with other clouds. The next stage, called a tropical depression, continues as increased air pressure at the top of the clouds causes the air pressure on the surface to drop. The storm becomes known as a tropical storm when the sustained winds exceed 39 mph. It becomes known as a tropical cyclone, another name for a hurricane or typhoon, when sustained wind speeds are 74 mph or above.