The key ingredient for hurricane formation is warm ocean waters about 80°F ( 27°C) or warmer. Hurricanes also need the atmosphere to cool quickly with height because rapidly rising air enhances convection and thunderstorm development. Additionally, there needs to be very little change in wind speed or direction as the air races upward through the atmosphere. Finally, these perfect environmental conditions require some sort of pre-existing weather disturbance that convection can converge around.

As air rises, the water vapor cools and condenses into clouds. Condensation releases heat. This heat warms the atmosphere making the air even lighter so it can continue to rise into the atmosphere. New air moves in near the surface creating the strong wind associated with hurricanes. The replacement air is always mild and moist due to the nearness to the warm ocean waters, helping the convection to continue.

Air spirals in toward the center of a hurricane in a counterclockwise pattern near the ocean (clockwise in the southern hemisphere), and out the top in the opposite direction. In the very center of the storm, air sinks, forming an "eye" that is mostly cloud-free.

Once the eye of the storm moves over land they tend to weaken rapidly, not because of friction, but because the storm lacks the moisture and heat that the ocean provided to produce convection (and thunderstorms) near the storm center. Without this convection, the hurricane rapidly diminishes.

You can use the following fader to shift from a visible image of Hurricane Iris to an enhanced infrared (IR) image. In the enhanced IR image, the eye is especially evident because the satellite is able to see all the way down to the warm ocean waters. In the visible image, the texture in the eye wall region suggests strong cumulonimbus clouds. Note that the single surface observation plotted on the images signifies counterclockwise (cyclonic) wind rotation. The scarcity of weather observations over the ocean is one reason why satellite derived winds are so important for forecasting the path of a hurricane.

In the Atlantic basin, hurricanes are classified by their wind speed at the surface using the Saffir-Simpson Hurricane Scale. The stronger the wind, the higher the category, and the more damage the hurricane can cause. The following table describes the 5 categories of hurricanes and the damages as a result of the strong wind.