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Typical hurricanes are about 300 miles wide although they can vary considerably in size, as shown in the two satellite images below.

Satellite image of Hurricane Danny Satellite image of Hurricane Fran

Size is not necessarily an indication of hurricane intensity. Hurricane Andrew (1992), the most devastating hurricane of the 20th century, was a relatively small hurricane.

The hurricane's structure includes the eye, the eye wall, and the rain bands. The eye at a hurricane's centre is a relatively calm, clear area approximately 20-40 miles across. The eye wall surrounds the eye and is composed of dense clouds that contain the highest winds in the storm. The storm's outer rain bands (often with hurricane- or tropical storm-force winds) are made up of dense bands of thunderstorms that extend out as little as 50 miles from the storm in small hurricanes to as much as 300 miles in large ones.

Hurricane-force winds (more than 74 mph) can extend from the centre outward to about 25 miles in a small hurricane and to more than 150 miles for a large one. Tropical storm-force winds (between 39 and 74 mph) can reach distances as far as 300 miles from the center of a large hurricane.

Do not focus on the eye or the forecast track - hurricanes are immense systems that can move in complex patterns that are difficult to predict. Be prepared for changes in size, intensity, speed, and direction.

Frequently, the right side of a hurricane is the most dangerous in terms of storm surge, winds, and tornadoes. The speed of the general atmospheric flow in which the hurricane is embedded (for example 30 mph) is added to the average hurricane wind speed (for example 100 mph) on the right side. This increase in wind speed (to 130 mph in the example) increases the danger in areas impacted by the right side of the storm. NHC forecasts take this effect into account in their official wind estimates.

Last Updated: 2010-08-15