WRAL WeatherCenter Blog

Hello! I am a student at Durant Road Elementary School. My class is doing a project on weather. I need to ask you questions about cyclones. What does a cyclone look like? Is it a tornado or a hurricane? What damage does it do? How big is a cyclone? What are the wind speeds? Thank you!

Posted April 14, 2007 11:30 a.m. EDT

MIKE MOSS SAYS:      Rikente,    I'll give you a brief rundown on cyclones here, but I encourage you to use your library and web search skills to find out more detailed information. Going in order of the questions you posed...

A cyclone is defined as any closed circulation in which the rotation of the winds involved is in the same direction as the rotation of the earth. For the Northern Hemisphere, that means winds flow around a cyclone in a counterclockwise manner. There is no certain way that a cyclone "looks," because they can exist in such variety.

Since a cyclone is defined by the flow of winds around a central location, there are a number of different type storms and systems that can be classified as cyclones. For example, large mid-latitude low pressure systems, like the nor'easters that sometimes move across North Carolina and up toward New England, are a type of cyclone. Likewise, hurricanes are a somewhat smaller but more intense form of cyclone. Most tornadoes are cyclones, but some tornadoes spin in the opposite direction (clockwise in the northern hemisphere) and those would be called "anti-cycloninc." Finally, a small dust devil that rotates counter-clockwise in our hemisphere would be a form of cyclone, but again, not all dust devils rotate in that direction.

Since a cyclone can take so many forms, the damage they can do likewise covers a large range. Many mid-latitude low pressure systems are weak enough that little or no damage occurs, and the same goes for dust devils at the other end of the size scale. Some low pressure systems are much more powerful, and can cause damaging winds, flooding through heavy rains and strong onshore flow along coasts, coastal erosion, and sometimes damage to structures and power transmission facilities due to snow and/or ice. Hurricanes can cause damage due to high winds, flooding rains and storm surge. Tornadoes can cause severe damage over a limited area due to very high wind speeds.

A small dust devil, or whirlwind, may be only a few feet in diameter, while some rare tornadoes may reach a mile or more in width (most are smaller). Hurricanes can be several hundred miles across, with an "eye" that averages 15-25 miles in diameter. Finally, some large mid-latitude low pressure systems cover more than a thousand miles from one side to the other.

Wind speeds can range from a few miles per hour in a small dust devil or on the edges of a stronger storm, up to around 100 miles per hour for especially strong nor-easters and similar mid-latitude lows, 200 miles per hour for very intense hurricanes, and around 300 miles per hour for the strongest tornadoes.