What is a Hurricane?



Have you ever really asked yourself, "What is a hurricane?" For those of you in North America, how many times have you turned on The Weather Channel only to see meteorologist Jim Cantore reporting from out in the middle of a massive storm coming off the coast? Well, if you can't catch Jim, who happens to be great at translating technical weather jargon into layman's terms, let us introduce you to the hurricane basics.

Hurricanes, while costly in terms of the amount of damage they may cause, are slightly easier to prepare for in the sense that they don't often sneak up on you. Hurricanes travel slowly over the Earth's oceans near the equator. Their paths are often projected by computer models having relatively decent accuracy, at least to the extent that you may make plans accordingly. Don't let that make you lazy in your preparations. There are times when a hurricane may change course, in which case the leadtime of a few days may become a matter of several hours.

Hurricane Formation

So what is a hurricane? Hurricanes are technically known as "tropical cyclones". Depending on the part of the world you live in, you may know them as typhoons (Western Pacific), hurricanes (Atlantic/Eastern Pacific) or cyclones (Indian Ocean). Hurricanes typically require water over 80 degrees F in order to form. As warm air rises over the ocean, additional air must move in to replace the air that is rising. This movement begins to rotate as clouds form and grow stronger. As long as the storm remains over warm waters, it will continue to grow. Once on land, not having the warm water to feed it the warm, moist air, a hurricane quickly dies out. Like tornadoes, hurricanes rotate cyclonically. This means they rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Hurricanes are given a numeric rating that "categorizes" the size of the storm. This rating system is known as the Sanffir-Simpson Hurricane Scale. It reads as follows:

  • Tropical Depression - winds <39 mph - no storm surge
  • Tropical Storm - winds 39-73 mph - storm surge up to 3 ft
  • Category 1 - winds 74-95 mph - storm surge 4-5 ft
  • Category 2 - winds 96-110 mph - storm surge 6-8 ft
  • Category 3 - winds 111-130 mph - storm surge 9-12 ft
  • Category 4 - winds 131-155 mph - storm surge 13-18 ft
  • Category 5 - winds >156 mph - storm surge >18 ft
Storm surge is the level in which the coastal waters rise above their normal tide level. Often it is the storm surge associated with hurricanes that causes the most damage.

Hurricane Myths

As with other weather phenomenon, there are many myths surrounding hurricanes. Two of the most popular are:

  • I should open some windows in my home to prevent the change in pressure from exploding my house - WRONG. You can cause more damage to your home by leaving your windows open during a hurricane.
  • It is safe to go outside during the eye of the storm - WRONG. Eventually the eye will pass and the moderate-to-calm weather will rapidly change back to a massive storm with the winds coming from the opposite direction. Stay inside!

Hopefully, this has helped you answer the question, "what is a hurricane?" As with any major weather phenomenon, get yourself prepared ahead of time. Be sure to review our hurricane emergency preparedness plan, particularly if you live in an area with the potential to experience a tropical cyclone.


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