Cyclone, hurricane, typhoon: What's the difference?

As Cyclone Vayu rages in the Indian ocean[1], you may be wondering what a cyclone even is. But if you've ever survived a hurricane or typhoon, you already know the answer.

In the Atlantic and northern Pacific, the storms are called "hurricanes," after the Caribbean god of evil, named Hurrican.

In the northwestern Pacific, the same powerful storms are called "typhoons." In the southeastern Indian Ocean and southwestern Pacific, they are called "severe tropical cyclones."

In the northern Indian Ocean, they're called "severe cyclonic storms." In the southwestern Indian Ocean, they're just "tropical cyclones."

To be classified as a hurricane, typhoon, or cyclone, a storm must reach wind speeds of at least 74 miles per hour (119 kilometers per hour).

If a hurricane's winds reach speeds of 111 miles per hour (179 kilometers per hour), it is upgraded to an "intense hurricane."

If a typhoon hits 150 miles per hour (241 kilometers per hour) then it becomes a "supertyphoon."

While the Atlantic hurricane season runs from June 1 through November 30, the typhoon and cyclone seasons follow slightly different patterns.

In the northeastern Pacific, the official season runs from May 15 to November 30. In the northwestern Pacific, typhoons are most common from late June through December. And the northern Indian Ocean sees cyclones from April to December.

Whatever you choose call them, these monster storms are powerful natural events with the capacity to wreak some serious havoc.

According to NOAA's National Hurricane Center[2], the average hurricane eye—the still center where pressure is lowest and air temperature is highest—stretches 30 miles (48 kilometers) across, with some growing as large as 120 miles (200 kilometers) wide.

The strongest storms, equivalent to Category 5 on the Saffir-Simpson scale[3], have sustained winds that exceed 155 miles per hour (250 kilometers per hour).

With the aid of satellites and computer models, such storms can be predicted several days in advance and are relatively easy to track.[4] But as Hurricane Sandy showed recently, predicting the path that a hurricane or typhoon or cyclone will take after it's formed is still tricky[5].

Effects of global warming?

In theory, warmer atmospheric temperatures should lead to warmer sea surface temperatures, which should in turn support stronger hurricanes.

The number of Category 4 and 5 hurricanes worldwide nearly doubled from the early 1970s to the early 2000s. Moreover, both the duration of tropical cyclones and their strongest wind speeds have increased by about 50 percent over the past 50 years.

"Average tropical cyclone maximum wind speed is likely to increase, although increases may not occur in all ocean basins," an Intergovernmental Panel on Climate Change report noted.

It is often difficult to assess the impact of a warming planet on any individual storm, but increasing computing power and more sophisticated weather modelling is allowing the science to progress[6].


  1. ^ rages in the Indian ocean (www.cnn.com)
  2. ^ NOAA's National Hurricane Center (www.nhc.noaa.gov)
  3. ^ Saffir-Simpson scale (www.nhc.noaa.gov)
  4. ^ easy to track. (news.nationalgeographic.com)
  5. ^ is still tricky (www.washingtonpost.com)
  6. ^ allowing the science to progress (news.nationalgeographic.com)

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