A hurricane has never crossed the equator. Here's why.

A meteorological principle related to the Earth's rotation dictates that tropical storms cannot cross the equator, but a couple have come close.

Did you know that a hurricane or tropical storm has never crossed the equator? The reason behind this fascinating phenomenon lies in a meteorological principle related to the rotation of the Earth: the Coriolis force.

The Coriolis force is responsible for deflecting winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

"This force is what gives tropical systems their iconic swirl — counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere," AccuWeather Lead Hurricane Expert Alex DaSilva explained.

At the equator, however, the Coriolis force is essentially zero, making it impossible for a tropical system to cross over from one hemisphere to another.

Typhoon Vamei in 2001 was the closest storm to the equator

Most tropical systems remain north of 5 degrees north latitude or south of 5 degrees south latitude. The closest a tropical storm or hurricane has ever come to crossing the equator was Typhoon Vamei in December 2001 in the western Pacific, which got within 100 miles of the equator, forming at only 1.4 degrees North latitude.

An unnamed tropical depression in 1973 formed farther south

The closest a tropical depression has ever formed to the equator was an unnamed storm in December 1973. This storm formed at 0.5 latitude. It later became a tropical storm around 0.7 latitude, according to the China Meteorological Administration. But their threshold for a tropical storm differs from NOAA's definition. NOAA says that the 1973 storm not have tropical-storm-force winds until later in its path, north of 10 degrees north latitude.

Another fact you may notice on the world tropical cyclone map is that there have been few tropical storms off the coast of South America. This is due to a number of factors.

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