What happens when a hurricane crosses the international date line?

By Chaffin Mitchell, AccuWeather staff writer
By Courtney Spamer, AccuWeather meteorologist
August 08, 2018, 12:36:29 PM EDT

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Tropical cyclones can be found in various ocean basins around the world, although depending on where you live, they can be called by a different name.

When a tropical cyclone reaches a certain intensity in the the western Pacific, it is called a typhoon. In the eastern Pacific and the Atlantic oceans, hurricane is the common designation. In the Indian and South Pacific oceans, they are simply referred to as cyclones.

On occasion, a hurricane in the eastern and central Pacific oceans will maintain its strength and intensity, giving the ability to reach and even cross the international date line.

The international date line is an imaginary line on the globe, separating 180 degrees east and 180 degrees west. The majority of this line runs through the middle of the Pacific Ocean, but it is used to divide the Central Pacific basin and the Western Pacific basin when it comes to tropical systems.

So what happens when a hurricane travels across the international date line and makes its way into typhoon territory?

"Protocol is for the storm to keep its name, but for hurricanes to become typhoons. Of course, they are the same storms with the same physics," AccuWeather Senior Meteorologist Jim Andrews said.

Tropical Weather Pacific

This satellite image provided by the National Oceanic and Atmospheric Administration shows a view of Hurricane Hector, Tuesday, Aug. 7, 2018. (NOAA via AP)


"In recent years since satellites, a tropical storm crosses the international date line roughly every year or two. Before satellite coverage, the remoteness of the area means that storms crossing the date line may have gone unobserved," Andrews said.

Once the storm crosses the international date line, the forecasting responsibilities switch from the United States' National Hurricane Center to the Japan Meteorological Agency.

Hurricane Hector is just the latest storm that could complete the transition from hurricane to typhoon.

hurricanes to typhoons updated


"The 2006 Category 5 Hurricane Loke became the strongest, lowest pressure, Central Pacific storm, crossing the date line as a Category 5. Its post-tropical remnant eventually battered southwestern Alaska," Andrews said.

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It is somewhat common for hurricanes to maintain their strength as they cross the international date line, and sometimes more than one can occur in a year.

However, the chances for such an occurrence vary from year to year, based on El Niño.

"During an El Niño year, or a developing El Niño year, the water temperature out in the Pacific raises slightly, and the area of the warm water shifts eastward and expands," said AccuWeather Senior Meteorologist Jason Nicholls.

Warm water is one of the critical environmental ingredients that allows a tropical system to develop and thrive. So an area of warmer water increases the chances that a hurricane will hold together long enough to reach the date line.

"Tropical systems can cross the international date line in a non-El Niño year, but it seems less common," Nicholls added.

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