Rare Switch for Genevieve: Hurricane to Super Typhoon

By , Senior Meteorologist
August 9, 2014; 4:29 AM ET
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Once-Hurricane Genevieve has achieved an extreme rare tropical feat that has been matched by only one other hurricane in the Pacific Ocean since 1950.

Genevieve intensified into a Category 4 hurricane Wednesday night EDT, then crossed the International Date Line, further strengthened and was classified as a super typhoon a few hours later.

Nothing structurally has changed with Genevieve, just its naming convention.

Tropical systems with the same strength as hurricanes in the Atlantic or eastern Pacific basins are called typhoons in the western Pacific Basin (west of the international date line) and severe tropical cyclones around Australia.

This satellite image of Genevieve, courtesy of NOAA, was captured midday Friday EDT.

Which part of the Indian Ocean that a tropical system reaches hurricane strength will determine whether it is called a severe tropical cyclone, very severe cyclonic storm or tropical cyclone.

Genevieve marks only the second time since 1950 that a hurricane that originated in the eastern Pacific crossed the international date line and became a typhoon.

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On average, eight to nine hurricanes develop each year in the eastern Pacific.

Hurricane John from 1994 is the other such storm but never became a super typhoon as Genevieve did. John does hold the records for the farthest-traveling (8,252 miles) and longest-lived (31 days) tropical system.

Hurricane Dora from 1999 narrowly missed the opportunity to join this elite group. Dora was weakening to a tropical storm as it crossed the international date line.

There have been some other hurricanes, the most recent being Ioke from 2006, that experienced a name change to typhoon or super typhoon. However, these originated in the central Pacific (between the 140th meridian west longitude and the international date line) and failed to travel as far as Genevieve and John.

"It is a war zone for tropical systems crossing the Pacific due to wind shear and the potential to re-curve into cooler waters," stated AccuWeather.com Tropical Weather Expert Dan Kottlowski when discussing the rarity of Genevieve's journey.

"Wind shear is a belt of upper-level winds that often shear tropical systems apart, while a high percentage of eastern Pacific systems re-curve before reaching the longitude of Hawaii."

"A lower percentage of storms stay along a western path and over the warmer waters," Kottlowski added.

The formation of Genevieve as a tropical storm took place about 1,490 miles east-southeast of the southernmost point of Hawaii during the morning hours of July 25. It took until Aug. 6 for Genevieve to become a hurricane as it approached the international date line.

Genevieve will remain over the open waters of the Pacific and pose only extreme hazards to shipping interests until it gradually weakens this weekend through early next week.

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