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While Hawaii residents will likely remember Hurricane Lane as a villainous storm that soaked the Big Island and struck fear into Oahu, last week’s weather saga also had a hero: the jet stream, which rose up from the southwest to smite Lane.
“The strong winds in the upper atmosphere decapitated it,” said Leigh Anne Eaton, a meteorologist with the National Weather Service in Honolulu. “They took its head off.”
Of course, it’s not quite that simple.
The weather systems that created Hurricane Lane and caused it to die before it tore into Oahu are enormously complex, but climate scientists concur that it was a wind pattern some 30,000 feet above the ocean that was largely responsible for subduing Lane, turning it from a lethal Category 5 hurricane into a tropical storm that drifted away from the islands.
Scientific models and research have long predicted that high, shearing winds could weaken hurricanes by knocking their tops off, said Pao-Shin Chu, professor at the University of Hawaii and the state meteorologist.
“But to see how it works is really, really amazing,” he said. “To see is to believe.”
The word “decapitated” might conjure up images of Perseus deftly beheading Medusa with a sword. But what happened with Lane was far more brutal, more like twisting Lane’s upper torso from its lower body.
As Hurricane Lane headed toward Hawaii early last week, Eaton explained, it was fueled by winds from the northeast, which created a storm that was turning counterclockwise, spinning like the weather version of the Tasmanian Devil.
Left alone, Lane likely would have kept spinning with terrific force as it moved westward past the Big Island along the arc of the Hawaiian archipelago.
The problem for Lane was the jet stream, high winds coming from the southwest and turning clockwise. Scientists sometimes refer to these as “shearing winds.” Imagine the Tasmanian Devil’s legs spinning in one direction while the jet stream twisted its upper body in the opposite direction.
“It tore the storm apart, really,” Eaton said.
Also helping were the Big Island peaks of Mauna Loa and Mauna Kea. Those blocked the flow of wind, disturbing and weakening the storm. University of Hawaii professor Jennifer Griswold likened the hurricane to a spinning top and the Big Island to something bumping it.
“Imagine how much faster it could spin if it didn’t get bumped by the Big Island,” she said.
Unlike the U.S. Gulf Coast, Hawaii rarely faces threats from hurricanes. Since 1950, only 14 hurricanes have passed within 200 miles of the Big Island, Maui, Honolulu or Kauai, Weather Underground reported, citing NOAA’s historical hurricane database.
The last one to do so was Category 1 Hurricane Ana in October 2014, whose center came within 70 miles of the far western main Hawaiian island of Niihau, Weather Underground reported.
The shearing winds from the southwest are one factor that helps protect Hawaii from hurricanes, said Maureen Ballard, a meteorologist with the National Weather Service in Honolulu. A hurricane also needs warm ocean surface temperatures, she said.
In addition, she said, there’s usually a high pressure ridge that prevents storms from turning northward to hit Hawaii. Finally, there’s the fact that Hawaii is a fairly small island chain in the vast Pacific.
Still, she said, Hurricane Lane showed how vulnerable Hawaii is if the factors line up against it.
“It’s not a question of if, but when,” she said of whether Oahu will be hit.
The last hurricane to hit Hawaii was Iniki in 1992, said Chu, the state meteorologist.
The storm merely brushed Oahu before making landfall on Kauai, but it still caused an estimated $2 billion in damage, Chu said.
A hurricane making landfall on Oahu could cause $50 billion in damage, he said.
Chu noted that there are still months to go before the end of hurricane season in November.
“Lane is kind of a wake-up call for Hawaii,” Chu said. “Don’t think we will not be hit by a hurricane. It’s just a matter of time.”
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