Isles’ hurricane season sets records

AN unprecedented number of hurricanes swirled through the Central Pacific this year, but Hawaii managed to dodge all eight of them, and the hurricane season officially ends today.

“This year we had a record number of hurricanes raging,” said state climatologist Pao-Shin Chu. “Historically we never had so many hurricanes and tropical storms. It’s a very busy season.

“Typically, the Hawaii region is not prone to hurricanes because we have very strong vertical wind shear in the atmosphere that will kill storms,” said Chu, a professor in the Department of Atmospheric Sciences at the University of Hawaii at Manoa. “Also, we are away from the area where hurricanes usually form in the monsoon trough.”

Altogether, 15 tropical cyclones entered the Central Pacific from June through November, a jump from the previous record of 11 in 1994. The eight hurricanes among them eclipsed the previous record of five hurricanes in the region in 1994.

The intense storm activity captured international attention in late August, when three Category 4 hurricanes spun through the Central North Pacific. The National Weather Service said it was the first time on record that so many Category 4 storms, with winds above 110 mph, occurred simultaneously in any ocean basin.

In August alone five hurricanes were tracked in the Central North Pacific: Guillermo, Hilda, Kilo, Loke and Ignacio. September saw Jimena, followed in October by Oho and Olaf, which just sent surf toward Hawaii. November had no tropical cyclones, although Hawaii did see plenty of rain.

Looking ahead, Hawaii can expect the state to start drying out soon. El Nino years typically have drier-than-normal winters, but November is often a wet prelude to that.

Another measure of tropical cyclones also set a new pace this hurricane season. Accumulated cyclone energy, or ACE, combines intensity, frequency and duration of storms into one number.

“This year did break the all-time record for North Central Pacific, thanks to Hurricane Olaf in October,” said Phil Klotzbach, research scientist in the Department of Atmospheric Science at Colorado State University in Fort Collins. “This season generated 127 ACE units, up from the previous record of 107 ACE units set in 1994.”

LAST year’s Central Pacific ACE score was only about 40. Three hurricanes moved through the Central Pacific last year. Iselle was downgraded to a tropical storm before it hit the Big Island, but still damaged 250 homes and destroyed 11.

A strong El Nino, which is a warming of sea surface temperatures in the eastern tropical Pacific, helped create conditions that generated a record number of tropical cyclones this year.

“We have a very strong El Nino, so the ocean water in the Central North Pacific is very warm, so this would allow hurricanes to maintain their intensity and also would allow the low-level wind convergence,” Chu said.

“There are other reasons,” he added. “Global warming can contribute to the longer-term trend of more hurricanes. The water gets warmer each year, so that also fuels the likelihood of more hurricanes forming in the sweet spot.”

Generally the state is protected somewhat from hurricanes by the jet stream, upper-atmosphere winds that weaken most storms before they hit the state and also help steer hurricanes away from the islands.

But in a couple of cases this year, the jet stream wasn’t over the islands as the storms approached, and so Hawaii simply lucked out, according to Robert Ballard, science and operations officer at the Central Pacific Hurricane Center.

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Star-Advertiser reporter Tim Hurley contributed to this report.