El Nino to dry state


POSTED: Wednesday, October 21, 2009

Thanks to El Nino conditions, islanders can expect drier-than-normal conditions during Hawaii's upcoming wet season but more tropical storm activity in the Central Pacific—with the possibility of hurricanes in the next 40 days, climate experts say.

Flash flooding also can occur from storms that flare up even in dry weather, they point out, urging residents to be prepared.

“;Think about what you would do in a hurricane or flood,”; advised Jim Weyman, director of the Central Pacific Hurricane Center and meteorologist-in-charge of the National Weather Service's Honolulu Forecast Office.

Weyman and Kevin Kodama, senior service hydrologist at the forecast office, described El Nino's potential impact in a media briefing yesterday.

An average of four or five tropical cyclones occur in the Central Pacific annually, and seven have occurred so far this year, including Hurricane Neki, currently south of Hawaii, Weyman said. Others were Lana in July and Felicia, Maka, Guillermo, Hilda and Tropical Depression 2C in August.

Hurricane season does not end until Dec. 1, Weyman emphasized, recalling that Hurricane Iwa struck Kauai late in the season, on Nov. 23, 1982.

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Four of the most active Pacific tropical storm seasons from 1971 to 2008 occurred during El Nino years, and one during a La Nina year.

El Ninos and La Ninas are phenomena representing large-scale changes in sea-surface temperatures across the equatorial Pacific that affect climate worldwide. Surface waters become warmer during an El Nino and cooler during a La Nina.

Central and Eastern Pacific waters began warming up at the end of April, turning into an El Nino in May and June, Weyman said. Waters are slightly warmer than normal—about 2 degrees Fahrenheit, he said.

That makes it a weak to moderate El Nino, but it is expected to strengthen and continue with above-normal sea-surface temperatures in December through February.

Regarding rainfall, Kodama said the state's dry season, which ended last month, was not as bad as the past two years except for the Big Island. Last year about 78 percent of the state had moderate drought conditions; this year it was about 51 percent, he said.

Rain in July and August relieved dry conditions on Kauai and Oahu and helped to stabilize Upcountry Maui's water supply, he said, but the Big Island remained dry, with severe drought in leeward areas.

October through April is considered Hawaii's wet season, but dry conditions will take hold in mid-December and continue through April, Kodama said.

“;When talking about El Nino dryness, we're not just looking at leeward areas, but statewide drier-than-normal areas, even those that are normally wet, like Hilo.”;

If there is no wet-season rain this month or in early December to relieve the drought, Kodama said, “;it will be that much worse.”;

He said the impacts will include continued restrictions on irrigation water, losses of nonirrigated crops, water shortages that require homes with catchment systems and ranchers to haul water, higher operational costs for ranchers and increased wildfire risks.

But Kodama warned, “;Drier than normal does not mean no rain at all.”; Significant flooding can occur in a drought, he said, recalling flash flooding in February 2003 during a weak to moderate El Nino.