No drought relief expected soon
By Jan TenBruggencate
Advertiser Science Writer
The Islands may be drifting into a fifth year of dry weather, the result of Pacific-wide climate patterns that are just now becoming understood.
Most of the state is already under at least a moderate drought condition, and experts say it could continue for another year or more.
University of Hawai'i oceanography professor Roger Lukas said the Islands can expect an El Nino climate event later this year, during which rainfall is normally reduced in Hawai'i.
And that's after four years of dry weather associated with the cold phase of another weather pattern called the Pacific Decadal Oscillation.
"It doesn't look like we have much drought relief in sight," said Lukas, who studies large-scale interactions between the ocean and atmosphere, and how they affect the weather.
For the Islands, while it may mean more sunny weather, it's bad news for firefighters, farmers and the folks who run the water systems. There are already voluntary or mandatory water restrictions in each county, because of low rainfall, higher use, and low water levels in wells.
Fire department and forestry officials this month warned of brush fire and forest fire danger on all islands, and expressed concerns that a dry summer could dramatically increase the risk of wildfires. Reservoirs used for irrigation are low, and ranchers worry that there won't be enough grass for their herds.
A national drought monitor published on the Web (enso.unl.edu/monitor/monitor.html) by the U.S. Department of Agriculture, the National Oceanographic and Atmospheric Administration and others, places most of the area in the Hawaiian Islands under conditions ranging from "abnormally dry" to "severe drought."
A few areas have received normal rainfall in recent months, much of it associated with trade winds on windward sides, but most of the state is dry. And the drought has dragged on for so long that even deep wells have been affected. The U.S. Geological Survey reports below normal rainfall, streamflow and groundwater levels at its Web site, hi.water.usgs.gov/recent/index.html.
It says water levels in wells in the Lihu'e Basin on Kaua'i are at record lows, having been dropping since 1996. On O'ahu, in the Pearl Harbor region, there are also record low levels. There are record lows as well on Maui.
In late May, Honolulu Board of Water Supply deputy manager and chief engineer Donna Kiyosaki said water levels at several O'ahu wells are at "alert" or "caution" levels. She called for voluntary conservation of water on O'ahu. Water managers on Maui and Kaua'i have done the same.
Lukas said the Hawai'i drought is associated with the same causes that have been linked to three years of dry weather in the western United States — the cold phase of a pattern called the Pacific Decadal Oscillation, or PDO.
Scientists are predicting more drought there, just as in Hawai'i.
"This continuing PDO pattern of the past three years signals more of the unusually dry conditions that have afflicted the North American west coast," said oceanographer William Patzert at the Jet Propulsion Laboratory in Pasadena, Calif.
A PDO is a longer time scale climate event than El Nino. While El Nino-La Nina cycles last three to five years, a PDO may run for 10 to 30 years. An El Nino occurs when a pool of warm water moves from the Western Pacific near the Equator to Central America. It is associated with changes in wind, rainfall and storm patterns, alterations in fishery productivity and much more.
The present phase of the PDO has a vast tongue of cooler-than-normal water extending from the coast of North America out into the Pacific, well past Hawai'i. A horseshoe of warmer-than-normal water surrounds it on the west, south and north sides.
Hawai'i had dry weather during the El Nino event of 1997-1998, and might have expected at least normal rainfall when the pattern changed to a La Nina. But the cold phase of the PDO overcame the La Nina signal, and is probably responsible for keeping it dry in the Islands, Lukas said.
Now, the La Nina is dying away, and appears to be being replaced by a weak or moderate El Nino late this year or next year, but there is no sign that the PDO is shifting.
"The El Nino is going to be adding its drought on top of the decadal dryness," Lukas said.
