WAILUKU - The wet weather that was a holiday bonus for the Department of Water Supply cleared to drier conditions over the first week of 2009, but water demand remained stable, Water Director Jeff Eng said in his weekly water use report.
While he expressed concern over a downturn in water flows into Upcountry reservoirs, Eng was hopeful a forecast of more rain this weekend would prove accurate.
He might be reassured by a national Climate Prediction Center forecast of higher rainfall through March across drought-stricken areas of Hawaii.
For the weekend, the National Weather Service in Honolulu predicted a fast-moving cold front will bring showers to most of the islands with the possibility of locally heavy showers late today in Maui County. But the system will pass rapidly "limiting the time any single place will likely have any heavy rainfall," the weather service.
Over the next week, the forecast is for an unusual shift to westerly winds ahead of another cold front that was forming near Japan on Friday and moving across the Pacific. Maui weather analyst Glenn James, on his hawaiiweathertoday.com site, said the wind pattern is more typical of what occurs at middle latitudes - the region of the Pacific north of Hawaii and the Tropic of Cancer.
"This zonal flow of air, from west to east, will keep changeable weather conditions around," he said.
The weather service monthly rainfall report said there was a shift in the patterns in the Pacific in December that resulted in the wet conditions in the islands through the last three weeks of the month. Most of the rain was generated by a series of "Kona lows" - cold fronts that drop in from northwest of the islands, causing southeasterly winds that pull in moist tropical air. The moist air reacts to the cold upper-level air carried on the frontal band to generate heavy showers and sometimes thunderstorms.
In Maui County, the result was normal to above-normal rainfall totals for December in most areas, with rain gauges on the southern and eastern slopes recording well above normal rainfall.
Kaupo Gap, with 34.48 inches in December was at 257 percent of normal for the month. The December rain in Kaupo was nearly half of the total for the entire year - 70.22 inches, 77 percent of normal.
Much of that rain fell in the last week of December, when the drenching storms washed out sections of Kaupo Road and damaged the Kalepa Gulch bridge.
But the December rains provided a healthy boost to the East Maui watershed, with the West Wailua Iki rain gauge at 147 percent of normal, recording 30.72 inches for the month. On the fringes of the watershed that's an essential Upcountry source, Hana recorded 12.46 inches, 204 percent of normal, while Haiku with 7.97 inches was at 105 percent of normal.
For the year 2008, West Wailua Iki received 161.09 inches or 78 percent of normal; Hana had 57.89 inches or 72 percent of normal; Haiku received 34.25 inches or 53 percent of normal.
The shortage of rain is reflected in the current U.S. Drought Monitor, which still rates parts of Central Maui and West Molokai as in drought - although the Climate Prediction Center forecasts improving conditions.
The slowdown in rainfall over the past week is showing up in the streamflow data in East Maui. The Wailoa Ditch, with a capacity of nearly 200 million gallons a day, was down to 80.7 mgd Friday. It had been running at 160 mgd at the end of 2008.
Eng reported Upcountry reservoir levels were also falling with reduced inflow, from 173.4 million gallons on Dec. 31 to 154.4 million gallons Friday.
"With the dry, sunny weather, our Upcountry reservoir levels have dropped," he said. "I'm hoping the rain expected this weekend will bring our reservoirs closer to their maximum of 180 million gallons."
Overall, he said, water demand was stable, increasing only slightly from 29.52 mgd for the week of Dec. 25-31 to 30.01 mgd for the period ended Jan. 7.
"The current water production demands on the various water systems give us a good indication of our baseline water demands," he said. "They should be kept in mind as we approach next spring and summer."
Edwin Tanji can be reached at citydesk@mauinews.com.
