A National Weather Service red flag warning triggered by dry conditions, low humidity and strengthening winds remains in effect today for leeward areas of the state, indicating the increased potential for runaway wildfires.

It is only the second time the agency issued the warning since the red flag system was implemented in Hawai'i in August 2008. The first time was Aug. 6, 2008, just three days after the program was put in place.

The warning issued by the National Weather Service yesterday is in effect until 5 p.m. today. Despite the fire-friendly conditions, firefighters on Moloka'i managed to make progress yesterday battling an 8,000-acre blaze, which reportedly was nearly 80 percent contained.

Also yesterday, O'ahu firefighters responded to six brushfires, with all but one of them small, said Honolulu Fire Department spokesman Capt. Terry Seelig. Although it was breezy at times, Seelig said weather conditions did not appear to have played a role in the fires starting or spreading.

Police closed a portion of the H-2 Freeway for about 45 minutes last night after a brushfire in Waiawa flared up. The highway was reopened just before 10 p.m.

Red flag warnings do not predict or guarantee that new fires will occur, but caution that fuel and weather conditions are conducive for new ignitions and control problems with existing fires, according to the weather service. Criteria for the warnings are relative humidity of 45 percent or less, sustained winds of 20 mph or greater, and a drought index number of 600 or more.

The U.S. Department of Agriculture's weekly U.S. Drought Monitor shows the leeward portions of Maui, Moloka'i and the Big Island in a severe drought, with South Kohala experiencing extreme drought conditions.

The Honolulu Fire Department already had assumed a state of increased readiness at the start of May, making sure adequate personnel are available and that water tankers and other vehicles and equipment are operational during the dry summer months, Seelig said.

"The possibility of a fire starting is greater because of the conditions, and if it does start, there's a greater probability of it spreading much more quickly," he said.

The largest of yesterday's fires on O'ahu was reported shortly before 3:30 p.m. in the Waiawa Ridge area, where several other wildfires have been reported this summer. As of 7 p.m., the blaze had scorched about 100 acres of former sugar cane land and had not been contained, Seelig said.

Later in the evening, the fire flared up and the H-2 Freeway was closed from about 9:15 to 10 p.m. as a precaution. The fire was not threatening to reach the freeway, but fire officials asked police to be prepared, Seelig said.

"The fire flared up, and it's moving in the southwest-by-west direction," Seelig said. "We're basically trying to keep it from spreading toward the freeway."

Seelig said firefighters would hold a fire watch last night and do a helicopter flyover today to determine what action to take. He said the biggest hindrance yesterday was the area's terrain and difficulty in reaching the fire.

"The wind hasn't been a factor much, although if they change overnight that could cause it to flare up faster than we'd like to because we know it's not going to be completely contained," Seelig said earlier in the evening. "But it's inaccessible and it won't be prudent for us to put firefighters in there at night under those conditions."

SCHOOL SPARED

Also yesterday, a small brushfire near 'Ewa Beach Elementary School caused some anxious moments because it got to within 15 yards of the school. Seelig said firefighters were able to quickly extinguish the fire, which did not cause any damage.

So far this year, 350 wildfires had been reported on O'ahu through July 31, most of them small but a good number burning up to 200 acres, Seelig said.

He said red flag warnings are a good opportunity to remind the public of the threat of brushfires and to take precautions to prevent flames from igniting and threatening property.

Precautions include quickly reporting fires and suspicious activity to the 911 emergency system, and curtailing outdoor activities, such as using tools or riding motorcycles near dry brush, that could spark a fire. Seelig said the owners of properties that abut open brush areas should clear a 30- to 100-foot-wide firebreak, removing cut grass and weeds from the buffer and leaving bare ground.

The red flag watches and warnings also are a tool for fire managers, who may want to take preventive actions such as prohibiting open burning during the critical conditions, said Jack Minassian, retired Pacific Island Fire Management Officer for the National Park Service.

Minassian, who retired from the National Park Service in 2004, said the two most important factors in Hawai'i wildfires are wind speed and relative humidity.

"Here in Hawai'i when the relative humidity starts to drop below 50 percent, that's when you get more extreme fire behavior, and if the winds pick up to over 20 mph, you're not going to be able to stop a fire. There's too much intensity there for the resources to put a fire out," said Minassian, an instructor in the fire science associate degree program at Hawai'i Community College in Hilo.

MISCONCEPTION

The red flag system also gives awareness to the public, he said. "A lot of people think that it's Hawai'i, and we have a lot of humidity and rain, so we don't have a fire problem out here. We do," Minassian said. "Hawai'i has a year-round fire season. In some drought years, January and February can be extremely dry months."

The red flag watch and warning system has been in effect on the Mainland for several years, but because relative humidity and other conditions are so different in Hawai'i, a unique set of criteria had to be established for the Islands, according to Ray Tanabe, warning coordination meteorologist with the National Weather Service.

"The criteria set on the Mainland didn't work for Hawai'i. They have relative humidity of 10 and 15 percent and that never happens here," Tanabe said.

Weather service officials worked with University of Hawai'i scientists and local firefighting agencies to devise "a more realistic criteria that wouldn't trigger too many events," he said. "We wanted to limit it to extreme cases."

Officials expect there may be four or five days a year when the fire watches or warnings are warranted.