Regional ozone readings soared again Saturday, but regulators did not issue a health alert because their forecasts failed to predict the rise.

"Sometimes we're wrong," said Christopher Dann, spokesman for the Colorado Department of Public Health and Environment. "We missed on Saturday. We weren't expecting anything above 75 parts per billion (the level at which alerts are issued), let alone something above 80 ppb."

Readings exceeded safety standards at five monitoring stations on Saturday near Golden, Rocky Flats, Chatfield Reservoir, South Boulder Creek and west of Fort Collins.

Despite the failure over the weekend, Dann said the agency's analyses of fast-changing ozone conditions are right "nine out of 10 times."

Jeremy Nichols, executive director of Rocky Mountain Clean Air Action, said the state has to do better, given that in July it officially fell out of compliance with federal clean air rules governing ozone.

Ozone alerts are used to warn the young and elderly, as well as those with respiratory diseases, to limit exposure and exercise, among other things. Forty-four alerts have already been issued this summer.

"The alerts are critical to some people," Nichols said. "The state can't afford to drop the ball."

Despite the lack of an alert, Dann said the health department did update its website and urged sensitive groups to take caution after Saturday's readings came in.

But the problem illustrates the complexity of regulating and tracking ozone, Dann said. Ground-level ozone is created when a mix of emissions from cars, refineries, power plants and other things combine and are exposed to sunlight and high temperatures. But almost as quickly as they rise, ozone levels can fall to non-dangerous levels when weather conditions change, Dann said.

One reason he believes forecasters missed the mark this past weekend is that strong winds they thought would disperse the ozone failed to do so.

The latest ozone problems come as the metro area is struggling to find a way to make next summer less troublesome than this summer has been, and as it seeks a way to meet tougher federal ozone standards now being crafted.

smithj@RockyMountainNews.com or 303-954-5474