The positive trend sweeping the nation’s job market bypassed Hawaii again in December with the state’s unemployment rate rising to its highest level in 15 months.

The seasonally adjusted unemployment rate in the state rose to 6.6 percent in December from 6.5 percent in November, the highest level since August 2010, according to a report released Tuesday by the state Department of Labor and Industrial Relations.

The rate has been climbing since hitting a cyclical low of 6 percent in June. Meanwhile, the national rate has been going the other way, falling to 8.5 percent in December from 9.1 percent in June.

Hawaii was one of only three states in which the unemployment rate was higher in December than in November.

And Hawaii’s rate is on track to rise again in January because of the shutdown of Hawaii Medical Center’s two hospitals on Oahu and subsequent layoffs, according to researchers at the University of Hawaii Economic Research Organization. The medical center laid off nearly 1,000 workers in late December and early January.

The number of unemployed rose by a net 400 in December to 41,900, not including the medical center’s layoffs.

The volatility in the unemployment rate in the past year reflects the uneven nature of the state’s economic recovery, UHERO said. After a surge in visitor arrivals boosted the economy in late 2010 and early in 2011, the pace of growth slowed in subsequent months.

The earthquake and tsunami in Japan in March, along with higher oil prices and airline fares, weighed on the visitor industry in the spring and summer, said Carl Bonham, UHERO executive director.

"It was that weakness in the summer that has kept us from really seeing the kind of recovery we would have liked," Bonham said.

The statewide unemployment numbers are adjusted for seasonal variations, such as an increase in hiring by retailers for the holiday season. The seasonal adjustment is intended to make it easier to compare monthly data and identify underlying economic trends.

Unemployment data for the counties are not seasonally adjusted, which accounted for a drop in the rate in each of them despite the rise in unemployment statewide. In Honolulu County the rate fell to 5.3 percent in December from 5.7 percent in November. The rate fell to 9.2 percent from 9.6 percent in Hawaii County, to 8.3 percent from 8.8 percent in Kauai County and to 7.3 percent from 7.7 percent in Maui County.

For all of 2011 the statewide seasonally adjusted rate averaged 6.3 percent, down from 6.6 percent in 2010.

The unemployment rate is largely derived from a random survey of households.

A separate survey of businesses showed that the number of nonfarm payroll jobs averaged 594,000 in 2011, up 7,100 from 2010. It was the first annual increase in nonfarm payroll jobs since 2007, according to the U.S. Bureau of Labor Statistics.