The number of autos sold in Hawaii fell sharply in the third quarter, setting the stage for an unexpected decline in sales for the full year, the Hawaii Auto Dealers Association reported today.

Dealers statewide sold 7,909 cars and light trucks during the July-through-September period, 15.1 percent fewer than the same period a year earlier, HADA said in its quarterly Hawaii Auto Outlook.

The decline prompted HADA to revise its full-year sales forecast down to 33,500 autos, which would represent a 1.5 percent drop from the 34,019 sold in 2010. HADA in July had forecast a 4.1 percent increase in auto sales this year.

HADA attributed part of the third-quarter drop in sales to a shortage of vehicles made in Japan as a result of factory shutdowns due to the March earthquake and tsunami there. Japanese brands account for 65 percent of the vehicles sold in Hawaii compared to 42 percent nationally.

The dealers group is forecasting auto sales to rebound by 10.4 percent in 2012 as pent-up demand is satisfied.