LOS ANGELES — The state budget shortfall in California has increased dramatically in the last six months, forcing state officials to assemble a series of new spending cuts that are likely to mean further reductions to schools, health care and other social programs already battered by nearly five years of budget retrenchment, state officials announced on Saturday.

Gov. Jerry Brown, disclosing the development in a video posted on YouTube, said that California’s shortfall was now projected to be $16 billion, up from $9.2 billion in January. Mr. Brown said that he would propose a revised budget on Monday to deal with it.

“We are now facing a $16 billion hole, not the $9 billion we thought in January,” Mr. Brown said. “This means we will have to go much further and make cuts far greater than I asked for at the beginning of the year.”

Mr. Brown disclosed the news in a video that had all the trappings of a campaign announcement. In it, he aggressively accounted for the steps he said he had taken to try to scale back a $26 billion deficit he found upon taking office. And he urged viewers to back an initiative he is putting on the November ballot that would increase sales taxes by 0.25 percent and impose an income tax surcharge on wealthy Californians to try to stave off more cuts.