The auto industry disruptions triggered by the disaster in Tohoku are about to get worse.

In the weeks ahead, car buyers will have difficulty finding the model they want in certain colors, thousands of auto plant workers will likely be told to stay home, and companies such as Toyota Motor Corp., Honda Motor Co. and others will lose billions of dollars in revenue. More than two weeks since the natural disaster, inventories of crucial car supplies — from computer chips to paint pigments — are dwindling fast as Japanese factories that make them struggle to restart.

Because parts and supplies are shipped by sea, the real drop-off has yet to be felt by factories in the U.S., Europe and Asia. That will come by the middle of April.