Japanese officials hope the achievement, in a test conducted off Japan's central Pacific coast, will win their resource-poor nation a measure of energy independence.

CNN: Japan warms to 'fire ice' potential

Tropical storm warnings were in effect for the Pacific coast of Central America from Costa Rica to El Salvador.

CNN: Few coast dwellers ready for a hurricane, poll shows

On Thursday, Tropical Storm Alma, the first one of the year in the eastern Pacific, formed near the west coast of Central America, according to the National Weather Service.

CNN: Few coast dwellers ready for a hurricane, poll shows