A powerful typhoon struck Japans main island on Wednesday, stranding thousands of commuters in Tokyo and threatening to pour heavy rain on the stricken Fukushima Daiichi nuclear plant in the nations tsunami-ravaged northeast. Evacuation advisories went out to more than 1 million people across the main island of Honshu as torrential downpours caused flash floods in low-lying areas. As of Wednesday evening, five people had been found dead and four others were missing, according to Japans national broadcaster, N.H.K. The storm, called Typhoon Roke, directly hit greater Tokyo, briefly shutting down Japans commercial and political center. Strong winds and rains brought most subways and commuter trains to at least a temporary halt, stranding tens of thousands at stations. Bullet train and airline service was canceled.