 An active monsoon trough was south of Guam . By late on September 4 , a surface low was apparent near 11N 130E . Late the next day , it became a tropical depression while moving generally to the west . By the next morning , it had strengthened into a tropical storm . Late on September 8 , the cyclone struck the southern tip of Luzon as a strong tropical storm . Moving through an inland sea route though the archipelago , Irving slightly weakened before turning northwest into the South China Sea . Irving became a compact typhoon while strengthening over open waters . Weakening back into a tropical storm due to land interaction with Hai @-@ nan and mainland China , the system made landfall about 205 kilometres ( 127 mi ) northeast of Hanoi , then rapidly dissipated as it moved inland . 
