 A persistent surface circulation developed on September 28 east of Ponape . On October 1 , the convection began to organize as the upper level environment improved and the system became a tropical depression that night . Moving west @-@ northwest , Mac passed nearby Guam as a strong tropical storm on the morning of October 3 . Heavy rains and high winds in the southern part of the island led to US $ 1 @.@ 5 million ( 1982 dollars ) in damage . Continuing to intensify rapidly , Mac soon became a typhoon , and by October 5 had become a super typhoon . Recurving northwest , the storm travelled into a weakness in the subtropical ridge , accelerating north @-@ northeast as it passed the ridge axis by October 6 . Acceleration into the main belt of the Westerlies continued while the cyclone slowly weakened , and Mac evolved into a typhoon @-@ strength extratropical cyclone on the afternoon of October 9 . 
