 The initial tropical disturbance formed near Majuro on September 15 . The system moved west @-@ northwest , becoming a tropical depression on September 18 and a tropical storm on September 19 . Thirteen perished on a fishing vessel passing by Pagan as Ben passed nearby . Ben turned north @-@ northwest for a day and a half , moving around an upper level cyclone in its vicinity , before resuming a west @-@ northwest track on September 20 . Vertical wind shear , caused by strong north @-@ northeast winds aloft , weakened Ben to minimal tropical storm intensity by September 21 . Ben entered a more favourable environment , achieving typhoon intensity on September 23 before rounding the southwest portion of the subtropical ridge . Ben recurved to the northeast on September 26 , moving well to the east of Japan , as vertical wind shear increased due to strengthening winds aloft from the southwest . Ben subsequently weakened back into a tropical storm on September 30 before transitioning into an extratropical cyclone later that day . 
