 In the middle of September , the monsoon trough spawned a rapidly organizing disturbance east @-@ northeast of Luzon , with weak wind shear and favorable conditions . On September 16 , the JMA classified it as a tropical depression , and the JTWC initiated advisories the next day . The system moved to the northwest due to the subtropical ridge to the northeast and later to the north . On September 18 , the JMA upgraded the depression to Tropical Storm Choi @-@ wan , the same day that PAGASA classified it as Tropical Storm Roskas . An eastward @-@ moving trough turned the storm to the northeast , bringing the track over Okinawa and Amami Ōshima on September 19 . Choi @-@ wan continued gradually intensifying , becoming a typhoon on September 20 to the southeast of Japan . That day , the JMA estimated peak winds of 130 km / h ( 80 mph ) , and the JTWC estimated peak 1 minute winds of 185 km / h ( 115 mph ) on September 21 , after Choi @-@ wan developed a well @-@ defined eye . The typhoon weakened due to increasing wind shear , deteriorating to severe tropical storm status on September 22 before JMA declared it extratropical on September 23 . The remnants of Choi @-@ wan continued to the northeast , exited the basin on September 24 , and eventually struck southern Alaska on September 25 . 
 In the middle of September , the monsoon trough spawned a rapidly organizing disturbance east @-@ northeast of Luzon , with weak wind shear and favorable conditions . On September 16 , the JMA classified it as a tropical depression , and the JTWC<a href='been_done' title='1'><mark></mark></a> initiated advisories the next day . The system moved to the northwest due to the subtropical ridge to the northeast and later to the north . On September 18 , the JMA upgraded the depression to Tropical Storm Choi @-@ wan , the same day <a href='null_relcl' title='2'><mark>that</mark></a>PAGASA classified it as Tropical Storm Roskas . An eastward @-@ moving trough turned the storm to the northeast , bringing the track over Okinawa and Amami Ōshima on September 19 . Choi @-@ wan continued gradually intensifying , becoming a typhoon on September 20 to the southeast of Japan . That day , the JMA<a href='been_done' title='3'><mark></mark></a> estimated peak winds of 130 km / h ( 80 mph ) , and the JTWC estimated peak 1 minute winds of 185 km / h ( 115 mph ) on September 21 , after Choi @-@ wan developed a well @-@ defined eye . The typhoon weakened due to increasing wind shear , deteriorating to severe tropical storm status on September 22 before JMA declared it extratropical on September 23 . The remnants of Choi @-@ wan continued to the northeast , exited the basin on September 24 , and eventually struck southern Alaska on September 25 . 
In da middle of September , the monsoon trough spawned a rapidly organizing disturbance east @-@ northeast of Luzon , w weak wind shear and favorable conditions . On September 16 , tdaJMA classified it as a tropical depression , and the JTWC done initiated advisories thdaxt day . The system moved to thedarthwest due to the datropical ridge to the northeast and later to the north . On September 18 , the JMA upgraded the depression to Tropical Storm Choi @-@ wan , the sda day PAGASA classified it as Tropical Storm Roskas . An eastward @-@ movin trough turned the stda to the nordaast , bringing the tracdava Okinawa and Amami Ōshima on September 19 . Choi @-@ wan continued gradually intensifying , becoming a typhoon on September 20 to the southdat of Japan . That day , the JMA done estimated peak winds of 130 km / h ( 80 mph ) , and the JTWC estimated peak 1 minute winds of 185 km / h ( 115 mph ) on September 21 , after Choi @-@ wan developed a well @-@ defined eye . The typhoodaeakened due to increasing wind shear , deteriorating to severe tropical storm status on September 22 before JMA declared it extratropical on September 23 . The remnantdaf Choi @-@ wan continued to the northeast , exited the basin on September 24 , and eventually struck southern Alaska on September 25 .