[2] The system increased in size and the convection organized further, prompting the Joint Typhoon Warning Center (JTWC)[nb 2] to initiate advisories on Tropical Depression 28W on October 13.

Early in the storm's duration, neither the JTWC nor most tropical cyclone forecast models anticipated significant strengthening beyond 1-minute winds of 185 km/h (115 mph); this was due to a fairly weak monsoon trough and normal atmospheric pressures in the region.

[5] On October 17, the JTWC estimated 1-minute peak winds of 295 km/h (183 mph), making Joan a super typhoon, the ninth of the season.

[8] On October 24, the typhoon turned to the northeast while losing tropical characteristics,[2] and that day the JMA ceased tracking Joan.

[2] Former Typhoon Joan merged with a cold front and re-intensified while approaching the Aleutian Islands, and was noted by the Mariners Weather Log as an extratropical storm on October 26.

[9] While passing about 80 km (50 mi) of Saipan, Joan produced wind gusts of 157 km/h (98 mph),[2] strong enough to destroy 37 homes and damage the roofs of several other houses.

Residents were slow to prepare for the typhoon, and as a result, three people were injured while boarding up their house during the arrival of the strong winds.

The passage of Joan left the entire island of Saipan without power,[10] although electrical crews quickly worked to restore the outages.

[13] While passing between Saipan and Anatahan in the NMI, the eye of Joan was visible by NEXRAD from Guam, despite being 285 km (177 mi) north of the island.

[2] An outer rainband moved across the island, producing 56 mm (2.2 in) of rainfall at Anderson Air Force Base and a wind gust of 66 km/h (41 mph) at the National Weather Service office in Tiyan.