High Quality Content by WIKIPEDIA articles! The 1991 North Indian Ocean Cyclone season was the period in which tropical cyclones formed to the north of the equator in the Indian ocean. During the season tropical cyclones were monitored by the India Meteorological Department (IMD) and the Joint Typhoon Warning Center. The IMD assigned all depressions that it monitored with BOB followed by a number in numerical order. The JTWC also assigned a number and either the letter A or B depending on where the depression was when the first advisory was issued.