In the Indian Ocean north of the equator, tropical cyclones can form throughout the year on either side of India, although most frequently between April and June, and between October and December. Sub-basins The North Indian Ocean is the least active basin, contributing only seven percent of the world's tropical cyclones. However the basin has produced some of the deadliest cyclones in the world, since they strike over very densely populated areas. The Regional Specialized Meteorological Centre (RSMC) is the India Meteorological Department (IMD) and it is responsible to monitor the basin, issues warning and name the storms. The basin is divided into two sub-basins the Bay of Bengal and the Arabian Sea. The Bay of Bengal, located in the northeast of the Indian Ocean. The basin is abbreviated BOB by the India Meteorological Department (IMD). The United States's Joint Typhoon Warning Center unofficially designates as B to classify storms formed in the Bay of Bengal. The Bay of Bengal's coast is shared among India, Bangladesh, Myanmar, Sri Lanka and western part of Thailand. This sub-basin is the most active and produces some of the deadliest cyclones of all time. The most intense cyclone in the bay was the 1999 Odisha cyclone. The Arabian Sea is a sea located in the northwest of the Indian Ocean. Tropical cyclones in the basin are abbreviated ARB by the India Meteorological Department (IMD). The United States's Joint Typhoon Warning Center unofficially designates as A to classify storms formed in the Arabian Sea. The Arabian Sea's coast is shared among India, Yemen, Oman, UAE, Iran, Pakistan, Sri Lanka, Maldives and Somalia. Monsoons are characteristic of the Arabian Sea and responsible for the yearly cycling of its waters. In summer, strong winds blow from the southwest to the northeast, bringing rain to the Indian subcontinent. Cyclones are rare in the Arabian Sea, but the basin can produce strong tropical cyclones. Cyclone Gonu was the strongest and the costliest recorded tropical cyclone in the basin. History of the basin The systematic scientific studies of tropical systems in the Bay of Bengal and Arabian Sea was started during the 19th century by Henry Piddington. Piddington utilised meteorological logs of vessels that navigated the seas and published a series of memoirs, in the Journal of the Asiatic Society of Bengal between 1839 and 1858. These memoirs gave accounts and tracks of individual storms in the Bay of Bengal