Typhoon Mireille, known in the Philippines as Typhoon Rosing, was the costliest typhoon on record, until it was surpassed by Typhoon Hagibis in 2019 (when not adjusted for inflation). Striking Japan in September 1991, it became the 20th named storm of the 1991 Pacific typhoon season, Mireille formed on September 13 from the monsoon trough near the Marshall Islands. It moved westward for several days as a small system, steered by the subtropical ridge to the north. The storm rapidly intensified to typhoon status on September 16, and several days later passed north of Saipan in the Northern Marianas Islands. Mireille intensified further after deleterious effects from a nearby tropical storm subsided. On September 22, the American-based Joint Typhoon Warning Center (JTWC) estimated maximum 1-