Typhoon Joan of October 1997 was the longest-lasting super typhoon at the time, maintaining 1-minute maximum sustained winds of at least 240 km/h (150 mph) for 4.5 days. Joan, concurrently with Typhoon Ivan to its west, also became the strongest typhoons at the same time in the northwest Pacific Ocean. The 25th named storm during the active 1997 Pacific typhoon season, Joan developed from the same trough as Typhoon Ivan on October 11. It moved northwestward and later to the west, undergoing explosive deepening to its peak intensity on October 15. One typhoon warning agency estimated that Joan was among the strongest storms on record in the basin, and that Ivan and Joan marked the first occurrence of simultaneous super typhoons. While near peak intensity, Joan passed between Anatahan and Sa