Typhoon Tip, known in the Philippines as Typhoon Warling (international designation: T7920, JTWC designation: 23W) was the biggest and strongest known tropical cyclone on record. It was the 19th tropical storm and 12th typhoon of the 1979 Pacific typhoon season. The typhoon formed out of a disturbance in a monsoon trough on October 4 near Pohnpei. At first, a tropical storm to the northwest prevented Tip from strengthening, but after it moved further north, the storm was able to gain more strength. After passing near Guam, it strengthened quickly and reached its highest winds of 305 km/h (190 mph) and a worldwide record low barometric pressure of 870 mbar (hPa, 25.69 inHg) on October 12. At its peak strength, it was also the biggest tropical cyclone on record, with a diameter of 2,220 km (1,380 mi). Tip slowly weakened as it kept moving towards the west-northwest, and later turned to the northeast. Tip made landfall on southern Japan on October 19, and became an extratropical cyclone shortly thereafter.