Late on October 13, Tropical Storm Megi became quasi-stationary, but a mid-latitude trough moving from the west caused the storm to resume a northwestward track.Throughout the morning of October 14, a central dense overcast developed over the center of Megi, allowing for intensification. According to data from a hurricane hunteraircraft, the system had attained winds just below typhoon status and the barometric pressure had decreased to 986 mbar (hPa; 29.11 inHg) at 0436 UTC. Later that day, an eye appeared on satellite imagery, resulting in the JTWC upgrading Megi to a minimal typhoon.
Megi progressed northwestward around the periphery of the subtropical ridge, strengthening to a category three typhoon on October 16. Later in the day, the storm turned westward, and strengthened to a category five on the SSHS. Megi, given the PASAGA name of "Juan", made landfall in Isabela Province in the Philippines on the morning of October 18. The typhoon weakened to a category two after traversing Luzon but rapidly regained strength over SST of 30 °C (86 °F) in the South China Sea, strengthening back to a category four on October 19. Megi slowed in forward speed due to the arrival of another trough over the South China Sea extending over the Taiwan Strait and breaking the ridge, turning the typhoon northwest, then north-northeast.
Typhoon Megi weakened to a category three on October 20 as wind shear started to increase, but significantly increased its eye diameter. On October 22, Typhoon Megi weakened to a category two, later a category one by colder SST. Megi lost its eyewall structure and weakened to a severe tropical storm in Taiwan Strait, made landfall inZhangpu County, Zhangzhou, Fujian province, China, and later weakened to a tropical storm on October 23. Early on October 24, it further dissipated to a tropical depression before dissipating completely, several hours later.
Track map of Typhoon Megi of the 2010 Pacific typhoon season. The points show the location of the storm at 6-hour intervals. The colour represents the storm's maximum sustained wind speeds as classified in the Saffir-Simpson Hurricane Scale (see below), and the shape of the data points represent the nature of the storm, according to the legend below.