Tropical Storm Nanmadol formed southeast of Taiwan on Saturday. At 8:00 p.m. EDT on Saturday the center of Tropical Storm Nanmadol was located at latitude 20.7°N and longitude 127.1°E which put it about 475 miles (765 km) southeast of Taipei, Taiwan. Nanmadol was moving toward the northwest at 24 m.p.h. (35 km/h). The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h). The minimum surface pressure was 1002 mb.
A center of circulation consolidated rapidly on Saturday in an area of thunderstorms southeast of Taiwan. A primary band of showers and thunderstorms wrapped around the northern and western side of the circulation. Other bands of showers and thunderstorms developed in the northern half of the circulation. The thunderstorms near the center began to generate upper level divergence which pumped out mass to the north of the tropical storm.
Tropical Storm Nanmadol will move through an area favorable for intensification during the next 24 hours. Nanmadol will move over water where the Sea Surface Temperature is near 30°C. An upper level ridge northeast of Nanmadol is producing southeasterly winds which are blowing toward the top of the tropical storm, but there is little vertical wind shear. Tropical Storm Nanmadol is likely to intensify on Sunday. When Nanmadol moves farther north, it will move over cooler water and it will be effected by the upper level westerly winds in the middle latitudes. Cooler water and more vertical wind shear will cause Nanmadol to start to weaken at that time.
Tropical Storm Nanmadol is moving around the western end of a subtropical ridge which is steering it quickly toward the northwest. Nanmadol will move in a general north-northwesterly direction on Sunday. It will turn toward the northeast in 24 to 36 hours when it begins to be steered by the mid-latitude westerlies. On its anticipated track Tropical Storm Nanmadol could approach the southernmost Ryukyu Islands including Ishigaki Jima in about 12 hours. The center is expected to pass west of Okinawa. Tropical Storm Nanmadol could approach Kyushu in a couple of days. An intensifying Tropical Storm Nanmadol will bring gusty winds and locally heavy rain to the southernmost Ryukyu Islands.