Tropical Storm Nanmadol brought wind and rain to the southern Ryukyu Islands on Sunday. At 11:00 a.m. EDT on Sunday the center of Tropical Storm Nanmadol was located at latitude 24.4°N and longitude 124.7°E which put it about 40 miles (65 km) east of Ishigaki, Japan. Nanmadol was moving toward the north-northwest at 21 m.p.h. (34 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 998 mb.
The core of Tropical Storm Nanmadol continued to organize on Sunday. A ring of thunderstorms wrapped tightly around the center of circulation. Additional bands of showers and thunderstorms formed outside the core. Thunderstorms were beginning to generate more upper level divergence which was pumping out mass in all directions. The circulation of Tropical Storm Nanmadol was fairly small. Winds to tropical storm force only extend out about 70 miles (110 km) from the center.
Tropical Storm Nanmadol will be in an environment that is very favorable for intensification for about another 24 hours. Nanmadol will be moving over water where the Sea Surface Temperature (SST) is near 29°C. The circulation of Tropical Storm Nanmadol is underneath the center of an upper level ridge and the upper level winds are very weak. Warm SSTs and almost no vertical wind shear will permit Tropical Storm Nanmadol to intensify during the next day and there could be a period of rapid intensification. Nanmadol could strengthen into a typhoon before it reaches a less favorable environment. The tropical storm will move over cooler SSTs and it will move into an area of stronger upper level westerly winds in a couple of days. Nanmadol will begin to weaken when that happens.
Tropical Storm Nanmadol is moving around the western end of a subtropical ridge which is steering it toward the north. A general northward motion is expected to continue for about another 24 hours. Nanmadol will reach the westerly winds in the middle latitudes in about a day and those winds will turn it toward the northeast. On its anticipated track the center of Tropical Storm Nanmadol will pass west of Okinawa. Nanmadol could approach Kyushu in about 36 hours. Tropical Storm Nanmadol will continue to cause gusty winds and locally heavy rain over the southern Ryukyu Islands for another 12 to 24 hours.