Tropical Storm Nari developed south of Japan on Thursday night. The Japan Meteorological Agency designated a low pressure system south of Honshu as Tropical Storm Nari when the maximum sustained wind speed reached 40 m.p.h. (65 km/h). At 11:00 p.m. EDT on Thursday the center of Tropical Storm Nari was located at latitude 30.2°N and longitude 136.9°E which put it about 350 miles (565 km) south of Nagoya, Japan. Nari was moving toward the north at 14 m.p.h. (22 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 1000 mb.
The circulation around Tropical Storm Nari exhibited more of a hybrid structure than the structure of a pure tropical cyclone. Tropical Storm Nari developed when an upper level low pressure system stalled south of the Japan. A surface circulation formed beneath the upper low and then more thunderstorms formed closer to the center of circulation. The original upper level low was located southwest of the surface low on Thursday night. The upper level low was producing southwesterly winds which were blowing across the surface low. Those winds were creating vertical wind shear. The circulation around Tropical Storm Nari showed evidence of the effect of that wind shear. The stronger thunderstorms were in a band that curved around north and west of the center of circulation. Bands south and east of the center consisted primarily of showers and lower clouds. The wind field around Tropical Storm Nari was also asymmetric. Winds to tropical storm force extended out about 115 miles (185 km) to the east of the center of circulation, but only extended out about 60 miles (95 km) to the west of the center.
Tropical Storm Nari will move through an environment only marginally favorable for intensification. Nari will move over water where the Sea Surface Temperature is near 28°C. The upper low will continue to cause vertical wind shear, which will inhibit intensification. The upper low will also pull some drier air around the southern side of the circulation. Nari could strengthen a little during the next 24 hours if more thunderstorms develop closer to the center of circulation. Tropical Storm Nari will move under stronger westerly winds in about a day or so. Those winds will cause more vertical wind shear and they should prevent further intensification.
Tropical Storm Nari will be steered by the interaction of the upper low and a subtropical ridge over the western North Pacific Ocean. Those two features are likely to steer Nari toward the north during the next 24 hours. On its anticipated track Tropical Storm Nari could approach the coast of Honshu near Nagoya in about 24 hours. Nari will move more toward the east when it reaches the stronger westerly winds in a day or so. Tropical Storm Nari could bring gusty winds and locally heavy rain to central Honshu on Saturday.