Tropical Storm Dolphin formed south of Japan on Monday. At 11:00 a.m. EDT on Monday the center of Tropical Storm Dolphin was located at latitude 26.0°N and longitude 135.0°E which put it about 365 miles (590 km) southwest of Tokyo, Japan. Dolphin was moving toward the north-northeast at 5 m.p.h. (8 km/h). The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h). The minimum surface pressure was 996 mb.
A distinct low level center of circulation developed near the southern side of an area of thunderstorms south of Japan on Monday and the Japan Meteorological Agency designated the system as Tropical Storm Dolphin. The circulation around Tropical Storm Dolphin was still organizing. The strongest thunderstorms were occurring in bands in the northern half of the circulation. Bands in the southern half of Dolphin consisted primarily of showers and lower clouds. Storms near the center of circulation generated upper level divergence which pumped mass away to the northeast of the tropical storm. Winds to tropical storm force extended out 125 miles (200 km) from the center.
Tropical Storm Dolphin will move through an environment somewhat favorable for intensification during the next 36 hours. Dolphin will move over water where the Sea Surface Temperature is near 28°C. An upper level trough approaching Japan from the west will produce southwesterly winds which will blow toward the top of Tropical Storm Dolphin. Those winds will cause moderate vertical wind shear and they will inhibit intensification of Dolphin. The shear will limit intensification, but Tropical Storm Dolphin is likely to get stronger during the next 36 hours.
Tropical Storm Dolphin will move around the northwestern part of a subtropical high pressure system over the Western North Pacific Ocean. The high will steer Dolphin toward the north-northeast during the next 24 to 36 hours. Tropical Storm Dolphin will reach the westerly winds in the middle latitudes after that period and those winds will steer Dolphin more toward the northeast during the middle of the week. On its anticipated track Tropical Storm Dolphin could approach the coast of Honshu near Tokyo in about 72 hours.