Tropical Storm Matmo formed over the South China Sea east of Vietnam on Tuesday. At 5:00 p.m. EDT on Tuesday the center of Tropical Storm Matmo was located at latitude 12.7°N and longitude 112.2°E which put it about 60 miles (260 km) east of Dai Lanh, Vietnam. Matmo was moving toward the west at 16 m.p.h. (26 km/h). The maximum sustained wind speed was 45 m.p.h. (75 km/h) and there were wind gusts to 60 m.p.h. (95 km/h). The minimum surface pressure was 998 mb.
More thunderstorms developed near the center of a low pressure system over the South China Sea east of Vietnam on Tuesday and the Japan Meteorological Agency designated the system as Tropical Storm Matmo. The circulation around Tropical Storm Matmo was still organizing. Thunderstorms were forming around the center of circulation. Bands of showers and thunderstorms were developing in the northern and western parts of the tropical storm. Bands in the eastern and southern parts of the circulation consisted primarily of showers and lower clouds. Storms near the center of circulation were beginning to generate upper level divergence.
Tropical Storm Matmo will move through an environment favorable for intensification during the next 12 to 18 hours. Matmo will move over water where the Sea Surface Temperature is near 29°C. It will move under the west part of an upper level ridge where the winds are weaker and where there is less vertical wind shear. Tropical Storm Matmo could strengthen during the next 12 hours. Matmo will near the coast of Vietnam in about 12 hours and it will start to weaken when the center moves over land.
Tropical Storm Matmo will move south of a ridge of high pressure over the Western North Pacific Ocean. The ridge will steer Matmo toward the west. On its anticipated track Tropical Storm Matmo could make landfall on the coast of Vietnam between Dai Lanh and Quy Nhon in 12 to 18 hours. Matmo will bring gusty winds to the coastal regions of southern Vietnam. Tropical Storm Matmo could also drop heavy rain over parts of southern Vietnam, Cambodia, southern Laos and eastern Thailand. Heavy rain could cause floods in some locations.