A tropical disturbance that may become Tropical Storm Mangkhut is currently in the South China Sea.
This system is heading west-northwest over very warm waters, so some strengthening is likely. However, a moderate amount of wind shear, which is changing wind directions and speed in the atmosphere, will likely not allow for explosive development. Weak or no wind shear, when combined with other atmospheric conditions, will allow a tropical system to develop quickly.
This system is on a path similar to the last tropical system, Jebi, just a tad farther south of Jebi's track. Thus, Hanoi Island and northern Vietnam that saw flash floods from Jebi will see the weather deteriorate yet again Wednesday afternoon through Thursday local time.
Heavy rainfall (5-10 inches, locally a foot or more in the mountains) will be the main impact once again. Flooding and mudslides are a major concern, since the ground is already saturated from Jebi's rain.
Hanoi, the capital of Vietnam, will be the biggest city impacted and will likely see more rain than the area experienced during Jebi.