As of 10 a.m. Friday, the tropical depression was about 290 km to the east of Da Nang and Binh Dinh Province, according to the National Center for Hydro-Meteorological Forecasting. Its maximum wind speed was 50 kph.
Within the next 12 hours, the tropical depression would move west at about 30 kph, before making landfall in central Vietnam, then devolving into a low-pressure area over southern Laos.
By 10 p.m. Friday, the low-pressure area would be above the mountainous area of central Vietnam, with a maximum wind speed of 40 kph.
Rough seas and strong winds should be expected in the East Sea, internationally known as the South China Sea, within the next 24 hours.
Central Vietnam should expect particularly heavy rain from now until Wednesday next week, according to the center. Ha Tinh, Quang Binh and southern Nghe An should expect a total rainfall of up to 900 mm during the period, while Quang Tri, Thua Thien-Hue and northern Nghe An should expect up to 500 mm.
Da Nang and its neighbor Quang Nam Province, home to popular ancient town Hoi An, should expect rainfall of up to 500 mm, while regions between Quang Ngai and Phu Yen should expect levels of up to 350 mm.
The Central Highlands should also expect heavy rain until Sunday, with rainfall of up to 250 mm.
Rains are expected to persist in central Vietnam even after Wednesday, the center noted.
Rainfall of 180 mm a day is considered heavy.
Since last week, central Vietnam has been hit by torrential rains, floods and landslides after a cold spell came in contact with tropical turbulence.
On Sunday, Storm Linfa intensified from the turbulence and made landfall over Quang Nam and Quang Ngai. The next day, Storm Nangka hit the coast between northern Thai Binh and central Thanh Hoa provinces.
At least 56 people have been killed, including two people killed when a landslide buried a group of workers at a hydropower plant in Thua Thien Hue Province and 13 others killed by another landslide while coming to rescue the workers.
Thousands of homes in the region have been flooded.
Natural disasters, mostly floods and landslides triggered by storms, killed 132 people and injured 207 last year.