Storm Con Son (named after a well-known historical site in Vietnam),is forecast to be off the coast from Quang Ninh province to Hai PhongCity - 21.3 degrees north and 107.9 degrees east - at 1pm on July 17.
Wind gusts of up to 102kmph are likely.
Heavy rain will fall in northern provinces, especially thenorthern highlands, says the centre.
Provinces suchas Ha Giang, Lao Cai and Lang Son have been alerted to possible flashfloods and landslides.
The eye of the storm was at16.5 degrees north and 113.9 degrees east, about 190km from the Hoang Sa(Paracel) Archipelago in the East Sea, at 1pm on July 15.
It was expected to generate rough seas in northern waters withwaves of between 5-7 metres.
The Border Guard HighCommand reports that its personnel have been in contact with almost52,000 vessels and 240,000 fishermen.
But 426fishermen aboard 33 ships from central Quang Ngai province have notsought safety.
The guards have been unable tocontact three vessels from Quang Nam province.
TheCentral Storm, Flood Prevention and Rescue Board met yesterday andAgriculture and Rural Development Minister Cao Duc Phat ordered thesecuring of tourist craft and port cranes to avoid serious damage.
The minister also asked Quang Ngai and Quang Nam provincesto do what ever possible to contact the three ships of Quang NamProvince so the crews could find safety.
Borderguards were also asked to advise the crews of the 33 vessels working indangerous seas to sail south or ask China for shelter if necessary.
Conson is expected to travel north-west at between10-15kmph during the next two days and hit near the border of Viet Namand China.
But it will weaken to a tropicaldepression with strongest gusts of up to 61kmph.
About 10-12 storms were forecast to hit the East Sea this year, two tothree less than previous years, said the National Hydro-meteorologicalForecasting Centre's medium and long-term forecast office meteorologistTran Thi Chuc.
But the number of storms affectingViet Nam directly would be higher - 6-7 - against the average 5-6, shesaid./.