According to Vietnam's National Centre for Hydro-Meteorological Forecasting (NCHMF), the storm was about 5,000 kilometres east of Luzon Island on Thursday morning, with sustained winds of Beaufort force 17.
Dolphin is the third typhoon to form over the northwestern Pacific this year, following Sinlaku and Bavi. It is forecast to move west-northwest over the next three days before turning west towards eastern China.
Current forecasts show no indication that the storm will enter the East Sea, although its circulation could strengthen winds over the area in the coming days.
The NCHMF said Dolphin is not expected to affect weather conditions over the East Sea through August 4. From around August 5, however, the storm could strengthen southwesterly winds over the southern East Sea as it approaches northern Taiwan.
Between August 6 and 7, southwesterly winds across parts of the northern, central and southern East Sea, including the Paracel and Spratly islands, could reach Beaufort force 6-7, with waves forecast at 3-5 metres, posing hazards to vessels at sea.
The weather agency said it is closely monitoring the storm's development.