Mainland weather forecasters on Saturday said a tropical storm threatening to hit Shanghai was now very likely to miss the financial hub, but warned of wind gusts and downpours in eastern industrial cities as it churned northwards off the coast.

Songda was 450km east of Qidong city, Jiangsu province, just north of Shanghai on Saturday morning, and was expected to move on a northwest path at 20kph, the National Meteorological Center said.

Gales in coastal areas from the northeastern part of the heavily industrialised Zhejiang province to Shanghai and the southern part of Jiangsu province were forecast to reach magnitudes of 6-7, a level that will rock power lines and impede pedestrian traffic.

The winds in some parts of the sea could be stronger, the forecasters said, in a region known for busy shipping lanes.

Songda, named after a river in Vietnam, is also expected to bring moderate to heavy rains to those areas from Saturday to Sunday, it added.

The storm is expected to weaken on Monday, turning into a tropical depression near the Korean Peninsula. (Reuters)