MANILA -  The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) on Thursday said residents in Central and Southern Luzon and the Visayas should expect occasional to frequent rains after a low pressure area east of Luzon developed into a tropical depression named "Ondoy."

As of 10 a.m, the tropical storm's center was estimated 480 kilometers east of Virac, Catanduanes and is moving west northwest at 11 kph.

It is forecast to reach 450 km east southeast of Casiguran, Aurora by Friday morning.

The weather bureau said Ondoy is expected to enhance the southwest monsoon and bring occasional to frequent rains over Central and Southern Luzon and Visayas. Residents in low lying areas and near mountain slopes are advised to take all the necessary precautionary measures against possible flashfloods and landslides.