MANILA, Philippines—(UPDATE) Tropical storm "Karen" (international codename: Nuri) strengthened as it moved closer to northern Luzon Monday afternoon, the Philippine Atmospheric Geophysical Astronomical Services Administration (PAGASA) said.

At 4 p.m., the storm, which packs maximum sustained winds of 85 kilometers per hour with gusts of 100 kilometers per hour, was located at 890 kilometers east of Casiguran town, Aurora province, the state weather bureau said.

Moving west at 22 kilometers per hour, the storm was forecast to be at 480 kilometers east southeast of Tuguegarao City by Tuesday afternoon, 140 kilometers north northeast of Tuguegarao by Wednesday afternoon, 260 kilometers west of Basco town, Batanes province by Thursday afternoon, PAGASA said.

Public storm signal number 1 (30-60 kilometer per hour winds) was raised in the provinces of Isabela and Cagayan, it said.

The storm will enhance the southwest monsoon, bringing rains to Southern Luzon, the Visayas, and Mindanao, particularly the western portions, it said.

The rest of the Philippines will continue to experience clear skies at least on Tuesday even if Tropical Storm "Karen" is hovering east of Central Luzon said PAGASA weather branch chief Nathaniel Cruz over the phone Monday.

"People may find it odd to experience consistent rains last week without a storm and have fair weather now that there is already one," he said.

"The public must know that it's the low pressure on South China Sea that is giving us good weather lately," Cruz continued.

Tropical storms pounding Philippine seas usually boost the southwest monsoon, bringing in winds and rains to the country.

The heavy rains that drenched Metro Manila and other areas in Luzon last week was brought about by the monsoon trough, he noted.

The country will experience fine weather conditions in the next 48 hours or until Tropical Storm "Karen" travels close to Cagayan Valley, which by then would usher in winds and rains in Luzon, including Metro Manila, he added.