MANILA, Philippines — As "Carina" intensified into a severe tropical storm, Signal No. 1 has been raised over some areas in extreme Northern Luzon, the Philippine Atmospheric Geophysical and Astronomical Services Administration (Pagasa) said on Monday.

Affected are the eastern portion of mainland Cagayan (Santa Ana, Gattaran, Baggao, Peñablanca, Lal-Lo and Gonzaga) and the northeastern portion of Isabela (Divilacan, Palanan and Maconacon) in Luzon, said weather specialist Rhea Torres.

Citing the agency's data, Torres said the center of the eye of the storm was estimated at 420 kilometers east of Tuguegarao City, Cagayan.

Moving westward slowly, the severe tropical storm has maximum sustained winds of 100 kilometers per hour (kph) near the center and gustiness of up to 125kph.

Carina will likely further intensify into a typhoon before it exits the Philippine Area of Responsibility either Wednesday night or early Thursday morning, the state-run weather agency said.

Torres said the severe tropical storm remained far from the Philippine landmass which would mean that it would not make landfall during the forecast period.

"But Carina is forecast to steadily intensify over the next four days due to the favorable environment," the Pagasa forecaster said.

Being enhanced by the storm, the southwest monsoon locally known as "habagat" would bring moderate to intense rainfall particularly over various localities in the western portion of Luzon, including Metro Manila, until Wednesday, according to the state weather bureau.