Tropical storm "Fabian" (international name "In-fa") has slightly intensified and will likely reach the severe tropical storm category within 12 hours, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) said on Monday morning, July 19.
The center of Fabian was estimated at 1,090 kilometers (km) east-northeast of extreme northern Luzon around 4 a.m.
It has maximum sustained winds of 85 kilometers per hour (kph) near the center and gustiness of up to 105 kph while moving north-northwest at 10 kph.
PAGASA said Fabian may become a severe tropical storm within the day and into a typhoon by Tuesday evening, July 20, or Wednesday morning, July 21.
Fabian and a tropical depression located at 900 km west of extreme northern Luzon, or outside the Philippine area of responsibility (PAR) will continue to enhance the southwest monsoon or "habagat" in the coming days.
The habagat may bring monsoon rains over Ilocos Norte, Ilocos Sur, La Union, Pangasinan, Zambales, Bataan, Occidental Mindoro, and Palawan in the next 24 hours.
Metro Manila, Cavite, Laguna, Batangas, Rizal, Quezon, Aklan, Antique, Capiz, Guimaras, Iloilo, and Negros Occidental may also have scattered rains showers and thunderstorms.
Meanwhile, Mindanao and the rest of Visayas will have partly cloudy to cloudy skies with rain showers or thunderstorms.
PAGASA warned against possible flash floods or rain-induced landslides during heavy or prolonged rainfall, particularly in areas that are highly susceptible to these hazards.
Residents and disaster managers in Batanes and Babuyan Islands were also advised to continuously monitor PAGASA's tropical cyclone bulletins as any further southward shift in Fabian's track may result in the hoisting of tropical cyclone wind signal number 1 over these areas.
"The tropical cyclone will maintain a north-northwestward or northwestward (track) before turning west-northwestward tomorrow (July 20). The tropical cyclone may exit the Philippine area of responsibility tomorrow evening or on Wednesday early morning," PAGASA said.
However, it noted that a southward shift in the orientation of the track forecasts has been observed in the past 24 hours.
"If the trend continues, there is an increasing possibility that Fabian will either re-enter the PAR or exit the PAR much later than the current forecast suggests," PAGASA pointed out.