The tropical cyclone formerly named Bising has developed into a severe tropical storm on Saturday night and is expected to reach typhoon category on Sunday.

According to its tropical cyclone advisory issued at 11 p.m., PAGASA raised Gale Warning No. 1 and warned of very rough seas of up to 4.5 meters in the seaboard of Batanes and the western seaboard of the Babuyan Islands.

“Sea travel is risky for all types of tonnage of vessels. All mariners must remain in port or, if underway, seek shelter or safe harbor as soon as possible until winds and waves subside,” the weather bureau said. 

Up to rough seas of up to 3.5 meters are expected in the western seaboard of Ilocos Norte, and mariners of small seacraft, including all types of motor bancas, are advised not to venture out to sea under these conditions, especially if inexperienced or operating ill-equipped vessels. 

Up to moderate seas of up to 2.5 meters are expected in the northwestern seaboard of Ilocos Sur and the remaining seaboards of Ilocos Norte; of up to two meters in the western seaboards of La Union, Pangasinan, and Zambales, and the remaining seaboard of Ilocos Sur.

“Mariners of motorbancas and similarly-sized vessels are advised to take precautionary measures while venturing out to sea and, if possible, avoid navigation under these conditions,” PAGASA said.

The severe tropical storm, now known as Danas, was spotted at 10 p.m. to be 410 km west of Basco, Batanes, outside the Philippine Area of Responsibility with maximum sustained winds of 110 kph near the center, and gustiness of up to 135 kph.

It was moving northeastward at 10 kph with strong to storm-force winds extending outwards up to 330 km from the center.

The severe tropical storm now known as Danas outside the PAR will continue moving generally northeastward in the next 72 hours. It will briefly pass the northwestern boundary of PAR between Sunday evening and Monday morning.

Danas intensified into a severe tropical storm at 8:00 p.m. on Saturday.

It is forecast to steadily intensify and may reach typhoon category by Sunday.