MANILA (UPDATE) - Tropical storm Siony maintained its strength while tropical storm Rolly nears the western limits of the Philippine Area of Responsibility, the state weather bureau said Monday night.

Siony (international name Atsani) was last spotted 595 kilometers east of Calayan, Cagayan as of 4 a.m., packing maximum winds of 75 km per hour and gusts of up to 90 kph, PAGASA weather forecaster Rob Guile said.

It is moving northward slowly and is forecast to gradually enter into an almost stationary state within the next 36 hours, PAGASA said.

The storm is forecast to hit land in extreme northern Luzon on Friday but its track may still change, according to Guile.

Meanwhile, Rolly, the world's strongest storm so far this year and a super typhoon at its peak, was last estimated 450 kilometers west of Iba, Zambales, packing maximum winds of 65 kph near the center and gusts of up to 80 kph.

It is moving west at 15 kph and is expected to exit PAR by Tuesday morning.

Between Monday night to Tuesday morning, light to moderate with at times heavy rains may be experienced over Batanes, Apayao, Cagayan, and Isabela due to the combined effects of the northeasterlies and the trough of Siony, PAGASA said.

Though having no direct effect on the country, the northeasterlies enhanced by Rolly and Siony will bring strong to near gale conditions with higher gusts over Batanes, Babuyan Islands, and the northern portions of Cagayan and Ilocos Norte, PAGASA added.

The combined effects of the two storms and the enhanced northeasterlies will bring rough to very rough seas, with waves between 2.8 to 4.5 meters, over the entire seaboards of Northern Luzon and the western seaboard of Central Luzon. Sea travel is risky over these waters, especially for those using small seacrafts.

Moderate to rough seas, with waves between 1.5 to 2.5 meters, will also be experienced over the remaining seaboards of Luzon and the eastern seaboards of Visayas and Mindanao.

The Philippines is currently experiencing the La Niña phenomenon, which brings more rain and cooler weather, PAGASA earlier said.

The country is battered by roughly 20 tropical cyclones annually, with Siony being the 19th this year.

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