Siony maintains strength, may target Cagayan Valley —PAGASA

Tropical Storm Siony maintained its strength late Monday morning as it accelerated west-northwestward over the Philippine Sea, according to PAGASA's latest update.

By Tuesday to Wednesday morning, Siony is expected to slow down "significantly" and "become almost stationary" as it moves toward extreme Northern Luzon.

"Due to the projected erratic movement of this system in the next 48 hours, there is high degree of uncertainty in the forecast track," PAGASA said in its 11 a.m. severe weather bulletin on Monday.

By Thursday morning, Siony -- which will likely remain within tropical storm category within 36 to 48 hours, according to PAGASA -- is expected to be at 345 km east of Aparri, Cagayan.

As of 10  a.m. on Monday, the center of Siony was estimated based on all available data at 620 km east of Aparri, Cagayan. It was moving west northwestward at 40 km/h packing maximum sustained winds of 65 km/h near the center and gustiness of up to 80 km/h.

At a press briefing with presidential spokesperson Harry Roque, a PAGASA forecaster said Tropical Cyclone Wind Signal No. 1 may be declared in Cagayan Valley areas, where it is expected to make landfall, on Thursday.

For Monday, PAGASA said Siony's trough "will bring light to moderate with at times heavy rains over Batanes, Cagayan, and Isabela."

It also warned that flooding, including flashfloods, and rain-induced landslides may occur during heavy or prolonged rainfall especially in areas that are highly or very highly susceptible to these hazards.  —KBK, GMA News