By Ellalyn de Vera-Ruiz Residents south of Metro Manila were stunned by a "rare" sighting of four tornadic waterspouts (ipo-ipo) simultaneously forming over the Laguna de Bay early Saturday evening. Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) (MANILA BULLETIN) Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) weather specialist Ariel Rojas said waterspouts usually form over tropical waters in areas near the equator, such as the Philippines, but is a rare occurrence in the country. Tornadic waterspouts originate from thunderstorms, Rojas said, while thunderstorms form from warm air with moisture. "Warm air rises into the sky and when it continues to bring moisture to the sky, clouds will be formed. When the warm air continues to climb, the clouds become larger to form thunderstorm clouds. As the warm air carrying moisture enter into the thunderstorm cloud, a sudden change in the direction and speed of wind occurs in rotating motion forming a vortex," he explained. The warm air rising above the sky cools down. When the cold air, which is heavier than the warm it enters the vortex, it pushes the warm air or part of the cloud down and becomes a waterspout. It is called a waterspout or 'ipu-ipo' if it hits the water or tornado or 'buhawi' if it hits the ground, he added.

READ MORE: LOOK: Multiple waterspouts spotted in Laguna de Bay

WEATHER IN THE NEXT FEW DAYS Rojas said that two warm weather-associated weather systems may continue to prevail across the country. The ridge of high pressure area extending across Luzon, and easterly winds affecting the rest of the country, will likely bring warm and humid mornings with a possibility of short-lived sudden rains or thunderstorms in the afternoon or evening. He advised the public to take extra precautions in the event of severe thunderstorms as flashfloods over low-lying areas or landslides in mountainous communities are likely. PAGASA earlier pointed out that the occurrence of short-lived heavy rains late in the day, is normal this time of the year as the country is about to transition to the southwest monsoon period or "habagat," associated with the rainy season. "Habagat" usually commences between the second half of May and first half of June. In 2019, the onset of "habagat" season was officially declared on June 14. For the rainy season to be officially declared, two criteria have to be met--a total rainfall amount of 25 millimeters (mm) or more with three consecutive days having at least 1 mm of rainfall per day in at least seven out of 14 stations monitored by PAGASA; and the prevailing winds should have westerly components over the western Philippines relative to the rain-associated weather patterns.