MANILA – Prepare your umbrellas.
Weather bureau Pagasa declared Wednesday the onset of the southwest monsoon, explaining that the southwesterly windflow has been dominant over the West Philippine Sea for several days now.
"This is due to the formation of semi-permanent trough over Northern Luzon-Taiwan area and the eastward migration of the North Pacific High Pressure Area which are the prominent indicators of the southwest monsoon onset in the country," Pagasa said.
It added that prevailing weather conditions in most parts of Luzon and Visayas, particularly the western section, is now warm and humid as characterized by occasional to frequent afternoon or evening rainshowers and thunderstorms.
"These developments signify the approaching onset of rainy season under Type 1 climate covering the western parts of Luzon and Visayas.
However, weather forecaster Samuel Duran said this does not mean that the rainy season is already here.
He said 5 of the 8 stations, including Metro Manila, have to meet certain criteria before rainy season is declared.
“Sa loob ng 5-day period, dapat tatlong araw na magkakasunod more than 25 mm ang rainfall,” he said.
So far, only the stations in Laoag, Sinait, and Iba have met the criteria. They are still waiting for results from other stations.
Pagasa said light to moderate rainshowers and isolated thunderstorm will prevail during the remaining days of May.
But this may be followed by short dry period called monsoon break.
"Occasional to frequent rains and thunderstoms in most parts of Luzon and Visayas will be experienced in the coming months due to southwest monsoon activity," it added.