PAGASA: La Niña officially over

The Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) declared yesterday that the La Niña weather phenomenon that prevailed in the equatorial Pacific Ocean from November last year up to last month has finally ended.

"Atmospheric and oceanic indicators have remained close to normal. Statistical and dynamical model forecasts suggest that neutral conditions will persist in the equatorial Pacific Ocean for the rest of 2006," said PAGASA deputy director Nathaniel Servando.

La Niña, which brings about and intensifies the effects of heavy rains and tropical storms, is attributed to abnormal cooling of the sea surface.

Servando said in an advisory that the weather conditions that affected the country last month were "easterly wave, tail-end of the cold front and inter-tropical convergence zone."

"The month was characterized by warm and relatively dry weather conditions in most parts of the country, particularly Luzon due to the prevalence of the ridge of high-pressure area," he said.

A ridge is an elongated area of relatively high pressure, generally associated with light winds and clear weather.

But rainfall analysis showed that large portions of Luzon and Visayas, including western Mindanao, experienced "below to way below average" rains with some patches of near to above average in a major part of central Luzon and eastern side of Visayas, including Palawan.  

Above to near average rainfall conditions, on the other hand, occurred in the CARAGA region and Central Mindanao. This was brought about by the inter-tropical convergence zone (ITCZ).

The PAGASA advisory said that for the month of May, rainfall conditions could be "near average" in most areas in central and northern Luzon, including Palawan, Cavite, Batangas, Nothern Samar, the southern part of Antique and Negros Occidental, Zamboanga del Sur, Autonomous Region in Muslim Mindanao and Central Mindanao.

The rest of the country will likely experience above-average rainfall conditions.

"Weather systems that may affect the country in May are the ITCZ, easterly wave, tail-end of the cold front, ridge of high-pressure area and southwest monsoon. There is a probability of one or two tropical cyclones to enter or develop in the Philippine area of responsibility," it said. — Sheila Crisostomo