La Niña’s gone but rains will linger till September

/ 04:28 AM June 30, 2011

La Niña may have ended her sway in the Philippines in June, but the little girl will continue to make her presence felt through September with even more rains, weather officials have warned.

Because of La Niña’s residual effects, Ondoy–like rains remain a possibility, according to Graciano Yumul, supervising science undersecretary of the weather bureau, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).


“The southwest monsoon will last until September. So when a storm makes landfall and combines with the monsoon, and they bring heavy rains, it will be Ondoy–like,” he said.

More storms


Pagasa Director Nathaniel Servando said there may even be more and stronger storms this year. The number may go up to 20 to 21, a little over the average 19 to 20 that visits the country each year, he said.

Yumul explained that La Niña’s residual effects are usually felt three months after it has left.

This means that the country will experience heavier rains, whether they will come from a typhoon, a storm, a low-pressure area, the tail end of a cold front or any other weather disturbance, he said.

“What does La Niña bring? A lot of water. So now, in all that has happened—the cold front, southwest monsoon, ITCZ—there has been a lot of water,” Yumul said.

La Niña, Spanish for “little girl,” refers to the abnormal cooling of sea surface temperature in the Pacific that brings heavy rains and adversely impacts the southwest monsoon in this part of the world.


Yumul noted that there was no La Niña in September 2009 when Tropical Storm “Ondoy” directly hit Luzon. But what happened was that Ondoy’s rains combined with the southwest monsoon—the seasonal winds that bring heavy rainfall from June to September or October—submerging much of Metro Manila and killing hundreds of people.


According to Yumul, the heavy rains being experienced in the country can also be attributed to global warming. With the rise in global temperatures, more water evaporates, and what is brought up has to go down, he said.

This would explain the current situation in Mindanao, which has experienced heavy rains the past few weeks, said Yumul. He noted that Mindanao is usually the drier part of the country, but recent weather disturbances have affected it. Northern Luzon, in contrast, has been quite dry, he added.

Clogged waterways

According to Yumul, heavy rains are to be expected during typhoons but now they accompany even low-pressure areas.

He said the rains that caused the flash floods in Davao are due not to any typhoon or even a low-pressure area, but to the intertropical convergence zone (ITCZ), a band of upwelling most air near the equator that moves with the seasons to the north or south and is characterized by heavy rainfall. The ITCZ is the breeding ground for tropical storms.

Yumul said the flash floods could have been caused by clogged waterways.

Even if the rains are heavy but the water is able to flow freely, there would be no problem, Yumul said.

As for the floods in Central Luzon, Yumul said these could be attributed to Tropical Depression “Egay.”

He said Egay’s rains had led to a “supersaturation” of the ground in the region. When Falcon came and caused the southwest monsoon to bring more rains, the ground could no longer absorb the moisture, he explained.

Calasiao, meanwhile, is the catchbasin of Pangasinan, which is why water flows toward it, Yumul said.

Yumul said people should be aware of the changing weather patterns in their areas so that they can prepare for floods or landslides.

Ronald Flores of the National Disaster Risk Reduction Management Council also said that local government units should take note of the changing weather patterns and adjust their disaster plans accordingly.

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TAGS: Geophysical and Astronomical Services Administration (Pagasa), Graciano Yumul, intertropical convergence zone (ITCZ), La Niña, Ondoy, Pagasa Director Nathaniel Servando, Philippine Atmospheric, Tropical Depression “Egay”, Tropical Storm “Ondoy”
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