La Niña is Here; Brace for Floods and Landslides

MANILA, Philippines — Brace for intense storms and wetter months as the state weather bureau announced the onset of a La Niña phenomenon this year.

Although only a weak to moderate La Niña episode is expected to affect the country adversely until the first quarter of 2011, the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) said precautionary measures should be taken by all concerned agencies against possible flooding, flashfloods, and landslides.

“La Niña conditions are present across the equatorial Pacific, which is expected to last at least through the northern hemisphere in 2010 to early 2011,” Dr. Flaviana Hilario, chief of the PAGASA’s Climatology and Agrometeorology Division, said.

As shown by the recent oceanic and atmospheric indicators, PAGASA said that early stages of cold conditions in the equatorial Pacific Ocean started last July, which continued to persist and further strengthened reaching the La Niña threshold.

Hilario explained that from July 7 to Sept. 22, the sea surface temperatures (SSTs) and anomalies in the central and eastern equatorial Pacific have become cooler, which is consistent with a La Niña phenomenon.

Another indicator of a La Niña episode is the atmospheric pressure, which indicated that the southern oscillation index has been positive in the past few months, signifying a full-blown or full-fledged La Niña.

“All key indicators of ENSO (El Niño-Southern Oscillation), which are cooler than average sea surface temperatures and the persistently stronger than average low-level winds, coupled with above average values of the Southern Oscillation Index (SOI), are at levels typical of La Niña,” Hilario said.

“With the persistent anomalous strength of the easterlies over the central and western tropical Pacific, enhanced rainfall during October-December season is likely, coinciding with the start of the northeast monsoon period. Near- normal to above- normal rainfall condition is expected over most areas of Luzon and generally, near normal over the rest of the country,” PAGASA said.

Hilario pointed out that from July to September, the western part of Luzon recorded 41 to 80 percent or below the normal amount of rainfall for these period, but near to above normal rainfall in Mindanao.

About five to nine tropical cyclones – three to four in October, one to two in November, and one to two in December – are still expected to enter the Philippine Area of Responsibility by the end of the year.

The country averages 19 to 20 tropical cyclones in a year however PAGASA recorded only nine tropical cyclones this year due to the El Nino event.

“La Niña is expected to bring more than average (above normal) rainfall in most parts of the country during the October t- December season, based on the forecast,” Hilario said.

Ellalyn de Vera, Manila Bulletin