What are 'siyam-siyam' rains?

Posted at 08/07/2012 1:47 AM | Updated as of 08/07/2012 3:56 PM

MANILA, Philippines - "Siyam-siyam" rains -- or literally 9 days and 9 nights of prolonged rains -- are behind the floods that swamped many parts of Metro Manila Monday night, a state weather bureau official said.

The rare phenomenon, which is caused about by the southwest monsoon or habagat weather system in the western Philippines, has not happened in years, said PAGASA weather forecaster Mario Palafox.

"Sa pagkaalala ko, matagal na hindi tayo nakakaranas ng siyam-siyam," he told ABS-CBN's "Bandila."

"Sa pagiging forecaster ko ng 17 years, ngayon lang ako nakaranas ng siyam-siyam," he said.

At the height of the Pinatubo lahar flows in the 1990s, the "siyam-siyam" phenomenon was blamed for the heavy rains that triggered cascading volcanic material flows into towns in Central Luzon, according to scientist Dr. Kevin Rodolfo.

Palafox said people should not be unduly worried about the continuous rains.

"Hindi naman po dapat ikabahala dahil nangyari na ito," he said.

He explained that the rains were caused by the  southwest monsoon that gained strength after being pulled into the Western Philippines by the passage of typhoon Gener last week.

Red warning

State weather bureau PAGASA has raised the red warning signal over Metro Manila because of heavy rains.

In its latest advisory issued 11:30 p.m., the weather agency said heavy and intense rains were observed over the metropolis Monday night.

PAGASA said torrential rains with a volume of 40.4mm were recorded in Manila in the past hour. Quezon City received 26.0 mm of rainfall, Taguig got 24.64mm, while 10mm to 30mm per hour of rainfall was observed over the rest of Metro Manila.

Earlier in the night, an accumulated rainfall of 83.5 mm was recorded in Quezon City while Marikina got 63.5mm in the past 3 hours,

PAGASA expects the heavy rains to continue throughout the night.

Overflowing dams

The weather bureau also monitored moderate to heavy rains in Cavite, Laguna, Batangas, Rizal, Quezon Province,  Ilocos Sur, La Union, Pangasinan, Benguet, Mountain Province, Bataan, Zambales, Tarlac, Pampanga, and Bulacan.

Aside from causing floods in the metropolis and nearby provinces, the heavy rains also caused water to overflow from the La Mesa and Ipo Dams.

The gates of the Ambuklao, Binga, and San Roque Dam have also been opened to release water and ease the pressure on the structures.

Authorities are also implementing forced evacuation of residents of Tumana and Malanday villages in Marikina amid the threat posed by the rising waters in the river in the city, local officials said. - with a report from Apples Jalandoni, ABS-CBN News