Tuesday, August 14, 2012

Measuring rainfall

From yellow to red – the public got a taste of color-coded rainfall alerts yesterday from the Philippine Atmospheric, Geophysical and Astronomical Services Administration, as heavy rains continued to pound Metro Manila and neighboring provinces. The PAGASA color-coding, launched in June this year, is helpful, but the system could use further fine-tuning. PAGASA forecasters did warn that the monsoon rains, which started Sunday night, would continue until yesterday, with the weather improving only starting today. And they did issue a “yellow alert” for about two hours of “intensive rain” early yesterday afternoon. By the time the alert was issued at past 1:30 p.m., however, the torrential rain had started pouring, triggering flooding and catching by surprise those who had gone to work in the morning when the weather seemed better. By mid-afternoon, traffic was at a standstill in many areas as floodwaters rose. There was more bad news for those who returned to work yesterday morning. By early evening, PAGASA raised a red alert, the highest, for more intensive rainfall during the night in the eastern and northern districts of Metro Manila and neighboring areas. After typhoon “Ondoy” devastated much of Luzon in September 2009, the state weather bureau sought to improve its capability to measure the amount of rainfall, through the acquisition of Doppler radars. Today two such radars – one in Subic and another in Tagaytay – do the job for Metro Manila and neighboring provinces. The color-coded rainfall alert system was made possible by the radars. Perhaps the technology is not yet perfect. Obviously, early warning, not real time alert, is preferred for disaster preparedness. A warning that heavy rain will last for two hours is useful, but not for those who are already trapped in the downpour and consequent flooding. The path and strength of tropical cyclones can be tracked. Is a similar system for the amount of rainfall not possible? Some of the worst floods experienced in Metro Manila were spawned by monsoon rains. If rainfall alerts are issued early enough, schools can suspend classes and everyone can make the necessary preparations for possible flooding. The alert system is better, but there’s room for improvement