Last January 16, three major weather systems were all present within the Philippine area of responsibility:
- Strong surge of the Northeast Monsoon (Amihan)
- Stationary Front extending from Central Visayas well into the open waters of the Pacific Ocean
- Weak Low Pressure Area (LPA) remnants of Tropical Disturbance 97W (LPA) hanging over the western portion of Central Mindanao
These complex weather systems conspired to generate incessant rain over a wide swath of Northern Mindanao, particularly in the cities of Dipolog, Iligan, and Cagayan De Oro.
Based on WeatherPhilippines’s data, Cagayan De Oro City experienced heavy to intense rainfall that day as indicated below:
(Fig. 1.0) 66.6 mm in just 1 hour, recorded at SM City, Cagayan De Oro City
(Fig. 2.0) A graphical representation of areas receiving flooding rains for a period of one hour.
(Fig. 3.0) 24-hour rainfall totals in select areas of Northern Mindanao ending 8am, January 17, 2017
(Fig. 4.0) A graphical representation of areas inundated by intense rainfall within a 24-hour period across Northern Mindanao, January 16-17, 2017
Using the 24-hour reading from the above automated weather station, it shows that accumulated rainfall has already exceeded the monthly norm in the area, which is 98.8 mm. (From DoST-PAGASA: http://www.pagasa.dost.gov.ph/index.php/climate/climatological-normals)
(Fig. 5.0) WeatherPhilippines Foundation’s Daily GraphSat for January 16-17, 2017. Image from https://weatherph.org
The sustained cycle of lifting of moisture provided ripe conditions for the development of a series of strong thunderstorms to develop overland. This has spawned flooding rains and, at times, windy conditions over a wide area, which lasted well into the overnight hours. While common afternoon thunderstorms do not last for more than two to three hours, this particular rain event was significant for Cagayan De Oro City and nearby areas.
(Fig. 6.0) Recorded lightning strikes over the past hour taken at 6:00pm on January 16, 2017. Image from https://weatherph.org/weather-maps/ provided by ©MeteoLogix AG
According to local authorities, the torrential rains combined with factors such as topography, elevation, clogged or poor drainage systems, and silted rivers and/or blocked waterways led to urban flooding.
While thunderstorms are hard to predict, bulletins issued by PAGASA as well as daily updates from private weather organizations like WeatherPhilippines may be used to anticipate and prepare for possible impacts of heavy rainfall brought by various weather systems. Education is key to protecting lives and property. Ultimately, it pays to be #WeatherWiser.