Tropical cyclones outside PH landmass more responsible for heavy rainfall during Habagat season
Heavy rainfall is more likely to be caused by tropical cyclones that do not make landfall than by those that do during the Southwest Monsoon (Habagat) season from July to September, according to a new study.
After examining 62 years of weather data (1961 to 2022), researchers from Ateneo de Manila University, the Manila Observatory, PAGASA, and Japanese partner institutions found that the indirect effect of tropical cyclones accounts for 33.1% of rainfall, more than twice as much as the direct effect (15.4%).
The remaining 51.5% is attributed to the monsoon itself, without tropical cyclone influence.
The rainfall measurements were taken from 11 stations along the western coast of the Philippines (Laoag, Baguio, Dagupan, Iba, Science Garden-Quezon City, Port Area-Manila, Sangley Point, Ambulong, Coron, Cuyo, and Iloilo).
''The peak of the typhoon season coincides with the peak SWM [Southwest Monsoon] months. This leads to the interaction between the two weather systems. In some cases, TCs [tropical cyclones] are able to 'enhance' the SWM. This usually happens when a TC is located to the northeast of the Philippines during the peak SWM months, bringing heavy rainfall especially over the western coast of the Philippines,'' the study said.
''The most recent example is Typhoon Gaemi (Carina) in 2024, which did not make landfall in the Philippines but still brought about extremely high amounts of rain over the country due to its enhancement of the SWM,'' it added.
''Two other examples of this phenomenon are the 'enhanced Habagat' cases of 2012 and 2013, which occurred from 6–10 August 2012 and 18–22 August 2013, respectively.''
The study also found that in the four rainiest years on record—1962, 1972, 2012, and 2018—rainfall totals soared above 2,000 millimeters during the Habagat season, with indirect effects of tropical cyclones accounting for 41.5 percent of total rainfall.
''By distinguishing between rainfall caused by the monsoon as well as the direct and indirect effects of tropical cyclones, the researchers hope to improve the way we anticipate extreme weather,'' Ateneo said.
''Understanding these distinctions is crucial for local governments and disaster response agencies, especially as climate change increases the unpredictability of both tropical cyclones and seasonal rainfall.''
Ateneo published the study on June 11. —GMA Integrated News
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
GMA Network
36 minutes ago
- GMA Network
30 reported dead due to Habagat, Crising, Dante, Emong —OCD
A drone view shows a village in Calumpit, Bulacan inundated by high tide and flooding brought by heavy rains from the Southwest Monsoon (Habagat) enhanced by Tropical Depression Emong (international name: Co-may) on July 25, 2025. REUTERS/Eloisa Lopez The reported number of fatalities amid the flooding and other effects of the Southwest Monsoon (Habagat) and tropical cyclones Crising, Dante, and Emong has reached 30, the Office of Civil Defense (OCD) said Saturday. "So in terms of casualties, umabot na sa 30 'yung na-report na namatay," OCD officer-in-charge Assistant Secretary Bernardo Rafaelito Alejandro IV said in an interview on Dobol B TV. (So in terms of casualties, the reported death toll has reached 30.) Of this number, one third has been validated, Alejandro said. These include nine fatalities in the National Capital Region (NCR) and two in Region III. Most of the casualties were due to drowning or electrocution, the OCD OIC said. Meanwhile, 10 injuries were reported and seven were still missing, he said. Authorities are validating the reported figures. Around 5.2 million individuals were affected by the weather disturbances in 5,900 barangays, Alejandro added. Some 55,000 families or close to 200,000 individuals are staying in 2,000 evacuation centers, he added. "So, karamihan diyan (evacuees) nasa NCR, Region III, CALABARZON, Region I and MIMAROPA," he said. (Most of them are in NCR, Region III, Calabarzon, Region I and MIMAROPA.) As for landslides, Alejandro said Kennon Road in Benguet remains closed. "'Yung landslide naman ang pinakasarado lang talaga 'yung Kennon Road. Kasi tuloy-tuloy 'yung pag-landslide doon," he said. (Kennon Road remains closed because of landslides.) "Sa floodings, mayroon pang maraming flooded areas. Halos 1,400 barangays pa ang reported na may flooding. Karamihan diyan Region III, Region I at dito sa NCR," Alejandro said. (As for floodings, there are still many flooded areas. Almost 1,400 barangays were reported to still have flooding. Most of them are in Region III, Region I, and NCR.) As of Saturday morning, 22 national roads remained not passable, he said. "Nangako naman ang DPWH na kaagad nilang iki-clear at aayusin ang national roads natin," Alejandro said. (The Department of Public Works and Highways promised to clear and fix our national roads.) Infrastructure damage has reached P5.2 billion, while agricultural losses topped P1.1 billion, according to the Department of Agriculture, he added. As for power interruptions, around 21 areas reported these on Friday, mostly in La Union and Pangasinan areas. Alejandro also said helicopters will deliver relief goods to isolated areas as soon as the weather permits. —KG, GMA Integrated News
GMA Network
3 hours ago
- GMA Network
Tropical Depression Emong exits PAR —PAGASA
Tropical Depression Emong has exited the Philippine Area of Responsibility (PAR) on Saturday morning, state weather bureau PAGASA said. Emong exited PAR at 7:10 a.m., it added. In its forecast for Saturday, PAGASA said the Southwest Monsoon (Habagat) will bring occasional rains over the Ilocos Region, Zambales, Bataan, and Occidental Mindoro and cloudy skies with scattered rains and thunderstorms over Metro Manila, the Cordillera Administrative Region, Cagayan Valley, CALABARZON, the rest of Central Luzon, and the rest of MIMAROPA. The rest of the country will see partly cloudy to cloudy skies with isolated rains or thunderstorms. —KG, GMA Integrated News
GMA Network
5 hours ago
- GMA Network
Wind signals lifted as Emong set for PAR exit
Wind signals have been lifted as tropical cyclone Emong continues to weaken on its way out of the Philippine Area of Responsibility. PAGASA said in its 5 a.m. Saturday tropical cyclone bulletin that Emong is now a tropical depression, with maximum sustained winds of 55 km/h and gustiness of up to 70 km/h. Last spotted 500 km northeast of Itbayat, Batanes, Emong was moving north northeast at 45 km/h. ''Emong will continue to accelerate generally north northeastward and exit the Philippine Area of Responsibility this morning. Due to [the] increasing unfavorable environment and fast translational speed of Emong, it will likely degenerate into a remnant low within the next 12 hours,'' PAGASA said. The Southwest Monsoon (Habagat) will bring occasional rains over the Ilocos Region, Zambales, Bataan, and Occidental Mindoro and cloudy skies with scattered rains and thunderstorms over Metro Manila, the Cordillera Administrative Region, Cagayan Valley, CALABARZON, the rest of Central Luzon, and the rest of MIMAROPA. The rest of the country will see partly cloudy to cloudy skies with isolated rains or thunderstorms. Extreme Northern Luzon will experience strong winds and rough coastal waters, while the western section of Luzon will have moderate to strong winds and moderate to rough seas. Light to moderate winds and slight to moderate coastal waters are forecast for the rest of the country. —VBL, GMA Integrated News
