Super Typhoon Rolly (Goni) left thousands homeless and possibly without power in the weeks leading to Christmas. This has happened before, at around the same time and in the same general area. In December last year, it was Typhoon Tisoy (Kammuri).
Seven years ago, Super Typhoon Yolanda (Haiyan), the most powerful storm on record to ever hit land, wiped out entire communities in the Eastern Visayas. The year before, in 2012, Typhoon Pablo (Bopha) struck southern Mindanao. There are many other storms, Ondoy (Ketsana) in September 2009 and Seniang (Jangmi) in December 2014.
During this time, it's a combination of the wet season and high pressure in mainland Asia that pushes storms that form in the Pacific Ocean downwards, in the direction of the Philippines' eastern coast, PAGASA forecaster Benison Estareja said.
This year, there's also La Niña, or a prolonged wet season, Estareja told reportr.
"Ang effect no'n ay mas maraming formation ng clouds malapit dito sa atin sa may Philippine Sea in the Western Pacific Ocean. Kapag may cloud formations at clusters, ito ay pwedeng pamumugaran ng low pressure areas or yung tinatawag na tropical cyclones such as typhoons," he said.
When Rolly slammed into the Bicol Region last Nov. 1, it was the planet's strongest storm of 2020. It came just weeks after storms Pepito and Quinta and was followed on the same week by Siony.
The Philippines' location as the first major landmass facing the Pacific cyclone belt makes it vulnerable to an average of 20 storms and typhoons each year. The number could rise to 25 this year due to La Niña, Estareja said.
In early October, PAGASA announced that the cooling of the sea surface temperature in the central and equatorial Pacific has reached the La Niña threshold. The weather pattern which occurs every three to five years on average will bring about more frequent rains than usual and will last up to five months—from the last quarter of 2020 to early 2021.
Most typhoons naturally arrive during the rainy season. Unlike countries located in temperate regions that experience up to four seasons, the Philippines only has two: wet and dry. It is determined by the amount of rainfall and not by the length of daylight nor the intensity of sunlight.
This year, the rainy season started in June, which also signaled the start of the typhoon months. During this time, the chances of a storm hitting land are not as high compared to later in the year.
"Mas mataas yung chance na maglandfall yung bagyo kapag November and December dahil ang nagdidictate sa direksyon ng bagyo ay yung malakas na high pressure area sa mainland Asia," Estareja said.
Instead of moving north east or away from the country, tropical cyclones move west-ward and cross the Philippine islands, he said.
The country's vulnerability to severe weather events is about to get worse due to climate change, as it is expected to increase the frequency of El Niño and La Niña events, the latest report from the Intergovernmental Panel on Climate Change (IPCC) said. It will intensify existing impacts, causing drier or wetter seasons.
"It's a cycle kaya these weather patterns happen regularly. Question nalang diyan ay ano yung effect ng climate change sa El Niño and La Niña, kung nagiging mas malakas ba sila. So far, ganon pa rin naman, may mga weak, strong, and moderate," said Estareja.