Our country is not new to typhoons and its devastating impacts. Each year, about 20 tropical cyclones traverse the Philippine Area of Responsibility (PAR). Tropical cyclones occur when the following conditions are present: (1) warm ocean, (2) ample convection (air rising), (3) humid environment, (4) low wind shear, (5) 500 km away from the equator, and (6) a pre-existing low level disturbance.  However, even if all these conditions are present, tropical cyclones may not form. Tropical cyclones that form over tropical oceans tend to move west and northward. It is often characterized by strong winds and intense rains that can bring destruction along its path.

Tropical cyclones form when thunderstorms in the monsoon trough (located over tropical waters east of the Philippines) group together and follow a spiral motion. Tropical cyclones can occur anytime of the year in the western Pacific due to the presence of an environment conducive to formation all year round. The Philippines, being located on the western rim of the western  Pacific, is vulnerable to tropical cyclones forming in the region.

In the Philippines, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAG-ASA) classifies tropical cyclones depending on their maximum wind strength. These classifications include—from lowest to highest—Tropical Depression, Tropical Storm, Severe Tropical Storm, Typhoon, and Supertyphoon.

Having different thresholds and categories with other countries, PAG-ASA categorizes a supertyphoon when a typhoon’s maximum winds reach >200 kmph. Some of the supertyphoons recorded in the Philippines are Bagyong Rolly in 2020 and Bagyong Lawin in 2016. Despite Yolanda’s wind speed passing as a super typhoon, it was only classified as a typhoon back then. Bagyong Yolanda was also the reason for PAGASA to adopt the term “super typhoon” as a classification.

Known internationally as Typhoon Haiyan, Bagyong Yolanda made its landfall in the country on November 8, 2013 in the Eastern Visayas region. It peaked at ~235 kph, affecting more than 14 million people and causing around 6,300 deaths. Apart from the strong winds, the most destructive was the storm surge that struck the Leyte Gulf. The City of Tacloban in Leyte was the most affected and was declared to be 100% destroyed after the typhoon. 

According to the Institute of Environmental Science and Meteorology Professor, Dr. Gerry Bagtasa, there is not enough data yet to conclude that climate change is one of the major causes of the increasing number of typhoons and its severity. “Several studies show a relationship between rising ocean temperature and typhoon intensity, however, weather records are rather short at ~40 years starting when satellites were developed. It is therefore difficult to have strong conclusions for now” he explains. In fact, the year 2021 was a strange one because the number of tropical cyclones so far recorded this year is way lower than the previous years.

Although the impact of climate change on tropical cyclones has not been directly observed yet, it is expected that the influence of climate change on tropical cyclones will become clear, and we will likely know this within our lifetime. It is also important that we always prepare for the adverse impacts of typhoons and impose policymakers to implement better disaster-management strategies and shift the focus to preventing damages from happening instead of fixing the damages as a result of typhoon occurrence.

References:

https://www.pagasa.dost.gov.ph/information/about-tropical-cyclone
https://windy.app/textbook/how-typhoons-form.htmlv
https://www.wired.com/story/what-is-a-super-typhoon-and-why-are-they-so-dangerous/
https://www.rappler.com/nation/lookback-super-typhoon-yolanda-haiyan-anniversary-2021
https://www.climate.gov/news-features/understanding-climate/climate-change-probably-increasing-intensity-tropical-cyclones