Text and Photos by Henrylito D. Tacio
Although the Philippines is still reeling from the effects of the El Niño phenomenon, Filipinos are urged to be prepared for the coming typhoons.
“There is no month in the Philippines which is free from typhoons,” says the Philippine Atmospheric, Geophysical and Astronomical Service Administration (PAGASA), which issues weather advisories for tropical cyclones.
“The Philippines is prone to tropical cyclones due to its geographical location which generally produce heavy rains and flooding of large areas and also strong winds,” the weather bureau says.
Every year, about 36 tropical typhoons pass through this part of the world. Fortunately, only 19 to 20 of these enter the country’s area of responsibility. Of the total, only 6 to 9 make landfalls.
Fewer number of typhoons expected despite the La Niña phenomenon
This year, there will be fewer typhoons predicted to enter the country. Most of these typhoons are expected to be experienced in the latter part of the year, as the country will be under the La Niña phenomenon.
“During La Niña, usually the number of our typhoons increases,” said Ana Solis, officer-in-charge of PAGASA’s Climatology and Agrometeorology Division, during a Palace briefing. “There’s a possible increase in potential tropical cyclone development closer to our waters.”
Only 13 to 16 typhoons are expected to enter the country’s area of responsibility, Solis was quoted as saying by Daily Tribune.
Science Secretary Renato Solidum, Jr. agreed the overall number of typhoons might be below normal. However, he urged Filipinos to remain vigilant and be prepared for the forthcoming typhoons.
Based on past records, among the areas that experience above-normal rainfall are Eastern Luzon, Eastern Visayas, and Northeastern Mindanao.
What is a typhoon
A typhoon is a mature tropical cyclone that develops in the northwestern part of the Pacific Ocean. In the eastern Pacific Ocean, identical phenomena are called hurricanes, but when these tropical cyclones move into the western Pacific they are re-designated as typhoons.
Within the northwestern Pacific, there are no official typhoon seasons as tropical cyclones form throughout the year. “On average, the northwestern Pacific features the most numerous and intense tropical cyclones globally,” reports Chris Landsea of the United States National Hurricane Center.
“Nearly one-third of the world’s tropical cyclones form within the western Pacific,” wrote James B. Elsner and Kam-Biu Liu in a paper which appeared in Climate Research. “This makes this basin the most active on Earth.”
Scientific studies have shown that Pacific typhoons have formed year round, with peak months from August to October. The peak months correspond to that of the Atlantic hurricane seasons.
Like any tropical cyclone, there are six main requirements for typhoon formation and development: sufficiently warm sea surface temperatures, atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough so-called “Coriolis force” to develop a low pressure center, a pre-existing low level focus or disturbance, and low vertical wind shear.
Meteorologists – those who study interdisciplinary scientific study of the atmosphere – explain that while these conditions are necessary for tropical cyclone formation, they do not guarantee that a tropical cyclone will form.
Bagyo trivia
Depending on the intensity and strength of the winds that they bring, tropical cyclones are classified as tropical depression, tropical storm, severe tropical storm, and typhoon. (For trivia fanatics: “Bagyo,” a Filipino word which means typhoon, arose after a 1911 storm in the city of Baguio had a record rainfall of 46 inches within a 24-hour period.)
The country’s weather bureau measures tropical cyclones, according to intensity scale. It is considered a tropical storm (TS) when it has maximum winds of 62-88 kilometers per hour (47 knots). When the winds go up from 89 to 117 kilometers per hour (63 knots), it is called a severe tropical storm (STS).
A typhoon (TY) happens when the winds move anywhere from 118 to 184 kilometers per hour (99 knots). When the winds exceed 185 kilometer per hour (more than 100 knots), a super typhoon (STY) is born.
Typhoon monitoring
The weather bureau releases tropical cyclone warnings in the form of Public Storm Warning Signals (PSWS).
PSWS 1 means a tropical cyclone will affect the locality. Winds of not more than 60 kilometers per hour (kph) may be expected in at least 36 hours.
In PSWS 2, a moderate cyclone will affect the locality and winds of 61 to 100 kph may be expected in at least 24 hours.
In PSWS 3, a strong tropical cyclone with winds of 101 to 185 kph may be expected in at least 18 hours.
PSWS 4 is a very intense typhoon with winds of more than 185 kph may be expected in at least 12 hours.
The movement of a full-fledged typhoon is closely watched by weathermen through radar and satellite images. The eye of the typhoon is used as a reference point on the location of the typhoon.
If the typhoon is within the range of the radar, the meteorologists won’t have much problem in monitoring the typhoon. According to PAGASA, the radar is more accurate because you see the eye of the typhoon more clearly.
It’s a different story with a satellite, which covers half of the globe and gives a full disc picture. The storm eye is sometimes covered by clouds. As such, meteorologists have a hard time knowing where a typhoon is “if you can’t see the eye.”
Other calamitous dangers
Aside from PAGASA, another agency that releases warning messages during calamities in the country is the Philippine Institute of Volcanology and Seismology (PHIVOLCS). Both are frontline agencies of the Department of Science and Technology (DOST).
Among the dangers associated with typhoons are heavy rainfalls and floods, strong winds, storm surge, landslides, and mudflows.
During typhoons, floods are common. The weather bureau issues Flood Early Warning System (FEWS). It has five basic elements: prediction, detection, communication, decision-making, and mobilization.
“Landslides can bury people alive and destroy properties,” PAGASA reminds. “Mudflows, on the other hand, are hazardous to people and properties, too.”
Storm surge, an abnormal rise of water, is another danger that people should watch out for. “Potentially disastrous surges occur along coasts with low-lying terrain that allows inland inundation, or across inland water bodies such as bays, estuaries, lakes and rivers,” PAGASA states.
For a typical storm, the surge affects about 160 kilometers of coastline for a period of several hours.
But there is one good thing about tropical cyclones. The chief of PAGASA’s climatology and agrometeorology division explained that the rainfall brought about by tropical cyclones increases the groundwater and water levels of dams.
“About 50% of the rainfall of the country comes from tropical cyclones,” she said.
According to PAGASA, “typhoons last for about six days, in general, before they enter the land or reach sub-tropical latitudes. However, some can be detected only a few hours or perhaps a day or two, while others are observed as long as a fortnight.” – ###
