Text and Photos by Henrylito D. Tacio
“Oftentimes, we make the mistake of interchanging climate and weather, but they are actually two different things,” said Dr. Jorge G. de las Alas, a professor of the Institute of Environmental Science and Meteorology at the University of the Philippines in Diliman, Quezon City.
Climate, Dr. de las Alas explained, is the statistical average of observed weather in a particular area of interest over a relatively long period of time. “Climate is not static,” he said. “It is ever changing like weather but its rate of change is small and generally imperceptible in periods comparable to man’s lifetime.”
In a recent climate forum for agriculture convened by the Department of Agriculture and UN Food and Agriculture Organization in Davao City, Anthony Joseph R. Lucero bared the Philippines has four types of climates.
“Davao City and the rest of Davao Region is under the Type IV,” Lucero, senior weather specialist of the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), pointed out. “The rainfall in these areas is more or less evenly distributed throughout the year.”
Other places in the country which has the same type of climate are Camarines Sur, Leyte, Bohol, Misamis Oriental, South Cotabato, Zamboanga del Sur, Sulu and Tawi-Tawi.
Areas with Type I have two pronounced seasons: dry from December to May and wet from June to November. Maximum rain period is from June to September. Areas characterized by this climate type are Ilocos Norte and Sur, Abra, La Union, Benguet, Nueva Ecija, Pangasinan, Tarlac, Zambales, Pampanga, Bulacan, and Bataan.
Metro Manila, Cavite, Batangas, Mindoro Occidental, Iloilo and the western section of Palawan have also this type. So do parts of Mountain Province, Ifugao, Nueva Vizcaya, Antique and Negros Oriental.
Those with Type II have no dry season with a very pronounced maximum rain period from December to January. Places with this type include Northern and Eastern Samar, Agusan del Sur, and some parts of Davao Oriental.
Seasons in areas with Type III are not very pronounced. It is relatively dry from November to April and wet during the rest of the year just like in Isabela, Rizal, Laguna, Aklan, Cebu, Bukidnon, and North Cotabato.
“Climate is what you expect,” said American humorist and novelist Mark Twain, “weather is what you get.”
Lucero seemed to agree with Twain’s observation when he said that climate in a particular place has been firmly established while the weather is a lot more unpredictable because “it has to do with the day-to-day changes in atmospheric conditions,” observed Lucero, who is with the climate monitoring and prediction section of PAGASA’s Climatology and Agrometeorology Division.
The Philippines, given the location and the topography of the country, experiences several weather-causing phenomena: thunderstorm, cold front, monsoons, easterly wave, intertropical convergence zone, low pressure area, and tropical cyclone.
Thunderstorms, called local storms, occur when towering cumulus clouds reach a height where the temperature is well below the freezing point. Among the associated hazards are heavy rain (which may cause flashflood) and lightning (which may cause death, burns or fire).
Cold front, which is prevalent in temperate countries, is formed when cold air moves over areas of warm air. Since cold air is heavier than warm air, the warm air is pushed aloft by the cold air giving rise to widespread cloudiness.
“Cold front does not pass the country’s area of responsibility,” Lucero said. “What we have is only the tail of the cold front. It is very unique in the Philippines as we have a weather that gives us cooler temperature. There are no such thing in our neighboring countries like Indonesia, Malaysia, and Singapore.”
There are two types of monsoon: Southwest and Northeast. In the former, the Asiatic continent becomes warmer than the surrounding seas and a low pressure cell develops over the continent. This causes a flow of moist southwest wind over the Philippine area. At times, when this southwest flow becomes thick in depth, it persists for a long period causing continuous rains which may last for weeks during the months of June to September.
The Southwest monsoon, locally called habagat, is responsible for the great portion of rainfall during the country’s wet season. “About 60% of the rainfall in the Philippines is associated with Southwest monsoon,” Lucero said.
The Northeast monsoon is known locally as amihan. “Northeast monsoon is a wind system that reverses in direction, from the southwest to the northeast,” Lucero said. “It originates in mainland Asia (particularly those in Siberia) and crosses the Philippines in northeast direction. During the amihan, malamig ang panahon sa Pilipinas, which is usually from October to March.”
Easterly waves are meanderings (waves) in the wind, which blows from the east (easterly). Some storms and minor typhoons originate from easterly waves. “Mahina ang hangin na dala ng easterly waves and it is easily overcome by Southwest and Northeast monsoons,” Lucero said.
The intertropical convergence zone (ITCZ), for the information of the uninformed, is an area where the northern hemisphere trades meet the southern hemisphere trades. According to the weather bureau, ITCZ is characterized by towering clouds of cumulonimbus clouds accompanied with showers of widespread thunderstorms.
“The axis of convergence, which is usually oriented in an east to west direction, does not remain stationery at the equator but migrates north or south of the equator,” PAGASA explains. In the Philippines, it oscillates during the months of May to October.
During the ITCZ, low pressure area (where the atmospheric pressure is lower than that of surrounding locations) is embedded. And once ITCZ leaves, low pressure area is left behind. Low-pressure systems, it is said, form under areas of wind divergence which occur in the upper levels of the troposphere, the lowest layer of Earth’s atmosphere.
This brings us to tropical cyclones. These are low pressure systems characterized by relatively low atmospheric pressure at the center with very strong winds blowing counterclock wise (in the northern hemisphere) towards and around the center.
In the Filipino dialect, tropical cyclones are called “bagyo,” a word which came after a 1911 storm in the city of Baguio, which had a record rainfall of 46 inches within a 24-hour period.
“The Philippines has the highest occurrences of tropical cyclone around the world,” Lucero said. “We are known to have the most number of cyclones: 19-21 cyclones a year.”
In the past, there were only four public storm warning signals (PSWS). The weather bureau recently added a fifth: Super Typhoon (STY). “Typhoons as strong as Super Typhoons with more than 220 kilometers per hour (kph) of sustained winds in the country is becoming more frequent,” PAGASA Acting Director Dr. Vicente Malano was quoted as saying during the launching of the modified PSWS.
The complete PSWS of tropical cyclones: Tropical Depression (TD) with 30-60 kph winds; Tropical Storm (TS) with 61-120 kph winds; Severe Tropical Storm (STS) with 121-170 kph winds; Typhoon (TY) with 171-220 kph winds; and Super Typhoon (STY) with more than 220 kph winds.
Most Super Typhoons don’t landfall,” Lucero said. “They just enter the Philippine Area of Responsibility and then exit without even touching the land.”
But when a Super Typhoon does, just like Sendong in 2011, Pablo in 2012 and Yolanda in 2013, the devastation is incomprehensible.
Among the dangers associated with typhoons are heavy rainfalls and floods, strong winds, storm surge, landslides and mudflows. “Landslides can bury people alive and destroy properties,” the weather bureau reminds. “Mudflows, on the other hand, are hazardous to people and properties, too.”
But there is one good thing about tropical cyclones. The weather bureau says that the rainfall brought about by tropical cyclones increases the groundwater and water levels of dams. In fact, about 50% of the rainfall of the country comes from tropical cyclones.
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