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Inquirer.net08/05/2007 MANILA, Philippines—The dry spell that a large swathe of the country has been experiencing over the past two months is unconventional because it is happening at a time when it is supposed to be the rainy season, according to the weather bureau.
Eight tropical cyclones should have entered the Philippine area of responsibility by this time. So far, only two did and they did not even make landfall. They were too far off to enhance the southwest monsoon or habagat that normally brings heavy rains to the western part of the country.
The intertropical convergence zone, which is characterized by cloud clusters, was also supposed to move from Mindanao to Luzon. It has stayed over Mindanao and the Visayas.
As a result, Luzon is suffering from a summer-like weather.
The dry spell has brought a host of problems such as the low water levels at dams, power outages due to the reduced generating capacity of hydroelectric plants, cutback in the amount of water supplied to farms in Central Luzon and households in Metro Manila, and a series of fires in the metropolis.
Should the dry spell persist this month, a drought will be declared next month. That would mean water rationing, longer power outages, outbreak of red tide and health problems. No wonder, people are praying for rains.
Because of the climate’s highly dynamic nature, a small perturbation or variability may cause an unprecedented impact like the dry spell that is happening now.
For instance, the failure of the monsoons would mean a delay in the planting season in both rain-fed and irrigated areas and result in low productivity. Likewise, deficits in the water levels of dams can lead to reduced capacity in hydropower generation and limited supply for irrigation and household use.
Due to its location, the Philippines is exposed to extreme climate and severe weather events that cause floods and droughts. The country is affected by an average of 19 tropical cyclones annually and by other severe weather systems such as the monsoons, and the intertropical convergence zone (ITCZ).
‘Siyam-siyam’
Tropical cyclones bring torrential rains (about 50 percent) and destructive winds in the country. The southwest monsoon or habagat is a weather system that normally brings prolonged rains or siyam-siyam in the western parts of the country during the months of May to September while the northeast monsoon or amihan affects the eastern parts of the country from November to March.
The ITCZ is characterized by the formation of cloud clusters associated with the convergence of equatorial winds blowing from the northeast and southeast. The ITCZ migrates from Mindanao to Luzon and back from March to December.
During this time of the year, the ITCZ is normally over Central and Southern Luzon and the Visayas. In some cases, two weather systems can affect different areas in the country at the same time.
In addition, the intensity, duration and spatial distribution of rainfall can also be influenced by large or planetary scale systems such as the subtropical high pressure area (which is associated with good weather) and pressure perturbations such as the Madden-Julian Oscillation (associated with rainfall occurrence when it is over our area).
What’s happening?
The more appropriate question would be “what is happening to the climate?” because the weather is always changing.
Weather and climate are two different things. Weather is what we experience on a day-to-day basis in terms of rainfall and temperature, cloud cover, wind and so on.
For instance, the weather may be cloudy and rainy today and overcast and humid tomorrow. Except in the equatorial region where most mornings are warm and sunny, cloudy by noon and stormy in the evening, the weather by its very nature is changeable. Other than the equatorial belt, the weather is not so predictable, hence the need for weather forecast.
Climate is the average weather for longer periods, say months and years.
In the second quarter of July, the province of Isabela complained that the planting season in rain-fed areas had been affected by the absence of rains.
Water levels of most major reservoirs in Luzon have persistently fallen below allowable levels necessary to meet the requirements for irrigation, domestic use and power. (See Table 1)
Due to the absence of rain, the energy sector has increased the use of coal and oil to compensate for the limited load from hydroelectric plants. National Power Corp. said that 18.95 percent on the average of the generation mix from 2001 to 2006 came from the hydro plants, peaking last year at 23 percent.
The generation mix is derived from coal, geothermal, hydro, natural gas and oil-based plants.
With the decrease in the capacity of hydroelectric plants to produce power, the slack is now being taken up by coal, oil, natural gas and geothermal energy-fed power plants.
It must be noted that in June and July, our coal and oil power plants should have not been operating because they were due for maintenance.
Fire
Fire incidence has increased in Metro Manila due to warmer weather in June and July.
Although officially, the Philippines is in the rainy season now, in reality, we are now experiencing summer-like weather. This makes the environment conducive to fires.
The unconventional weather is not only being experienced in the Philippines.
China, Europe
China has been hit by a record storm that killed a lot of people. Weather extremes are happening in England and other parts of Europe. There are floods in Australia, Indonesia, China, India and Malaysia. Even Japan has been hit by more cyclones this year.
There are five oceans and regions where tropical cyclones are most likely to occur. The busiest region is the Northwestern Pacific, followed by the Tropical North Atlantic and the Carribean, and the Northeastern Pacific, the Southern Indian Ocean and the Southwestern Pacific.
As per records in July, the Northwestern Pacific is relatively silent. Is it because it has become so tired due to the series of super typhoons it produced last year?
The dry spell we are having now is unconventional. It is happening during the rainy season. Furthermore, unlike the 1997-1998 drought which occurred during an El Niño event, the June-July 2007 dry spell is occurring during a La Niña-like event. There is cooling or a developing La Niña in the Pacific. During this period, the sea surface temperature east of the Philippines is warm. This should result in evaporation and convection and the eventual formation of rain. This is not happening. As will be shown later this is due to the presence of a high pressure area east of Luzon.
What we expected
By the end of July, eight tropical cyclones should have entered the Philippine Area of Responsibility (PAR). The weather charts should have shown a southwest wind flow at the surface and upper levels of the atmosphere, which would normally trigger the onset of the rainy season.
The ITCZ would have filled the water capacity of the parched soils in Central and Southern Luzon with its showers and thunderstorms. The country should have experienced the siyam-siyam of the habagat, which has its peak in July and August.
Our farmers would have already planted rice by June because the southwest monsoon would have set in by the end of May or early June. The watersheds of our major reservoirs would have been saturated with the rains in May and June and would have started to rise in July.
Only two cyclones
All of these did not happen. Only two cyclones entered PAR and did not even make landfall. The amount of rain these cyclones generated were not much. Luzon experienced summer-like conditions in June and July. The farmers started having problems with rain-fed fields.
But where are the rains? Are they falling in the right places?
For July, news of the landslides in Compostela Valley and Bukidnon due to heavy and continuous rains were typical in the months of December and January.
July was supposed to be a dry month in Mindanao. Satellite photo shows that last month, the ITCZ was generally over Mindanao and the Visayas as shown in Figure 2. This should not be the case in July, as the ITCZ should already be in Luzon.
The summer-like weather in Luzon, the nonformation of rain, the failure of the southwest monsoon that resulted in less rain and nonmigration of the ITCZ were due to the high pressure area east of Luzon. These weather systems dominated, resulting in the dry spell we are experiencing.
Two tropical cyclones entered the PAR, one in May and the other in July but their paths were off the average tracks occurring during these months.
Cause for alarm
The cyclones were too far to enhance the southwest monsoon that would have brought the much expected rains over the western sections of the country.
Is there a cause for alarm?
Definitely, “yes!” The observed rainfall in June and July 2007 was 40-percent below normal or average rainfall and the outlook for August is still generally dry. (See Figure 3.)
Metro Manila and parts of Northern, Central and Southern Luzon have either been very dry (> 40 percent) or have remained below normal or average rainfall (40 to 80 percent). This is a result of the dry spell.
Some of the signatures of a dry spell and drought include the presence of toxic algae bloom, adverse effects on agriculture, warmer-than-normal air temperature, decreased power supply, low water level, occurrence of bush and urban fires, and health problems related to a weird weather condition.
It is in this regard that the national government is being proactive. We are no longer waiting for the dry spell to turn into a more serious problem. Even before a drought condition is in effect in the country, interventions are being made now to mitigate the adverse effects of this unconventional dry spell.
Based on the weather over the past two months, some areas are now experiencing the impact of a dry spell. But are we heading toward a drought condition? The Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa) defines drought as three consecutive months of below 50-percent rainfall from the normal or average, hence, meteorologists and climatologists alike are closely monitoring the rainfall pattern in August.
Local climate and meso-scale weather systems such as tropical disturbances, monsoons and ITCZ are usually contributory to the normal rainfall condition this rainy season. However, with the extended dry spell in July, the effects of planetary weather systems appear to be dominant. Globally, the weather is not normal as it used to be.
Three scenarios
Based on the forecasts from different climate prediction centers, three scenarios may develop for the rest of the year:
Transition to a La Niña condition in the last quarter of 2007. Under this scenario, above average rainfall will be experienced in the later part of the year and would normalize the rainfall in Luzon.
The ridge of high pressure area will still prevail over Luzon and cause dry spell and drought until the end of year.
Normal-to-average rainfall in the last quarter similar to the 2004 conditions. Under this scenario, a number of tropical cyclones would hit Luzon and other parts of the country before the end of the year.
There is so much uncertainty in the climate forecast and this is clearly shown by the ensemble of forecasts from the various climate prediction centers. Despite these uncertainties, the Pagasa-Department of Science and Technology (DOST) was vigilant enough in observing the indicators of the impending dry spell and had issued the alarm to the National Disaster Coordinating Council before it was too late to mitigate the damage.
What can de done?
As a result, the national government initiated various intervention measures. What are these measures?
1. Supply side
Immediate
Optimum water allocation and utilization
Water supply distribution
- valving operations
- setting up of stationary and mobile water tanks
-chlorination to ensure water quality
Cloud-seeding operations
Monitoring and evaluation of droughts
Repair of dikes and other impounding infrastructures
Adoption of water impounding projects and shallow tube wells
1.2 Long-term
Rehabilitation of deep wells
Water harvesting
2. Demand side
2.1 Immediate
Water conservation
Use of resistant crops with less water requirement and early maturing varieties
Public awareness and understanding the nature of dry spell and drought and their impact.
2.2 Long-term
Enhancement of irrigation efficiency
Modified cropping calendar
Reduction of water leakage.
The dry spell and the proactive stand that the government and our people are doing show once again the resiliency of the Filipino nation. It is in having this sense of urgency to mitigate the adverse impact of the dry spell that the nation will once again rise to the challenge.
(Graciano P. Yumul Jr. is an undersecretary for Research and Development at the DOST, while Susan R. Espinueva is a senior weather specialist at the Pagasa.)
