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Common Hydrometeorological Phenomena
Transcript of Common Hydrometeorological Phenomena
On the average, the Philippines experiences almost 20 typhoons annually. PAGASA issues public storm warning signals based on speed, intensity, size of circulation, and direction of winds. Some of the hazards associated with typhoons are:
Monsoons are seasonal winds. The Philippines experiences two monsoons every year, the
Changes in season are indicated by reversing winds.
blows to the east while
blows to the west.
The rotating spiraling winds are a result of the conservation of angular momentum which is manifested in Earth's rotation on its axis. Air flows inward towards the axis of rotation. The direction of the cyclone depends on its location on Earth. The Northern Hemisphere, where the Philippines is located, would have counterclockwise direction of cyclones.
A tornado or locally known as ipo-ipo is a rapidly swirling condensation funnel whose narrow end comes in contact with the ground. Usually, the violent swirling air column carries debris and other objects that it can pick up from the ground.
Prevention and Management of Hydrometeorological Hazards
Hydrometeorological hazards can be predicted more precisely as they follow a cyclic pattern because they are influenced by seasons. They occur at a particular period or season, as compared with other natural hazards that may occur unpredictably.
Tropical cyclones (also known as typhoons for those occurring in the Northwest Pacific region, and hurricanes for those developing in the Atlantic and Northeast Pacific regions) are storm systems characterized by rapidly spiraling storms, low-pressure center, and intensely strong winds. Typically, they begin over warm tropical waters. They derive their energy from the evaporation of water from the warm ocean surface, which ultimately recondenses into clouds and rain, while the moist air rises and cools in the atmosphere.
Cyclones can have increased strength of wind. When this happens, they can develop into tropical depressions. As the strength of the wind increases, the tropical depression (45 to 62 km/h) develops into a storm (63 to 117 km/h), then into a typhoon (118 to 239 km/h), and finally into a super typhoon (240 km/h or higher.)
When classes are suspended because of a typhoon, how do you usually feel? Should you be happy or sad?
The strength of winds can destroy lightweight structures and uproot plants and trees. Super typhoons can even wipe out an entire community, leaving families homeless.
Heavy rainfall leading to flooding
Some typhoons are associated with continuous and heavy rains. The identified primary causes of immediate flooding stem from either clogged drainage or low elevation of affected areas. Flooding can even worsen in places with high density of population and narrow spaces. During rainy seasons, rainwater may not subside for days if the drainage systems are clogged, or there are obstructions in the pathways of water. This can lead to more problems such as:
Disruption of commercial and industrial operations, leading to loss of income;
Displacement of affected families;
Damaged properties resulting from corrosion and water intrusion; and
Health diseased including leptospirosis, and pathological diseases caused by waterborne agents.
The amihan or the northeast monsoon is characterized by cold, gusty wind with little or no precipitation. It begins in early September up to May or June. The cool wind is from northern China and Siberia gradually moving southward as it reaches the Philippines. Hazards associated with amihan are thunderstorms, lightning, heavy rainfall, and flooding, all of which may lead to property damage and health risks.
The habagat or the southwest monsoon is characterized by hot and humid atmosphere with frequent heavy rainfall. It begins in early June and ends in August or September. In some cases, habagat may bring about problems and hazards during extreme heat and drought. Here, water shortage challenges all sectors of the society, especially the agricultural industries. Lack of water for irrigation can decrease crop yield.
Tornadoes occur anywhere in the Philippines at an average of 12 to 24 times in a year (PAGASA, 2011). Among the immediate hazards of tornadoes are:
Strong whilring winds
As the winds move toward the center (centripetal force), the impact breaks objects along its path. Depending on strength, the whirling wind can also pick up objects as heavy as vehicles. From midair going down, these objects can smash other objects or hit people as they fall to the ground.
Flying debris and dust
Fragments of destroyed objects are hurled away, and soil particles scatter around the area, potentially hitting or slamming onto a structure or person.
Tornadoes can destroy power lines and cause fire. At night, sparks seen fro tornado site can mean snapping power lines that have been damaged by the passing tornado.
Hydrometeorological Hazard-prone Areas in the Philippines
The map shown here is a composite risk map that considers projected rainfall change, risk to projected temperature increase, risk to typhoons, and risk to El Niño-induced drought. The combination of all these meteorological hazards has recently caused disasters to the islands of Luzon and Visayas, where most of the risks are concentrated.
The pattern of typhoon tracks has been frequenting the eastern portion of the country, such that more disaster preparedness efforts are now centered on Eastern Visayas. These weather disturbances increase the risks in areas whose topographical features are prone to landslide and flooding. Sadly, most of the rural areas in the Visayas have been exploited of their natural resources, the effects of which are characterized by degradation and instability of land. With this profile, the susceptibility of these areas to hydrometeorological hazards is high.
PAGASA has installed various weather stations all over the country to accurately detect, observe, measure, and forecast any of possible meteorological hazards. It is then important to be aware and be prepared at the onset of the season for specific hazards so that disasters may be minimized if not totally prevented.
As soon as PAGASA issues a warning for any hydrometeorological hazard:
1. Check your emergency kit.
2. Make plans for evacuation to higher ground especially if you live in a coastal area.
3. Participate in cleanup activities to clear pathways of rainwaters to avoid flooding.
4. Cut dead or rotting trees and trim tree branches that could otherwise fall off from the force of winds and cause injury or damage.
5. Reinforce supports or foundations in your house to withstand strong winds or water.
6. Transfer valuables and other furniture to higher ground especially if your place is flood-prone.
7. Secure objects found outside that could be blown away or cause damage to property or bring harm to people.
8. Unplug any electronic equipment.
During any hydrometeorological hazard:
1. Stay indoors. Do not go to isolated or open areas.
2. Stay updated with PAGASA's official announcements by listening to the news.
3. If the electricity is out, use battery-operated radios.
4. Stay away from corded devices such as telephones, air conditioners, computers, and lightning fixtures. Power surges from lightning can cause serious damage.
5. Do not go near windows, doors, and porches.