Philippine Institute for Development Studies Surian sa mga Pag-aaral Pangkaunlaran ng Pilipinas December 2005
Economic Issue of the Day
Vo l u m e V N u m b e r 3
Tropical cyclone signals: bracing for the wind (First of two parts)
T
yphoons, tropical storms, tropical depressions and other weather disturbances are usual occurrences in the Philippines. According to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), an average of 19-20 tropical cyclones visit the country every year, some of which may cause deaths to many people and millions of pesos in damaged property. But how strong can tropical cyclones be and how much damage can they cause? What is their pattern of occurrence? These questions are important to consider especially for a typhoon-frequented country like the Philippines so that one can be better prepared to deal with them and thereupon prevent possible damages and loss of lives. In a nutshell, the various terms listed herein are actually interchangeable, depending on the intensity of the weather disturbance and location. By international agreement, tropical cyclone is the general term for all storm circulations that originate over tropical waters. It is called hurricane over the Atlantic Ocean, cyclone over the Indian Ocean and typhoon over the Pacific Ocean. In meteorology, a tropical cyclone is a low-pressure system wherein the central region is warmer than the surrounding atmosphere. Its strongest winds are concentrated close to its center. From pictures taken above the earth, a tropical cyclone resembles a huge whirlpool of white clouds. It has a disc-like shape with a vertical scale of tens of kilometers against horizontal dimensions of hundreds of kilometers.
Types of tropical cyclones Tropical cyclones are categorized into three types: ❋ Tropical depression – a tropical cyclone with maximum surface winds ranging from 37 to 62 kilometers per hour (kph) (20 to 33 knots). ❋ Tropical storm – a tropical cyclone with maximum surface winds in the range of 63 to 117 kph (34 to 63 knots). ❋ Typhoon/hurricane – a tropical cyclone with maximum surface winds of 119 to 239 kph (64 to 129 knots).
What is a tr opical tropical cyclone? In meteorology, a tropical cyclone is a low-pressure system wherein the central region is warmer than the surrounding atmosphere. Its strongest winds are concentrated close to its center. From pictures taken above the earth, a tropical cyclone resembles a huge whirlpool of white clouds. Tropical cyclone is the general term for all storm circulations that originate over tropical waters. It is called hurricane over the Atlantic Ocean, cyclone over the Indian Ocean and typhoon over the Pacific Ocean.
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Economic Issue of the Day
December 2005 Volume V Number 3
The Economic Issue of the Day is one of a series of PIDS efforts to help in enlightening the public and other interested parties on the concepts behind certain economic issues. This dissemination outlet aims to define and explain, in simple and easy-to-understand terms, basic concepts as they relate to current and everyday economics-related matters. This Issue was prepared by Barbara Gualvez, Executive Assistant III at PIDS, under the supervision of Jennifer Liguton of PIDS, and Ernesto Verceles of PAGASA. The article is part of the dissemination program being conducted for the project Bridging the gap between seasonal climate forecasts (SCFs) and decisionmakers in agriculture, a four-year collaborative undertaking that aims to identify and close the gap between the potential and practical application of SCFs to agricultural systems and policies in the Philippines and Australia. The project is funded by the Australian Centre for International Agricultural Research (ACIAR) and implemented by PAGASA, PIDS, LSU, SARDI, NSW-DPI and University of Sydney. Most of the facts and information are based on PAGASA materials taken from the PAGASA website and lecture notes. The views expressed are those of the author(s) and do not necessarily reflect those of PIDS or the project's sponsors. ❋❋❋
Philippine Institute for Development Studies NEDA sa Makati Building, 106 Amorsolo Street Legaspi Village, Makati City Telephone Nos: 8924059 and 8935705 Fax Nos: 8939589 and 8161091 URL: http://www.pids.gov.ph
TROPICAL CYCLONE SIGNALS
A super typhoon is a term used by the U.S. Joint Typhoon Warning Center in Guam for typhoons that reach maximum surface winds of at least 242 kph (130 knots). The areas affected by these tropical cyclones, as indicated by their respective term, are those in the tropics, the region of the earth centered on the equator and sandwiched between the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern hemisphere. Countries that are situated in these areas are found in Africa, Asia, South and Central America, the Carribean, and those in the Indian and Pacific Oceans. Most of these are developing countries such as Kenya, Mozambique, the Philippines, Indonesia, Malaysia, Egypt, Mexico, Ecuador, Brazil, Saudi Arabia, and the Bahamas, among others. It also includes southern China, Australia, and Chile.
Philippine storm warning signals For the Philippines, PAGASA devised four warning signals that describe the meteorological conditions and impact of the winds of an approaching tropical cyclone as shown below: Signal No.
Wind Speed and Time of Occurrence
1
30-60 kph within the next 36 hours
2
60-100 kph within the next 24 hours
3
100-185 kph within the next 18 hours
4
Greater than 185 kph within the next 12 hours
Impact of Winds
Twigs and branches may be broken; some banana plants may be tilted; houses of very light material may be unroofed; flowering rice crop may be damaged; in general, very little or no damage may be experienced by the community. Some coconut trees may be tilted and broken; few big trees may be uprooted and many banana plants may be downed; rice and corn may be adversely damaged; many nipa and cogon houses may be partially or totally unroofed and old galvanized iron roofings may be peeled off; in general, winds may bring light to moderate damage to the community. Many coconut trees may be broken or destroyed; almost all banana plants may be downed while many trees may be uprooted; rice and corn crops may suffer heavy losses; majority of nipa and cogon houses may be unroofed or destroyed and there may be considerable damage to structures of light to medium construction; widespread disruption of electrical power and communication services may also occur; in general, moderate to heavy damage may be expected, practically in the agricultural and industrial sectors. Coconut, rice and corn plantations may suffer extensive damage and many large trees may be uprooted; most residential and institutional buildings of mixed construction may also be severely damaged; electrical power distribution and communication services may be disrupted; in general, damage to affected communities can be very heavy.