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 4
Tropical cyclone signals: bracing for the wind (Second of two parts)
A
n average of 100 tropical cyclones are formed every year around the world. Of this total, the bulk is formed in one region or area—the western north Pacific Ocean. An average of 30 cyclones every year are formed here. They usually move westward approaching the Philippines. Once in the Philippine area of responsibility (PAR), these tropical cyclones, now called typhoons, usually move northwest; in the process, leaving destruction to the provinces in northern Luzon. The typhoons then exit the PAR and head toward Taiwan, southern China or Japan.
Seasons and path of potential destruction What has been the pattern of frequency that tropical cyclones or typhoons enter the Philippines? When and where can they bring potential destruction? PAGASA estimates that the monthly average frequencies of tropical cyclones that enter the PAR from January to April are 0.4, 0.3, 0.3 and 0.5, respectively. This suggests that these months have the slimmest chance of tropical cyclone activities in the Philippines throughout the year. Starting May and June, however, an average of one tropical cyclone for each month occurs and then jumps to about three each for the months of July, August and September. By October and November, an estimate of about two per month occurs, signaling the start of descent of the cyclone activities in the Philippines, with just about one occurrence for the month of December. Although there is a recession in the number of tropical cyclone occurrences in the months of October to December, it is to be noted nevertheless that most of the destructive cyclones/ typhoons that have taken place were recorded during this period. This is due to the fact that the paths of these disturbances have, as seen in the illustrations in the next page, a much wider range of possible tracks over Luzon and Visayas during this period. At the same time, there is also a high probability that these cyclones tend to cross the archipelago, creating much damage to the populace. Is there any change in the cyclones/typhoons' path when seasonal phenomena like El Niño and La Niña take place? At the moment, the weather bureau is in the process of further tracking the average paths of tropical cyclones and determining if there is a difference in their usual path during the periods of El Niño and La Niña.
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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TROPICAL CYCLONE SIGNALS
Economic Issue of the Day
December 2005 Volume V Number 4
Tropical cyclone average tracks 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. 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. ❋❋❋
Jan to Mar
Apr to Jun
Jul to Sep
Oct to Dec
References http://hurricanewaves.org http://www.hko.gov.hk/informtc/nature.htm http://www.ndcc.gov.ph http://www.pagasa.dost.gov.ph http://www.typhoon2000.ph/info.htm http://www.wikipedia.org Lucero, Anthony. Warning system for tropical cyclones in the Philippines. Powerpoint presentation. PAGASA. Verceles, Ernesto. Climate concepts, climate of the Philippines and ENSO. Powerpoint presentation. PAGASA.
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
The project Bridging the gap between seasonal climate forecasts (SCFs) and decisionmakers in agriculture is 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 the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Philippine Institute for Development Studies (PIDS), Leyte State University (LSU), South Australian Research and Development Institute (SARDI), New South Wales Department of Primary Industries (NSW/DPI) and University of Sydney.