UNDERSTANDING TYPHOONS module 2 Overview

Every year the Philippines is hit by typhoons. No part of the country is spared. All provinces have been visited by a typhoon at one time or another. In recent years, the Philippines had been overwhelmed by powerful tropical cyclones.

Who could forget the terrible flood brought byTropical Storm Ondoy in 2009? Or the peopleswept out to sea during Tropical Storm Sendongin 2011? Or the poor community of New Bataanburied in mud spawned by Typhoon Pablo in2012?According to the Philippine Atmospheric,Geophysical, and Astronomical ServicesAdministration (PAGASA), about 20 tropicalcyclones enter the Philippine Area ofResponsibility each year. We have to beknowledgeable about tropical cyclones if wewant to prevent the loss of more lives.

WHAT IS TYPHOON?

Typhoon tropical storm: a violent tropical storm in the

western Pacific and Indian oceans.

are known as tropical cyclones, which is thegeneral name for all such storms includinghurricanes and typhoons.

Hurricane, name given to violent storms thatoriginate over the tropical or subtropical waters ofthe Atlantic Ocean, Caribbean Sea, Gulf of Mexico,or North Pacific Ocean east of the InternationalDate Line. Such storms over the North Pacific westof the International Date Line are called typhoons.

We all know what a typhoon is. Ormore accurately, we know what toexpect when a typhoon comes. Weget a lot of rain and strong winds.Now, you may not have noticed it butthe winds in a typhoon move in acertain direction. They go around acentral area.

Figure 1. A super typhoon as seen from high above the Earth; at the center isthe “eye” of the super typhoon. Image by NASA EarthObservatory

Table 1. Tropical Cyclone Categories

Category Maximum Wind Speed kilometers per hour (kph

Tropical Depression 64

Tropical Storm 118

Typhoon 200

Super typhoon greater than 200

If the wind speed is less, from 119 to 200 kph, then it iscalled a typhoon. If the wind speed is between 65 and 118kph, it is called a tropical storm. And when the windspeed is between 35 to 64 kph, it is a tropical depression.

Tropical depression, tropical storm, typhoon, and supertyphoon are categories of tropical cyclones (Table 1). Insimple terms, a tropical cyclone is a system ofthunderstorms that are moving around a center. As thewinds intensify or weaken, the category is upgraded ordowngraded accordingly.

In a super typhoon, the wind speed is greater than 200kilometers per hour (kph).

The term typhoon is used only in the northwesternpart of the Pacific Ocean. In the northeastern partof the Pacific Ocean and in the northern part of theAtlantic Ocean, the equivalent term is hurricane.Thus, a hurricane on one side of the Pacific Oceanwill be called a typhoon if it crosses into the otherside.

In the Philippines, we use the same word for allcategories of tropical cyclones. We call it bagyowhether it is a tropical depression, a tropical stormor a typhoon.

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