Supertyphoon Haiyan (photo: NASA).The words typhoon or hurricane mean the same thing. A typhoon is an intense tropical cyclone in the Pacific Ocean. In the Atlantic Ocean, typhoons are called hurricanes. A cyclone is a low pressure system. The air in the low pressure system revolves around the center of the cyclone. In a typhoon, the air moves at high speeds and produces dangerous winds.

Photo: Supertyphoon Haiyan approaching the Philippines (Creative Commons: NASA).

What are Tropical Cyclones?

A tropical cyclone is an area of low air pressure. They form near the equator over warm ocean waters. If conditions are right, the cyclone becomes more intense with winds that move faster and faster. Air rises at the center or eye of the cyclone. This results in formation of clouds and rain.

Tropical cyclones are classified on the basis of their wind speed. The list below is based on the system used by the Japanese Meteorological Agency.

  • Tropical Depression: wind speed less than 62 kilometers per hour.
  • Tropical Storm: wind speed from 62 – 88 kilometers per hour.
  • Severe Tropical Storm: wind speed from 89 – 117 kilometers per hour.
  • Typhoon: wind speed from 118 – 149 kilometers per hour.
  • Severe Typhoon: wind speed from 150 – 189 kilometers per hour.
  • Super Typhoon: wind speed more than 189 kilometers per hour.

Most Destructive Typhoons

Super Typhoon Haiyan (or Yolanda) struck the Philippines in 2013. It had the highest wind speeds ever recorded for a typhoon. Haiyan’s wind speeds reached 195 kilometers per hour. The hurricane killed over 6,300 people and affected 11 million people.

The most destructive typhoon was Typhoon Nina which hit China in 1975. The typhoon caused many reservoirs of water to fail. This resulted in flooding that killed as many as 100,000 people.

The destructive power of a typhoon comes from its strong winds. These winds also create a storm surge that can cause a lot of damage.

Hurricane Driven Storm Surge Video

Video: storm surge during Typhoon Haiyan (source: YouTube).

In the video, you can also observe the power of the storm surge. These are waves driven by the winds of the typhoon. The storm surge can cause widespread flooding.

Typhoon Season

Typhoons can occur in any month of the year. However, they occur most frequently in the months from June to November. The typhoon usually begins as a tropical depression. If the cyclone moves over warm waters, it will usually become more intense. Winds begin to move faster around the eye of the cyclone and it may develop into a typhoon.

Improving Your Reading and Thinking Skills

Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.


How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.


What is the Difference Between a Hurricane, Cyclone and Typhoon?, NOAA.