science education

Exploring Nature Science Education Resource:

Life Science, Earth Science, and Physical Science Resources for K-12

Storms - Hurricanes

Storms - Hurricanes

About This Storm

Hurricanes, also called tropical cyclones, are fierce storms that start over warm, tropical waters and grow into giant, wind-driven cyclones. They can do terrible damage to anything in their path.

Hurricanes start as tropical storms in the warmer areas (tropical and subtropical latitudes) of the northern Atlantic. This area is often just referred to as the tropics. Hurricanes are called by many names. The hurricanes that form in the western Pacific Ocean are called typhoons, while hurricanes in India are often called cyclones.

 

What Events Form This Kind of Storm?

Tropical storms form because the tropics have lots of warm sunshine that heats the ocean and evaporates ocean water into rising cumulus clouds. In the tropics these clouds often become thunderstorms by late afternoon. If many thunderstorms form in a row in this region it is called a squall line. As a squall line passes, it brings gusty wind and heavy rain.

If a line of tropical thunderstorms form over warm ocean water with humid air and winds, this can come together to form a tropical wave (or tropical disturbance). The tropical wave can grow into a tropical depression as the winds pick up. Soon it can grow into a tropical storm. At this point, meteorologists give it a name. Sometimes a tropical storm then grows into a hurricane. It has officially become a hurricane if the winds reach 75mph (64 knots).

The National Weather Service started naming hurricanes with women’s names in 1953. In 1978, storm names began alternating between male and female names and including Spanish, French and Dutch names. For any given year, storm names are decided (ahead of time) by the World Meteorological Organization. If a storm takes many human lives, that name is never used again.

An average hurricane is about 300 miles (about 500 km) wide. They are circular storms that spin counter clockwise in the Northern Hemisphere and wrap around a central eye. Interestingly, hurricanes in the Southern Hemisphere, hurricanes spin clockwise! Hurricanes form between 5° and 20° latitudes and not on the equator. This is because there is no spinning wind force at the equator.

 

Weather Conditions That Are Good for This Kind of Storm

Hurricanes build when surface winds over the ocean meet to form a “wave” – an area of low pressure. Low pressure leads to convection – this is when warm air rises and cold air sinks. The conditions for forming a hurricane are best in June through November when the ocean temperature is about 80° (26°C).

It is thought that all the hurricanes that form in the Atlantic begin with a tropical wave over Africa – but only if Africa is having a wet year. In drought years in Africa, there are fewer hurricanes over the Atlantic. Most hurricanes last less than a week. They begin to lose power when they hit colder water or land.

 

Storm Dangers

The eye of a hurricane has few clouds and only light wind. When the eye of a hurricane passes over an area, sometimes people think the storm is over. As a matter of fact, this is a very dangerous time to be outside during a hurricane. The eye of a hurricane is surrounded by a ring of strong thunderstorms called the eye wall. The hurricane eye wall has some of the storm’s strongest and most damaging wind. As the eye passes over an area, serious damage can result from the wind, rain and lightening in the following eye wall. The high winds of a hurricane come with heavy rain and big waves. This can cause dangerous hurricane flooding.

 

Historic Examples of This Kind of Storm

The deadliest hurricane on record in the United States happened in 1900. It made land fall in Galveston, Texas. Though it was not the most powerful hurricane on record, it caused the most deaths – more than 6,000 people. This happened for several reasons. First, in 1900, weather officials did not have the modern technology we have today for tracking storms. They could not judge where the hurricane would travel in enough time to warn people.  The second reason was Weather Bureau policy at the time – that a hurricane warning might cause people to panic. This policy changed after that storm.

In more recent history, hurricane Katrina hit U.S. shores in 2005. The storm surge destroyed the levee protecting New Orleans, Louisiana and flooding the city. More than 1,300 people died in the storm and following flood.

 

Quick Storm Facts

  1. A tropical storm is called a hurricane when its winds are more than 74 miles per hour (64 knots).
  2. An average hurricane is about 300 miles (about 500 km) wide.
  3. Hurricanes are circular storms that spin counter clockwise in the Northern Hemisphere and wrap around a central eye.
  4. In the Southern Hemisphere, hurricanes spin clockwise.
  5. The eye of a hurricane has few clouds and only light wind.
  6. When the eye of a hurricane passes over an area, the storm is not over!
  7. The eye of a hurricane is surrounded by a ring of strong thunderstorms called the eye wall.
  8. The eye wall has some of the storm’s strongest and most damaging wind.
  9. The high winds of a hurricane come with heavy rain and big waves.
  10. Hurricanes form best when the ocean temperature is about 80° (26°C).
  11. The conditions for hurricane formation are best in June through November.
  12. Hurricanes form between 5° and 20° latitudes.
  13. Hurricanes do not form on the equator (latitude 0°) because there is no spinning wind force there.
  14. Hurricanes start when a low pressure area over the ocean leads to convection – warm air rising and cold air sinking.
  15. Hurricanes may form in the Atlantic with a tropical wave over a rainy season in Africa.
  16. Most hurricanes last less than a week. They begin to lose power when they hit colder water or land.

Citing Research References

When you research information you must cite the reference. Citing for websites is different from citing from books, magazines and periodicals. The style of citing shown here is from the MLA Style Citations (Modern Language Association).

When citing a WEBSITE the general format is as follows.
Author Last Name, First Name(s). "Title: Subtitle of Part of Web Page, if appropriate." Title: Subtitle: Section of Page if appropriate. Sponsoring/Publishing Agency, If Given. Additional significant descriptive information. Date of Electronic Publication or other Date, such as Last Updated. Day Month Year of access < URL >.

Here is an example of citing this page:

Amsel, Sheri. "Storms - Hurricanes" Exploring Nature Educational Resource ©2005-2019. October 22, 2019
< http://www.exploringnature.org/db/view/Storms-Hurricanes >

Exploringnature.org has more than 2,000 illustrated animals. Read about them, color them, label them, learn to draw them.

cheetah, tiger, panda, fox, bear, cougar