Hurricanes for Middle School Science

Feb 20

4 min read

Hurricanes are one type of extreme weather. They are an example of what happens when the water cycle goes into overdrive because of excess heat. The topic of hurricanes can be confusing because there are many different names for these tropical storms. Other names include tropical cyclones and typhoons. All of these names describe the same type of powerful storms.

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Hurricanes

Hurricane is one name for a tropical cyclone. Tropical cyclones are called typhoons in the Western North Pacific around the Philippines, Japan, and China. In the Western South Pacific around the Indian Ocean, they remain tropical cyclones, and in the Caribbean, North Atlantic, and Northern Pacific regions, we call the storms hurricanes. All of these names describe the same intense storms formed over warm ocean waters and made up of extreme wind and rain.

All hurricanes start as tropical disturbances. A tropical disturbance forms when warm water evaporates from the ocean. The water vapor rises, and as the air temperature drops, condenses into clouds made up of liquid water. Water vapor has more energy than liquid water, so the excess energy is released as heat that warms the air.

At first, this process creates puffy cumulus clouds, but as the clouds rise, they meet more clouds higher in the atmosphere. These clouds combine to form dark grey cumulonimbus clouds full of even more water droplets. Inside the clouds, warm air rises to form updrafts and cool air sinks, forming downdrafts. The downdrafts carry rain down through the cloud. All of the moving air and water molecules build up electrical charges inside the cloud. These charges can lead to a thunderstorm full of lightning.

When the winds within the tropical disturbance reach 23 miles per hour, scientists classify it as a tropical depression. At 39 miles per hour, it becomes a tropical storm, and at 74 miles per hour, it becomes a tropical cyclone or hurricane.

For a hurricane to form, the top 150 feet of the ocean water must be at least 80 degrees Fahrenheit because the evaporation of warm ocean water fuels the storm. Then, the heat released when the water vapor condenses into liquid water continues to power the wind within the storm.

The winds in a hurricane come from low pressure in the center of the storm. Air molecules always move from areas of high pressure to areas of low pressure. The winds spin as a result of the Coriolis Effect. The Earth spins on an axis, so ocean surface water and air molecules are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. A hurricane in the northern hemisphere will rotate counterclockwise due to the Coriolis Effect.

Hurricanes are giant storms. They can be 200 miles in diameter and 9 miles tall. Scientists organize hurricanes into three regions. The outer region is the largest part of the storm. It is about 130 miles wide, with winds pushing toward the center of the hurricane. The outer region is full of rainbands, thunderstorms that spiral around the center of the storm.

The second region is called the eyewall of the storm. It is only about 10 miles thick. The eyewall contains the strongest winds and most torrential rainfall of the hurricane. It surrounds the interior region of the hurricane that scientists call the eye. The eye is around 20 to 40 miles wide. It contains clear skies and warm temperatures. The low atmospheric pressure inside the eye of the hurricane drives the winds around it.

Scientists use the Saffir-Simpson Hurricane Scale to classify hurricanes. Category 1 hurricanes have wind speeds between 74 and 95 miles per hour. Category 2 hurricane wind speeds are between 96 and 110 miles per hour, category 3 are between 111 and 129 miles per hour, category 4 are between 130 and 156 miles per hour, and category 5 are higher than 157 miles per hour. Category 5 hurricanes are the most deadly storms.

In 1978, the World Meteorological Organization began naming hurricanes using alternating male and female names. Scientists reuse the names every six years. The names of the most intense, damaging, and infamous hurricanes are retired and replaced with new names.

When hurricanes reach land, the effects are devastating to people living along the coast. The intense wind tears buildings apart, and the heavy rains and storm surge cause flooding. The circular winds can also generate tornadoes around the hurricane.

However, hurricanes can't sustain their power over land for long because they lose the power created by the evaporating water from the warm ocean. Hurricanes will also fall apart if they move over colder water.

Hurricane season in the northern hemisphere of the Atlantic Ocean runs from June 1 to November 30 because the ocean water is the warmest during this time. To protect the people living in Florida and along the Gulf Coast of Mexico, scientists use weather satellites to spot and track forming hurricanes. The National Oceanic and Atmospheric Administration also sends out special weather planes that fly inside a hurricane to gather information about the storm. This information helps scientists make predictions about what the storm will do and teaches them more about hurricanes.