Hurricanes and Tropical Storms- Free Lesson

Hurricanes are one of nature’s most powerful storms. They produce strong winds, storm surge flooding, and heavy rainfall that can lead to inland flooding, tornadoes, and rip currents.

States of Development

A storm evolves through different stages before it is labeled a hurricane. Initially a tropical disturbance, which has thunderstorms and rotating winds, or what scientists call cyclonic circulation. Next is a tropical depression, which is similar to a tropical disturbance, but has winds between 23 and 39 miles per hour. A tropical storm is the next level, which has stronger wind speeds between 40 and 73 miles per hour. Once winds reach 74 miles per hour, the storm is officially classified as a hurricane. The winds pick up energy from the warm surface ocean water. Hurricanes rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Hurricanes can vary in size and can grow to have a diameter of up to 600 miles, which is longer than the entire state of Florida! As a hurricane crosses over land, it begins to dissipate, or break apart and reduce in strength. This is because it is no longer over the warm ocean water that it needs for energy. At this point, a hurricane can still cause a lot of damage because of high winds, rain, and flooding, but unless it makes its way back over the open ocean, it is downgraded from a hurricane back to a tropical storm.

Predicting Hurricanes

What's the difference between a hurricane watch and a hurricane warning? During a hurricane watch, there is the possibility that a hurricane will make landfall within 36 hours, and people are advised to prepare for a possible storm ahead. When a hurricane warning is issued, a hurricane is definitely on the way, and will make landfall within 24 hours. The National Hurricane Center, located in Miami, Florida issues watches and warnings before hurricanes approach the coastline. They use computers with satellite images to figure out where and when a hurricane will come on shore. Sometimes, if a hurricane is strong enough, officials may require citizens to evacuate, or leave their homes, and travel to a safer place. Can you imagine flying a plane through a hurricane? If you're a hurricane hunter, it's your job! Hurricane Hunters, who work for the Air Force Reserve, fly airplanes called WC-130's on weather missions to help the National Hurricane Center make predictions about hurricanes, and gives them the information needed to issue accurate warnings. Pilots determine how fast the winds are blowing, how big the hurricane is, and which direction it's moving. This helps people to be better prepared for hurricanes as they approach shore.

Categories of Hurricanes

There are five categories of hurricanes, which are based on wind speeds. The categories help to make people aware of how much damage a hurricane may cause because the greater the wind speed, the more dangerous the storm. Category 1 – Winds 74 – 95 mph Winds snap branches, uproot trees, and overturn mobile homes that aren't secured to the ground. Category 2 – Winds 96 -110 mph Winds are strong enough to destroy weak doors and windows, and create 8-foot ocean waves. Category 3 – Winds 111 - 130 mph Intense winds cause major flooding near the coast, which can destroy homes and businesses. Category 4 – Winds 131 - 155 mph Winds are strong enough to destroy some buildings. Causes heavy damages to building roofs. Category 5 – Winds greater than 155 mph Buildings along the shorelines are washed away. Buildings can be completely destroyed.

Hurricane Names

Hurricanes and tropical storms are given names to help people identify them. Scientists refer to hurricanes and storms by name as they track them across the ocean. Before 1953, hurricanes were not given official names. From 1953 through 1978, hurricanes were only given female names, like Isabel, Camille, Claudette, and Wilma. Beginning in 1979, hurricanes were given the names of both women and men. Today, the names alternate by gender, and they are named alphabetically. For example, in 2010, storms were named as follows: Alex (male) Bonnie (female) Colin (male) Danielle (female) Earl (male) and so on... There are six different lists of names that change, so the same names are used every six years. The only way that a new name is added is when a hurricane has been particularly deadly or costly and the name is retired, then replaced with a new one.

Hurricane Safety Tips

There is no way to stop a hurricane or make it change direction, so if you ever find yourself in the path of a hurricane, be sure to be follow any emergency procedures that your community has in place. Here are some other hurricane safety tips.

• Be sure you have a battery-powered radio, batteries, fresh drinking water, and a supply of food. Also, if anyone in your family needs special medication, be sure you have a full supply.

• Tell neighbors, friends, and family members your emergency plans. Tell them where you'll go if you need to leave your home.

• If you live near the ocean, in low-lying area, or in a mobile home, leave your home and travel inland to a safe place. You could stay with a friend or family member, in an inland hotel/motel, or in an emergency shelter area.

• Keep listening to the radio if a hurricane is approaching. If local authorities instruct you to evacuate, do it immediately.

• Before a hurricane arrives, be sure your family's car is filled with fuel. If the electricity goes out, the fuel pumps at gas stations will not work.

• Stay inside during the storm. You could be seriously injured if you go outside.