Hurricanes: Formation and Characteristics

Hurricane Definition

• Hurricanes form over warm waters in tropical areas, characterized by high-speed winds within a large rotating storm.
• To be classified as a hurricane, a storm must have sustained winds of at least 74 miles per hour.
• Hurricanes must have an area of low air pressure in the center, known as the "eye".
• In the Northern Hemisphere, hurricanes rotate counterclockwise; in the Southern Hemisphere, they rotate clockwise due to the Coriolis effect.

Other Names

• The scientific name for a hurricane is tropical cyclone, but the storms have different names depending on their location.
• In North America and the Caribbean, these storms are called "hurricanes."
• In the Indian Ocean, they are known as "cyclones."
• In Southeast Asia, they are called "typhoons."

Hurricane Formation

• Hurricanes form over warm ocean water in the tropics.
• Warm, moist air rises over the water and is replaced by cooler air.
• As cooler air warms, it also rises, and this cycle continues until huge storm clouds form.
• These clouds begin rotating with the Earth's spin in an organized system.
• Sufficient warm water and increased wind speeds lead to hurricane formation.

Parts of a Hurricane

• Eye: The hurricane's center, which is is typically 20–40 miles wide, has low air pressure, generally no clouds, and calm winds. The most dangerous part of the storm is the edge of the eye, called the eye wall
• Eye Wall: A wall made up of very heavy clouds around the edge of the eye.
• Rainbands: Large spiral bands of rain that can drop huge amounts of rainfall, causing flooding once the hurricane hits land.
• Diameter: Hurricanes can span a diameter of over 600 miles.
• Height: Storm clouds in powerful hurricanes can become extremely tall, reaching nine miles into the atmosphere.

Time and Place

• Tropical cyclones occur near the equator over the ocean in areas where the water is warm, which favors storm formation.
• Seven major areas worldwide are susceptible to producing tropical cyclones.
• In the Caribbean and Atlantic, hurricane season occurs between June 1st and November 30th.

Effects of Hurricanes

• Hurricanes can cause massive damage, primarily due to flooding and storm surge.
• Rising ocean levels at the coastline are caused by the storm's power.
• High-speed winds can blow down trees and power lines and damage homes.
• Small tornadoes can develop inside hurricanes, causing destruction.

Naming Hurricanes

• The World Meteorological Organization names hurricanes in the Atlantic.
• An alphabetical list of names is used, and the first storm of the year always starts with the letter "A."
• Six lists of names exist, with a new list used each year.
• The letters Q, U, X, Y, and Z are not used for the first letter of naming hurricanes.
• The names alternate between boy and girl names throughout the list.

Hurricane Categories

• Sustained wind speed is used to categorize tropical cyclones.
• Tropical Depression: 38 mph or less
• Tropical Storm: 39-73 mph
• Category 1 Hurricane: 74-95 mph
• Category 2 Hurricane: 96-110 mph
• Category 3 Hurricane: 111-129 mph
• Category 4 Hurricane: 130-156 mph
• Category 5 Hurricane: 157 mph+

Hurricane Safety

• Hurricanes are natural disasters that can be tracked days in advance.
• Areas may be required to evacuate, depending on the severity of the hurricane.
• People planning to stay home should build an emergency kit beforehand.
• During the storm, stay away from windows and doors and remain inside.
• Seek shelter in a closet or bathroom, and be careful when venturing outside after the storm.