Hurricanes: Formation and Characteristics

Hurricane Definition

• Hurricanes form over tropical waters and consist of a large rotating storm with high-speed winds.
• To be considered a hurricane, a storm must have sustained winds of at least 74 miles per hour and a low air pressure center called the "eye".
• Hurricanes rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere due to the Coriolis effect (Earth's rotation).

Hurricane Names

• Hurricanes, cyclones, and typhoons are all the same thing, just different names based on location.
• In North America and the Caribbean they are "hurricanes."
• In the Indian Ocean, they are called "cyclones."
• In Southeast Asia, they are called "typhoons."
• The scientific name for a hurricane is tropical cyclone.

Hurricane Formations

• Hurricanes form over warm ocean water in the tropics.
• Warm, moist air rises, which leads to cooler air replacing the warm air.
• This cycle continues, resulting in large storm clouds that begin to rotate with the Earth's spin.
• Hurricanes form if there is enough warm water, in addition to increasing storm cloud sizes and wind speed.

Parts of a Hurricane - Eye

• The hurricane's center is called the eye, ranging from 20–40 miles wide.
• The eye has very low air pressure.
• The eye generally has no clouds.
• The eye has calm winds.
• The edge of the eye, called the eye wall, is the most dangerous part of the storm.

Parts of a Hurricane - Eye Wall

• The eye wall is a wall of heavy clouds around the edge of the eye.

Parts of a Hurricane - Rainbands

• Rainbands are large spiral bands of rain.
• Rainbands can drop large amounts of rain, causing flooding.

Parts of a Hurricane - Diameter and Height

• Hurricanes are measured from one side to the other.
• Hurricane can span a diameter of over 600 miles.
• Storm clouds in hurricanes can become extremely tall.
• Hurricanes can reach nine miles into the atmosphere.

Time and Place

• Tropical cyclones occur near the equator over the ocean where the water is warm.
• There are seven major areas in the world that are more susceptible to producing tropical cyclones.
• Hurricane season in the Caribbean and Atlantic oceans occurs between June 1st and November 30th.

Effects

• Hurricanes can cause massive damage if they strike land.
• Most damage is caused by flooding and storm surge, where the ocean level rises at the coastline.
• High-speed winds can blow down trees and power lines and damage homes.
• Small tornadoes can develop inside hurricanes.

Names

• The World Meteorological Organization names hurricanes in the Atlantic.
• An alphabetical list of names are used as storms appear, starting with the letter "A."
• Six lists of names exist, with a new list being 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 male and female names.

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+.

Safety

• Hurricanes are natural disasters that can be tracked in advance.
• Areas may be required to evacuate, depending on the severity.
• Build an emergency kit if you plan to stay home.
• Bring in anything that may become airborne in high winds.
• Stay away from windows and doors and remain inside during the storm.
• Seek shelter in a closet or bathroom.
• Be careful when venturing outside after the storm.