What is a Hurricane Anyway?
Before hurricane season even begins, it’s a good idea to become familiar with what they are and some of the terminology associated with them. There are four steps to a storm becoming a hurricane and five categories of the storm once it reaches hurricane status.
Hurricanes begin as thunderstorms that hold their shape and intensity for more than 24 hours, according to the Hurricane Center at the National Weather Service. These storms, known as a tropical disturbance, generally move across the warm waters of the Atlantic, Caribbean, or the Gulf of Mexico from west to east.
Once the disturbance maintains a wind speed of 23 to 38 mph, or 20 to 34 knots, it becomes a tropical depression and is assigned a number that is used for tracking the storm.
A tropical depression that reaches and maintains a minimum wind speed of 39 mph, or 34 knots, will then be classified as a tropical storm. A tropical storm will develop distinct outer rain bands and the convection is concentrated near the center of the storm. The number of the storm is then replaced with a name. The National Weather Service maintains a list of names for hurricanes that change from year to year. The names are recycled every three years. A name will be retired when it was given to a storm that caused major loss of life and financial damage.
A tropical storm that continues in favorable conditions and continues to strengthen will be considered a hurricane when the winds reach and maintain a minimum speed of 74 mph or 64 knots. In the center of the hurricane is an area known as the eye. Often, the weather will be calm in the eye of the storm with blue skies during the day or starry skies at night. This is considered the most dangerous part of the storm, as it is where the winds are the highest and conditions will change within a matter of minutes. The winds within the eye wall are the worst of the storm and will die, sometimes, suddenly and completely as the eye of the storm approaches. Once the eye passes, the winds will come from the opposite direction in a speed equal to what has just been experienced. It is extremely important to understand the eye of the storm. Many people have lost their life due to thinking the storm was over, when in fact, it was only the eye passing over.
Hurricanes have five different categories according to the Saffir-Simpson hurricane intensity scale. This scale measures the intensity of the storm, the damage to be expected and the amount of storm surge. Storm surge is the water that moves onshore ahead of the eye.
A category 1 storm has wind speeds between 74 and 95 mph, or 64 to 82 knots, a storm surge of 3 to 5 feet and damage will be minimal. Damage will primarily be to trees and shrubbery. There will be some flooding to low-lying coastal areas.
A category 2 storm has wind speeds between 96 and 110 mph, or 83 to 95 knots, a storm surge of 6 to 8 feet with moderate damage. There will be damage to shrubbery and trees, with some trees being blown down. Major damage to mobile homes that are not properly tied down. Some damage will be done to roofing materials, as well as some windows and doors. Escape routes inland may be cut off by rising water as early as 2 to 4 hours before the arrival of hurricane’s eye. Considerable damage to piers can be expected. Small craft not properly anchored may be torn from moorings. Evacuation of some shoreline residences and low-lying areas will be required.
A category 3 storm has wind speeds between 111 to 130 mph, or 96 to 113 knots, a storm surge of 9 to 12 feet and extensive damage. Large trees, as well as poorly constructed signs will be blown down. Some damage to roofing, windows and doors. Some structural damage to smaller buildings is to be expected. Mobile homes not properly anchored may be destroyed. Battering waves and floating debris may damage large structures near the coast, while smaller structures will be seriously flooded or destroyed. Evacuation routes inland may be cut by rising water 3 to 5 hours before the hurricane’s center arrives. Flooding may reach inland 6 miles or more. Evacuations will be required.
A category 4 storm has wind speeds between 131 and 155 mph, or 114 and 135 knots, a storm surge of 13 to 18 feet and damage will be extreme. Trees will be blown down, as well as most signs. Extensive damage will be done to roofing, windows, and doors. Many small residences will completely lose their roof. Complete destruction of mobile homes not properly anchored. Flooding may be possible inland as far as 8 miles. Major damage to lower floors of structures near shore due to flooding and battering by waves and floating debris is to be expected. Evacuation routes inland may be cut off by rising water 3 to 5 hours before the hurricane center arrives. Major beach erosion will occur. A mandatory evacuation will be issued.
A category 5 storm has wind speeds of 156 mph, or 136 knots, and above, a storm surge of 19 feet or more and damage will be catastrophic. Shrubs and trees will be blown down along with considerable damage to roofing and signs. Severe and extensive damage to windows and doors is to be expected. Many residences and industrial buildings will experience loss of the roof as well as extensive shattering of glass in windows and doors. There will be some complete building losses with smaller buildings being overturned or blown away. Complete destruction of mobile homes may occur even when homes are properly tied down. Escape routes inland will be cut by rising water 3 to 5 hours before hurricane’s eye arrives. Massive, mandatory evacuation will be issued.
Once a hurricane moves away from its power source, water, it quickly begins to lose its tropical characteristics. It will, however, continue to be a powerful source of severe weather with heavy rains, strong winds and tornadoes for several more days.