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Additional Hurricane Hazards and Preparedness Topics
A hurricane is a type of tropical cyclone or severe tropical storm that forms in the southern Atlantic Ocean, Caribbean Sea, Gulf of Mexico, and in the eastern Pacific Ocean. A typical cyclone is accompanied by thunderstorms, and in the Northern Hemisphere, a counterclockwise circulation of winds near the earth’s surface.
Tropical cyclones are among nature’s most powerful and destructive phenomena. If you live in an area prone to tropical cyclones, you need to be prepared. Even areas well away from the coastline can be threatened by destructive winds, tornadoes and flooding from these storms.
All Atlantic and Gulf of Mexico coastal areas are subject to hurricanes. Parts of the Southwest United States and the Pacific Coast also experience heavy rains and floods each year from hurricanes spawned off Mexico. The Atlantic hurricane season lasts from June to November, with the peak season from mid-August to late October.
The Eastern Pacific hurricane season begins May 15 and ends November 30.
Hurricanes can cause catastrophic damage to coastlines and several hundred miles inland. Hurricane can produce winds exceeding 155 miles per hour as well as tornadoes and mircrobursts. Additionally, hurricanes can create storm surges along the coast and cause extensive damage from heavy rainfall. Floods and flying debris from the excessive winds are often the deadly and destructive results of these weather events. Slow moving hurricanes traveling into mountainous regions tend to produce especially heavy rain. Excessive rain can trigger landslides or mud slides. Flash flooding can occur due to intense rainfall.
How great is the danger?
For 1970-2010, the average numbers per year were as follows:
- Atlantic Ocean, Caribbean or Gulf of Mexico: 11 tropical storms, 6 of which became hurricanes
- East Pacific Ocean: 15 tropical storms, 8 of which became hurricanes.
- Central Pacific Ocean: 4 tropical storms, 2 of which became hurricanes.
Over a typical 2-year period, the U.S. coastline is struck y an average of 3 hurricanes, 1 of which is classified as a major hurricane.
Between 1970 and 1999, more people lost their lives from freshwater inland flooding associated with land falling tropical cyclones than from any other weather hazard related to tropical cyclones.
Familiarize yourself with these terms to help identify a hurricane hazard:
Tropical Depression - An organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds of 38 MPH (33 knots) or less. Sustained winds are defined as one-minute average wind measured at about 33 ft (10 meters) above the surface.
Tropical Storm - An organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds of 39–73 MPH (34–63 knots).
Hurricane - An intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds of 74 MPH (64 knots) or higher.
Understanding the difference between National Weather Service watches and warnings is critical to being prepared for any dangerous weather hazard, including hurricanes.
A watch lets you know that weather conditions are favorable for a hazard to occur. It literally means "be on guard!" During a weather watch, gather awareness of the specific threat and prepare for action - monitor the weather to find out if severe weather conditions have deteriorated and discuss your protective action plans with your family.
A warning requires immediate action. This means a weather hazard is imminent - it is either occurring (a tornado has been spotted, for example) - or it is about to occur at any moment. During a weather warning, it is important to take action: grab the emergency kit you have prepared in advance and head to safety immediately. Both watches and warnings are important, but warnings are more urgent.
Hurricane / Tropical Storm Alert
Hurricane / Tropical Storm WATCH - Hurricane/tropical storm conditions are possible in the specified area of the watch, usually within 48 hours of the onset of tropical storm force winds.
Action: Prepare your home and review your plan for evacuation in case a Hurricane/Tropical Storm Warning is issued. Listen closely to instructions from local officials.
Hurricane / Tropical Storm WARNING - Hurricane/tropical storm conditions are expected in the specified area of the warning, usually within 36 hours of the onset of tropical storm force winds.
Action: Complete storm preparations and immediately leave the threatened area if directed by local officials.
Extreme Wind WARNING - Extreme sustained winds of a major hurricane (115 mph or greater), usually associated with the eyewall, are expected to begin within an hour.
Action: Take immediate shelter in the interior portion of a well-built structure.
Additional Watches and Warnings may be issued to provide detailed information on specific threats such as floods and tornadoes. Local National Weather Service offices issue Flash Flood/Flood Watches and Warnings as well as Tornado Warnings.
Hurricane Wind Scale
Hurricanes are classified into five categories based on their wind speed, central pressure, and damage potential. Category Three and higher hurricanes are considered major hurricanes, though Categories One and Two are still extremely dangerous and warrant your full attention.
The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based on a hurricane's sustained wind speed. This scale estimates potential property damage. Hurricanes reaching Category 3 and higher are considered major hurricanes because of their potential for significant loss of life and damage. Category 1 and 2 storms
are still dangerous, however, and require preventative measures. In the western North Pacific, the term "super typhoon" is used for tropical cyclones with sustained winds exceeding 150 mph.
||Types of Damage Due to Hurricane Winds
|Very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days.
|Extremely dangerous winds will cause extensive damage:
Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks.
|Devastating damage will occur:
Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes.
|Catastrophic damage will occur:
Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months.
|157 mph or higher
137 kt or higher
252 km/h or higher
|Catastrophic damage will occur:
A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months.
Wind damage from Hurricane Charley, August 2004 Orlando, Fl/Orlando Sentinel, Copyright 2004.
Additional Hurricane Preparedness Topics