Hurricane Katrina, 2005
A tropical cyclone is a rotating, organized system of clouds and thunderstorms that originates over tropical or subtropical waters and has a closed low-level circulation. Tropical cyclones rotate counterclockwise in the Northern Hemisphere. The Atlantic hurricane season runs from June 1st to November 30th, however, these storms can develop before or after the season.
Conditions Which Must Be Present in the Development of a Tropical
- 1. Low-pressure system
- 2. Warm temperatures over the Ocean
- 3. Moist environment (precipitation)
- 4. Tropical wind patterns over the equator
INLAND FLOODING - In the last 30 years, inland flooding has been responsible for more than half the deaths associated with tropical cyclones in the United States.
HIGH WINDS - Hurricane-force winds can destroy poorly constructed buildings and mobile homes. Debris such as signs, roofing material, and small items left outside become flying missiles in hurricanes.
TORNADOES - Hurricanes can produce tornadoes that add to the storm's destructive power. Tornadoes are most likely to occur in the right-front quadrant of the hurricane.
Graphical Hurricane Local Statement:
Issued by local National Weather Service offices to provide more specific information about potential impacts of a tropical storm or hurricane on a particular area. View your Hurricane Local Statement from the National Weather Service at http://www.weather.gov/ghls/.
For future hurricane season names, click here: http://www.nhc.noaa.gov/aboutnames.shtml
|Eye: The eye is the "hole" at the center of the storm. Winds are light in this
area. Skies are partly cloudy, and sometimes even clear.
Eye wall: The eye wall is a ring of thunderstorms. These storms swirl around the eye. The wall is where winds are strongest and rain is heaviest.
Rain bands: Bands of clouds and rain go far out from a hurricane's eye wall. These bands stretch for hundreds of miles. They contain thunderstorms and sometimes tornadoes.
Tropical Depression: A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 38 mph (33 knot) or less.
Tropical Storm: A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) ranges from 39 mph (34 knots) to 73 mph (63 knots). Hurricane: A tropical cyclone in which the maximum sustained surface wind (using the U.S. 1-minute average) is 74 mph (64 knots) or more.
Storm Surge: An abnormal rise in sea level accompanying a hurricane or other intense storm, and whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. Storm surge is usually estimated by subtracting the normal or astronomic high tide from the observed storm tide. Storm surge can reach heights well over 20 feet and can span hundreds of miles of coastline.
Storm Tide: The actual level of sea water resulting from the astronomic tide combined with the storm surge.
Hurricane Warning: An announcement that hurricane conditions (sustained winds of 74 mph or higher) are expected somewhere within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds.
Hurricane Watch: An announcement that hurricane conditions (sustained winds of 74 mph or higher) are possible within the specified area. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical-storm-force winds.
Tropical Storm Warning: An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are expected somewhere within the specified area within 36 hours.
Tropical Storm Watch: An announcement that tropical storm conditions (sustained winds of 39 to 73 mph) are possible within the specified area within 48 hours.
The greatest potential for loss of life related to a hurricane is from the storm surge, which historically has claimed nine of ten victims.
Storm surge is simply water that is pushed toward the shore by the force of the winds swirling around the storm. This advancing surge combines with the normal tides to create the hurricane storm tide, which can increase the mean water level 15 feet or more. In addition, wind waves are superimposed on the storm tide. This rise in water level can cause severe flooding in coastal areas, particularly when the storm tide coincides with the normal high tides. Because much of the United States' densely populated Atlantic and Gulf Coast coastlines lie less than 10 feet above mean sea level, the danger from storm tides is tremendous.
The level of surge in a particular area is also determined by the slope of the continental shelf. A shallow slope off the coast (right, top picture) will allow a greater surge to inundate coastal communities. Communities with a steeper continental shelf (right, bottom picture) will not see as much surge inundation, although large breaking waves can still present major problems. Storm tides, waves, and currents in confined harbors severely damage ships, marinas, and pleasure boats.
The intensity of the storm (as given by the Saffir-Simpson Hurricane Scale) affects the possibility of flooding from storm surge at two locations. Storm surge also affects rivers and inland lakes, potentially increasing the area that must be evacuated.
Obviously, the more intense the storm, and the closer you are to its right-front quadrant, the larger the area you will have to evacuate. The problem is, how do you know what category storm is going to hit you?
Wave and current action associated with the tide also causes extensive damage. Water weighs approximately 1,700 pounds per cubic yard; extended pounding by frequent waves can demolish any structure not specifically designed to withstand such forces.
The currents created by the tide combine with the action of the waves to severely erode beaches and coastal highways. Many buildings withstand hurricane force winds until their foundations, undermined by erosion, are weakened and fail.
In estuaries and bayous, intrusions of salt water endanger the public health and send animals, such as snakes, fleeing from flooded areas.
- Coordinate your departure with people who will be traveling with you. Notify an out-of-area person of your plans.
- Secure your home.
- Put your disaster supplies kit in your vehicle. Double check evacuation routes and leave.
Who Should Plan to Leave Early
- Residents of low-lying areas
- Persons living in manufactured housing
- Persons with special needs -- including health or mobility related concerns
Secure Your Home
- Turn off gas, water & electricity
- Board up windows
- Draw drapes across windows
- Brace garage doors
- Bring in outdoor furniture and other loose objects, anchor items you cannot bring inside
- Place boats on trailers, tie them down close to home and fill with water
- Lock all windows and doors
- Make arrangements for animals (most shelters do not allow pets)
- Keep your vehicle in good repair with a full tank of fuel
- Check on friends and neighbors who may have special needs
- Prepare you disaster supplies kit now. Take it with you when you evacuate
- Secure you home quickly -- evacuate when asked to do so
- Have an out-of-area point of contact whom family and friends can call to learn your evacuation plans
- If possible, take a CB Radio or cell phone with you. Use it only in emergencies.
- Monitor Emergency Alert Stations (EAS) for the latest news or information.
Your Disaster Supplies Kit:
- Can Opener
- 3-Day Supply of Non-Perishable Food
- Bedding or Sleeping Bags
- Fire Extinguisher
- Bleach (no lemon or other additives)
- Mosquito repellent
- Extra Prescription Medicine (or refill information)
- Baby food, diapers and formula
- First Aid Kit
- Water (gallon per person per day)
- Eating Utensils
- Tarp, Rope & Duct Tape
- Toilet Paper
- Batter-Operated Radio
- Extra Batteries
- Extra Keys
- Eyeglasses (or prescription)
- Hearing Aid or Other Special Items
- Important Papers including Insurance, Money, Checks or Credit Cards
- Name, Address and Telephone Number of Out-of-Area Contact Person
After A Severe Tropical Storm or Hurricane
Stay out of disaster areas which could be dangerous and where your presence will interfere with essential rescue and recovery work. Do not drive unless you must. Roads should be left clear for emergency vehicles and debris removal equipment. Remember, debris-filled streets are dangerous.
Along the coast, soil may erode beneath pavement or bridge supports, which could collapse under the weight of a car. Be wary of inland flooding. Citizens returning home should expect the worst and take precautions to assure their safety.
Precautions to take when returning home:
- Do not use the telephone except for major emergencies.
- Beware of loose or dangling power lines. Many lives are lost through electrocution.
- Walk or drive cautiously. Watch out for snakes.
- Do not use water until you receive word that it is safe. Eat only foods you are absolutely sure are safe. If power has been out, food that was refrigerated or frozen may not be safe to eat.
- Don't light candles. Do not attempt to turn on utilities.
- Be wary of dangerous or frightened animals.
- Use care handling power tools, gas lanterns, generators and matches.
- Call your insurance company to file a claim if your home is damaged, ask your insurance company for financial help.
- Listen to local radio stations for official disaster relief information and instructions.
- State of Louisiana Hazard Mitigation Strategy – Volume I
- State of Louisiana Hazard Mitigation Plan Update – Final Draft, March 10, 2011
- Hurricane FAQs - http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqHED.html