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SEVERE WEATHER INFO
thunderstorms and lightning...THE UNDERATED KILLERS
thunderstorms...and their offspring
Thunderstorms affect relatively small areas when compared with hurricanes and winter storms. The typical thunderstorm is 15 miles in diameter and lasts an average of 30 minutes. Nearly 1,800 thunderstorms are occurring at any moment around the world. That's 16 million a year!
Despite their small size, all thunderstorms are dangerous. Every thunderstorm produces lightning, which kills more people each year than tornadoes. Heavy rain from thunderstorms can lead to flash flooding. Strong winds, hail, and tornadoes are also dangers associated with some thunderstorms.
Of the estimated 100,000 thunderstorms that occur each year in the United States, only about 10 percent are classified as severe.
Your National Weather Service considers a thunderstorm severe if it produces hail at least 3/4-inch in diameter, wind 58 mph or higher, or tornadoes.
Take the time NOW to understand these dangers and learn basic safety rules!
Flash Floods/Floods
The number ONE thunderstorm killer...nearly 140 fatalities each year.
Most flash flood deaths occur at night and when people become trapped in automobiles.
Lightning
Occurs with ALL thunderstorms.
Averages 93 deaths and 300 injuries each year.
Causes several hundred million dollars in damage to property and forests annually.
Straight-line Winds
Responsible for most thunderstorm wind damage.
Winds can exceed 100 mph!
One type of straight-line wind, the downburst, can cause damage equivalent to a strong tornado and can be extremely dangerous to aviation.
During the summer in the western states, thunderstorms often produce little rain but very strong wind gusts and dust storms.
Large Hail
Causes nearly $1 billion in damage to property and crops annually.
Costliest United States hailstorm: Denver, Colorado, July 11, 1990. Total damage was million.
Tornadoes
Nature's most violent storms.
Winds can exceed 200 mph.
Result in an average of 80 deaths and 1,500 injuries each year.
Most fatalities occur when people do not leave mobile homes and automobiles.
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what makes a thunderstorm?
Every Thunderstorm Needs:
Moisture - to form clouds and rain.
Unstable Air - relatively warm air that can rise rapidly.
Lift - fronts, sea breezes, and mountains are capable of lifting air to help form thunderstorms.
Life Cycle of a Thunderstorm
Developing Stage
Towering cumulus cloud indicates rising air.
Usually little if any rain during this stage.
Lasts about 10 minutes.
Occasional lightning during this stage.
Mature Stage
Most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes.
Storm occasionally has a black or dark green appearance.
Lasts an average of 10 to 20 minutes but may last much longer in some storms.
Dissipating Stage
Rainfall decreases in intensity.
Some thunderstorms produce a burst of strong winds during this stage.
Lightning remains a danger during this stage.<
when are thunderstorms most likely?
Thunderstorms are most likely to happen in the spring and summer months and during the afternoon and evening hours but can occur year-round and at all hours.
Along the Gulf Coast and across the southeastern and western states, most thunderstorms occur during the afternoon.
Thunderstorms frequently occur in the late afternoon and at night in the Plains states.
Thunder and lightning occasionally accompany snow or freezing rain. During the blizzard of March 1993, lightning resulted in power outages near Washington, D.C.!
Who's Most At Risk From Thunderstorms?
From Lightning:
People who are: outdoors, especially under or near tall trees; in or on water; or on or near hilltops.
From Flooding:
People who are in automobiles when flash flooding occurs near them.
From Tornadoes:
People who are in mobile homes and automobiles.
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thunderstorm winds and hail
downbursts
A small area of rapidly descending air beneath a thunderstorm
Can cause damaging winds in excess of 100 mph.
The strong winds usually approach from one direction and may be known as "straight-line" winds.
In extreme cases, straight-line winds can reach speeds equal to a strong tornado, causing significant damage to some buildings.
Strong winds may or may not be accompanied by rain.
Large Hail
The strong rising currents of air within a storm, called updrafts, carry water droplets to a height where freezing occurs.
Ice particles grow in size, finally becoming too heavy to be supported by the updraft and fall to the ground.
Large hailstones fall at speeds faster than 100 mph.
lightning... nature's fireworks
What is Lightning?
The action of rising and descending air within a thunderstorm separates positive and negative charges. Water and ice particles also affect the distribution of electrical charge.
Lightning results from the buildup and discharge of electrical energy between positively and negatively charged areas.
The average flash could light a 100-watt light bulb for more than 3 months.
Most lightning occurs within the cloud or between the cloud and ground.
Your chances of being struck by lightning are estimated to be 1 in 600,000 but could be reduced by following safety rules.
Most lightning deaths and injuries occur when people are caught outdoors.
Most lightning casualties occur in the summer months and during the afternoon and early evening.
The air near a lightning strike is heated to 50,000øF hotter than the surface of the sun! The rapid heating and cooling of air near the lightning channel causes a shock wave that results in thunder.
Many fires in the western United States and Alaska are started by lightning. In the past decade, over 15,000 lightning-induced fires nationwide have resulted in several hundred million dollars a year in damage and the loss of 2 million acres of forest.
In recent years, people have been killed by lightning while:
boating
standing under a tree
playing soccer
swimming
riding on a lawnmower
fishing in a boat
golfing
talking on the telephone
mountain climbing
bike riding
loading a truck
lightning can strike anywhere!
In recent years, sophisticated lightning detection equipment has monitored cloud-to-ground lightning strikes. The map at right shows which areas were MOST prone to lightning during one year.
Which way does lightning travel?
A cloud-to-ground lightning strike begins as an invisible channel of electrically charged air moving from the cloud toward the ground. When one channel nears an object on the ground, a powerful surge of electricity from the ground moves upward to the cloud and produces the visible lightning strike!
Lightning Myths and Facts
MYTH: If it is not raining, then there is no danger from lightning.
FACT: Lightning often strikes outside of heavy rain and may occur as far as 10 miles away from any rainfall.
MYTH: The rubber soles of shoes or rubber tires on a car will protect you from being struck by lightning.
FACT: Rubber-soled shoes and rubber tires provide NO protection from lightning. However, the steel frame of a hard-topped vehicle provides increased protection if you are not touching metal. Although you may be injured if lightning strikes your car, you are much safer inside a vehicle than outside.
MYTH: People struck by lightning carry an electrical charge and should not be touched.
FACT: Lightning-strike victims carry no electrical charge and should be attended to immediately. Contact your local American Red Cross chapter for information on CPR and first aid classes.
MYTH: "Heat lightning" occurs after very hot summer days and poses no threat.
FACT: What is referred to as "heat lightning" is actually lightning from a thunderstorm too far away for thunder to be heard. However, the storm may be moving in your direction!
environmental clues
When skies darken or thunderstorms are forecast, look AND listen for
Increasing wind.
Flashes of lightning.
Sound of thunder.
Static on your AM radio.
To estimate the distance in miles between you and the lightning flash, count the seconds between the lightning and the thunder and divide by five.
Advanced Weather Radar Sees "Inside" the Storm
Doppler Radars, which are being strategically deployed around the country, are capable of seeing "inside" a thunderstorm to detect hazardous weather conditions. New storms often form along leading edge of the storm's cool-air outflow; this feature is able to be detected on Doppler Radar.
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WHATS YOUR PLAN?
STAY INFORMED ABOUT THE STORM
by listening to NOAA Weather Radio, commercial radio, and television for the latest severe thunderstorm WATCHES and WARNINGS.
When conditions are favorable for severe weather to develop, a severe thunderstorm WATCH is issued.
Weather Service personnel use information from weather radar, satellite, lightning detection, spotters, and other sources to issue severe thunderstorm WARNINGS for areas where severe weather is imminent.
Severe thunderstorm warnings are passed to local radio and television stations and are broadcast over local NOAA Weather Radio stations serving the warned areas. These warnings are also relayed to local emergency management and public safety officials who can activate local warning systems to alert communities.
NOAA WEATHER RADIO IS THE BEST MEANS TO RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE
The National Weather Service continuously broadcasts updated weather warnings and forecasts that can be received by NOAA Weather Radios, which are sold in many stores. The average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature that automatically alerts you when a watch or warning is issued.
What to Listen For...
SEVERE THUNDERSTORM WATCH: tells you when and where severe thunderstorms are more likely to occur. Watch the sky and stay tuned to know when warnings are issued. Watches are intended to heighten public awareness and should not be confused with warnings.
SEVERE THUNDERSTORM WARNING: issued when severe weather has been reported by spotters or indicated by radar. Warnings indicate imminent danger to life and property to those in the path of the storm. Also listen for Tornado Watch or Warning and Flash Flood Watch or Warning.
Also...listen for Tornado Watch or Warning and Flash Flood Watch or Warning.
FAMILY DISASTER PLAN
Families should be prepared for all hazards that could affect their area. NOAA's National Weather Service, the Federal Emergency Management Agency, and the American Red Cross urge every family to develop a family disaster plan.
Where will your family be when disaster strikes? They could be anywhere_at work, at school, or in the car. How will you find each other? Will you know if your children are safe? Disaster may force you to evacuate your neighborhood or confine you to your home. What would you do if basic services_water, gas, electricity or telephones_were cut off?
Follow these basic steps to develop a family disaster plan...
I. Gather information about hazards. Contact your local National Weather Service office, emergency management office, and American Red Cross chapter. Find out what type of disasters could occur and how you should respond. Learn your community's warning signals and evacuation plans.
II. Meet with your family to create a plan. Discuss the information you have gathered. Pick two places to meet: a spot outside your home for an emergency, such as fire, and a place away from your neighborhood in case you can't return home. Choose an out-of-state friend as your "family check-in contact" for everyone to call if the family gets separated. Discuss what you would do if advised to evacuate.
III. Implement your plan.
(1) Post emergency telephone numbers by phones;
(2) Install safety features in your house, such as smoke detectors and fire extinguishers;
(3) Inspect your home for potential hazards (such as items that can move, fall, break, or catch fire) and correct them;
(4) Have your family learn basic safety measures, such as CPR and first aid; how to use a fire extinguisher; and how and when to turn off water, gas, and electricity in your home;
(5) Teach children how and when to call 911 or your local Emergency Medical Services number;
(6) Keep enough supplies in your home to meet your needs for at least three days. Assemble a disaster supplies kit with items you may need in case of an evacuation. Store these supplies in sturdy, easy-to-carry containers, such as backpacks or duffle bags. Keep important family documents in a waterproof container. Keep a smaller disaster supplies kit in the trunk of your car.
A DISASTER SUPPLIES KIT SHOULD INCLUDE:
A 3-day supply of water (one gallon per person per day) and food that won't spoil
one change of clothing and footwear per person
one blanket or sleeping bag per person
a first aid kit, including prescription medicines
emergency tools, including a battery-powered NOAA Weather Radio and a portable radio, flashlight, and plenty of extra batteries
an extra set of car keys and a credit card or cash
special items for infant, elderly, or disabled family members.
IV. Practice and maintain your plan. Ask questions to make sure your family remembers meeting places, phone numbers, and safety rules. Conduct drills. Test your smoke detectors monthly and change the batteries two times each year. Test and recharge your fire extinguisher(s) according to manufacturer's instructions. Replace stored water and food every 6 months. Contact your local National Weather Service office, American Red Cross chapter, or local office of emergency management for a copy of "Your Family Disaster Plan"
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Tornadoes....
Tornado!
Although tornadoes occur in many parts of the world, these destructive forces of nature are found most frequently in the United States east of the Rocky Mountains during the spring and summer months. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries. A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Once a tornado in Broken Bow, Oklahoma, carried a motel sign 30 miles and dropped it in Arkansas!
What causes tornadoes?
Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.
During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.
Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.
Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.
Tornado Variations
Some tornadoes may form during the early stages of rapidly developing thunderstorms. This type of tornado is most common along the front range of the Rocky Mountains, the Plains, and the Western States.
Tornadoes may appear nearly transparent until dust and debris are picked up.
Occasionally, two or more tornadoes may occur at the same time.
Waterspout
Waterspouts are weak tornadoes that form over warm water.
Waterspouts are most common along the Gulf Coast and southeastern states. In the western United States, they occur with cold late fall or late winter storms, during a time when you least expect tornado development.
Waterspouts occasionally move inland becoming tornadoes causing damage and injuries.
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How Do Tornadoes Form?
Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.
Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
A lower cloud base in the center of the photograph identifies an area of rotation known as a rotating wall cloud. This area is often nearly rain-free. Note rain in the background.
Moments later a strong tornado develops in this area. Softball-size hail and damaging "straight-line" winds also occurred with this storm.
Tornadoes Take Many
Shapes and Sizes
Weak Tornadoes
69% of all tornadoes
Less than 5% of tornado deaths
Lifetime 1-10+ minutes
Winds less than 110 mph
Strong Tornadoes
29% of all tornadoes
Nearly 30% of all tornado deaths
May last 20 minutes or longer
Winds 110-205 mph
Violent Tornadoes
Only 2% of all tornadoes
70% of all tornado deaths
Lifetime can exceed 1 hour
Winds greater than 205 mph
Tornado Myths:
MYTH: Areas near rivers, lakes, and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes. In the late 1980's, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain.
MYTH: The low pressure with a tornado causes buildings to "explode" as the tornado passes overhead.
FACT: Violent winds and debris slamming into buildings cause most structural damage.
MYTH:Windows should be opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds to enter the structure. Leave the windows alone; instead, immediately go to a safe place.
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Tornadoes Occur Anywhere
Carolinas Outbreak:
March 28, 1984, afternoon-evening
22 tornadoes
57 deaths
1,248 injuries
damage million
37% of fatalities in mobile homes
Pennsylvania-Ohio Outbreak:
May 31, 1985, late afternoon-evening
41 tornadoes, including 27 in PA and OH
75 deaths in U.S.
1,025 injuries
damage million
Plains Outbreak:
April 26-27, 1991, afternoon of 26th through early morning 27th
54 tornadoes
21 deaths
308 injuries
damage + million
15 deaths in/near mobile homes, 2 deaths in vehicles
Weather Radar Watches the Sky
Meteorologists rely on weather radar to provide information on developing storms. The National Weather Service is strategically locating Doppler radars across the country which can detect air movement toward or away from the radar. Early detection of increasing rotation aloft within a thunderstorm can allow life-saving warnings to be issued before the tornado forms.
Frequency of Tornadoes
Tornadoes can occur at any time of the year.
In the southern states, peak tornado occurrence is in March through May, while peak months in the northern states are during the summer.
Note, in some states, a secondary tornado maximum occurs in the fall.
Tornadoes are most likely to occur between 3 and 9 p.m. but have been known to occur at all hours of the day or night.
The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70 mph.
The total number of tornadoes is probably higher than indicated in the western states. Sparce population reduces the number reported.
STAY INFORMED ABOUT THE STORM
by listening to NOAA Weather Radio, commercial radio, and television for the latest tornado WATCHES and WARNINGS.
When conditions are favorable for severe weather to develop, a severe thunderstorm or tornado WATCH is issued.
Weather Service personnel use information from weather radar, spotters, and other sources to issue severe thunderstorm and tornado WARNINGS for areas where severe weather is imminent.
Severe thunderstorm warnings are passed to local radio and television stations and are broadcast over local NOAA Weather Radio stations serving the warned areas. These warnings are also relayed to local emergency management and public safety officials who can activate local warning systems to alert communities.
NOAA WEATHER RADIO IS THE BEST MEANS TO RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE
The National Weather Service continuously broadcasts updated weather warnings and forecasts that can be received by NOAA Weather Radios sold in many stores. The average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.
What To Listen For...
TORNADO WATCH: Tornadoes are possible in your area. Remain alert for approaching storms.
TORNADO WARNING: A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your pre-designated place of safety.
SEVERE THUNDERSTORM WATCH: Severe thunderstorms are possible in your area.
SEVERE THUNDERSTORM WARNING: Severe thunderstorms are occurring.
Remember, tornadoes occasionally develop in areas in which a severe thunderstorm watch or warning is in effect. Remain alert to signs of an approaching tornado and seek shelter if threatening conditions exist.
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Environmental Clues
Look out for:
Dark, often greenish sky
Wall cloud
Large hail
Loud roar; similar to a freight train
Caution:
Some tornadoes appear as a visible funnel extending only partially to the ground. Look for signs of debris below the visible funnel.
Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.
Other Thunderstorm Hazards
These dangers often accompany thunderstorms:
Flash Floods: Number ONE weather killer - 146 deaths annually
Lightning: Kills 75-100 people each year
Damaging Straight-line Winds: Can reach 140 mph
Large Hail: Can reach the size of a grapefruit - causes several hundred million dollars in damage annually to property and crops
Contact your local National Weather Service office, American Red Cross chapter, or Federal Emergency Management Agency office for a copy of the "Thunderstorms and Lightning...The Underrated Killers" brochure (NOAA PA 92053) and the "Flash Floods and Floods...The Awesome Power" brochure (NOAA PA 92050).
Tornado Safety
What YOU Can Do
Before the Storm:
Develop a plan for you and your family for home, work, , school and when outdoors.
Have frequent drills.
Know the county/parish in which you live, and keep a highway map nearby to follow storm movement from weather bulletins.
Have a NOAA Weather Radio with a warning alarm tone and battery back-up to receive warnings.
Listen to radio and television for information.
If planning a trip outdoors, listen to the latest forecasts and take necessary action if threatening weather is possible.
If a Warning is issued or if threatening weather approaches:
In a home or building, move to a pre-designated shelter, such as a basement.
If an underground shelter is not available, move to an interior room or hallway on the lowest floor and get under a sturdy piece of furniture.
Stay away from windows.
Get out of automobiles.
Do not try to outrun a tornado in your car; instead, leave it immediately.
Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned.
Occasionally, tornadoes develop so rapidly that advance warning is not possible. Remain alert for signs of an approaching tornado. Flying debris from tornadoes causes most deaths and injuries.
It's Up To YOU!
Each year, many people are killed or seriously injured by tornadoes despite advance warning. Some did not hear the warning while others received the warning but did not believe a tornado would actually affect them. The preparedness information in this brochure, combined with timely severe weather watches and warnings, could save your life in the event a tornado threatens your area. After you have received the warning or observed threatening skies, YOU must make the decision to seek shelter before the storm arrives. It could be the most important decision you will ever make.
Who's Most At Risk?
People in automobiles
The elderly, very young, and the physically or mentally impaired
People in mobile homes
People who may not understand the warning due to a language barrier
Tornado Safety in Schools
EVERY School Should Have A Plan!
Develop a severe weather action plan and have frequent drills,
Each school should be inspected and tornado shelter areas designated by a registered engineer or architect. Basements offer the best protection. Schools without basements should use interior rooms and hallways on the lowest floor and away from windows.
Those responsible for activating the plan should monitor weather information from NOAA Weather Radio and local radio/television.
If the school's alarm system relies on electricity, have a compressed air horn or megaphone to activate the alarm in case of power failure.
Make special provisions for disabled students and those in portable classrooms.
Make sure someone knows how to turn off electricity and gas in the event the school is damaged.
Keep children at school beyond regular hours if threatening weather is expected. Children are safer at school than in a bus or car. Students should not be sent home early if severe weather is approaching.
Lunches or assemblies in large rooms should be delayed if severe weather is anticipated. Gymnasiums, cafeterias, and auditoriums offer no protection from tornado-strength winds.
Move students quickly into interior rooms or hallways on the lowest floor. Have them assume the tornado protection position (shown at right).
Hospitals, nursing homes, and other institutions should develop a similar plan
Your National Weather Service, Federal Emergency Management Agency, and American Red Cross educate community officials and the public concerning the dangers posed by tornadoes. YOU can prepare for the possibility of a tornado by learning the safest places to seek shelter when at home, work, school, or outdoors. You should also understand basic weather terms and danger signs related to tornadoes. Your chances of staying safe during a tornado are greater if you have a plan for you and your family, and practice the plan frequently.
FAMILY DISASTER PLAN
Families should be prepared for all hazards that affect their area. NOAA's National Weather Service, the Federal Emergency Management Agency, and the American Red Cross urge each family to develop a family disaster plan.
Where will your family be when disaster strikes? They could be anywhere - at work, at school, or in the car. How will you find each other? Will you know if your children are safe? Disasters may force you to evacuate your neighborhood or confine you to your home. What would you do if basic services - water, gas, electricity or telephones - were cut off?
Follow these basic steps to develop a family disaster plan...
I. Gather information about hazards. Contact your local National Weather Service office, emergency management or civil defense office, and American Red Cross chapter. Find out what type of disasters could occur and how you should respond. Learn your community's warning signals and evacuation plans.
II. Meet with your family to create a plan. Discuss the information you have gathered. Pick two places to meet: a spot outside your home for an emergency, such as fire, and a place away from your neighborhood in case you can't return home. Choose an out-of-state friend as your "family check-in contact" for everyone to call if the family gets separated. Discuss what you would do if advised to evacuate.
III. Implement your plan.
(1) Post emergency telephone numbers by phones;
(2) Install safety features in your house, such as smoke detectors and fire extinguishers;
(3) Inspect your home for potential hazards (such as items that can move, fall, break, or catch fire) and correct them;
(4) Have your family learn basic safety measures, such as CPR and first aid; how to use a fire extinguisher; and how and when to turn off water, gas, and electricity in your home;
(5) Teach children how and when to call 911 or your local Emergency Medical Services number;
(6) Keep enough supplies in your home to meet your needs for at least three days. Assemble a disaster supplies kit with items you may need in case of an evacuation. Store these supplies in sturdy, easy-to-carry containers, such as backpacks or duffle bags. Keep important family documents in a waterproof container. Keep a smaller disaster supplies kit in the trunk of your car.
A DISASTER SUPPLIES KIT SHOULD INCLUDE:
A 3-day supply of water (one gallon per person per day) and food that won't spoil
one change of clothing and footwear per person
one blanket or sleeping bag per person
a first-aid kit, including prescription medicines
emergency tools, including a battery-powered NOAA Weather Radio and a portable radio, flashlight, and plenty of extra batteries
an extra set of car keys and a credit card or cash
special items for infant, elderly, or disabled family members.
IV. Practice and maintain your plan. Ask questions to make sure your family remembers meeting places, phone numbers, and safety rules. Conduct drills. Test your smoke detectors monthly and change the batteries at least once a year. Test and recharge your fire extinguisher(s) according to manufacturer's instructions. Replace stored water and food every six months.
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flash floods and floods
flash floods
#1 weather-related killer in the United States!
How do flash floods occur?
Several factors contribute to flash flooding. The two key elements are rainfall intensity and duration. Intensity is the rate of rainfall, and duration is how long the rain lasts. Topography, soil conditions, and ground cover also play an important role.
Flash floods occur within a few minutes or hours of excessive rainfall, a dam or levee failure, or a sudden release of water held by an ice jam. Flash floods can roll boulders, tear out trees, destroy buildings and bridges, and scour out new channels. Rapidly rising water can reach heights of 30 feet or more. Furthermore, flash flood-producing rains can also trigger catastrophic mud slides. You will not always have a warning that these deadly, sudden floods are coming. Most flood deaths are due to FLASH FLOODS.
Most flash flooding is caused by slow-moving thunderstorms, thunderstorms repeatedly moving over the same area, or heavy rains from hurricanes and tropical storms.
Occasionally, floating debris or ice can accumulate at a natural or man-made obstruction and restrict the flow of water. Water held back by the ice jam or debris dam can cause flooding upstream. Subsequent flash flooding can occur downstream if the obstruction should suddenly release.
June 9, 1972 Black Hills
Rapid City, SD
15 inches of rain in 5 hours
238 fatalities
in damages
Source: National Weather Service
PLAN AHEAD:
Identify where to go if told to evacuate. Choose several places...a friend's home or a motel in another town, or a shelter.
GO TO HIGHER GROUND
Know your area's flood risk. For information, call your local National Weather Service office, Red Cross chapter, or local emergency management agency. Check your homeowner's or renter's insurance. Homeowners' policies do not cover flooding. Contact your insurance agent to find out how to get flood insurance.
flooding can occur NATIONWIDE!
Even 6 inches of fast-moving flood water can knock you off your feet, and a depth of 2 feet will float your car! NEVER try to walk, swim, or drive through such swift water. If you come upon flood waters, STOP! TURN AROUND AND GO ANOTHER WAY.
SOME HISTORICAL NWS DATA
Dam Break
May 31, 1889 Johnstown, Pennsylvania...
the worst flood in United States history..
36-40 ft. wall of water...2,200 dead.
River Flood
December 1991/January 1992 South-central Texas...
wide-spread river flooding on the Guadalupe, Brazos, Trinity, and Colorado River Basins...
up to 17 inches of rain...15 dead...damages .
Flash Flood Events
June 14, 1990 Shadyside, Ohio...
4 inches of rain in less than 2 hours produced a 30-foot high wall of water...
26 dead...damages -8M.
August 1, 1985 Cheyenne, Wyoming...
6 inches of rain in 3 hours...
12 dead...damages .
Flooding Takes Many Forms...
Flash flooding occurs within 6 hours of the rain event.
Flooding is a longer term event and may last a week or more.
RIVER FLOOD
Flooding along rivers is a natural and inevitable part of life. Some floods occur seasonally when winter or spring rains, coupled with melting snows, fill river basins with too much water, too quickly. Torrential rains from decaying hurricanes or tropical systems can also produce river flooding.
COASTAL FLOOD
Winds generated from tropical storms and hurricanes or intense offshore low pressure systems can drive ocean water inland and cause significant flooding. Escape routes can be cut off and blocked by high water. Coastal flooding can also be produced by sea waves called tsunamis (tsoo-n„ -m z), sometimes referred to as tidal waves. These waves are produced by earthquakes or volcanic activity.
NOTE: Coastal flooding caused by the storm surge associated with hurricanes is described in publication NOAA/PA 78019, "Storm Surge and Hurricane Safety."
URBAN FLOOD
As land is converted from fields or woodlands to roads and parking lots, it loses its ability to absorb rainfall. Urbanization increases runoff 2 to 6 times over what would occur on natural terrain. During periods of urban flooding, streets can become swift moving rivers, while basements can become death traps as they fill with water.
FLASH FLOODING IN ARROYOS/WASHES
An arroyo is a water-carved gully or normally dry creek bed. Arroyos can fill with fast-moving water very quickly. Flash flooding at this arroyo in Arizona took only 58 seconds to develop.
ICE JAM
Floating ice can accumulate at a natural or man-made obstruction and stop the flow of water.
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Environmental Clues...
Listen for...
distant thunder runoff from a faraway thunderstorm could be headed your way.
Look out for...
water rising rapidly
Nearly half of all flash flood fatalities are auto related!
In your automobile...
look out for..flooding at highway dips, bridges, and low areas.
MANY FLASH FLOODS OCCUR AT NIGHT...BE PREPARED TO TAKE QUICK ACTION
How can a foot or two of water cost you your life?
Water weighs 62.4 lbs. per cubic foot and typically flows downstream at 6 to 12 miles an hour.
When a vehicle stalls in the water, the water's momentum is transferred to the car. For each foot the water rises, 500 lbs. of lateral force are applied to the car.
But the biggest factor is buoyancy. For each foot the water rises up the side of the car, the car displaces 1,500 lbs. of water. In effect, the car weighs 1,500 lbs. less for each foot the water rises.
Two feet of water will carry away most automobiles.
Before the flood...
What YOU can do:
Know your flood risk and elevation above flood stage.
- Do your local streams or rivers flood easily? If so, be prepared to move to a place of safety. Know your evacuation routes.
Keep your automobile fueled; if electric power is cut off, gas stations may not be able to operate pumps for several days.
Store drinking water in clean bathtubs and in various containers. Water service may be interrupted.
Keep a stock of food that requires little cooking and no refrigeration; electric power may be interrupted.
Keep first aid supplies on hand.
Keep a NOAA Weather Radio, a battery-powered portable radio, emergency cooking equipment, and flashlights in working order. Install check valves in building sewer traps to prevent flood water from backing up into the drains of your home.
Assemble a disaster supplies kit containing: first aid kit, canned food and can opener, bottled water, rubber boots, rubber gloves, NOAA Weather Radio, battery-powered radio, flashlight, and extra batteries.
What YOUR community can do:
Assist hospitals and other operations which are critically affected by power failure by arranging for auxiliary power supplies.
River/rainfall readings are valuable to local emergency management agencies (EMA) and the National Weather Service (NWS) in assessing flood conditions and taking appropriate actions. Advanced warning provided by early detection is critical to saving lives. Automatic flood detection systems are available commercially for flood-prone communities. Contact your local NWS office or emergency management agency for further information on LOCAL FLOOD WARNING SYSTEMS.
STAY INFORMED ABOUT THE STORM
by listening to NOAA Weather Radio, commercial radio, and television for the latest flash flood/flood WATCHES, WARNINGS, and ADVISORIES.
NOAA WEATHER RADIO IS THE BEST MEANS TO RECEIVE WARNINGS FROM THE NATIONAL WEATHER SERVICE. The National Weather Service continuously broadcasts updated weather warnings and forecasts that can be received by NOAA Weather Radios sold in many stores. Average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.
What to Listen For...
FLASH FLOOD OR FLOOD WATCH: Flash flooding or flooding is possible within the designated WATCH area be alert.
FLASH FLOOD OR FLOOD WARNING: Flash flooding or flooding has been reported or is imminent take necessary precautions at once.
URBAN AND SMALL STREAM ADVISORY: Flooding of small streams, streets, and low-lying areas, such as railroad underpasses and urban storm drains, is occurring.
FLASH FLOOD OR FLOOD STATEMENT: Follow-up information regarding a flash flood/flood event.
The rule for being safe in a flooding situation is simple: HEAD FOR HIGHER GROUND AND STAY AWAY FROM FLOOD WATERS!
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TAKE ACTION!
When a flash flood WATCH is issued Be alert to signs of flash flooding and be ready to evacuate on a moment's notice.
When a flash flood WARNING is issued for your area, or the moment you realize that a flash flood is imminent, act quickly to save yourself. You may have only SECONDS!
Go to higher ground Climb to safety!
Get out of areas subject to flooding. This includes dips, low spots, canyons, washes, etc.
Avoid already flooded and high velocity flow areas. Do not attempt to cross flowing streams.
If driving, be aware that the road bed may not be intact under flood waters. Turn around and go another way. NEVER drive through flooded roadways!
If the vehicle stalls, leave it immediately and seek higher ground. Rapidly rising water may engulf the vehicle and its occupants and sweep them away. Remember, it's better to be wet than dead!
Be especially cautious at night when it is harder to recognize flood dangers.
Do not camp or park your vehicle along streams and washes, particularly during threatening conditions.
When you receive a FLOOD WARNING:
If advised to evacuate, do so immediately.
Move to a safe area before access is cut off by flood water.
continue monitoring NOAA Weather Radio, television, or emergency broadcast station for information.
During the flood:
Avoid areas subject to sudden flooding.
If you come upon a flowing stream where water is above your ankles, STOP! Turn around and go another way.
Do not attempt to drive over a flooded road. The depth of water is not always obvious. The road bed may be washed out under the water, and you could be stranded or trapped.
Children should NEVER play around high water, storm drains, viaducts, or arroyos.
After the flood:
If fresh food has come in contact with flood waters, throw it out.
Boil drinking water before using. Wells should be pumped out and the water tested for purity before drinking. If in doubt, call your local public health authority.
Seek necessary medical care at the nearest hospital. Food, clothing, shelter, and first aid are available from the Red Cross.
Do not visit disaster areas. Your presence might hamper rescue and other emergency operations.
Electrical equipment should be checked and dried before being returned to service.
Use flashlights, not lanterns, torches or matches, to examine buildings. Flammables may be inside.
Report broken utility lines to appropriate authorities.
FAMILY DISASTER PLAN
Families should be prepared for all hazards that affect their area. NOAA's National Weather Service, the Federal Emergency Management Agency, and the American Red Cross urge each family to develop a family disaster plan.
Where will your family be when disaster strikes? They could be anywhere at work, at school, or in the car. How will you find each other? Will you know if your children are safe? Disasters may force you to evacuate your neighborhood or confine you to your home. What would you do if basic services water, gas, electricity or telephones were cut off?
Follow these basic steps to develop a family disaster plan...
I. Gather information about hazards. Contact your local National Weather Service office, emergency management or civil defense office, and American Red Cross chapter. Find out what type of disasters could occur and how you should respond. Learn your community's warning signals and evacuation plans.
II. Meet with your family to create a plan. Discuss the information you have gathered. Pick two places to meet: a spot outside your home for an emergency, such as fire, and a place away from your neighborhood in case you can't return home. Choose an out-of-state friend as your "family check-in contact" for everyone to call if the family gets separated. Discuss what you would do if advised to evacuate.
III. Implement your plan.
(1) Post emergency telephone numbers by phones;
(2) Install safety features in your house, such as smoke detectors and fire extinguishers;
(3) Inspect your home for potential hazards (such as items that can move, fall, break, or catch fire) and correct them;
(4) Have your family learn basic safety measures, such as CPR and first aid; how to use a fire extinguisher; and how and when to turn off water, gas, and electricity in your home;
(5) Teach children how and when to call 911 or your local Emergency Medical Services number;
(6) Keep enough supplies in your home to meet your needs for at least three days. Assemble a disaster supplies kit with items you may need in case of an evacuation. Store these supplies in sturdy, easy-to-carry containers, such as backpacks or duffle bags. Keep important family documents in a waterproof container. Keep a smaller disaster supplies kit in the trunk of your car.
A DISASTER SUPPLIES KIT SHOULD INCLUDE:
A 3-day supply of water (one gallon per person per day) and food that won't spoil
one change of clothing and footwear per person
one blanket or sleeping bag per person
a first aid kit, including prescription medicines
emergency tools, including a battery-powered NOAA Weather Radio and a portable radio, flashlight, and plenty of extra batteries
an extra set of car keys and a credit card or cash
special items for infant, elderly, or disabled family members.
IV. Practice and maintain your plan. Ask questions to make sure your family remembers meeting places, phone numbers, and safety rules. Conduct drills. Test your smoke detectors monthly and change the batteries at least once a year. Test and recharge your fire extinguisher(s) according to manufacturer's instructions. Replace stored water and food every six months.
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