By Howard Lestrud
ECM Online Managing Editor
What really is a tornado? Definition of a tornado on the Web is: a localized and violently destructive windstorm occurring over land characterized by a funnel-shaped cloud extending toward the ground.
Unless you don’t have a high value of your life, find cover immediately. The National Weather Service has confirmed that a single monster tornado is to blame for 10 deaths two weekends ago in Mississippi. It was initially unclear if a single massive twister, or multiple smaller ones, caused the deaths and damaged about 700 homes in the state.
The state’s chief Weather Service meteorologist, Alan Gerard, said that the tornado followed a nearly 150-mile track from Tallulah, La., through Mississippi, before dissipating in Oktibbeha County in northeastern part of the state.
Let’s analyze more carefully what a tornado really is. Some of the most valuable storm information can be found on the national Oceanic and Atmospheric Administration (NOAA) Web site at http://www.noaa.gov/
To find information at the NOAA site just on tornadoes, go to http://www.nssl.noaa.gov/edu/safety/tornadoguide.html
Bookmark this NOAA tornado information and read it carefully.
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.
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.
Every workplace and every home should have a plan for tornado safety. Here’s what NOAA says about tornado safety.
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.
In our ECM readership area, severe destruction was caused by tornadoes in Anoka (1939) and in Fridley (1965). The Anoka tornado of June 28, 1939 took nine lives, injured 200 and ruined over 250 homes. Go to http://www.gendisasters.com/data1/mn/tornadoes/anoka-tornado-jun1939.htm
Six tornadoes struck the Twin Cities on May 6, 1965. Go to http://tinyurl.com/3xd368v