No other country has more tornadoes than the United States. This is because arctic and tropical winds clash directly over the Midwestern states in an area famous today as Tornado Alley. It is estimated that 850 tornadoes touch down each year. No tornadoes outside the United States have caused the same death and destruction.
The National Weather Service has been observing, studying, predicting, and reporting tornadoes since 1953. Before that year, twisters killed about 230 people per year. After the service began its tornado-warning system, the death rate dropped to 120 people per year. In 1962, only 28 people lost their lives to tornadoes.
In 1870, the U.S. government decided to take charge of the tornado problem and give citizens in Tornado Alley a warning system of when and where tornadoes would hit. The job was given over to the U.S. Army Signal Corps, which decided to issue “probabilities” or “severe local storms.” They feared that the forecast of a tornado striking a specific town or area would cause panic.
Later, the National Weather Service took over and the same cautionary proceedings were taken. In 1896, experts were sure tornadoes were going to hit Saint Louis. However, the forecast mentioned only “local thunderstorms.” The tornadoes ended up killing 100 unprepared residents. Almost 100 more died in East Saint Louis. The public uproar that followed compelled the weather service to begin making more specific tornado predictions.
During World War II, many Midwestern production plants and army air bases were severely damaged by tornadoes. Because of this, the weather service began cooperating with the army to build a tornado watcher network, volunteers who phoned a station the moment funnel clouds were seen. Officials would then radio or phone tornado warnings to towns, factories, and airfields in danger.
In 1973 the weather service began to use scientific instruments to chase and chart Great Plains tornadoes. Those studies helped the service make better predictions of tornado size, strength, and behavior, as well as where and when to expect them.
In the last few years, we have learned much more about tornadoes because of studies conducted by the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma, working together with the University of Oklahoma and other universities.
The NSSL sends out teams of scientists to chase storms down and study them. The teams locate and intercept the twisters, keeping in touch by radio and mobile phone. Their vans are fully equipped with computer-controlled electronic equipment, remote-control video cameras, and sensitive detection systems.
At first, these teams dropped a 400-pound barrel called TOTO (Totable Tornado Observatory) in the path of a tornado. This device measured the twister’s wind speed, temperature, direction, and atmospheric pressure. However, the TOTO was usually blown over as soon as the storm winds reached 150 miles an hour. Starting in 1987, it has been replaced by a Doppler radar unit with a range of 3 to 5 miles. This new device can identify a mesocyclone two to four hours before it develops into a tornado. It also knows whether tornado winds are moving toward or away from it and how fast. More recently, Next-Generation Weather Radar systems have been introduced, which track and analyze mesocyclones better than ordinary radar. A second radar network called Profilers can also measure winds in the upper atmosphere, 20 miles above the earth. These can help predict possible mesocyclones, and will work with weather balloons to give wind direction and speed at different altitudes.
The life of a storm chaser can be a great adventure. These brave scientists try to get close enough to a tornado to observe the inside of the funnel. However, the twisters can move faster than expected or suddenly change direction. Their lives depend on the ability to escape quickly.
In 1969 the Environmental Science Services Administration (ESSA) set up SKYWARN, an expanded network of volunteer tornado watchers. More people became actively involved in getting people to safety and spreading warnings.
In Kansas City, Missouri, there is a special National Severe Storms Forecast Center (SELS), which keeps track of mesocyclones that may produce tornadoes. When the possibility of a tornado is clear, SELS issues a tornado watch, which indicates that tornadoes may occur in the next several hours in a specific area. The area at risk is usually about 100 miles wide and 250 miles long. The people there are advised to be ready to take shelter at once if a tornado is sighted. Local weather stations, TV and radio stations, ham radio operators, and the tornado-spotter network then work together to get warning out to people.
When twisters have actually been seen or detected by radar, it is the local weather stations’ responsibility to issue the tornado warnings. Warnings are sent out as quickly as possible over TV and radio, reporting areas in danger, times of detection, and expected strikes. The weather stations can see the tornadoes on radar, as a revolving “6” shape dangling down from a mesocyclone image.
SELS must decide when to issue a tornado watch. The U.S. has over 100,000 thunderstorms a year, and only 1% of those produce tornadoes. The storm center tries to determine when those killer tornadoes will appear, so they can put a watch out two to six hours in advance. On the other hand, it is not good to put out too many tornado watches that end up becoming false alarms because people will stop paying attention.
Many Tornado Alley communities set up alarm systems that go into action when local weather stations issue tornado warnings. In May 1947, a telephone official in Leedey, Oklahoma saw a tornado funnel in the distance and immediately sounded the alarm. When the twister actually hit town, two-thirds of the town was destroyed, but only six perished. Most of the population fled or took shelter beforehand.
Warnings are crucial, even if they are given a few minutes before the disaster strikes. It can mean a few precious seconds between life and death.