Capturing a Tornado

The weather forecasted severe thunderstorms for the afternoon of June 5, 2009. As storm conditions intensified, most people descended into their storm cellars. Another group of people was out in the wind, setting up their equipment in formation around the growing funnel cloud.

Predicting tornadoes

Scientists know what the conditions are that can form a tornado. They can give warnings of up to 13 minutes in advance of a tornado forming. But they still cannot predict how big it will be, or what direction it will head. And for some people, 13 minutes is not enough time to get to a safe shelter.

VORTEX

The largest single collaboration of tornado scientists is called Verification of Rotation in Tornadoes Experiment (VORTEX) and its successor, VORTEX2. In the 1990's, VORTEX scientists observed hundreds of tornadoes. The data they collected resulted in an improvement in identification of tornados and extended the warning time that people have to respond to them. This time, in VORTEX2, as many as 200 researchers, technicians, and students representing an international collaboration of universities, have come together to intercept and observe tornadoes even more closely. Their equipment is carried on a fleet of 35 highly specialized vehicles. These include 10 flatbed trucks mounted with large radar dishes, called Doppler on Wheels (DOWs) as shown in Figure 1. VORTEX2 also has thirteen trucks outfitted as automated weather stations, called mobile mesonets, four mobile ballooning systems, and 24 sticknets--a network of tripods mounted with sensors for measuring conditions on the ground close to the tornado. The crew includes teams of photographers trained to capture images of cloud formation.

Chasing severe weather

During five weeks of the 2009 tornado season, the huge fleet crossed nine states of the Great Plains region, covering over 16,000 km of roads and highways, following extreme weather for possible tornadoes. Every morning the scientists met to analyze weather patterns, looking for regions where the development of supercells would be most likely. On days when the weather within a day's drive was calm, they practiced their tornado intercept strategy.

On that afternoon in June2009, VORTEX2 made history when the scientists detected rotation in a supercell in the Wyoming sky. Like they had done on numerous practice runs, they positioned the DOW's in strategic locations in front and behind the storm, shown in Figure 2 arranged the sticknets at intervals of about one kilometer crossing the path of the storm, and aligned the mobile mesonet trucks close to the base of the storm. The team observed the rotating clouds develop into an EF2 tornado. They watched the tornado travel 10 km towards some of their camera operators, and they observed it as the tornado began dying down. The tornado in Goshen county Wyoming lasted less than an hour, but the data would take months for the scientists to completely analyze, and would become known for years as the world's most thoroughly studied tornado.

Teacher's Edition for Feature Capturing a Tornado

Purpose

Students will learn about how scientists in the field collaborate to study tornadoes.

Background

Meteorologists understand the conditions under which a tornado can form, but cannot yet accurately predict the size a tornado will reach, or where it will move. Verification of Rotation in Tornadoes Experiment (VORTEX) is a mobile research project involving meteorologists and students in pursuit of a tornado to observe using a complex network of technology, and improve scientific understanding of how tornadoes form and develop.

Teaching Strategies

• Some of your students might have seen Storm Chasers on TV. They might recognize that VORTEX has certain elements in common with Storm Chasers. In fact, the Tornado Intercept Vehicle that is featured in Storm Chasers travels with one of the Doppler on Wheels (DOW) in the Discovery Channel show. Explain to the class that VORTEX is the scientific research that is only sometimes shown in the TV show.

• Discuss with the students the differences between tornadoes in the real world and the aspect of tornadoes seen in extreme weather shows like Storm Chasers. Students should realize that tornadoes are potentially deadly, having violent winds that can destroy a house. In the event of a tornado, it is important to go into a basement, or an interior room of a house for protection, and never to linger outside to catch a glimpse at the tornado.

• Project this interactive activity on the board and discuss with students the stages in the formation of a tornado. [link]