Tornadoes, also called twisters, are columns of air rotating dangerously fast. The air is in motion because of the difference in pressure between the center of a tornado (very low pressure) and the outer edge of the tornado (high pressure). Some tornadoes are narrow, only 250 feet (75 meters) across where they touch the ground. Other, massive tornadoes can be up to two miles across. Often a tornado will touch the ground for only a few minutes and travel less than a mile. But some tornadoes touchdown for much longer, plowing through several towns, neighborhoods, or farms. Tornadoes can occur anywhere in the world. About 75% of the world’s tornadoes form in the United States - most in an area of the central United States called Tornado Alley.
After a tornado has come and gone, scientists look at the amount of damage that it caused to figure out the strength of the twister. They use the Enhanced Fujita (EF) Scale - six categories that describe how tornado damage relates to wind speeds. According to the scale, EF0 is the weakest tornado category with gusts up to 85 mph (135 kph) and EF5 is the strongest tornado with wind gusts over 200 mph (320 kph).
On May 22, 2011, a catastrophic tornado struck Joplin, Missouri. This EF5 tornado was almost 1 mile wide and traveled approximately 22 miles. This tornado caused tremendous damage. Nearly 7,000 homes were destroyed by the tornado, and an additional 850 were damaged. Approximately 25% of the town of Joplin sustained damage, and 160 people died in the storm. Hundreds of people were injured. This violent tornado was a reminder of how dangerous tornadoes can be.
The National Weather Service defines a blizzard as a storm with large amounts of snow or blowing snow, winds greater than 35 mph (56 kph), and visibility of less than ¼ mile (0.4 km) for at least three hours. Some blizzards, called ground blizzards, have no falling snow. Instead, snow that had fallen before the blizzard is blown around or drifts in a way to create these conditions. In the United States, blizzards are common in the upper Midwest and the Great Plains but can occur in most areas of the country except for the Gulf Coast and the California coast.
Conditions of a blizzard can be severe. Travel becomes dangerous when the blowing snow causes whiteout conditions in which both sky and ground look white. Roads can be partially or fully blocked by snowdrifts – piles of snow formed by the wind. Many times cold temperatures that can cause frostbite or hypothermia are part of a blizzard and can last for days after the storm has ended.
The February 5-6, 2010 blizzard, known as Snowmageddon, was a large blizzard that dropped 20 to 35 inches (50 to 90 cm) of snow in parts of Pennsylvania, West Virginia, Virginia, Washington, D.C., Maryland, Delaware, and New Jersey. This storm was the second of three storms that occurred in the Mid-Atlantic States over a twelve-day period. Twelve inches fell across Virginia on January 30m 2010, and 28 inches fell in Maryland and Pennsylvania on February 9-10, 2010. The word “Snowmageddon” is one of several versions of the word “snow” that have been used to describe blizzards in recent years. Others include Snowpocalypse and Snowzilla.
Hurricanes form from disturbances in the atmosphere over warm, tropical ocean water. They die down when they move over land or out of the tropics and into cooler latitudes. These storms are called hurricanes in the Atlantic and typhoons or tropical cyclones in other areas of the world. Because of the Coriolis effect, the storms rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. At the center of the rotating storm is a small area of calm weather and clear skies called the eye of the storm. Surrounding the calm of the eye are the most intense winds of the storm and thick clouds of the eyewall. Hurricanes are huge storms – the average hurricane spreads across 340 miles.
When a hurricane approaches land, strong waves and wind batter coastal towns. Hurricanes also cause a tremendous amount of rain in a short amount of time, which can cause rivers to flood their banks and flood areas that are both near the coast and further inland. But most coastal hurricane damage is typically flooding caused by storm surge – the temporary rise in sea level that happens as winds of the storm push water towards the coast. The low pressure of the storm also causes some storm surge. If a storm surge happens at the same time as a high tide, the effect is more intense, and more areas are flooded.
Hurricane Sandy was the most destructive tropical cyclone of the 2012 Atlantic hurricane season. This hurricane developed in the western Caribbean Sea on October 22, 2012, and moved over Cuba and the Bahamas before making landfall in New Jersey on October 29, 2012. Hurricane Sandy merged with a frontal weather system coming from the western United States, strengthening the storm over the northeast U.S. By the time Hurricane Sandy dissipated on October 31, 2012, at least 285 people had died and billions of dollars in damages occurred in countries throughout the Caribbean, much of the eastern U.S., and southeastern Canada. New Jersey and New York were hit especially hard by Hurricane Sandy.
Why Is Weather in the News?
News media outlets (including newspapers, T.V. news, websites, blogs) carry stories about weather for several reasons. Of course, weather forecasts for the next several days are a staple in news (everyone wants to know if they should bring an umbrella!) but when there is a severe weather event, news outlets carry the story with different sorts of coverage. There are forecast reports, stories about how communities are preparing for the event and the devastation that the event caused, and editorials about the storm.
Activity developed by Lisa Gardiner and Becca Hatheway of the UCAR Center for Science Education