Monday, May 27, 2013

Tornado Season in the Midwest

Yesterday, President Barack Obama called the destruction of the last week's tornado wrought in Moore, Oklahoma, "hard to comprehend" and vowed to provide long-term federal help in rebuilding.

Last week tornado was rated at the top of a five-step scale used to measure the destructive power of twisters. It killed 24 people - including seven children at the school site THAT President Obama visited yesterday. It ripped a 17-mile-long (27-km-long) corridor of destruction through the suburb of Oklahoma City, flattening entire blocks of homes, two schools and a hospital causing billions of damages to property.

Tornadoes are indeed very scary and destructive, similar to hurricanes and earthquakes. Have you seen or heard a tornado so close that you thought you will die? Or just far enough to scare you? My family and I have seen and heard a tornado when we were still living in Kansas City in the 1980's. It was close enough, we all have to run for cover in the basement. Luckily, it was a small and weak tornado (probably a f0 or f1) in the FUJITA scale. It dissipated fast enough in the opposite direction where our house was located. It did topple a couple of trees in the backyard of our next-door neighbor though. It was still scary since one will never know if it is your house that will be in its direct path.

A tornado (often referred to as a twister or, erroneously, a cyclone) is a violent, dangerous, rotating column of air that is in contact with both the surface of the earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud.

Tornadoes come in many shapes and sizes, but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris and dust. Most tornadoes have wind speeds less than 110 miles per hour (177 km/h), are approximately 250 feet (80 m) across, and travel a few miles (several kilometers) before dissipating. The most extreme can attain wind speeds of more than 300 mph (480 km/h), stretch more than two miles (3 km) across, and stay on the ground for dozens of miles (more than 100 km).

Tornadoes have been observed on every continent except Antarctica. However, the vast majority of tornadoes in the world occur in the Tornado Alley ( Midwest) region of the United States, although they can occur nearly anywhere in North America. They also occasionally occur in south-central and eastern Asia, the Philippines, northern and east-central South America, Southern Africa, northwestern and southeast Europe, western and southeastern Australia, and New Zealand. Tornadoes can be detected before or as they occur through the use of Pulse-Doppler radar by recognizing patterns in velocity and reflectivity data, such as hook echoes, as well as by the efforts of storm spotters.

There are several different scales for rating the strength of tornadoes. The Fujita (F)scale rates tornadoes by damage caused, and has been replaced in some countries by the updated Enhanced Fujita Scale(EF). An F0 or EF0 tornado, the weakest category, damages trees, but not substantial structures. An F5 or EF5 tornado, the strongest category, rips buildings off their foundations and can deform large skyscrapers.

There are people who loved chasing tornadoes, but not me. A F0 tornado I experienced in Kansas City 25 years ago is enough to scare me for life.

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