The atmosphere is considered to be the mass of air that surrounds the earth; it is the air in a particular place or area (Merriam Webster). The biosphere includes all living organisms on earth, together with the dead organic matter produced by them. A tornado is one of the many atmospheric events that can affect the earth’s biosphere. Tornadoes come from the energy released in a thunderstorm. Science does not yet completely understand how part of a thunderstorm’s energy sometimes gets focused into a tornado.
While the detection of tornadoes is still relatively young, the invention of weather radar, doppler radars, and geostationary operational environmental satellites, have made it possible to give advanced warning when conditions are favorable, and save lives.
The National Weather Service (NWS) defines a tornado as a violently rotating column of air in contact with the earth’s surface (land or water) and commonly associated with a severe thunderstorm. The most violent tornadoes are capable of tremendous destruction with wind speeds of two hundred and fifty miles per hour or more.
Damage paths can be in excess of one mile wide and fifty miles long. In an average year, eight hundred tornadoes are reported nationwide, resulting in eighty deaths and over one thousand five hundred injuries.
A total of 12 tornadoes blew through seven different central Iowa counties in July 2018 according to the National Weather Service. Two of those tornadoes were rated EF-3, with wind speeds that reached 144 mph. Those storms swept through Pella and Marshalltown, while a less powerful EF-2 tornado struck Bondurant.
The Pella and Marshalltown twisters are the strongest to hit Iowa since a June 22, 2015, tornado of the same strength passed through Marion, Lucas and Monroe counties. The tornado that hit Marshalltown flung the clock tower from the historic courthouse, ripped the walls off a 911 communications center and devastated the Lennox heating and air conditioning plant, one of the town’s largest employers. Officials say the storm destroyed about 50 buildings and damaged hundreds more. In Pella, a tornado damaged several buildings at the Vermeer manufacturing facility, and several homes were damaged in Bondurant.
Two funnel clouds are shown between Altoona and Bondurant on Thursday, July 19, 2018, Kyra Alcott/Special to the Register—Photo: Erik Garnass/Special to the Register
The average tornado is usually split up into categories based on the strength of the tornado. Most tornadoes are considered weak, which means they usually last between one and ten minutes, have winds less that one hundred ten miles per hour, and the percentage of deaths that occur during these are less than five percent. Strong tornadoes can last about twenty minutes; having winds between one hundred ten and two hundred five miles per hour. The last category for tornadoes is violent ones; with these comes winds greater than two hundred five miles per hour. They can last up to an hour, and account for seventy percent of all deaths from tornadoes.
Some variations of tornadoes can be found in the early stages of rapidly developing thunderstorms. Tornadoes may appear nearly transparent until dust and debris are picked up. Occasionally, two or more tornadoes may occur at the same time. The average tornado moves from southwest to northeast, but they have been known to move in any direction. The average forward speed is about thirty miles per hour but can vary to seventy miles per hour before it really gets going.
Tornadoes occur at any time of the year; In the southeastern states, peak tornado occurrence is March through May, while peak months in the northern states are during the summer months. Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm’s energy sometimes gets focused into something as small as a tornado.
The damage from tornadoes comes from the strong winds they contain. It is generally believed that tornadic wind speeds can be as high as three hundred miles per hour in most violent tornadoes. Wind speeds that high can cause automobiles to become airborne, rip ordinary homes to shreds, and turn broken glass and other debris into lethal missiles.
The biggest threat to living creatures, including humans, from tornadoes is from flying debris and from being tossed about in the wind. Today, the development of Doppler radar has made it possible, under certain circumstances, to detect a tornado’s winds with a radar. However, human beings remain an important part of the system to detect tornadoes because not all of them occur in situations where radar can ‘see’ them. Ordinary citizen volunteers make up a network of storm spotters who work with their local communities to watch out for approaching tornadoes, so that those communities can take appropriate action in the event of a tornado. Spotter information is relayed to the National Weather Service, which operates the Doppler radars and issues warnings, usually relayed to the public by radio and television, for communities ahead of the storms using all the information they can obtain from weather maps, modern weather radars, storm spotters, monitoring power line breaks, and so on.
Tornadoes can be predicted, but only to a limited extent. Although the process by which tornadoes form is not completely understood, scientific research has revealed that tornadoes usually form under certain types of atmospheric conditions. Those conditions can be predicted, but not perfectly. When forecasters see those conditions, they can predict that tornadoes are likely to occur. However, it is not yet possible to predict in advance exactly when and where they will develop, how strong they will be, or precisely what path they will follow.
There are some ‘surprises’ every year, when tornadoes form in situations that do not look like the right conditions in advance, but these are becoming less frequent. Once a tornado is formed and has been detected, warnings can be issued based on the path of the storm producing the tornado, but even these cannot be precise about who will or will not be struck.
Some clues to look for in the environment that could give you an idea that a tornado is coming are that the sky gets dark and sometimes green, there are walls of clouds everywhere, even close to the ground, large hail comes down, and loud roars, like a freight train. These are all things that help us to determine if we may experience a tornado.