Definition: a mobile, destructive vortex of violently rotating winds having the appearance of a funnel-shaped cloud and advancing beneath a large storm system.
Why and How do Tornadoes form? No one really knows exactly why tornadoes form but there are many theories as to why they form and here is one well, firstly they start off as thunderstorms. For them to form you need warm, moist air and cool, dry air . When these two air masses meet, they create instability in the atmosphere. A change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere. Rising air within the updraft tilts the rotating air from horizontal to vertical. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
What do Tornadoes look like? Tornadoes can appear as a traditional funnel shape, or in a slender rope-like form. Some have a churning, smoky look to them, and other contain "multiple vortices", which are small, individual tornadoes rotating around a common center. Even others may be nearly invisible, with only swirling dust or debris at ground levels as the only indication of the tornado's presence
How long can tornadoes last for and how do they stop?? Tornadoes can last from a few seconds to over an hour, although most last less than 10 minutes. It is not fully understood about how exactly tornadoes form, grow and die. Tornado researchers are still trying to solve the tornado puzzle, but for every piece that seems to fit they often uncover new pieces that need to be studied.
When are tornados most likely to occur? Tornadoes can happen at any time of the year and at any time of the day. In the southern states, peak tornado season is from March through May. Peak times for tornadoes in the northern states are during the summer. A few southern states have a second peak time for tornado outbreaks in the fall. Tornadoes are most likely to occur between 3 p.m. and 9 p.m.
Where are tornadoes most likely to occur? The geography of the central part of the United States, known as the Great Plains, is suited to bring all of the ingredients together to forms tornadoes. More than 500 tornadoes typically occur in this area every year and is why it is commonly known as "Tornado Alley". Texas, Oklahoma, Kansas, Nebraska, South Dakota, North Dakota, Iowa, Missouri, Arkansas and Louisiana all make up Tornado Alley.
Facts: Tornadoes can occur at any time of the year, 69% of all tornadoes are labeled "weak tornadoes" meaning they have a lifetime of 1-10+ minutes and winds less than 110 mph, 29% of all tornadoes are labeled "strong tornadoes" meaning they last 20 minutes or longer and winds reach 110-205 mph, and 2% of all tornadoes are labeled "violent tornadoes" and can last over an hour.