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Answer these questions on a separate sheet of paper.

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Answer these questions on a separate sheet of paper.

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Brief, simplified description of the formation of air masses.

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Brief, simplified description of atmospheric high pressure areas.

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Brief, simplified description of atmospheric low pressure areas.

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Warm Front: transition zone from cold air to warm air

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A warm front is defined as the transition zone where a warm air mass is replacing a cold air mass. Warm fronts generally move from southwest to northeast and the air behind a warm front is warmer and more moist than the air ahead of it.

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Cold Front: transition zone from warm air to cold air

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A cold front is defined as the transition zone where a cold air mass is replacing a warmer air mass. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it.

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Occluded Fronts - Windows to the Universe

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Windows to the Universe, at http://windows2universe.org/ from the National Earth Science Teachers Association (NESTA). The Website was developed in part with the support of UCAR and NCAR, where it resided from 2000 - 2010. © 2012 National Earth Science Teachers Association. Windows to the Universe® is a registered trademark of NESTA.

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Monthly Tornado Occurrence Maps

Because a tornado is part of a severe convective storm, and these storms occur all over the Earth, tornadoes are not limited to any specific geographic location. In fact, tornadoes have been documented in every state of the United States, and on every continent, with the exception of Antarctica (even there, a tornado occurrence is not impossible). In fact, wherever the atmospheric conditions are exactly right, the occurrence of a tornadic storm is possible. See NOAA's National Severe Storms Laboratory (NSSL) Severe Weather 101 information for more on the conditions necessary for tornado formation.

However, some parts of the world are much more prone to tornadoes than others. Globally, the middle latitudes, between about 30° and 50° North or South, provide the most favorable environment for tornadogenesis. This is the region where cold, polar air meets against warmer, subtropical air, often generating convective precipitation along the collision boundaries. In addition, air in the midlatitudes often flows at different speeds and directions at different levels of the troposphere, facilitating the development of rotation within a storm cell. Interestingly, the places that receive the most frequent tornadoes are also considered the most fertile agricultural zones of the world. This is due in part to the high number of convective storms delivering needed precipitation to these areas. Simply because of the large number of convective storms and the favorable environment, the odds are increased that some of these storms will produce tornadoes.

In terms of absolute tornado counts, the United States leads the list, with an average of over 1,000 tornadoes recorded each year. Canada is a distant second, with around 100 per year. Other locations that experience frequent tornado occurrences include northern Europe, western Asia, Bangladesh, Japan, Australia, New Zealand, China, South Africa, and Argentina. In fact, the United Kingdom has more tornadoes, relative to its land area, than any other country. Fortunately, most UK tornadoes are relatively weak.

Recent Tornado Reports and Information
A summary of recent tornadic activity in the contiguous United States, including monthly tornado counts and descriptions of significant events.

Historical Records and Trends
Historical records and trends for tornadoes, including graphs and maps showing timing and occurrences over approximately 60 years.

Tornado Alley
In the United States, there are two regions with a disproportionately high frequency of tornadoes.

Deadliest Tornadoes
Most tornadoes do not result in death. As a result of improved forecasting and early warning systems, the death toll has dropped.

Regions of the World with Increased Likelihood of Experiencing Tornadoes Larger Image
Special Reports

Additional Information

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Monthly Tornado Occurrence Maps Because a tornado is part of a severe convective storm, and these storms occur all over the Earth, tornadoes are not limited to any specific geographic location. In fact, tornadoes have been documented in every state of the United States, and on every continent, with the exception of Antarctica (even there, a tornado occurrence is not impossible).

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Maps: Satellite & Radar - The Weather Network

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Weather maps provide past, current, and future radar and satellite images for local, Canadian and other North American cities.