Storms. Some people absolutely love them, other people are petrified of them. They can be beautiful with the displays of lightning or devastating with hail, damaging winds or even a tornado. What are the conditions that actually cause these storms to happen?
Most people roll their eyes when an older person says that they can tell that is going to storm by their knees or back. There are old sayings (that many times turn out to be true), like “red at night, sailor's delight- red at morn, sailor's be warned”. There is a science behind all of this.
Meteorologist’s study weather patterns, specifically the high altitude, high speed winds (in the U.S. known as the Jet Stream) that encircle the globe. Depending on the latitude they may go from west to east or east to west. There are many factors that cause this phenomenon. The heating and cooling of the Earth's surface by the Sun along with the rotation of the planet can cause these winds to exceed 100 mph.
These “streams” of fast moving wind meander north and south periodically. As the move they will bring warm, moist tropical air north or drier cold air south (in the Northern Hemisphere).
The fact that warm air will rise, cold air will sink causes turbulence in the atmosphere at the boundary line of these air masses.
It is at this boundary that most storms will form.
It is another set of conditions that will cause other types of storms. Hurricanes (or cyclones) will form in the tropical waters. They move in a circular motion. Depending on the hemisphere, they will rotate either clockwise or counterclockwise. These storms are more complicated than the average thunderstorm, but the concept is still the same.
Warm, moist air collides with cool dry air. The difference in temperature and humidity (along with the Earth's rotation) will cause a chain reaction.
It is this set of circumstances that cause storms to form. Of course, it is much more technical than this. People spend their entire professional careers studying this question. This is just the basic idea behind the idea though. As long as you make sure that you are safe, enjoy an afternoon thunderstorm. Although the science may be technical, the awesome power witnesses is not to be missed. It can be better than any fireworks display you have every seen.
Just remember, ANY storm can suddenly change from fun to deadly in almost no time. Stay safe.