Talking About the Weather

In This Chapter

>■ The simple causes behind the weather”s complex behavior

V Labeling and categorizing clouds

V Understanding and avoiding turbulence

V Severe storms and you

>■ The pilot as amateur weather forecaster

All pilots are students of the weather. From their very first flight, pilots begin to develop an instinct for weather. Weather affects all aspects of a flight, from the wind whose direction determines which runway you’ll take off from to the make-up of clouds that signal the onset of stomach-turning turbulence.

Even pilots with a private pilot certificate in their pocket and hundreds of hours scribbled into their logbook keep a close watch on the weather. Without an instrument rating and special training in weather flying, private pilots are grounded by bad weather.

Weather is one of the most common factors cited as contributing to accidents, including the one in 1999 that killed John F. Kennedy Jr., his wife, and her sister. (We’ve dedicated Chapter 20, “John F. Kennedy Jr.’s Final Flight,” to examining all aspects of Kennedy’s accident, including tips on flying in clouds and in bad weather.) Even a rudimentary understanding of how the weather works can be a valuable tool for the pilot.

What Makes the Weather?

Weather on earth is created by two fundamentals of astronomy: The sun generates enormous heat, and the earth spins on its axis. All weather begins from those two simple conditions. Of course, from that simple starting point, weather can take many forms, depending on many variables, and become a quite complex science—a science called meteorology.

Weather is generated when the sun heats different parts of the earth unevenly. The rotation of the earth complicates matters by adding a circular element to the movement of huge air masses that flow like liquid over the earth’s surface.

But there’s more—the interaction between water and air. Some of the ocean’s currents transport cold water into the warm tropics and others move warm water into the chilly polar regions. The colliding boundaries between warm air, which holds large amounts of water vapor that evaporated from the warm ocean water, and cold air, which is comparatively dry, results in precipitation in the form of rain, snow, and ice.

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Water is another major player in weather. In meteorological terms, the power of water lies in its ability to absorb and radiate heat when it changes state, going from liquid to vapor and back to liquid again. Water is a primary factor in the development of severe weather, such as thunderstorms, tornadoes, and hurricanes, which we’ll discuss shortly.

The rotation of the earth is responsible for the circulation patterns of the atmosphere and for the spinning of air around high – and low-pressure areas.

Because of a phenomenon called the “Coriolis effect,” high-pressure areas rotate in a clockwise direction in the Northern Hemisphere, while low-pressure areas rotate counterclockwise. In the Southern Hemisphere, high-pressure areas rotate counterclockwise, while low-pressure areas rotate clockwise. The direction of rotation around high-and low-pressure areas dictates the direction of wind flow.