Introduction

Weather is an important factor that influences aircraft
performance and flying safety. It is the state of the atmosphere
at a given time and place, with respect to variables such as
temperature (heat or cold), moisture (wetness or dryness),
wind velocity (calm or storm), visibility (clearness or
cloudiness), and barometric pressure (high or low). The term
weather can also apply to adverse or destructive atmospheric
conditions, such as high winds.

This chapter explains basic weather theory and offers pilots
background knowledge of weather principles. It is designed
to help them gain a good understanding of how weather
affects daily flying activities. Understanding the theories
behind weather helps a pilot make sound weather decisions
based on the reports and forecasts obtained from a Flight
Service Station (FSS) weather specialist and other aviation
weather services. Be it a local flight or a long cross-country flight, decisions based on weather can dramatically affect the safety of the flight.