.  
DO be sure to get all the weather information you need.  If you are flying in IMC or MVFR that could deteriorate, don’t en d the briefing without knowing which direction (north, south, east, west) to turn to fly toward better weather, and how far you would have to fly to reach it.

Process – Analyzing Weather Information
Obtaining weather information is only the first step.  The critical next step is to study and evaluate the information to understand what it means for your circumstances.
The knowledge tests for most pilot certificates include questions on weather theory and use of weather products in aviation.  However, it takes continuous study and experience to develop your skill in evaluating and applying weather data to a specific flight in a GA airplane. You might find it helpful to approach the task of practical, real world weather analysis with several basic concepts in mind.
What creates weather?  Most pilots can recite the textbook answer -- “uneven heating of the earth’s surface” – but what does that mean when you are trying to evaluate weather conditions for your trip? Let’s take a look.
The three basic elements of weather are:
.
Temperature (warm or cold);

.
Wind (a vector with speed and direction); and 

.
Moisture (or humidity).  

Temperature differences (e.g., uneven heating) support the development of low pressure systems, which can affect wide areas.  Surface low pressure systems usually have fronts associated with them, with a “front” being the zone between two air masses that contain different combinations of the three basic elements (temperature, wind, and moisture).

The illustration shows the “classic” northern hemisphere low pressure system with the associated cold and warm fronts. Remembering that air circulates counterclockwise around a low pressure system in the Northern Hemisphere will help you visualize the overall temperature, wind, and moisture patterns in a given area. Because weather is associated with fronts, which are in turn associated with low pressure systems, you can get some idea of possible conditions just by looking to see where the low
pressure systems are in relation to your route.
What can weather do to you? Temperature, wind, and moisture combine to varying degrees to create conditions that affect pilots.  The range of possible combinations is nearly infinite, but weather really affects pilots in just three ways. Specifically, the three basic weather elements can:
.
Reduce visibility

.
Create turbulence

.
Reduce aircraft performance

How do you evaluate weather data? One approach to practical weather analysis is to review weather data in terms of how current and forecast conditions will affect visibility, turbulence, and aircraft performance for your specific flight.  
　
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：General Aviation Pilot’s Guide to Preflight Weather Planning, Weather Self-Briefings, and Weather Decision Making(6)