This manual provides Army aviation personnel with the general principles of modern meteorology required to assist them in planning and conducting day-to-day flight operations. It will also be useful as a supplemental text and a ready reference. It covers theoretical aspects of meteorological phenomena, the weather facilities available at airfields, severe weather warnings, types of forecasts, and information which will enable Army aviation personnel to interpret and evaluate weather conditions. Although the general information contained in this manual is required background information for weather forecasters, the manual does not include operational forecasting techniques.