Regardless of where you are forecasting, the factors and parameters favorable for thunderstorm, hail, and gust forecasting should be systematized into some sort of checklist to determine the likelihood and probability of thunderstorms and the attendant weather. Figure 5-12 is a suggested format and checklist to ensure that all parameters have been given due consideration.

LEARNING OBJECTIVES: Analyze areas conducive to tornadic activity. Identify the three general types of tornadoes. Recognize the difference between tornadoes and waterspouts. Tornadoes are violently rotating columns of air extending downward from a cumulonimbus cloud. They are nearly always observed as funnel clouds. Their relatively small size ranks them as second in the severity of the damage they cause, with tropical cyclones ranking first. They occur only in certain areas of the world, and are most frequent in the United States in the area bounded by the Rockies to the west and the Appalachians to the east. Tornadoes also occur during certain preferred seasons of the year in the United States,

with their most frequent occurrence during May. The season of occurrence varies with the locality. In the United States, 80 percent of the tornadoes have occurred between noon and 2100 local time.

Complete details on the forecasting of these phenomena are beyond the scope of this training manual. You should consult the U.S. Department of Commerce, Forecasting Guide No. 1, Forecasting Tornadoes and Severe Thunderstorms, and the many other excellent texts and publications for a complete understanding of this problem. The senior Aerographers Mate should have a basic understanding of the factors leading to the formation of such severe phenomena, to recognize potential situations, and to be able to forecast such phenomena.

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