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UNCLASSIFIED

 DEFINITIONS

JUST FLY. 	The amount of time (in percent) the primary operational threshold of ceilings above 10,000 feet (or no ceilings) were actually observed. JUST FLY measures the expected percent-of time an aircrew would have favorable target weather if no weather information were available and they "Just flew." 

PERSISTENCE. The conditions observed currently will remain through the entire period. A persistence forecast is a "no-change" forecast. PERSISTENCE i5 one way to measure a forecast technical skill capability for changing conditions. 

NO SKILL FORECAST. The control against what a forecast is measured. In this study, two "no skill" forecast measures were used: "JUST FLY" and PERsistence. F JUST.FLY gives an indications of the forecast skill measured against climatology, persistence against change.



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