WEATHER» WINDY WORDS Direction: The true compass direction from which the wind is originating. (An exception is that wind directions given by a control tower are the magnetic direction, because runway numbers are based on magnetic directions.) Gust: A sudden, brief increase in wind speed, reported in weather observations when the peak wind speed reaches at least 16 knots and variation in speed between the peaks and lulls is at least 9 knots. The duration of a gust is usually fewer than 20 seconds. Knot: One nautical mile per hour. (Multiply by 1.15 to convert to statute miles per hour.) Speed: In the United States, the one-minute average speed, known as the sustained wind speed. Squall: A strong wind 16 knots or faster than the sustained wind that happens suddenly and lasts for at least 2 minutes. Surface winds: Official measurements of wind speeds and directions are taken 10 meters (32.81 feet) above the surface in a location away from trees or buildings that could affect the wind. BE MINDFUL OF WINDS. When a pilot is in the air he or she has to remain aware of whether the airplane is following the planned route. Crosswinds that differ from the forecast could be pushing it off course. A stronger-than-forecast headwind could be slowing the flight. When this happens, the pilot must decide whether an unplanned fuel stop would be good insurance against an emergency landing with empty fuel tanks. Pilots have another reason to remain aware of winds that are different from the forecast used to plan a flight. Since the wind is only a part of an area's big weather picture, a wind forecast that isn't turning out to be correct should alert a pilot to watch for other failed forecasts. Jack Williams is an instrument-rated private pilot. Variable wind: A wind of 7 knots or faster that changes direction by 60 degrees or more. His latest book is The AMS Weather Book: The Ultimate Guide to America's Weather.http://www.rodmachado.com