These four images are a sequence of wind speed and wind direction measurements collected by NSCAT every 12 hours during September 20 and 21, 1996. Typhoons Violet and Tom appear as yellow-orange spiral features; Violet is the one immediately south of Japan. During the two days of observations, typhoon Violet moved landward, causing death and severe property damage. The background color indicates wind speed: blue for low winds, red for moderate winds and yellow for high winds. The white arrows show the direction of the wind. Data like these are being used by the National Weather Service in its global forecast models.