This is a colour-filled contour map of the wind speed where the atmospheric pressure is 300 hPa. Arrows showing the direction the wind is blowing at that level are overlaid. A pressure of 300 hPa corresponds to an altitude of approximately 8000 - 10000 meters above ground--the altitude where the jet stream is typically found. The data shown is the 6-hour forecast from the AVN computer model, which is run twice daily at 00 and 12 GMT by the National Center for Environmental Prediction (NCEP).