Pilot Balloon Data (PIBAL) (WBAN-20)

Pilot Balloon Data are historical Winds Aloft Computation Sheets available at the National Climatic Data Center (NCDC). These are in the WBAN 20 form types for pilot balloons (PIBAL). The sheets were prepared by the U.S. Air Force, the U.S. Navy, the National Weather Service and its predecessor the Weather Bureau, and other U.S. organizations, for selected stations around the world. A WBAN 20 sheet recorded azimuth and elevation angles at one minute intervals during the balloon ascent. The height of the balloon above the surface and the distance the balloon had drifted from the observation point were determined and entered in the appropriate columns. The position of the balloon at each minute (determined by the azimuth angle and the distance from observation point) were plotted, and the wind direction and speed was then evaluated for each minute and for every even minute above 7 km., and entered on the sheet. Wind data were entered in the appropriate blocks. Maximum wind speed data were entered when speeds reached 45 meters per second (100 mph). Wind directions were coded to the nearest 5 deg., and wind speeds were coded in knots.