Successful free-ballooning depends on meteorology, and especially on the study of free-air conditions. The International Balloon Race from Birmingham, Ala., October 23, 1920, was the first occasion of its kind in this country where meteorological upper air and surface reports were made available to the pilots and where assistance was provided to guide them in the interpretation and use of the telegraphic reports which the Weather Bureau supplied from the eastern and central United States. It is clear that more extensive free-air observations are necessary. Advices and up-to-the-minute data were of unusual value in this race, owing to the complex atmospheric conditions, which demanded a cautious nicety of control by the aeronauts. Conditions were not unfavorable at the surface, and were nearly normal in the free air. An analysis of the cyclonic conditions has been made in terms of the Bjerknes hypothesis of stream lines, and the application of this method explains the peculiarities encountered by the balloonists.

Explicit forecasts were made for the race. These were right, and the winning teams were those who followed closely the course mapped out by the Weather Bureau. Not merely the horizontal currents of the atmosphere but also the thermal activity and the radiation, condensation and equilibrium values must be given due consideration in the modern aerial weather forecasts for free ballooning. Likewise, efficiency on the part of the aeronauts demands that they make the greatest use and allowance for the weather factor. Aerial transport of every character will do well to study this weather factor in order to promote greater efficiency.