appeared to be the pressure gratient ~tween Wake Id-and and Eniwetok. When this gradient was of the order of two millibars, the winds becw light and variable. f. In the forecastingof shaer activity, the presence of the typic~ tr~e wind inversion seemed to be conductive to shower activity early in the morning when the nwd.mum amount of radiational cooling has occurraL A minimum azmunt of shower activity seemed to occur when there was not inversion. Typical examples of this phenomena occurred on X-day when marked shower activity developed after an almost clear ni~t, while on YOKE and ZEBRA mornings when there was no inversion noted, no measurable shower activity occurred. 11. RadiologicalSafety Comuutation8 . ● The radiologistwas responsible for declaring whether the wind conditio~ were such that the atomic bomb could be fired wltho~ fall-out radioactive contaminationhazatis. The method of computation of the co-called Safety Sector is based upon the speed and direction of the upper winds and upon assumed rates of fall for various sizes or radioactivedebris. Considerationshould be given to a mre precise method for calculating the fall-out hazard taking account of rates of diffusion awl dilution in the atmosphere aa well as tho p~sical fall-out of radioactive debris. ,$ 78 SECTION XXI