X-Ray Day WaS quite succe=f ul, the run reaching 80,000 feet. The coding of the winds for transmission at 5,000 foot intervals above 20,000 feet was de-d inadequate;first, because the exact location of the sheer level was important and second, the rate of iateral diffusion ani the subsequent visual character of the atomic cloud could only be predicted by detailed upper wind observations. Instmctions we~ therefore issued to code all levels of the balloon rune in 1,000 foot intervals during the period from noon of the previous day to ~on of the day of the scheduled shot. In addition, high level balloon runs were schedulad for subsequent firings at H Hour minus three ad H Hour plus two. c. A tendencywas noted to believe the weather observations taken one to three hours before explosion time would be representative of the weather at zero tinm. Cloui masses in the lower westerly winds can, as a rule, be expected to migrate uith these wlmls ami the future positions of any si.gnlficantcloti areas can be fairly accurately extrapolated. However, in the X-Ray situationwhere nearly clear skies prevailed at ni@t, it had been previously noted that this condition appeared to correlatewith the rapid developannt of showers at dawn, and this development could obviously not be reported by the aircraft. The need exists for analertnesa on the part of the meteorologistfor new weather developmentswhich will not be reported by aircraft reconnaissanceno matter how comprehensiveami current the local weather observationsmay be. @ SECTION XXI