Ce Steps were taken both during and after the CASTLE Operation in line with the abowe. Many of the concepts of the role of weather and ite effects on the cperation were changed. For example, the increasing importance of the problem of deposition of radioactive debris in the test area led to the beginning of a complete re-evaluation of the techniques of forecasting areas of fall-out and greater consideration of the longrange effects of the wind flow. It was found advisable to have a duty forecaster work directly with radsafe personel during periods just prior to the shot. It was necessary for this forecaster to be completely familiar with the current flow patterns at all levels, and the forecast changes through twenty-four hours after the valid time of the forecast in line with the procedure for constructing air particle trajectory forecasts, In order to take into account the effect of the wind, the forecaster was prepared to give wind forecasts for levels as high as ninety thousand feet for a : period of twenty-four hours over an area of approximately 500 miles in radius. The problem reached such a magnitude during CASTLE that continuing extensive work is to be done at the Loe Alams Scientific Laboratories utilising the services of a qualified forecaster experienced in PPG weather requirements and the talent and know-how of scientists presently on duty there. It is felt that this problem is one of the most important to be solved for future weapons test operations. Of equal importance is the further research into improvement of weather forecast techniques and procedures for the Marshall Islands area, currently being extensively investigated by Dr. C. £. Palmer of the Calm Research Center at Wheeler All of the above represents attempts to improve the systans 7 ee AFB. Hawaii.