relative amount of effort which should be expended in ths future to get such_enswere. = (>) The method of elliptisal approximations of the infinity isodese lines as nentgoned in le (5) above was used @m all forecests fran abcut H minus 18 hours up through the final pre-shct forecast. In goneral, the method consisted of eireumseribing ellipace over the hodograph between major shear levels, The minor axes of the ellipses were determined by the amount of angular shear in the intorval, and the roentgen velues of the elliptical tsodose Lines and the over-all envelopes were determined by sealing. The entire asthod is based on eapirical data from the NPG, however its suseeseful use om the low yield shots at that proving ground, gave rise to an increasing amount of confidence in the ability of the system to prediet the fall-crt area after wome of the difference between high and low yield shots had been pro= gressively resolved during C.STLE. 2. RESPlots? a. In general, RADEXES ant Pall-out Plots suffer from the same “disease”, namely, thoir complete dependence om the forecasts of the wind Meld. It is this ome factor alone which primarily precludes the attaimment of high precision in fall-out forecasting, Much has been " done on Operation C:STLE to define the significant cloud heights for fallq out fram high yield shots and to put mumbers on predicted isodose lines. There is now a better appreciation of the time involved for significant fall-out to coeur. The effect of the conditions of the shot site are better understood. Purther, a significant step has been taken to release 69