"ce, . wwe From a comparison of unweighted hodographs, it appears that a significantly greater number of acceptable (high-yield) shooting days occur at Taongi than at Eniwetok/Bikini, As can be seen from Figure 9, this results primrily from the geography of the area rather than from any marked climatological differences. At Taongi, and assuming fallout on the test site can be accepted, the normal wind structure produces east-west fallout patterns which do not interfere with populated areas; at Eniwetok/Bkini similar patterns cannot be accepted. Comparative danger areas are shown in Figure 9 for the two locations." Dr. Vay Shelton has stated: “The number of good weather days at Taongi for shots of the Hardtack class will, as indicated in Commnder Rex’s report, be substantially greater than at Bikini. A study of the 45 cases submitted in lis report indicates that his estimated number of good days of 32 may be high by 9 or 10 because this many of the 32 "good" days are quite marginal and would probably not be acceptable to those responsible for firing. He considered a day as good if the fallout axis missed all of the inhabited Mershells and Wake. There are still about three times as mony good days at Taongt as at Bikini, however." Taking the least optimistic viewpoint, as just expressed, and based on 22 good shooting days versus 7 for Bikini out of the total of 45, the probability of being able to fire the first shot at Taongi or Bikini on any day during the period analysed is respectively 50% and 15%. This merely states that whatever the average weather delay at Bikini is, the same average is 1/3 as large at Taongi. In the above typical schedules, we have based the shot intervals between large shots at Bikini on a minimm of four days technical preparedness and six days average weather delay. At Taongi, we have based the shot intervals on five days technical preparedness and two days average weather deley. The 3:1 ratio is a conservative figure based on Dr. Shelton’s interpretation of the accuracy of the determinations in the JIF 7 report and it 1s pertinent to mention that Commander Rex believes the interpolated hedograph data to be accurate to only 20% in vind velocities and 20° in direction. There is general agreement between the JTF 7 Meteorological Center and UCRL in considering Taongi as a test site. The problem of checking the validity of the above data should also be considered. Establishment of weather observation capability early in the Taongi area to record data as long as possible prior to Operation Hardtack is deemed advisable. Such data would be valuable not only as a checls on the interpolated data accuracy but would lend con- siderable help toward more accurate Taongi forecasts. Weather informtion locally in the Taongi area can be well covered from the diagnostics ship. It is also deemed necessary to observe the weather further out from Taongi, probably from ships to the northwest and east. Late checks on the weather in such locations can likely be obtained from destroyers. It ds not obvious that weather ships whose sole mission is weather observation are necessary for this purposes. | ene 5 ay