jyome RESTRAEROSUITS — sneeNesogpicts 6 —Spetieieniianlaiaiadsdiatn-G) | . . . Explanation of Trajectories — - é (Continued from previous page.) XRAY DAY tie upper winds over the Eniwetok area near bomb time on XRAY Day indicate that air parcels renresenting the cloud at the 5,000 and 19,000 foot elevations moved off at an approximate apeed of 12 Imots toward the west-northwest and northwest, ZEBRA DAY-~2 study of the upper winds over Eniwetok Atoll on ZEBRA Day shows the winds beclinc from southeusterly at 5,000 feat to southwesterly at 10,000 feet and then to west-scutimesterly at 20,000 feet and above, The 5,000 foot trmjectory went to the respectively, The constant pressure charta for 850 and 700 millibars subsequent to bomb time show the material continued to move to the west at varying velocities with the 5,000 foot trajectory passing 300 miles north of Guam in about § days, This time nortimest after leaving Eninetok and changed slowly to the west and west-southwest an the second ond third day. Similerly, the 10,000 foot trajectory which started moving to the northeast chanred rupidly to the sest after 24 hours and continued on a westerly Cniwetok and Guam, The 20,000 foot trajectory proved to be quite complex due to light and variable winds over the Marshal] Islenda on ERAT Day. By using the 500 millitmr constunt vressure chart, an average movement was commuted rhich showed the materinl at that vicinity of Gunm cuused the 5,000 and 19,000 foot narcels to increase rapidly in velocity and nove to the northwest. The 2C,000 foot trajectory wis leas doubtful on ZEBRA Day thin on the vrevions test days, Fairly strong and consistent winds at Eniwetok, plus a nt that altitude persisted; so that the resulting trajectory indicated vary little move- moved directly towards Midnay Island and reached Midway in 72 houry. difference was due to the lighter winds found at 10,000 feet in the area between level started off to the east, Howaver, on the following days, light and variable winds ment fron the Eniwetok area for a period of approximtely eight days. Due to the light and varjable winds over such a long period of time, it was very doubtful as to when the milerial actually left the area, The 20,000 foot trajectory is, for this reason, of doubtful walue. The 30,060 and 40,000 foot trajectories are much more renresentative. A study of the vind over Eniwetck on IRAY Day showed versistent west-scuthwest and south- west winds at these lewels which caused the cloud materials to move off to the eastnortheast and northonst at the velocities of 12 and 25 knots, resnectively. Subsequent heading, However, on the third and fourth day following ZEBRA Day, a typhoon in the steudy wind flow on the 500 miliibar constant pressure chart, indicate that the trajectory The 30,000 ond 40,000 foot trajectories left the Snivetok area with moderately strong westerly winds and continued moving to the east. The 3C,000 cnd 40,000 foot trajectories passed south of Havadi in sppro:cimatcly 3 and 2 days, resvectively, j upper air charts show the material at 30,000 and 40,000 feet gradually shifting 30 that it headed in a more easterly direction with the 40,000 foot trajectory passing south of awaid in two and one-half or three days, The 30,000 foot trajectory passed south of ‘Inwaii in epproximately three and one-half to four days, YOKE DAY>-the trajectories for 5,000; 10,000; 30,000; and 40,000 feet followed a pattern sinilar to thoee for IRAY Day, 4 atudy of the winds aloft over Eniwetok for YORE Day shows easterly (& to ESE) winds to near 16,000 feet shifting slowly through south to southwest at 30,000 feet and above, As might be expected, the 5,000 and 10,000 fool trajectories moved off to the west and weat-nortiwest, Using the constant pressure charts to extrapolate wind velocities and directions, it was found that the 5,000 and 16,000 foot trajectories continued moving westward, passing south of Guam in approx - mately four dayr, and reached the Philippine Inlands in approximately seven to eight days. The 20,000 foot trajectory started to the north from Eniwetok and ms then caught in a belt of easterly winds, These easterlies caused the mterial at the level to veer to the west and reach the Guam area in approximately four days also, However, due to the variable wind conditions over Eniwetok on the test day, thie trajaectcry could be emuidermbly in error although there is less doubt about it than the trajectory for the same altitude on TRAY Day, The 30,000 and 40,000 foot trajectories moved off rapidly to the northeast from Eniwetok. The subsequent constant pressure charts for these levels showed the winds shifted slowly back te westorly and caused the trajectories to pass south of the Hawaiian Islands, The 40,000 foot trajectory passed the Hawaiian Islands aren in approrimately 48 hours while the 30,000 foot trajectory arrived 72 hours after bomb tines -BEGTRIOFED= Atomic. Enorgy-Actsnt-1940—