AN EVALUAPYON OF WEATHER FOREQASTS FOR KOON = . ae - _le_Smmary of woather immodiately prior to X-Days: On 31 March a forecast wee issuod for 2 .pril- that indicated southerly winds for levels~06,000 through 50,000 feet. This admittodly ms a long range forecast with onl¥ fair confidence. Twenty-four hours lstcr, howevory** it was evident thet no forosceable development of the circulation aleft would give appreeiable southerly compononts to the winds aloft. .4% doop trough dominated uppir level flow between Johnston and the Marshayls giving persistcnt winds with northerly components. On the morning of 4 ipril, the trough showed a tendency to fill, and a woak outdraft began to form east of Majuro. Tho development wma Slow; only at 40,000 fcet was it consistent and progressively more pronounced. On the morning of & .pril a foreesst based on the develop= mont of the outdraeft was issued. Ry aftarmoon of the 4°8 a firm trend had not been astablished and a forecast giving winds of 1 northerly component was issued. .fter this wactilation over a three day poriod the trend for tha developmont of tho outdraft nusr Majuro became firmly established on the morning of 5 ..pril. The cutlook wag issued that chances were good for southerly winds on 6 .pril, and if not that day, certainly om the following caye . 2. The Weather Forecast: 3/8 cumilus, base 2000; 2/8 altostratus, base 20,000 feet; 6/8 cirrus, base 39,000 fact; scattered light and moderate showers; increased buildupe in cirrus to south of area; shower activity greater in Fniwetok area. a. Observed weather: 3/8 cumlus, 3/8 stratocumlus, 2/8 alto- curmlus at 15,000 feet; scattered rain showers reported at Eniwetok. b, Comments on weather: Wilson 1 (reconraissance aircraft near shot site) reported 2/8 cumlus and 8/8ths altostratus at 16,000 feet one hour prior to shot time. at Eniwetok the cumulus layer increased to become broken from 1400M to 1800M following the shot. 3. The Wind Forecast: HEIGHT (Thsds Ft) He=2h Hel5 90 090/40 090/45 80 70 65 090/30 090/20 60 070/10 50 250/25 55 270/10 H~8 Heol, 090/40 090/40 120/15 120/15 130/15 240/20 240/20 250/18 230/35 240/35 230/20 230/20 090/30 090/15 090/30 090/30 100/20. ...100/20.... __.... 150/35 180/12 230/15 120/10 230/15 270/30 250/20 40 35 230/25 230/25 230/20 ~- 240/30 230/30 230/28 25 240/15 260/14 45 30 INCLOSURE 1 240/25 240/15 OBSERVED BIKINI 0900M 240/30 260/20 250/15 ore. M=6 230/15 290/13 270/30 260/32 260/37 230/35 230/28 230/19 250/33 2L0/24 - 250/21 200/20