) <0canretiothtGainesrheinenvalhinte-0 needyvinbalith:eAemnA mae the e . e. Acritical problem in predicting fall-out ise as forecasting the stability or lack of stability of tbe “- .attern after snot time. Since radioactive particle tree ~“ | determined primarily by the winds at each level, it is *- wd that winds must be from favorable directions o> vasy=*- (shin the outer limits on fevorable directions during the * .¢ fallout. The criticel fallout period was considered to "she order of trelve to eighteen hours fo> significant .2 tO occur. The variation in tine arises froz considera- of wind shear, with more diffuse and less sigziticast ine ie8 at a given time associated with lerge anguler aad _, skear. For this reason, it was required that actuel wind ‘ eatLons and forecasts immsdiately before shot tine and “" 20ut shot day be continuously considered in their relation <9 forecast conditions for. the first twenty-four hours :3e shot. PRE-SHOT BRIEFINGS: The following were presented at . se~Shot command briefings: a. Weather on Gs Weather conditions during the five days prior to ' adicated a favorable trend for BRAVO day witheasterly - - elow 15,000 feet and winds of a southerly co=poneaot . The situation presented at E-6 hours for the subdsequest <- period (18 hours after shot tine) was satisfactory. The + - > period to begin 18 hours after shot time was predicted * an unfavorable trend as northwest winds were forecast # 10,000 to 20,000 foot levels. be (1) Resultant wind diagrams including latess e £ “4 winds and forecast winds for H Hour and the 72 hour _ cajectories, which save a fellout pattern in a narrow "* the east northeast and a wide (140°) sector to the “ch very slow resultant winds. (See Figure 1). 1| o . (2) Surface radex, H to H plus 6 hours. men athens (3) Outlooks for: (a) Bixini: (See _ Unfavorable; Eniwetok: Favorable; Favorable, end the native populated atolls in southeast from ground zero favorable, since resultant winds in tion of these areas were considered too slow to nove at fallout to the atolls involved. nde. mu RadSafe (>) Tesk Force fleet: Favorable, provided 14 out at least SO ciles. S } a . * soa eee