1 MWareb 1954 r a MELOZANDUM FOR RECORD: SUBJECT: Command Briefing, 0000, 1 March 1954 Manbers present: Gen. P.W. Clarkson, Gen. B. UeGinley, seo. He Estes, Dr. AC. Graves, Dr. W. Ogle, ar. J. Reeves, Cr. De Sewell , Capt. W.L. Knickeroocker, Col. W.S. Cowart, Capt. R. na. Maynurd, Lt Col ¢.D. Bonnot, Lt Col R.&. House. 1. Ino generel, the forecast presented at the aldnight briefing was canfirmed, except that in the levels between 5 end 15 thousend feet the forecast was light and varieble. In an attercpt to celineate direction to these winds, it was determined that the best forecest that could be given was for vue 10 thousand foot level. This was forecest to be westerly et 10 knots as the most pessiszistic situation. Consequently, toe hogosraph plot vas made using the 10 thousend foot westerly wind in arder to present the most pessimistic situation which would occur. This picture save resultant winds in the direction of Rongelap end Rongerik, nowever, it was cansidered that the - G@istence to Ronselap and Rengerik cocpared to the resultant Wiad speeds were such that no fell~out should reach those atolls. From the forecast hodiogreph the time of travel to Rongelap weuld Reve peen about 12 to 15 hours. The hodograph plot did however stow that certeinly TARE site would be heavily contacinated, end most likely NsN. The hodogreph gave two general fall-out areas. The lower level running from 260 degrees around through south to 90 degrees with a six hour fall-out line in the directica cf the populeted atolls in the southeast quadrent about 15 to 20 miles out fram ground zero. The high level redex ran froa edout 45 degrees to SO degrees with a six hour fall-out line to 7C miles. (Since-the 6 hour fall-out lines were computed on abcut 105 gicron particle size, it vas recomasnoded that the distance pe doubled for sefety. This atounted to considering particle sizes down to about 70 microns). 2. 6ehange in the 72 hour cloud trajectories. 3e ndtsere Outlooks were xodified es follows; . a. 2ikini atoll wes changed from feverable to unfavcrable. be. Eniwetok etoll recained very favcreble. c. Ujelang etoll remeinec very favorebdle.