eee CLIMATOLOGY OF THE ENIWETOK ~ BIKINI AREA FOR THE MONTHS OF JANUARY, FEBRUARY, MARCH AND APRIL 1. This period of the year is generally known as the "dry" season in the Marshall Island area, particularly in the Eniwetok ~ Bikini area, It is better known as the "trade" season, Over this area east~northeast te northeast winds prevail in the lower levels, the wind speeds ranging between 10 to 20 knots. Small amounts of cumulus clouds, usually not exceeding },/8 coverage, are found in this current, and the cloud tops do not usually extend above 6,000 feet. Rain sometimes falls from these clouds, usually as showers. No extensive upper middle Cloud decks are found. Although the lower winds are northeast and quite fresh, as one goes aloft, one finds that the winds turn more westerly with elevation until at about 20,000 feet they lie between northwest and southwest. The westerlies then extend upwards to the tropopause increasing in speed to about 35 knots at 45,000 feet. If the upper winds are mainly southwesterly, rain from the trade cumulus is likely and the amount of cloud may increase to 6/8 er 7/8. If the upper winds are, however, chiefly northwesterly, the cumulus clouds will decrease to as little as 1/8 or 2/8 and showers are less likely. 2. Occasionally during this period, the winds throughout the entire Marshall Islands will show speeds of less than 10 knots from the northeast or east-north-east. Cloud cover will, however, be only 2/8 or 3/8 with tops below March and April. Again, as during the normal trade flow which is found during ,006 feet, interspersed with stationary lines ef cumulonimbus and heavy showers and an occasional thunderstorm, There will be an extensive sheet of altostratus and altocumulus which will make aircraft operations above 20,000 feet difficult and occasionally hazardous. This situation is more particularly true in late this time of the year, the easterly winds will vary in direction with height, becoming very strong westerlies above 30,000 feet and reaching as high as 108 knots at 45,0CO feet on occasion. These winds are associated with a weather system aloft which can become quite intense and which-can persist for periods in excess of a week, This situation is the one to be the most wary of during this period of operations, 3. In summary, normal trade flow weather is to be expected during the greater part of the period of CASTILE eperation, Day to day fluctuations from the normal will be those elements of digression which will have to be forecast. Appendix J eet COPIED/DOE LANL RC Wl, -29a” 3 5 Fe