Marshall Islands during Operation GREENHOUSE, Though typhoons are small in area in these longitudes, they can be extremely violent and can cause as much damage as the great Western Pacific typhoons, The damage, of courses, is more restricted in area; usually being confined to one or more atolls unfortunate enough to lie directly in the track of the storm, A vortex which is intensifying affects the winds up to 40,000 feet and above; and if a vortex should happen to form south of Ma-~ jure and move in a northwest direction to a position south of Eniwetok while intensifying, very bad weather accompanied by cumulonimbus and extensive decks of alto-stratus and cirro-stratus clouds may be expected in the test area, A good rule of thumb states that the right semi-circle of the storm is the most dangerous both for ‘air and sea transportation as well as for fixed installations, Since Bikin2 and Eniwetok are situated just north of the usual sum mer tracks for the vortices, test operations in the period of August to October are subject to hazard, As earlier mentioned, there is a slight seasonal tendency in the weather of the Marshall Islands and this now can be evaluated. The three classes of weather situation can occur in any one month of the year and any one may succeed the other. However, the low- level cyclone situation tends to be more frequent between the months of July to November than during the remainder of the year; though Typhoon GHORGIA was an exception which shows how unreliable this rule is. Similarly, the trade situation, while it can occur at any 170