.
-
‘evel cyclone situation oppeors to hove little, if any, dependence on ‘season. , Because of
its persistence “(up to 10 days), if must always be taken into account in planning any
operation ‘in the .northern Marshalls. -Thus, although Operation ‘Ivy was planned for the
fall when low level cyclones .were expected, the last part of October was dominated by”
high level cyclones and one time it appeared as if this weather sitoation would .seriously
yy
hamper the plans of. Task Force 132. ,
3., Meteorological Incompatability in Relation to Weapon Testing
It -Is probably safe in planning future weapon fests in the Marshall -Islonds to assume
that each of the three situations described in the previous section will occur at least
once during a period longer than one month _ As already stated, there will be a tendency
for low level cyclones to be more frequent In summer and fall, while the trade situation
‘should be expected at highest frequency in winter and spring., In the post there has been
o
@ fendency in planning the more complicated operations to assume that the wind systems
‘
aloft are associated only at random with cloud and-weather , For example, there have been
requirements in past operations that the winds over the Marshall Islands up to 40,000 feet
be, in the period following a detonation, from the southeast or south., Aft the same time,
concomitant air operations have been predicated on the assumption that trade cumulus without middle or upper cloud would prevail over an “area including Kwajalein and Eniwetok. ,
Obviously, this is asking for an incompatible distribution of the weather elements. It is
true that such conditions may occur at long intervals of time and for short periods; how-
ever, they will represent a transition from one fypical situation to another and cannot be
counted upon for a sufficient length of time to ensure the success of a complicated
weapon test. Other meteorological incompatibilities would be the association on strong
westerly winds (above 50 knots), above 20,000 feet in the Eniwetok - Bikini region, and
cloud conditions appropriate for photography on the ground and in the air. Undoubtedly
such cerditions Love existed on past operations, notably on | Sandstone, , but they can be
regarded as lucky accidents, of short duration... The occurrence ‘of such accidents, and
the ability of meteorologists to forecast them, cannot be counted ‘on in planning operations.
Finally, it should be emphesized that the most that can be done, .in the present state
of knowledge of tropical meteorology, is to forecast broad-scale situations, involving, in the |
most general terms, the association of wind systems with average cloud cover and precipitation., It is not possible to say that an individual cumulus cloud will be located
in :quéh- and such.@ spot et such and such atime, 24 hours. cheod |
The average life-
time of a tropical cumulus of any magnitude ‘is only 45 minutes; its rate of movement
depends only partly on the wind speed and direction. Its shape and the height to which
it will reach, the amount of overhang, the sate of dissipation of the tops, will all depend
on the micro-structure of the air - a problem in turbulence theory which is beyond the
power of any aerodynamist or meteorologist to forecost 24 hours before the event.. Precipitation in the form of showers, likewise, depends upon complicated physico! processes
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