\fie en en49 ANNEX E pO OPER..TICNS ORDER No. 1-53 CLIUATOLOGY OF BININI-MITBIO: ahBa FOR MOVIES OF JANUARY THROUGH APRIL 1, INTRODUCTIGN: a, The following information for planning purposes is based on weather records collected during tiorld war II and during post-war activities at the ENIVETOK Proving Ground, “eather statistics are useful but prove nothing unless the results are subject to a complete physical explanation, Most meteorological phenomena are not subject to such explanations, but brief reference is made to the latest hypotheses which are the results of intensive research on tropical weather, During short periods of a month or a season the atmosphere may behave in a marmer strikingly different than past records may lead a planner to expect, The variatims from emditions anticipzted on the basis of past records are the responsibility of the Task Force weather units to detect, evaluate, ani predict, 2, GENERAL: a, During this period, the "dry" or "trade” season in the Marshall Islands, northeasterly winds blow with great persistence in the lower levels, Overlying the northeasterly or trede winds, the winds tend to become westerly. Both the trade winds and the higher predominantly westerly winds are subject to frequent cyclonic circulations or disturbances in the form of eddies, vortices, or minor pertubations, Many of the variations of the weather over the Marshalls are attributed to these disturbances, In the lower levels the eddies are most intense along the equatorvard edge of the trade circulatim (0 to 10QN in the Northern Hemisphere), These low level eddies are rapidly damped to the north am-rarely pass directly over the northern Mershalis, However, their formation, movement and decay contribute to significant day to day changes in the ENIVET OXK~BIKINI weather, 3. FRONTS: a, The terms "Intertropical Front" ani "Equatorial Front” are in actuality misnomers, A density discontinuity ami proper wind shear must exist to define a front, Rather conclusive evidence exists that significant horizontal density discontinuities do not exist in the Marshalls. The areas formerly designated "Intertropical or Equatorial Fronts" are in reality the paths of the low level eddies and vortices, The pattern of circulation about these disturbances produces areas ard lines conducive to vertical motion, It is along these lires md in the areas where vertical motions are predaminantly upward that middle ami high cloudiness becomes extensive, precipitation .general, amd thunderstorms develop, The weather associated with these lines appears similar to the weather accampanying the true fronts of higher latitudes, How- ever, these lines do no& form, do not move, nor are they subject to the same forecasting techniques as true fronts, 4. WEATHER: a, The term "dry" for this season is relative only, Small, widely scattered showers falling from the prevalent "trade" cumulus clouds are nearly always within sight of ENICETG ad BIKINI, The science of meteorology has not developed to the point where the precise location of individual showers can be reliably predicted, b. During these four months in the years 1950 through 1953, inclusive, ceilings have never been observed at 500 feet or less, observed below 3 miles on m average of one day in 20, TASK GROUP 7.4 CPRS ORDER NO, 1-53 Awd : ANNEX E,APIDK3 Attachment #1 Visibilities have been Precipitation, including get 9 EL aepein