It is easy to see that an evaluation of the effect of a given monthly 

 pressure distribution must take the factors discussed into account. 

 For example, strong offshore winds may be classified as very favorable 

 if grounded bergs are returned to the transporting agency, A month 

 of strong onshore winds might be classified favorable if it follows 

 a history of offshore winds. A month of light winds might be classi- 

 fied as unfavorable if grounded bergs remained so. A month of winds 

 effecting an alongshore drift paralleling the current may not be neces- 

 sarily favorable if grounded bergs were unable to drift free. 



In addition to the assumptions that must be made when evaluating 

 the effect of mean surface wind on the drift of a berg group, many 

 uncertainties exist. The monthly mean pressure distribution might 

 mask significant shorter period patterns. For example, the first 2 

 weeks of a given month might have strong onshore flow sufficient to 

 permanently trap a large portion of the crop in such areas as Hudson 

 Strait, Belle Island, and where shoals protrude well offshore. The 

 last 2 weeks might be featured by strong offshore winds unable to 

 free the bergs. The monthly mean winds would appear neutral while 

 their true affect was very unfavorable. The Baffin Island and Lab- 

 rador coastline is featured by precipitous moimtains. This geological 

 factor probably causes a local deviation in gradient winds to more 

 closely parallel the coastline than the monthly pressure distribution 

 might indicate. Other uncertainties, including oceanographic factors, 

 exist. Oceanographic data is sparse and impracticable to obtain in 

 upstream northern areas before or during the ice season. Unknown 

 factors affecting iceberg drift probably exist. In spite of the assump- 

 tions that must be made and the resulting uncertainties, it is believed 

 that an analysis of monthly mean pressure distribution and all factors 

 involved will permit an educated estimate of its effect on the Grand 

 Banks potential iceberg supply and will yield a good indication of 

 the severity of the coming iceberg season. 



In order to test the validity and usability of the method described 

 for forecasting, U.S. Weather Bureau monthly mean sea level atmos- 

 pheric pressure charts were evaluated in the manner described for 

 the years 1957-64. See table III. Positions of berg concentrations 

 were based almost entirely on assumption during the preseason months 

 for the years 1957-62. Preseason northern survey observations were 

 available only for the 1963 and 1964 ice seasons. The classification 

 of each monthly mean pressure distribution for each half of the berg 

 crop for each year is shown in table III. The monthly means for 

 November-April were evaluated for their effect on drift of the first 

 half of the crop toward the Grand Banks, and the monthly means for 

 November-June were evaluated for their effect on drift of the second 

 half of the crop. It was assumed that the first half of the berg 

 crop arrived near the Grand Banks by early May, thus the months 



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