Statistical studies of the irregular week to week fluctuations of the general circulation pattern of the Northern Hemisphere indicate the reality of large‐scale changes and inter‐relationships between the branches of the general circulation of the sort which conform to the ideal high and low index patterns as defined by the strength of the zonal westerlies. On the other hand, lag correlations of these indices fail to establish any significant lag relationships between the branches of the general circulation of the sort that might be expected if these large‐scale changes are controlled by some internal mechanism of operation. This result is particularly discouraging for the possibility of statistical long‐range forecasting.The question is raised as to what extent this failure to detect cause and effect relationships in the major changes of the general circulation pattern may be due to inadequacies in the observational data or in the technique of statistical analysis, or to what extent it may be due to the operation of independent external factors of control, such as irregular solar variability.This possibility of direct solar influence on the short‐period irregular changes of the general circulation pattern is further suggested by the marked similarity in pattern of the long‐period changes of the general circulation, and the strong evidence which exists for the direct role of irregular solar variability of the sunspot type in these latter changes. Suggestions are offered as to further investigations which might throw additional light on the question as to what extent external (solar) influences may be the primary cause of large‐scale changes of the general circulation.