Basis for prediction of the sharp reversal of climate from autumn to winter 1988–1989

Abstract

AbstractA major reversal in the pattern of temperature anomalies occurred over the contiguous United States of America between autumn of 1988 and winter 1988–1989, a climatic break which reflected a change in phase of the prevailing midtropospheric wind pattern over much of the Western Hemisphere. This transformation is described and attributed to forcing by remote and persistent circulations acting in concert with seasonal forcing. Practically all conventional forecast tools, especially those involving local persistence and climatic contingencies, failed to predict the break. However, the instability of autumn's and November's flow pattern was indicated by: (i) conserving the standardized November height anomalies into winter; (ii) testing the stability of this new hypothetical pattern with the help of statistically derived teleconnections; (iii) applying a modified mean barotropic model to the hypothetical chart; and (iv) extrapolating the winter pattern from trends of circulation within the autumn months. Making use of all this material, a forecast was made for winter at the end of November that turned out highly successful despite the failure of persistence between seasons.