An Appraisal of the Circulation and Temperature Pattern for Winter 1978–79 and a Comparison with the Previous Two Winters

Abstract

The mean Northern Hemispheric circulation and United States temperature pattern of the winter 1978?79 are discussed and compared with those of the previous two winters. It is found that, although the Arctic and North Atlantic mean circulation for the three winters had some similarities, the North Pacific mean circulation was quite dissimilar in the winter 1978?79 compared with the previous two winters. With regard to the United States temperature anomaly pattern, the winter 1978?79 had below-normal temperatures coast to coast, which implies a westward expansion of the below-normal temperature regime when considering the last three winters in chronological order. A westward displacement of the core of the below-normal regime was also seen. Possible large-scale air-sea interaction in the North Pacific is also reviewed for each of the three winters. It is proposed that major changes in the sea surface temperature pattern in the North Pacific, which occurred between the winters of 1977?78 and 1978?79, were largely responsible for the observed changes seen in the North Pacific circulation between these two winters. It is observed that the downstream circulation over eastern North America and the North Atlantic in 1978?79 did not behave as expected based on the use of teleconnection charts for the winter season. Possible reasons for this are discussed. Finally, within the context of the foregoing, various winter temperature forecasts are discussed and verified qualitatively. It was noted that most of these shared the error of forecasting above-normal temperatures for the southeastern portion of the United States.