The paper by Wallace and Gutzler examines teleconnections in the geopotential height field during Northern Hemisphere winter, aiming to identify and document recurrent spatial patterns indicative of standing oscillations in planetary waves with time scales of a month or longer. The authors review existing literature and identify four primary teleconnection patterns: the North Atlantic Oscillation (NAO), the North Pacific Oscillation (NPO), a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes, and the Pacific/North American pattern. Using a 15-year dataset of NMC monthly mean sea level pressure and 500 mb height analyses, they calculate temporal correlation coefficients between all possible pairs of grid points to identify and describe the strongest teleconnection patterns. The five leading patterns are compared with the leading eigenvectors of the correlation matrix, and the reproducibility of these patterns is tested using an independent dataset. The NAO and Pacific/North American patterns are strongly evident in both datasets, with the NAO associated with fluctuations in the strength of the climatological mean jet stream over the North Atlantic and the Pacific/North American pattern known to operational long-range forecasters since the 1950s. The analysis reveals that sea level pressure statistics are dominated by negative correlations between polar and temperature latitudes, while 500 mb statistics show more regional-scale patterns with a nearly equivalent barotropic structure. Most regional patterns have one or two well-defined centers of action at the Earth's surface, but at mid-tropospheric levels, they exhibit a wavelike appearance with multiple centers of action, resembling forced stationary waves on a sphere.The paper by Wallace and Gutzler examines teleconnections in the geopotential height field during Northern Hemisphere winter, aiming to identify and document recurrent spatial patterns indicative of standing oscillations in planetary waves with time scales of a month or longer. The authors review existing literature and identify four primary teleconnection patterns: the North Atlantic Oscillation (NAO), the North Pacific Oscillation (NPO), a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes, and the Pacific/North American pattern. Using a 15-year dataset of NMC monthly mean sea level pressure and 500 mb height analyses, they calculate temporal correlation coefficients between all possible pairs of grid points to identify and describe the strongest teleconnection patterns. The five leading patterns are compared with the leading eigenvectors of the correlation matrix, and the reproducibility of these patterns is tested using an independent dataset. The NAO and Pacific/North American patterns are strongly evident in both datasets, with the NAO associated with fluctuations in the strength of the climatological mean jet stream over the North Atlantic and the Pacific/North American pattern known to operational long-range forecasters since the 1950s. The analysis reveals that sea level pressure statistics are dominated by negative correlations between polar and temperature latitudes, while 500 mb statistics show more regional-scale patterns with a nearly equivalent barotropic structure. Most regional patterns have one or two well-defined centers of action at the Earth's surface, but at mid-tropospheric levels, they exhibit a wavelike appearance with multiple centers of action, resembling forced stationary waves on a sphere.