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Chart showing point correlations between Northern Hemisphere 500 hPa height and PNA index, based on spring–summer (March–August) anomalies. Contour interval is 0.2. Note the most prominent patterns of positive PNA—highs over western North America and lows in the Gulf of Alaska and southeastern USA. Data and software for the figure obtained from the NCEP/NCAR Reanalysis Project (Kalnay et al. 1996).
