East Atlantic (Wallace–Gutzler)

½Z*(55°N,20°W) − ¼Z*(25°N,25°W) − ¼Z*(50°N,40°E), Z* = seasonally standardized daily Z500 anomaly; result re-standardized. Positive = high heights west of the British Isles. Coefficients are the commonly cited WG81 values (not re-checked against the paper). Not the same as CPC's rotated-PCA EA (whose sign convention is roughly opposite). — Wallace & Gutzler 1981, Mon. Wea. Rev. 109, 784–812, doi:10.1175/1520-0493(1981)109<0784:TITGHF>2.0.CO;2