Five-month running mean (solid line) and individual
monthly mean (dots) of the standardized 850-hPa
zonal wind anomaly index in the latitude belt 5N-5S for 135E-180
(top), 175W-140W (middle) and 135W-120W (bottom). Anomalies
are departures from the 1981-2010 base period means and are normalized
by the mean annual standard deviation.The x-axis labels are centered on
January. Positive (negative) values indicate easterly (westerly) anomalies.