Mean (top) and anomalous (bottom) 200-850 hPa vertical wind shear magnitude (m s^-1) and vector for the last 10 days. In top panel only total vertical shear values less than 8 ms^-1 are shaded. In bottom panel the anomalous vertical shear magnitude (shaded) is calculated as the magnitude of the observed total shear vector minus the climatological mean (observed shear - climatological shear). A reference vector with amplitude of 10 ms^-1 is shown below each panel. Anomalies are departures from the 1979-95 base period daily means.