Figure 7
(a) The 700 mbar geopotential height (m) pattern corresponding to the 16 months with highest lightning occurrence from June, July, August, and September months, 1985–2000. The geostrophic flow represented by this pattern illustrates the strong influence of west-to-east flow into California from the North Pacific, and also more subtle northward flow around subtropical high centered over Gulf Coast US. (b) The associated mean precipitable water (Kg m−2) pattern for these high lightning occurrence summer months. The stars indicate the location of the Sierra Nevada bioregion.