Caption: +500 hPa geopotential height (solid contours every 6 dam). +500 hPa quasi-geostrophic potential vorticity (thick contours every 0.25 PVU; dashed>0). +Total RHS of QGPV form of QG height tendency equation [shaded according to the colorbar (10-13 s-3)]. Cold (warm) colors denote regions of forcing for 500 hPa geopotential height falls (rises). +Image was generated from 1.0x1.0o NCEP-GFS data smoothed by 20 passes of a 9-point local smoother.