Caption: +250 hPa wind (standard barbs in knots). +250 hPa potential vorticity (solid black contours every 1.0 PVU). +250 hPa streamfunction (solid green contours every 8.0x106 m2 s-1). +250 hPa PV advection by the nondivergent wind (shaded according to the color bar in PVU/day). +Image was generated from 1.0x1.0o NCEP-GFS data. The PV and PV advection was smoothed by 20 passes of a 9-point local smoother. +The latitude-longitude lines are every 15o centered on the central point of 30oN/15oE.
