Caption: +700 hPa geopotential height (thin contours every 3 dam). +700 hPa warm advection computed using the nondivergent wind (thick contours every 5.0 K day-1 starting at 5.0 K day-1). +700 hPa 2-D Petterssen frontogenesis computed using the nondivergent wind [shaded according to the colorbar in K (1000 km)-1 (3 h)-1]. Warm (cold) colors denote regions of 700 hPa frontogenesis (frontolysis). +Warm advection and frontogenesis were computed from 0.5x0.5o NCEP-GFS data smoothed by 5 passes of a 9-point local smoother. The geopotential height data was not smoothed.
