Dynamic tropopause potential temperature (shaded in K), wind (standard barbs in knots), and 925-850 hPa layer-mean relative vorticity (solid contours every 5x10-5 s-1 starting at 5x10-5 s-1).
These plots are derived from the NCEP GFS analyses and forecasts on a 0.25x0.25o latitude-longitude grid. The dynamic tropopause is defined as the 2.0 PVU surface.