Comment on “Anomalous Gradient Winds: Existence and Implications”

Abstract

The solutions to the quadratic gradient wind equation are examined using 200-mb data for two selected cases. Under conditions of anticyclonic flow, both solutions are shown to have relevance. The normal solution is valid for wind speeds less than twice geostrophic, whereas the “anomalous” solution applies for wind speeds greater than twice the geostrophic value.For both cases, wind speeds of more than three times the geostrophic value were detected synoptically over large areas of the United States. Areas of negative absolute vorticity were generally found within the anomalous flow regions. The absolute value of the absolute vorticity approached the local value of the Coriolis parameter.Although cause–effect relationships are difficult to ascertain, the coexistence of negative absolute vorticity and anomalous flow implies stability. Instability would be expected in regions where the anomalous flow alone was observed. Manifestation of this instability in the form of clear-air turbulence (CAT) is suggested.Many numerical models exclude anomalous flow and/or negative absolute vorticity by use of physical constraints. Some aspects of this exclusion are examined.Now at National Severe Storms Forecast Center, NOAA, Kansas City, Mo.Now at Experimental Meteorology Laboratory, NOAA, Coral Gables, Fla.