Mid-tropospheric frontogenesis is investigated for a case study in which special three-hourly rawinsonde data are available. Isentropic analyses are generated by objective means. Detailed machine isentropic trajectories lead to the three-dimensional description of the velocity field in space and time accompanying the frontogenesis. Ertel potential vorticity calculations serve as a check on traj...

An idealized supercell simulation using the Regional Atmospheric Modeling System (RAMS) produced an elongated low-level mesocyclone that subsequently collapsed into a concentrated vortex. Though vorticity continually increased in the mesocyclone due to horizontal convergence, the collapse phase was additionally characterized by rapidly decreasing pressure, closed streamlines, and the creation o...

Hurricane Opal (1995) crossed the Gulf of Mexico rapidly intensifying to a 130-kt storm, then fortunately weakening before landfall on the Florida panhandle. This intensification was underforecast by the National Hurricane Center. Forecast fields from the 1997 version of the Geophysical Fluid Dynamics Laboratory Hurricane Prediction System (GFDL model) for Hurricane Opal are used to diagnose th...

A second order numerical method for the primitive equations (PEs) of large-scale oceanic flow formulated in mean vorticity is proposed and analyzed, and the full convergence in L2 is established. In the reformulation of the PEs, the prognostic equation for the horizontal velocity is replaced by evolutionary equations for the mean vorticity field and the vertical derivative of the horizontal vel...

A midlatitude mesoscale convective complex (MCC), which occurred over the central United States on 23– 24 June 1985, was simulated using the Regional Atmospheric Modeling System (RAMS). The multiply nestedgrid simulation agreed reasonably well with surface, upper-air, and satellite observations and ground-based radar plots. The simulated MCC had a typical structure consisting of a leading line ...

The authors employ data from the NOAA Wind Profiler Network to present a scale-discriminating vorticity budget for a mesoscale convective vortex (MCV) that was generated by a mesoscale convective system (MCS) in Oklahoma and Kansas on 1 August 1996. A spatial bandpass filter was used to divide observed wind into mesoscale and synoptic components. Then the authors sought sources and sinks of vor...

Two aspects of vorticity associated with cold pools are addressed. First, tilting of horizontal vortex tubes by the updraft at a gust front has been proposed as a means of getting near-ground rotation and hence a tornado. Theory and a numerical simulation are used to show that this mechanism will not work because warm air parcels approaching the gust front decelerate in strong adverse pressure ...