AN APPLICATION OF POTENTIAL VORTICITY INVERSION TO IMPROVING THE NUMERICAL PREDICTION OF THE MARCH 1993 SUPERSTORM

In this study, a methodology is proposed to improve the model initial conditions, based on available surface temperature observations from s hips, buoys. and drifters. It is tested with the numerical prediction of the 12-14 March 1993 superstorm that is initialized at its incipien t stage over the Gulf of Mexico. In this methodology, the authors make use of the piecewise potential vorticity (PV) inversion technique and treat the temperature errors at the lowest level as a surrogate PV an omaly. After inverting the wind and mass perturbations from the surfac e thermal anomaly and its pertinent interior PV anomaly, a three-dimen sional, dynamically consistent set of ''errors'' are obtained and adde d to the model initial conditions to improve the representation of the lower troposphere over the data-sparse ocean. It is found that the nu merical model prediction, initialized with the modified initial condit ions, exhibits significant improvements in the early rapid deepening a nd the track of the superstorm over ocean, the development of a prefro ntal squall line, and the central sea level pressure traces during the life cycle of the cyclone, as verified against observations. These re sults show that the methodology proposed is promising in improving the representation of lower-tropospheric meteorological variables in the model initial conditions, based on available surface observations over data-sparse regions.