| A mesoscale ensemble prediction system (MEPS) was designed and its application for mid-latitude cyclones was explored in this paper. The uncertainties existing in the initial data, model physics, and lateral boundary conditions were considered and incorporated into the MEPS. Three separate ensemble subsets were created with respect to the three uncertainties, respectively. Three mid-latitude cyclones that occurred over the United States were chosen for implementation of the MEPS using the Penn State-NCAR fifth-generation Mesoscale Model (MM5), which has been shown to be a very useful tool in short-range ensemble forecasting.; The perturbations used to represent the initial condition errors in this study were generated by three breeding methods, the Bred Monte-Carlo Perturbations method (MC), the Breeding of Growing Modes method (BGM) and the Perturbed Observations method (PO). Uncertainties in model physics were explored through the use of multiple model physical parameterizations (MPEF), while the use of bred perturbations in the outermost domain generated the lateral boundary ensemble subset (LBEF). Each ensemble subset consisted of 20 48-h forecasting members except for MPEF, which had 48 members.; A unique aspect of this work was the assessment of these multiple, distinct mesoscale ensemble subsets, incorporating initial condition, model physics and lateral boundary uncertainties present in mid-latitude cyclone prediction. The use of separate ensemble subsets permitted direct comparison of the contributions from different uncertainty sources. Through the examination of the ensemble prediction results for cyclone central pressure, cyclone track, etc., and through statistical analysis, we gained an understanding of the utility of the MEPS for mid-latitude cyclone prediction. The BGM and PO breeding methods were found to be far superior to the MC method in generation of a set of initial conditions for ensemble prediction. A notable characteristic of the model physics perturbation ensemble is its ability to alleviate the problems caused by the unperturbed lateral boundary condition. The new technique for generating lateral boundary perturbations was successfully implemented and tested, and showed promising results. The large spread values in the lateral boundary ensembles demonstrated the importance of lateral boundary uncertainties in the mesoscale ensemble system. |
