We benefited from discussions with Drs. Bin Wang, Adam Sobel, and Lloyd Shapiro. We also appreciate thoughtful reviews from Dr. George Kiladis and two anonymous reviewers. Gridded analyses from the European Centre for Medium-Range Weather Forecasts were obtained from the National Center for Atmospheric Research (NCAR), which is supported by the National Science Foundation. This work was supported by National Science Foundation Grants ATM-0201752 and ATM-0513428.
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