This paper benefited tremendously from the encouragement, historical perspective, guidance, and review provided by Dan Keyser. Fred Sanders and Mark Stoelinga also provided very detailed and thorough reviews on earlier versions of this manuscript. I would also like to thank the following people for their discussions and input: George Bryan, Phil Cunningham, Charles Doswell, Robert Johns, Steve Koch, John Locatelli, Chester Newton, Michael Reeder, Robert Serafin, and Jay Shafer. Mark Stoelinga recommended including the argument in section 2 that prefrontal troughs need to be supported by the thermal structure of the overlying atmospheric column. Kerry Emanuel provided insight into the implications of Emanuel (1985b). Joan O’Bannon drafted Fig. 10. Funding was provided by NOAA/OAR/NSSL under NOAA–OU Cooperative Agreement NA17RJ1227.
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