Near-Term Enhancements to Probable Maximum Precipitation: The Smethport Challenge

The 18 July 1942 Smethport, Pennsylvania storm produced the world rainfall accumulation of 780 mm in 4.5 hours and controls current Probable Maximum Precipitation (PMP) estimates for short durations and small areas over a large region of the eastern US. We reexamine rainfall estimates for the 18 July 1942 Smethport storm based on analyses of observations from the storm, regional climate model reconstructions of the storm and storm environment, and analyses of rainfall fields developed for analog storms during the polarimetric radar era. We examine aspects of the climatology of Smethport-like storms through analyses of near-record sub-daily rainfall accumulations in the Upper Ohio Valley and Central Appalachians. Implications for near-term enhancement of PMP estimates are discussed, focusing on development of modernized storm catalog data, storm transposition, moisture maximization and orographic enhancement.