The Largest United States Area-Averaged Precipitation Events

We compare area-averaged (1000-50,000 sq mi) accumulated (2-y day) storm totals from six objective gridded precipitation analyses and one semi-objective system to identify the largest precipitation events every recorded in the United States. Such events occur exclusively along the West Coast from mid-fall to late winter and along the Gulf and Southeast coasts in summer and early fall. Gulf and Southeast events tend to dominate the shorter accumulation periods while West Coast events dominate the longer accumulation periods, although Hurricane Harvey dominates just about everything. There is also a distinct tendency for Gulf and Southeast storms to have occurred in recent decades and West Coast storms in earlier decades. Event totals are estimated taking into account the virtues and limitations of the various available analyses, with discrepancies among analyses largest for West Coast events.