The Meteorological Conditions Leading to Two Historic Floods Along the Lower Meramec River Basin (29)

Mark Britt, National Weather Service Forecast Office St. Louis, Missouri, St. Louis, MO

James Sieveking, National Weather Service Forecast Office St. Louis, Missouri

Patrick Walsh, National Weather Service Forecast Office St. Louis, Missouri



This study will examine two separate multi-day cool season precipitation events in which heavy rain fell in the Meramec River Basin that covers southeast and east central Missouri. The first event occurred on December 2-5, 1982 which caused record flooding at all of the forecast points along the lower Meramec River. The second event occurred December 26-29, 2015 and established a new flood of record at most of the river guages below Sullivan, Missouri. Both floods caused significant impacts to homes, businesses, and transportation.

Rainfall observations from both events showed some similarities to where the heaviest rainfall occurred in each basin. The North American Regional Reanalysis Dataset was used to compare the mean daily synoptic patterns and climatological anomalies. Both cases were characterized by strongly forced systems caused by the entrance region of upper jet streaks and an approaching deep mid-level troughs. In addition, strong moisture transport from the Gulf of Mexico allowed for anomalously high amounts of moisture needed for historic rainfall in December.