Understanding Subseasonal Extremes: The Missouri Floods of December 2015

In December 2015, the U.S. state of Missouri was flooded at an unprecedented level after 3 days of heavy rainfall.  Analysis presented here indicates a combination of both the El Niño and a strong Madden Julian Oscillation (MJO) episode setting the stage for the stormy event, with the strongest subseasonal contribution coming from the MJO.  Attribution analysis suggests that the observed intensification in the El Niño teleconnection has become increasingly likely to couple with transient weather patterns that are prone to high-amplitude precipitation.  A series of midlatitude short waves spanning the North Pacific and North America added to the synoptic forcing.

The subseasonal-to-seasonal (S2S) forecast of the National Multi-Model Ensemble (NMME) and the Climate Forecast Systems, as well as 15-day forecast of weather prediction models, was analyzed to diagnose the predictiability spectrum across these different climate/weather modes at different timescales.  Riding on a success forecast of the December 2015 MJO phasing and the El Niño, the result suggests that a hybrid empirical-dynamical prediction approach may reduce the current gap in the S2S prediction for events such as the December 2015 Missouri flood.