Spring Tornado Activity in the United States Related to the GWO

Prediction of tornado activity beyond one week presents a challenging task due to the space and time scales involved. We show that revisiting a prior global dynamic framework with new perspective explains nearly an order of magnitude of the variability in U.S. tornado occurrence. Tornadoes are more (less) likely to occur in low (high) angular momentum base states. Composite environmental analysis suggests increases/decreases in tornado occurrence are associated with anomalies in tropospheric ingredients necessary for tornadic storms. Results herein provide a significant contribution to our understanding of U.S. peak-season tornado variability and a uniting framework for extended range forecasting of these extreme weather events. Given that the GWO includes the MJO (and other extratropical forcing such as mountain and frictional torque), using the GWO may serve to increase the predictive capability of the MJO for endeavors.