A Case Study of an Exceptional Atmospheric River and Explosively Deepening Cyclone Over the US Central Plains in March 2019

Abstract

In March 2019, a strong atmospheric river (AR) originating from the Gulf of Mexico transported abundant moisture inland and fueled a record-breaking bomb cyclone in Colorado, resulting in widespread winter weather hazards across several states. Experimental model simulations and trajectory analysis indicate that mid-tropospheric latent heat release (LHR) coincided with the strength of the warm conveyor belt and played a key role in the deepening of the cyclone. The LHR promoted the generation of a lower tropospheric positive potential vorticity (PV) anomaly and a stronger low-level cyclonic circulation, enhancing the cyclone, low-level jet stream, and associated water vapor transport. Additionally, it generated an upper tropospheric negative PV anomaly and strong upper-level anticyclonic circulation, influencing the structure of the trough-ridge couplet and the associated Rossby wave. Reductions in the initial intensity of the AR and disallowing LHR both weakened the cyclone. However, disallowing LHR significantly disturbed the synoptic-scale structure of the storm and embedded Rossby wave, resulting in a stronger impact. Thus, the reduction of diabatic PV generation, under the influence of AR activities, was crucial in the explosive intensification of the cyclone. Additionally, the reductions in AR intensity and the magnitude of cyclone weakening did not show a linear relationship. Few studies have explored interactions between ARs and continental cyclones, and this paper highlights the need for further research on AR-associated extreme weather events inland.