Mechanisms Linking Easterly Waves and the North American Monsoon System

In northwestern Mexico and the southwestern United States, the North American Monsoon System (NAMS) is a major source of precipitation from mid-June through early September. The precipitation from NAMS is associated with a monsoon circulation that brings low-level moisture into the NAM region from the tropical eastern Pacific, Caribbean, and Gulf of Mexico. Precipitation events are also dependent on synoptic weather patterns within the region. Easterly waves have been shown to influence both the amount and location of NAM precipitation events, however the physical mechanisms linking the waves to these events are not well understood. In this study, we use the Advanced Research Weather, Research and Forecasting (WRF-ARW) regional model and an objective tracking routine to investigate the interaction between tracked easterly waves and monsoon events. We focus on 2004 when field observations are available from the North American Monsoon Experiment (NAME). We will evaluate model simulations of select NAME case studies using NAME datasets. We will then show the tracks of easterly waves and their flow patterns during these events to indicate the specific role of these waves for the cases selected. This study is part of a more general 10-year analysis examining the interaction of easterly waves and NAM precipitation events.