Case Studies from the 2013 North American Monsoon Transect Experiment

Significant weather events during the 2013 North American Monsoon Season (NAMS) were simulated using the Advanced Research Weather and Forecasting modeling system (WRF-ARW). Our WRF-ARW configuration uses three nested domains with spatial resolutions of 30 km, 10 km, and 2.5 km and boundary/initial conditions derived from the 32-km resolution North American Mesoscale Forecast System (NAM) and the 0.5-degree resolution Global Forecast System (GFS). “Perfect” boundary conditions were provided by the North American Regional Reanalyses (NARR). As part of collaborative effort between the University of Arizona (UA) and the Universidad Nacional Autónoma de México (UNAM), ten (10) GPS-Met sensors were deployed across the northern Sierra Madre Occidental (SMO) and along the coastal plains of Sonora and Sinaloa during the 2013 NAMS. These sensors provided atmospheric column water vapor observations at a 5-minute temporal resolution in areas where mesoscale convective complexes initiate and mature during the NAMS. The water vapor observations from these sensors are being assimilated into our model simulations to investigate their impact on NAMS severe weather forecasts. Our case studies focus on the southern Arizona and northwest Mexico region. The goal of this project is to improve the accuracy of thunderstorms forecasts during the NAMS by determining the sensitivity of the NAMS short-term forecasts to atmospheric water vapor observations.