Abstract

Like other global monsoon systems, the North American Monsoon (NAM) exerts a key control on the warm season hydroclimate North America, driving high impact events from weather to climate timescales. It is simultaneously a provider of seasonal rains critical to agriculture and water resources whil... Show moreLike other global monsoon systems, the North American Monsoon (NAM) exerts a key control on the warm season hydroclimate North America, driving high impact events from weather to climate timescales. It is simultaneously a provider of seasonal rains critical to agriculture and water resources while also an arbiter of destructive weather events. These events include heavy rainfall in complex terrain, flash flooding, land-falling tropical storms, dry lightning, and fast moving dust storms and, every year, result in significant loss of life and property. From a climate perspective, variability of the NAM system both drives and responds to regional patterns of sea-surface temperatures, land surface moisture conditions, moisture transport mechanisms, as well as mesoscale and synoptic scale transient features of the atmosphere. The reduction of disaster risks through improved forecasts of high-impact weather, is put forward at an ideal time with regard to the NAM as it arrives near the end of a ten-year, internationally coordinated research program known as the North American Monsoon Experiment (NAME). The NAME research program has produced significant advances in the understanding of many NAM processes responsible for mean state and extreme event manifestations of the NAM climate. Furthermore, the NAME has coordinated a series of model evaluations, data impact, and model forecast assessments as well as societal capacity to deal with monsoon climate and weather related events. This work reviews several major components of the NAM system that are linked to high-impact weather events. Attention is paid to the status of operational forecast models in their reliability to predict such processes. To the degree possible, we also discuss which large-scale NAM processes cascade downscale to drive regional and local severe weather events. The review concludes with a set of recommendations for improving NAM predictions through the use of integrated regional climate observing systems as well as a summary of unresolved research questions which currently inhibit the ability to forecast monsoons across timescales. Show less