Sub-seasonal predictability of North American Monsoon precipitation

However, NAM rainfall is highly variable and water managers lack skillful guidance on summer rainfall that could help inform their management decisions and operations. Here we show that NAM season (June-October) precipitation can be forecasted by the European Centre for Medium-Range Weather Forecast's model months ahead at catchment scales.

This is possible by identifying the frequency of days with synoptic-scale moisture advection into the NAM region, which greatly improves predictability over directly utilizing modeled precipitation. Other forecasting systems fail to provide useful guidance due to deficiencies in their data assimilation systems and biases in representing key synoptic features of the NAM including its teleconnections.