Potential extents for ENSO-driven hydrologic drought forecasts in the United States

The relationship between the El Niño-Southern Oscillation (ENSO) and hydrologic variability in the United States is investigated using Empirical Orthogonal Function (EOF)/Principal Component Analysis (PCA). The multivariate ENSO index (MEI) is utilized to identify strong coherences associated with multiple months (1-, 2-, 4-, 6-, 12-, 24-, 48-month) of the Log-Standardized Hydrologic Drought Index (LSHDI) in the conterminous states for the period 1950-2005. Based on 56 years of monthly streamflow data for 102 forecast climate divisions, this research explores the spatial and temporal variation of hydrologic responses corresponding to ENSO events. Preliminary results show that a potential predictor of the dominant streamflow modes in the northern Great Plains is identified from streamflows in western Arizona. Also, positive relationships between hydrologic drought and El Niño were found in the Pacific Northwest (Washington, Oregon, and northern California), whereas negative relationships were detected in southern California and the northern Great Plains. These findings will provide useful insights to help improve streamflow forecast potential and capabilities, and minimize the impacts of hydrologic events (e. g. floods and droughts) associated with ENSO events.