Advances in Sub-seasonal to Seasonal Prediction Relevant to Water Management in the Western United States

July 26, 2022

CW3E researcher Agniv Sengupta, along with co-authors Mike DeFlorio (CW3E), Bohar Singh and Andrew W. Robertson (International Research Institute for Climate and Society, Columbia University), Colin Raymond and Duane E. Waliser (NASA Jet Propulsion Laboratory), Xubin Zeng (University of Arizona, Tucson), and Jeanine Jones (California Department of Water Resources) recently published a paper titled “Advances in Sub-seasonal to Seasonal Prediction Relevant to Water Management in the Western United States” in the Bulletin of the American Meteorological Society. The work contributes to the goals of CW3E’s 2019-2024 Strategic Plan to support Subseasonal to Seasonal (S2S) Prediction of Extreme Weather and Emerging Technologies by sharing insights from the recent S2S Water Workshop jointly organized by IRI, NASA-JPL, University of Arizona, and CW3E. Funding support for this work was provided by the California Department of Water Resources as part of the Atmospheric River Program.

This publication presents a summary of the 2022 Virtual Workshop on S2S Forecasting for Water Management in the Western U.S. During this three-day virtual event (15-17 March 2022), scientists and stakeholders (~80 participants) came together to discuss forecast priorities for the western United States water resource management and to review existing and emerging methodologies that have the potential to improve prediction of precipitation, circulation regimes, and atmospheric rivers at lead times of weeks to months. The workshop provided a platform for cross-community dialog between researchers and stakeholders with participation from several federal agencies (e.g., NOAA, NASA, Department of the Interior, U.S. Army Corps of Engineers), state agencies (e.g., California Department of Water Resources, Western States Water Council), research centers (e.g., CW3E, IRI), and universities.

The invited stakeholder talks at the workshop highlighted the need for reliable S2S prediction of precipitation, snowpack, and streamflow, and their potential value in operational decisions on both short-term and long-term horizons (Figure 1). The workshop provided an up-to-date assessment of our current capabilities and challenges in simulating processes governing S2S predictability in the U.S. West. Specifically, insights were provided into the key physical phenomena governing predictability from landfalling atmospheric rivers to the tropical-extratropical teleconnections associated with the Madden-Julian Oscillation and tropical Pacific sea surface temperature variability, interactions between the stratosphere and the troposphere, and land-atmosphere interactions. Another focus of the workshop was on the emerging technical methods, including empirical, dynamical, hybrid, and machine learning approaches, for improving S2S prediction. The meeting showcased a suite of experimental sub-seasonal and seasonal forecast products (both probabilistic and deterministic) with potential for uptake as decision support tools by the applications community. In addition, success stories from programs like the Forecast Informed Research Operations (FIRO) and collaborative projects (such as the multi-university project led by NASA-JPL involving research and academic partners like CW3E/Scripps, IRI, and U. Arizona) provided promising pathways for research and operations partnerships.

The S2S timescale represents a frontier that shows promise for providing reliable outlooks weeks to months in advance for supporting efficient water management. The findings and discussions of the S2S Water Workshop, highlighted by Sengupta et al. (2022), will hopefully foster future investigations into underlying physical phenomena and processes governing predictability and aid in the development of efficient decision support tools.

Figure 1: Lead times necessary for different drought preparedness and response measures vary over daily to monthly timescales during the climatological wet season (winter), demonstrated here as a function of forecast certainty and discretion that water managers have in decision making. Note that initial water allocations must be made several months in advance when forecast uncertainty is the greatest. (From J. Jones’s workshop talk).

Sengupta, A., Singh, B., DeFlorio, M., Raymond, C., Robertson, A. W., Zeng, X., Waliser, D. E., & Jones, J. (2022). Advances in Sub-seasonal to Seasonal Prediction Relevant to Water Management in the Western United States, Bulletin of the American Meteorological Society (published online ahead of print 2022), https://doi.org/10.1175/BAMS-D-22-0146.1.