A new paper, titled “Assessment of Sub-seasonal-to-Seasonal (S2S) Precipitation Forecast Skill for Reservoir Operation in the Yaque Del Norte River, Dominican Republic,” has been published in the journal Water. This collaborative effort was led by HRC Hydroclimatologist Dr. Norman Pelak and co-authored by Senior Research Scientist Dr. Eylon Shamir, Chief Operating Officer Dr. Theresa Modrick Hansen, and Hydraulic Engineer Dr. Zhengyang Cheng, each bringing their unique perspective and expertise to the study.
Reliable forecasts at the S2S timescale (generally defined as between 2 weeks and 2 months into the future) are crucial in water resources, emergency management planning, and agriculture. The findings of this study not only enhance our ability to manage these resources and plan for emergencies but also pave the way for a more optimistic future in these fields. However, this timescale is challenging to forecast due to its intermediate time frame between short-term weather and seasonal trends, which are dominated by initial conditions and climate trends, respectively.
This recent study has produced precipitation forecasts for the S2S timescale using three distinct methods: 1) bias-adjusted output of the Climate Forecast System (CFS), 2) stochastic weather generator (WG) output driven by historical precipitation data and climate indices, and 3) satellite-derived mean areal precipitation (MAP) time series conditioned on CFS forecasts. These forecasts were evaluated against observed precipitation and reservoir inflow data. The results indicated varying performance of each method by season, with the MAP methods demonstrating the strongest overall performance. This suggests a potential approach for combining the strengths of these methods to develop an ensemble forecast product.
This paper outlines the ongoing efforts to establish an S2S forecast system for the Yaque del Norte River basin in the northwestern Dominican Republic as an extension of the existing Haiti and Dominican Republic Flash Flood Guidance System (HDRFFGS). It marks a significant progression of HRC’s S2S forecasting capabilities for use in the Dominican Republic and beyond. This research study was made possible through funding from the “Capacity Development for Weather, Water, and Climate Forecasting and Disaster Risk Reduction” grant provided by the U.S. NWS (award no. NA22NWS4670002).
“Cumulative seasonal precipitation for a sample forecast (initialized 1 March 2014) showing the precipitation traces from each of the 3 methods vs. the observed precipitation time series: (a) CFS-BA: an ensemble of bias-adjusted outputs from Climate Forecast System; (b) WG: a 100-member ensemble of outputs from the weather generator method; (c) MAP: an ensemble of outputs from the MAP historical analog method.”