Atmospheric rivers: research: forecasting methods: experimental tools.

Senator Caballero's atmospheric river forecasting legislation expands California's water management capabilities by requiring the Department of Water Resources to incorporate experimental seasonal and subseasonal prediction tools into its existing research program. The bill adds these longer-range forecasting requirements to the department's Atmospheric Rivers Research and Forecast Improvement Program, which currently focuses on improving predictions of these moisture-laden weather systems that deliver up to half of California's annual precipitation.

The legislation defines two new forecasting timeframes: seasonal forecasts covering one to six months ahead, and subseasonal forecasts spanning two to six weeks. These experimental tools would complement the program's existing work on reservoir operations, flood protection, and water capture during atmospheric river events. The department must make all forecasting data available to federal, state and local agencies to support coordinated planning and response.

According to the bill's findings, atmospheric rivers cause 94% of California's flood damages, averaging $620 million annually. The 2022-2023 winter storms alone affected 40 counties and generated an estimated $30 billion in damages and economic losses. With one in five Californians living in flood-prone areas and $900 billion in property at risk, the authors point to improved long-range forecasting as a key tool for protecting communities and infrastructure while maximizing opportunities to capture and store water when these weather systems arrive.