Legis
Environment
SB 599, Chapter 650, Statutes of 2026 · Sunday 27 September 2026

Atmospheric rivers: research: forecasting methods: experimental tools

California requires atmospheric-river research to include experimental seasonal and subseasonal forecasting tools.

Longer-range forecasts can improve planning for floods, reservoir operations, water supply, and related hazards.

What the law does ​

  • Directs the Department of Water Resources’ AR/FIRO Program to use experimental tools that produce seasonal atmospheric-river forecasts covering about one to six months.
  • Directs the program to use experimental tools that produce subseasonal atmospheric-river forecasts covering about two to six weeks.
  • Keeps the resulting research available to relevant federal, state, and local agencies for reservoir, flood-control, and water-storage decisions.

Who it affects ​

  • The Department of Water Resources and its Atmospheric Rivers Research and Forecast Improvement Program.
  • Water, flood-control, and emergency-planning agencies that use atmospheric-river information.
  • Communities and water users affected by flooding, drought, and reservoir operations.