[Mick]

Mick, do you have a source for that regional risk summary?

I. Primary, Authoritative Data Sources (Observed Precipitation)
These are the core systems used by hydrologists, state agencies, and climate scientists.
1. NOAA / RCC ACIS (Applied Climate Information System)

• Website: https://www.rcc-acis.org
  
• API Endpoint: https://data.rcc-acis.org
  
• Maintained by: NOAA Regional Climate Centers
  
• Used for:
  • Station-level daily precipitation
    
  • County aggregation
    
  • Season-to-date calculations
    
  • Normals-to-date comparisons (via normal=1)
    
• Gold standard for county-level precipitation analysis
  
• Primary backbone of the compilation
  

---

2. NOAA National Centers for Environmental Information (NCEI)

• Website: https://www.ncei.noaa.gov
  
• Used for:
  • Historical precipitation records
    
  • Station metadata
    
  • Long-term climate continuity checks
    
• Feeds ACIS and many downstream tools
  

---

3. NOAA COOP / GHCN-Daily Station Network

• Website: https://www.ncei.noaa.gov/products/land-...work-daily
  
• Used for:
  • Daily rainfall at long-running stations
    
  • Rural and agricultural coverage
    
• Critical for interior counties and long-term normals
  

---

II. Normals, Baselines & Climate Context
These sources establish what “normal” means for the exact date range (10/1 → 1/5).
4. NOAA Climate Normals (1991–2020)

• Website: https://www.ncei.noaa.gov/products/land-...te-normals
  
• Used for:
  • Precipitation normals
    
  • Percent-of-normal calculations
    
• Normals embedded directly into ACIS outputs
  

---

5. Western Regional Climate Center (WRCC)

• Website: https://wrcc.dri.edu
  
• Used for:
  • Western-U.S. precipitation climatology
    
  • Orographic and regional precipitation interpretation
    
• Cross-checks Sierra vs valley behavior
  

---

6. California Nevada River Forecast Center (CNRFC – NOAA)

• Website: https://www.cnrfc.noaa.gov
  
• Used for:
  • Basin-scale precipitation patterns
    
  • Storm impact interpretation
    
  • Flood vs water-supply risk context
    

---

III. California-Specific Water & Climate Agencies
Used to ground-truth and interpret risk, not to replace NOAA data.
7. California Department of Water Resources (DWR)

• Website: https://water.ca.gov
  
• Key Portals:
  • Snow surveys
    
  • Water supply outlooks
    
• Used for:
  • Sierra snowpack relevance
    
  • Reservoir sensitivity context
    

---

8. California Data Exchange Center (CDEC)

• Website: https://cdec.water.ca.gov
  
• Used for:
  • Precipitation gages
    
  • Snow-water equivalent
    
• Helpful for understanding county variability
  

---

9. California Climate Tracker (UC / State collaboration)

• Website: https://californiaclimate.org
  
• Used for:
  • Regional anomaly visualization
    
  • Climate trend validation
    

---

IV. Supplemental / Analytical Cross-Checks
These are not primary data but help validate spatial patterns.
10. PRISM Climate Group (Oregon State University)

• Website: https://prism.oregonstate.edu
  
• Used for:
  • Gridded precipitation context
    
  • Orographic bias correction understanding
    
• Especially useful in mountainous counties
  

---

11. NOAA Physical Sciences Laboratory (PSL)

• Website: https://psl.noaa.gov
  
• Used for:
  • Large-scale pattern context (ENSO-neutral, ridging)
    
  • Storm-track behavior explanation
    

---

12. National Weather Service (NWS) Forecast Offices (CA)

• Examples:
  • https://www.weather.gov/mtr (Bay Area)
    
  • https://www.weather.gov/lox (Los Angeles)
    
  • https://www.weather.gov/sto (Sacramento)
    
• Used for:
  • Local storm summaries
    
  • Event-scale confirmation
    

---

V. Risk Interpretation & Sector Implications
Used to translate rainfall anomalies into practical risk.
13. U.S. Drought Monitor

• Website: https://droughtmonitor.unl.edu
  
• Used for:
  • Early-season drought signal confirmation
    
  • SoCal & Central Valley risk framing
    

---

14. CAL FIRE Fire Hazard Mapping

• Website: https://www.fire.ca.gov
  
• Used for:
  • Wildfire risk interpretation tied to precipitation deficits
    

---

15. USDA Climate Hubs (California)

• Website: https://www.climatehubs.usda.gov/hubs/california
  
• Used for:
  • Agricultural sensitivity context
    
  • Central Valley implications
    

---

Summary (Plain English)

• Observed precipitation: NOAA ACIS (via RCC + NCEI stations)
  
• Normals: NOAA Climate Normals (1991–2020), embedded in ACIS
  
• Spatial sanity checks: WRCC, PRISM, CDEC
  

Methodology Overview
Includes data sources, assumptions, and analytical methods used to compile the California Regional Rainfall and Risk Summary (Water Year-to-Date, Oct 1, 2025 – Jan 5, 2026).

Primary Data Source
NOAA Regional Climate Centers – Applied Climate Information System (ACIS)
https://www.rcc-acis.org | https://data.rcc-acis.org
Used for station-level daily precipitation, county aggregation, season-to-date totals, and normal-to-date comparisons using NOAA 1991–2020 climate normals.

Supporting Federal Sources
NOAA National Centers for Environmental Information (NCEI) – station metadata and historical continuity
https://www.ncei.noaa.gov
NOAA Cooperative Observer Program (COOP) / GHCN-Daily – long-running daily precipitation stations
https://www.ncei.noaa.gov/products/land-...work-daily

Regional & State Cross-Checks
Western Regional Climate Center (WRCC) – western U.S. precipitation climatology
https://wrcc.dri.edu
California Department of Water Resources (DWR) – snowpack and water supply context
https://water.ca.gov
California Data Exchange Center (CDEC) – precipitation and snow-water-equivalent gages
https://cdec.water.ca.gov

Analytical & Spatial Validation
PRISM Climate Group (Oregon State University) – gridded precipitation and orographic context
https://prism.oregonstate.edu
NOAA California-Nevada River Forecast Center (CNRFC) – basin-scale precipitation patterns
https://www.cnrfc.noaa.gov

Risk Interpretation Sources
U.S. Drought Monitor – drought classification and early-season signals
https://droughtmonitor.unl.edu
CAL FIRE – wildfire risk and fuel moisture context
https://www.fire.ca.gov
USDA Climate Hubs (California) – agricultural impact context
https://www.climatehubs.usda.gov/hubs/california

Key Assumptions & Notes
• Aggregation is based on county-average station observations; no area-weighted gridding was applied.
• 'Normal' refers to NOAA 1991–2020 climate normals for the same date range.
• Sierra Nevada counties are heavily influenced by snow-water equivalent and orographic effects.
• Risk implications are qualitative and intended for planning and briefing purposes.

[Mick]

Mick, do you have a source for that regional risk summary?

I. Primary, Authoritative Data Sources (Observed Precipitation)
These are the core systems used by hydrologists, state agencies, and climate scientists.
1. NOAA / RCC ACIS (Applied Climate Information System)

• Website: https://www.rcc-acis.org
  
• API Endpoint: https://data.rcc-acis.org
  
• Maintained by: NOAA Regional Climate Centers
  
• Used for:
  • Station-level daily precipitation
    
  • County aggregation
    
  • Season-to-date calculations
    
  • Normals-to-date comparisons (via normal=1)
    
• Gold standard for county-level precipitation analysis
  
• Primary backbone of the compilation
  

---

2. NOAA National Centers for Environmental Information (NCEI)

• Website: https://www.ncei.noaa.gov
  
• Used for:
  • Historical precipitation records
    
  • Station metadata
    
  • Long-term climate continuity checks
    
• Feeds ACIS and many downstream tools
  

---

3. NOAA COOP / GHCN-Daily Station Network

• Website: https://www.ncei.noaa.gov/products/land-...work-daily
  
• Used for:
  • Daily rainfall at long-running stations
    
  • Rural and agricultural coverage
    
• Critical for interior counties and long-term normals
  

---

II. Normals, Baselines & Climate Context
These sources establish what “normal” means for the exact date range (10/1 → 1/5).
4. NOAA Climate Normals (1991–2020)

• Website: https://www.ncei.noaa.gov/products/land-...te-normals
  
• Used for:
  • Precipitation normals
    
  • Percent-of-normal calculations
    
• Normals embedded directly into ACIS outputs
  

---

5. Western Regional Climate Center (WRCC)

• Website: https://wrcc.dri.edu
  
• Used for:
  • Western-U.S. precipitation climatology
    
  • Orographic and regional precipitation interpretation
    
• Cross-checks Sierra vs valley behavior
  

---

6. California Nevada River Forecast Center (CNRFC – NOAA)

• Website: https://www.cnrfc.noaa.gov
  
• Used for:
  • Basin-scale precipitation patterns
    
  • Storm impact interpretation
    
  • Flood vs water-supply risk context
    

---

III. California-Specific Water & Climate Agencies
Used to ground-truth and interpret risk, not to replace NOAA data.
7. California Department of Water Resources (DWR)

• Website: https://water.ca.gov
  
• Key Portals:
  • Snow surveys
    
  • Water supply outlooks
    
• Used for:
  • Sierra snowpack relevance
    
  • Reservoir sensitivity context
    

---

8. California Data Exchange Center (CDEC)

• Website: https://cdec.water.ca.gov
  
• Used for:
  • Precipitation gages
    
  • Snow-water equivalent
    
• Helpful for understanding county variability
  

---

9. California Climate Tracker (UC / State collaboration)

• Website: https://californiaclimate.org
  
• Used for:
  • Regional anomaly visualization
    
  • Climate trend validation
    

---

IV. Supplemental / Analytical Cross-Checks
These are not primary data but help validate spatial patterns.
10. PRISM Climate Group (Oregon State University)

• Website: https://prism.oregonstate.edu
  
• Used for:
  • Gridded precipitation context
    
  • Orographic bias correction understanding
    
• Especially useful in mountainous counties
  

---

11. NOAA Physical Sciences Laboratory (PSL)

• Website: https://psl.noaa.gov
  
• Used for:
  • Large-scale pattern context (ENSO-neutral, ridging)
    
  • Storm-track behavior explanation
    

---

12. National Weather Service (NWS) Forecast Offices (CA)

• Examples:
  • https://www.weather.gov/mtr (Bay Area)
    
  • https://www.weather.gov/lox (Los Angeles)
    
  • https://www.weather.gov/sto (Sacramento)
    
• Used for:
  • Local storm summaries
    
  • Event-scale confirmation
    

---

V. Risk Interpretation & Sector Implications
Used to translate rainfall anomalies into practical risk.
13. U.S. Drought Monitor

• Website: https://droughtmonitor.unl.edu
  
• Used for:
  • Early-season drought signal confirmation
    
  • SoCal & Central Valley risk framing
    

---

14. CAL FIRE Fire Hazard Mapping

• Website: https://www.fire.ca.gov
  
• Used for:
  • Wildfire risk interpretation tied to precipitation deficits
    

---

15. USDA Climate Hubs (California)

• Website: https://www.climatehubs.usda.gov/hubs/california
  
• Used for:
  • Agricultural sensitivity context
    
  • Central Valley implications
    

---

Summary (Plain English)

• Observed precipitation: NOAA ACIS (via RCC + NCEI stations)
  
• Normals: NOAA Climate Normals (1991–2020), embedded in ACIS
  
• Spatial sanity checks: WRCC, PRISM, CDEC
  

Methodology Overview
Includes data sources, assumptions, and analytical methods used to compile the California Regional Rainfall and Risk Summary (Water Year-to-Date, Oct 1, 2025 – Jan 5, 2026).

Primary Data Source
NOAA Regional Climate Centers – Applied Climate Information System (ACIS)
https://www.rcc-acis.org | https://data.rcc-acis.org
Used for station-level daily precipitation, county aggregation, season-to-date totals, and normal-to-date comparisons using NOAA 1991–2020 climate normals.

Supporting Federal Sources
NOAA National Centers for Environmental Information (NCEI) – station metadata and historical continuity
https://www.ncei.noaa.gov
NOAA Cooperative Observer Program (COOP) / GHCN-Daily – long-running daily precipitation stations
https://www.ncei.noaa.gov/products/land-...work-daily

Regional & State Cross-Checks
Western Regional Climate Center (WRCC) – western U.S. precipitation climatology
https://wrcc.dri.edu
California Department of Water Resources (DWR) – snowpack and water supply context
https://water.ca.gov
California Data Exchange Center (CDEC) – precipitation and snow-water-equivalent gages
https://cdec.water.ca.gov

Analytical & Spatial Validation
PRISM Climate Group (Oregon State University) – gridded precipitation and orographic context
https://prism.oregonstate.edu
NOAA California-Nevada River Forecast Center (CNRFC) – basin-scale precipitation patterns
https://www.cnrfc.noaa.gov

Risk Interpretation Sources
U.S. Drought Monitor – drought classification and early-season signals
https://droughtmonitor.unl.edu
CAL FIRE – wildfire risk and fuel moisture context
https://www.fire.ca.gov
USDA Climate Hubs (California) – agricultural impact context
https://www.climatehubs.usda.gov/hubs/california

Key Assumptions & Notes
• Aggregation is based on county-average station observations; no area-weighted gridding was applied.
• 'Normal' refers to NOAA 1991–2020 climate normals for the same date range.
• Sierra Nevada counties are heavily influenced by snow-water equivalent and orographic effects.
• Risk implications are qualitative and intended for planning and briefing purposes.