Intermountain West Drought & Climate Outlook Webinar: September 17, 2024

Welcome to the Intermountain West Drought Briefing 

Speaker: Dr. Gretel Follingstad | Cooperative Institute for Research in Environmental Sciences (CIRES)/University of Colorado Boulder; NOAA’s National Integrated Drought Information System (NIDIS)

• Welcome to the September 2024 Intermountain West Drought Briefing.
• Sign up for NIDIS emails as well as drought alerts.
• Stay tuned for the October 2024 Water Year and North American Monsoon Special Drought Status Update.
• View past webinar recordings at drought.gov/webinars.
• Introducing today's speakers:
  • Dave Simeral: Dave is an Associate Research Climatologist at the Desert Research Institute & Western Regional Climate Center in Reno, Nevada and has served as a national author for the U.S. Drought Monitor since 2012.
  • Peter Goble: Peter Goble received his B.S. in meteorology from the University of Northern Colorado and his M.S. in atmospheric science from Colorado State University. He is the Colorado Assistant State Climatologist. He specializes in climate variability and drought. Recent projects include investigating the sources of error in western Colorado water supply forecasts, determining areas of Colorado most suitable for expansion of the wine grape industry, using climate models to investigate the future of precipitation variability in Colorado, and increasing both observational and modeled soil moisture monitoring efforts in Colorado.

Current Drought Conditions and Outlook 

Speaker: Dave Simeral | Desert Research Institute at the Western Regional Climate Center

• Current drought conditions show drought improvements for various areas of the Intermountain West, in southern Colorado and central and northern New Mexico.  However, drought conditions have degraded in eastern Wyoming. 
  • Arizona: 39.9% in drought (0% in D3-D4)
  • Colorado: 15.4% in drought (0% in D3-D4)
  • New Mexico: 38.6% in drought (2.7% in D3)
  • Utah: 9.5 % in drought (0% in D3-D4)
  • Wyoming: 58.1 % in drought (5.3% in D3–D4)
• The water year to date is warmer than normal. For the past 3-month period (June–August), Phoenix, Arizona had its warmest mean (99.4°F), max (110.6°F),and  minimum (88.2°F) temperatures on record.
• 33.19% of the Intermountain West region is currently in drought (D1–D4), according to the U.S. Drought Monitor. 
• The most severe drought conditions are in northeastern Wyoming and southern New Mexico. 
• Reported agricultural impacts in Wyoming, east-central and southern Colorado, and central Utah​ include poor rangeland conditions, reduced crop yields, reduced irrigation water, water hauling for livestock, supplemental feeding, decreased stock weights, and dry creeks/stock ponds.
• Lake Powell and Lake Mead have well-below-normal storage levels for the date, compared to long-term averages.​
• The NOAA Climate Prediction Center’s seasonal outlooks show a greater likelihood of  warmer and drier conditions from September–November.
• El Niño–Southern Oscillation (ENSO): Currently, conditions are ENSO-neutral, but  La Niña is favored to emerge (71% chance) during September–November 

On the Sources of Water Supply Forecast Error in Western Colorado

Speaker: Peter Goble | Colorado Climate Center at Colorado State University

• Peak flow forecasts based on water year to date precipitation and peak snowpack from SNOTEL stations are often quite accurate (to this point). 2020-2021 was more the exception than the rule. 
• Spring precipitation beyond peak snowpack season impacts peak flow more than antecedent conditions, regardless of the soil moisture model used. Wet springs like 1995 and 2015 lead to large errors in streamflow forecasts
• Antecedent soil moisture information did improve 2021 seasonal runoff hindcasts. This year saw the lowest antecedent soil moisture conditions on record for all models (< -2 sigma). Perhaps this information is more useful during extreme conditions
• Physically, antecedent soil moisture conditions must influence streamflow. Why don’t we see a stronger signal? 
  • Potential hypotheses: 40 years of data is too small a sample to establish this relationship, measurements may not be deep enough, or the models have too many foibles to be useful for this application. 
• Adjusted streamflow measurements and snowpack measurements themselves are imperfect. It is unlikely that better soil moisture information would eliminate non-forecast-based errors.
• Bottom line: Without improved seasonal-to-subseasonal forecasting skill, significant water supply forecast error is inevitable.

Conclusion

Speaker: Dr. Gretel Follingstad | CIRES/CU Boulder, NOAA/NIDIS