Seasonal Drought Forecast For the Intermountain West
2024/2025 Winter
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Figure 1: Downscaled NMME forecasts for total precipitation (left) and anomalous precipitation (right) from December 2024 to February 2025 in the Western United States.
Figure 2: Downscaled NMME forecasts for average temperature (left) and anomalous temperature (right) from December 2024 to February 2025 in the Western United States.
Positive anomalies indicate above-average values for temperature or precipitation, while negative anomalies indicate below-average. Both temperature and precipitation anomalies are calculated as deviations from the mean from 2013-2023.
The NMME forecasts (Kirtman et al., 2014) were trained from 1982-2012 and then statistically downscaled using the analog method (Gutmann et al., 2022), with 4-kilometer PRISM data as the observational record (Daly et al., 2008). The analog method identifies historical patterns that closely match the forecast for a specific month and uses these patterns to refine the forecast based on the resolution of the observational dataset.
References
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Gutmann, Ethan D., et al. En-GARD: A Statistical Downscaling Framework to Produce and Test Large Ensembles of Climate Projections. Journal of Hydrometeorology, 23.10 (2022): 1545-1561. doi:10.1175/JHM-D-21-0142.1.
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Kirtman, Ben P., et al. The North American multimodel ensemble: phase-1 seasonal-to-interannual prediction; phase-2 toward developing intraseasonal prediction. Bulletin of the American Meteorological Society, 95.4 (2014): 585-601. doi:10.1175/BAMS-D-12-00050.1.
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Daly, Christopher., et al. Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States. International Journal of Climatology. 28.15 (2008): 2031-2064. doi:10.1002/joc.1688
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Vernon, B., Zhang, W., and Chikamoto, Y. Statistical downscaling as a method for improving seasonal forecasting in the Western United States. (In preparation). 2024.
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This utility has been developed in partnership with the Bureau of Reclamation and the Utah Agricultural Experiment Station