EDDI (Evaporative Demand Drought Index)

The Evaporative Demand Drought Index, or EDDI, is a drought index that can serve as an indicator of both rapidly evolving “flash” droughts (developing over a few weeks) and sustained droughts (developing over months but lasting up to years) and that has been shown to provide earlier warning of drought than many established drought indices, such as the US Drought Monitor. EDDI is currently under development at NOAA’s Physical Sciences Laboratory and the Desert Research Institute and is slated for operationalization at the National Water Center by May, 2019. However, it is currently available on a quasi-operational basis from PSL for the whole of CONUS, and it may be tailored to your specific region on request.

EDDI examines how anomalous the atmospheric evaporative demand (E0; also known as "the thirst of the atmosphere") is for a given location at various timescales from 1 week through 12 months. By using a fully physical E0, EDDI captures drought dynamics from the demand perspective. This approach offers both early warning and a more-nuanced appreciation of the meteorological drivers of drought beyond the traditional reliance on precipitation and temperature. More information on EDDI, including current conditions and a user manual, is available in this 2-page handout (http://wwa.colorado.edu/publications/reports/EDDI_2-pager.pdf) and on the EDDI webpage.