The Evaporative Demand Drought Index (EDDI): Updates and Improvements

Mike Hobbins, Hailan Wang, Yutong Pan, Ada Uzoma

NOAA/OAR Physical Sciences Laboratory/CIRES, NOAA National Weather Service Climate Prediction Center

Tuesday, Mar 24, 2026, 1:00 pm MT
DSRC Room GC402

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Abstract

A joint team from NOAA/OAR Physical Sciences Laboratory (PSL) and NOAA/NWS Climate Prediction Center (CPC) recently completed the transition from PSL research to CPC operations (R2O) of NOAA’s Evaporative Demand Drought Index (EDDI) from its original home as an experimental product at PSL to an experimentally operational status at CPC, pending completion of NWS procedures for implementing a new product. This presentation will summarize this R2O process and, more importantly, the improvements made to EDDI–to its estimation and its dissemination to users–and explain some new value-added products to users, and inform users as to where the new EDDI may be accessed.

Prior to the transition, EDDI was produced and disseminated in a multi-step process across three NOAA centers–a process that was prone to failure. The recent transition to CPC has streamlined all aspects of the production of EDDI and housed it in a single operational center–the CPC. A significant advantage of CPC hosting EDDI is that they use it in NOAA’s official U.S. Drought Outlook products (Rapid Onset Drought risk product within the 8-14 Day U.S. Hazards Outlook, the Monthly Drought Outlook), and they host authors of the U.S. Drought Monitor, who are among EDDI’s most significant and influential users. This R2O process also yielded significant improvements to EDDI, namely: (i) the climatology of reference evapotranspiration (RefET) underpinning EDDI was upgraded from 1980-2015 to 1980-2021, allowing for better discrimination of more-extreme events; (ii) maps of changes in EDDI through time now allow users to track ongoing changes in droughts; and (iii) a decomposition technique was developed to quantify how much each driver (temperature, humidity, wind, solar radiation) contributes to changes in RefET. This diagnosis is the first-ever decomposition of atmospheric evaporative demand implemented in near-real-time, with implications beyond drought monitoring.

The EDDI product at CPC incorporates the R2O improvements described above as well as a cloud-hosted interactive viewer for user-friendly browsing and visualization. Specifically, it provides maps and data showing current conditions of EDDI category, changes in EDDI category, the decomposition of RefET changes, and historical EDDI time series for a user-selected region and timescale. It also hosts an archive of historical EDDI category maps (from January 1, 1980 to the present, with a 5-day latency). Additionally, a Geographic Information System (GIS) display is available through the National Weather Service (NWS) Web Map Service (WMS) for current EDDI conditions and their changes, allowing users to pan, zoom, and examine EDDI at specific geographic locations. For more information, please visit the CPC EDDI webpage.

Presenter Affiliations:

• Mike Hobbins, University of Colorado-Cooperative Institute for Research in Environmental Sciences (CIRES), at NOAA/OAR Physical Sciences Laboratory
• Hailan Wang, NOAA/NWS Climate Prediction Center
• Yutong Pan, Earth Resources Technology, at NOAA/NWS Climate Prediction Center
• Ada Uzoma, Earth Resources Technology, at NOAA/NWS Climate Prediction Center