US Drought Monitor Update and How it Works

August 16, 2019 8:22 AM
Blog Post

We've gone from being too wet to the other extreme of being dry in parts of the state. Below is a summary of the most recent US Drought Monitor (USDM) map for the state of Iowa and a brief explanation of what data goes into making the USDM.

Current Conditions in Iowa.

Yesterday (August 15), the latest USDM map was released.  As of Tuesday, August 13, Abnormally Dry (D0) conditions covered 43.1% of Iowa, up from 36.39% the previous week. Additionally, 9.5% of the state is now considered to be in a Moderate Drought (D1).

Below is a table from explaining the various levels of drought.

What determines these levels of drought?

Weekly recommendations to the USDM author are based on a variety of variables and on-the-ground impact reports. Recommendations are formed using a “convergence of evidence” approach in which data such as rainfall deficits, top and sub-soil conditions and various moisture indices are considered and compared to physical impact reports. When a majority of the evidence supports a drought class designation (D0-D4), a recommendation is submitted to the USDM author after data cut off at 7:00 am CDT on Tuesday. The final map is released at 7:00 am CDT the following Thursday. The USDM map is not a forecast but rather a representation of current conditions.The monitor focuses on broad-scale conditions, and local conditions may vary.