Drought relinquishing 12-month grip over most of Northern Plains
The US Drought Monitor published July 12, 2018 reflected the above-normal amount of rain that fell in the central and northern Plains and into the upper Midwest, due to an active weather pattern that brought thunderstorms across the region. The recent storms brought some parts of Montana and the Dakotas out of drought status for the first time in over a year.
The weekly USDM map is the veritable picture worth a thousand words for managers of water utilities, ag producers, USDA field personnel, extension agents, policymakers and city-dwellers aware of maintaining landscapes and access to a steady flow of household and drinking water. Produced by the National Drought Mitigation Center, the map provides a composite view of the many variables that indicate whether an area has experienced a departure in water availability from a “normal” or expected level for the season to what could be characterized as some level of drought.
“People are often surprised to learn how many citizens, scientists, agencies and streams of data are part of the production of the map,” said Mark Svoboda, NDMC director and co-founder and former author of the USDM. “That is why we emphasize that what we’ve expanded upon and improved since first producing the USDM map in 1999 is a methodology, not a computer program. The accuracy of the USDM depends upon weaving together strands of knowledge from human observers, technology and historical record.”
These strands include data gathered from local observers, regional weather monitoring networks, data models, remote sensing satellites and other well-known sources of weather measurement and analyses such as the Palmer Drought Severity Index, the Standardized Precipitation Index, the Surface Water Supply Index and other indicators of vegetation health and evapotranspiration. Current data and historical climate records are then analyzed by a nationwide team of climate scientists who consult with one another to develop the depiction of drought’s advance, retreat or holding pattern across all 50 states and Puerto Rico during the preceding seven days.
“The power of the USDM is that it incorporates all of this information, and all of these viewpoints, which cannot be accomplished by one tool, model, index or drought perspective alone,” Svoboda said.
Areas of the country not showing indications of drought during the reporting period are shown in white on the map. As dryness increases in intensity, map colors for areas in drought change from yellow, indicating a pre-drought, but dry category, to increasingly darker hues of tan, orange, red and brown. The darker the color, the drier the region.
Supplementing the information provided by the color codes are black lines often encapsulating areas and labelled with the letters “S” or “L”. An “S” indicates an area experiencing a drought of short duration, usually of six months or less, and an “L” indicates a drought of longer than six months.
Data used in producing the map reflect conditions through Tuesday morning of the week the map is produced. “There is about a 48-hour period between the time we stop incorporating new weather data in to the map, and the time the map is distributed via listservs, websites and social media,” explained Svoboda. “The good, soaking rain an area received on a Tuesday night won’t be reflected in the map distributed the following Thursday, nor will an unexpected blast of desiccating heat that strikes an area Tuesday into Wednesday. So the map provides a record of and look back at conditions that unfolded from Tuesday of one week to the next week, not a look forward.”
The U.S. Drought Monitor is produced through a partnership between the NDMC at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration.
This week’s map and other drought data for the U.S. through July 10, 2018 are available at droughtmonitor.unl.edu. Additional NDMC resources for drought data include:
Drought Impact Reporter at droughtreporter.unl.edu
Quick Drought Response Index (QuickDRI) at quickdri.unl.edu
U.S. Agricultural Commodities in Drought at agindrought.unl.edu
Vegetation Drought Response Index (VegDRI) at vegdri.unl.edu