National Drought Mitigation Center


Sept. 4 U.S. Drought Monitor shows Isaac brought needed rains to Midwest but Plains drying out

September 6, 2012

The slow-moving rains from Hurricane Isaac eased drought over Louisiana, Arkansas, Missouri, Illinois, Indiana and Ohio, according to the U.S. Drought Monitor map released today, but drought intensified over Nebraska and surrounding states.

 “The big story of this week has been the track of the remnants of Isaac,” said Brian Fuchs, a climatologist at the National Drought Mitigation Center at the University of Nebraska-Lincoln and this week’s U.S. Drought Monitor author. “We saw two-category improvements in some areas of Missouri, Illinois and Arkansas, but other places such as northwest Arkansas and southwest Missouri completely missed out on any precipitation.”

Despite dramatic rainfall totals in some areas – parts of Louisiana saw 10 inches, which brought major flooding; and areas in Missouri, Illinois and Indiana recorded 2-6 inches – drought intensified over much of the Great Plains. Statistics released with the map showed that the area of the United States in moderate drought or worse actually increased to 53.06 percent of the country, up from 52.63 percent last week.

Outside Isaac’s wake of drought relief, exceptional drought expanded to cover nearly all of Nebraska, extending into Wyoming, South Dakota, Iowa and Kansas. “We determined that conditions and indicators within the last 90 to 120 days were at extreme levels,” Fuchs said. “The agricultural impacts are being realized, and we’re seeing fires due to the dryness in northwest Nebraska and into South Dakota.

In Louisiana, which was mostly drought-free last week, moderate drought or worse receded to 15.24 percent from 26.21 percent; Arkansas saw reductions in all categories of drought; Missouri saw the area in extreme or worse drought drop to 31.88 percent from 97.44 percent; Illinois had reductions in all categories, with all exceptional drought erased from the map, and extreme drought declining to 6.96 percent from 69.56 percent; and Indiana saw 39.22 percent in extreme and 10.8 percent in exceptional drought disappear from the map, reduced to severe or less.

In the other direction, the portion of Nebraska in exceptional drought jumped to 70.58 percent this week from 23.33 percent the previous week. In Kansas, exceptional drought increased to 60.61 percent from 55.18 percent. Wyoming saw overall intensification, with the largest increase in extreme drought, up to 58.48 percent from 37.05 percent. South Dakota also showed overall intensification in all categories of drought.

An area labeled “L” for long-term over Arkansas, Missouri, Illinois and Indiana means that “the short-term indicators such as soil moisture were relieved substantially, but there are still long-term concerns such as river levels and streamflow through much of the area,” Fuchs said. “Rivers and streams peaked and we’re seeing them come back down after the runoff has subsided. They’re still declining.”

To the west, extreme drought receded in the Four Corners region in Utah and Colorado, thanks to a consistent wet pattern, Fuchs said.

In addition to the slight increase in the area in moderate drought or worse, the map showed 35.53 percent in severe drought or worse, compared with 35.42 percent a week earlier; 17.99  percent in extreme drought or worse, compared with 19.38 percent the week before; and 5.13  percent in exceptional drought, compared with 5.05 percent the preceding week.

Crops in Drought

Brad Rippey, meteorologist, Office of the Chief Economist, U.S. Department of Agriculture, said analysis of this week’s maps showed:

  • U.S. corn in drought dropped two percentage points to 83 percent, well below the July 24 peak of 89 percent.
  • U.S. soybeans in drought dropped two percentage points to 80 percent, below the July 24 peak of 88 percent.
  • U.S. hay in drought remained steady at 63 percent for the fifth consecutive week, down from a high of 66 percent on July 17 and 24.
  • U.S. cattle in drought remained unchanged at 72 percent, one point below the July 17 and 24 peak of 73 percent.
  • Over the last week, crops and cattle in extreme to exceptional drought (D3 to D4) decreased somewhat from 48 to 36 percent of the corn; from 45 to 30 percent of the soybeans; from 31 to 27 percent of the hay; and from 37 to 35 percent of the cattle.


The patterns in place now are likely to persist, Fuchs said, referring to the latest Seasonal Drought Outlook, released today and valid through Nov. 30. “It shows improvements over the southwestern U.S., especially in Arizona and the Four Corners region,” he said. “But drought is likely to persist through much of the Great Basin, Rocky Mountains, and central and southern Plains. It’ll keep improving over the Midwest and Southeast and New England. Drought will persist and develop throughout the Hawaiian Islands.”

About the U.S. Drought Monitor

Drought Monitor authors synthesize many drought indicators into a single map that identifies areas of the country that are abnormally dry (D0), in moderate drought (D1), in severe drought (D2), extreme drought (D3) and exceptional drought (D4).

The U.S. Drought Monitor map is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the National Oceanic and Atmospheric Administration, the U.S. Department of Agriculture, and about 350 drought observers across the country. It is released each Thursday based on data through the previous Tuesday.

Statistics for the percent area in each category of drought are automatically added to the U.S. Drought Monitor website each week for the entire country and Puerto Rico, for the 48 contiguous states, for each climate region, and for individual states:

The National Climatic Data Center maintains drought data based on the Palmer Drought Severity Index, calculated to the beginning of the historic record:

U.S. Drought Monitor:

Seasonal Drought Outlook:

U.S. Department of Agriculture’s running tally of farm and food impacts from the Drought of 2012:

-- Kelly Helm Smith, National Drought Mitigation Center