NewsJuly 26, 2012

Drought Tightens Its Grip on High Plains, Central States

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Andrew Freedman

By Andrew Freedman

The massive U.S. drought, which is already driving food prices skyrocketing and prompting federal disaster declarations, has only grown worse during the past week. According to the latest edition of the U.S. Drought Monitor, released Thursday morning, between July 17 and July 24, the portion of the country affected by “extreme” to “exceptional” drought jumped from 14 percent to about 21 percent. The portion of the country affected by exceptional drought, which is the most significant drought category, rose from 1 percent last week to 2.4 percent this week. 

U.S. Drought Monitor released on July 26. Click on the image for a larger version. Credit: NOAA/USDA.

In all, 33 of the lower 48 states were experiencing moderate drought or worse, with every state in the lower 48 experiencing at least “abnormally dry” conditions. For the fourth straight week, the U.S. set a record for the largest area of moderate drought conditions or worse since the U.S. Drought Monitor began in 2000. And climate outlooks for the next few months don't offer much hope for sustained rainfall in the most severely affected drought regions, with above-average temperatures and below-average precipitation likely during the rest of the summer.

As it has for most of the summer so far, the weather pattern across the U.S. was dominated by a huge dome of High Pressure, more popularly referred to as a “heat dome,” that brought stifling air to the Central states. High temperatures were in the 100s Fahrenheit from the Great Plains to the Midwest. St. Louis, Mo., for example, set a record for the most days with a high temperature of 105°F or greater in a single calendar year with 11. That beat the record of 10 such days, set during the Dust Bowl year of 1934, and included a high temperature of 108°F on July 25.

While the drought is likely related to natural climate variability, including a long-lasting La Niña event that is still winding down, manmade climate change has likely made the drought worse by making the drought hotter than it otherwise would be. Extreme heat can help perpetuate drought conditions, since soils dry faster during periods of higher temperatures. This dynamic occurred during the 2011 Texas drought and heat wave, which cost farmers and ranchers in that state billions in losses.

“This drought is two-pronged,” said Brian Fuchs, a climatologist at the National Drought Minitgation Center in Lincoln, Neb., said in a press release. “Not only the dryness but the heat is playing a big and important role. Even areas that have picked up rain are still suffering because of the heat.”

The drought mainly intensified in the region that was under the influence of this High Pressure area, since the sinking air near the High prevented showers and thunderstorms from forming. In Nebraska, for example, the area affected by extreme-to-exceptional drought increased from about 5 percent on July 17 to 64 percent on July 24, a 13-fold increase. Similarly, in Illinois the area affected by extreme-to-exceptional drought jumped from about 8 percent to about 71 percent. Large increases in the most severe drought categories were also seen in Indiana and Kansas.

Estimated rainfall totals for July 25, showing the dry weather in areas under the influence of the large “heat dome” over the Central States. Click on the image for a larger version. Credit: NOAA/Climate Central.

Some beneficial rainfall has occurred in the Midwest, Northeast, and parts of the Mid-Atlantic states, including rains that fell since July 24. However, the rain has been too little, too late to help farmers, and little rain fell in the most hard-hit drought areas.

According to the latest national drought summary, 55 percent of the country's pasture and rangeland was in poor to very poor condition, setting a record that was originally set just last week. On July 25, the U.S. Department of Agriculture expanded its drought disaster declaration to cover 76 additional counties, for a total of 1,396 counties in 31 states.

In Kansas, Arkansas, Missouri, Illinois, and Indiana, more than 80 percent of the pasture and rangeland was rated in poor or very poor condition, the drought summary said. “Corn, soybean, sorghum, and alfalfa losses continued to mount, ponds dried up, and wells failed in several of the[se] states,” the summary said.