Midwest heatwave in late August 2013

A heat wave struck the Midwest in late August and early September 2013. Daytime highs were 6 degrees above average, and nighttime lows were 11 degrees above average in late August. (In contrast, the first three weeks of the month had temperatures 2 to 8 degrees below average.) Through September 8, all-time daily record highs were tied or broken at 328 weather stations in the Midwest and High Plains.

This map shows the hottest temperatures in the United States between August 25 and September 8, 2013, based on data from NOAA's Real-Time Mesoscale Analysis. Areas with higher temperatures appear red and magenta; areas with lower temperatures appear light yellow. The heart of the country, from southern Texas northward through the Dakotas, saw wide areas where temperatures on at least one day topped 100 degrees.

On August 29, the National Weather Service reported, "An expansive upper level ridge will keep the central and southern plains hot and dry. Temperatures will be as much as 20 degrees above normal in some locations with highs nearing 100 degrees today." A high-pressure system extended from Mexico northward through South Dakota, and from Arizona eastward to the Georgia coast. The high-pressure ridge brought hot, dry conditions to the Central Plains.

Heat waves and cold snaps can occur in any climate system, and indeed the Central Plains experienced cooler-than-normal temperatures for most of August 2013. But in a warming climate, the odds of heat waves increase. A 2009 report by the U.S. Global Change Research Program (USGCRP) named more frequent heat waves among the risks for the Great Plains over the 21st century. A 2012 study using a high-resolution climate model experiment indicated that by the mid-21st century, heat waves would likely be more frequent and longer lasting.

Thanks to Steven Levine and others at the NOAA National Center for Environmental Prediction for their explanations of the RTMA data product. 

References

Climate.gov. (2012, August 29). With rising greenhouse gases, U.S. heat waves to become more common and longer-lasting. Accessed September 3, 2013.

Karl, T.R., Melillo, J.M., Peterson, T.C., eds. (2009). Global Climate Change Impacts in the United States. Cambridge University Press.

National Weather Service Weather Prediction Center. (2013, August 29 - September 3). Short Range Public Discussion. Accessed September 3, 2013.

Eise, J. (2013, Sept. 2). Personal communication.

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John Eise - NWS Central Region Headquarters