Heat and Drought Surge Once Again in Oklahoma

Published: Thursday, July 19, 2012

The drought plaguing much of the interior United States continues to stretch its tendrils into Oklahoma. Some experts claim the country’s current drought is the worst in a generation and possibly the largest since the great droughts of the 1930s and 1950s. In Oklahoma, significant heat along with mounting rainfall deficits have allowed drought to flourish once again. This morning’s release of the U.S. Drought Monitor report indicates severe to extreme drought had crept into the state from both the east and the west, with 64 percent of Oklahoma now portrayed in at least severe drought. That is the highest such level since Nov. 22, 2011, when the drought had just begun to diminish following its zenith in October. Approximately 15 percent of the state is considered in the extreme drought category, the highest percentage since early March when the drought appeared headed towards extinction. The Drought Monitor’s intensity scale slides from moderate-severe-extreme-exceptional, with exceptional being the worst category.

Unfortunately, the drought-quenching rains that extended through winter into March disappeared as the state’s primary rainy season approached. According to data from the Oklahoma Mesonet, the statewide average rainfall deficit from April 1 through July 18 grew to more than 5 inches. The statewide average total over that period was 8.95 inches, the fourth driest on record dating back to at least 1921. Parts of eastern Oklahoma are up to a foot below normal, while the northwestern corner of the state is running a comparable 6-8 inch deficit. The rainfall deficits steepened deeper into the rainy season. Since May 1, the statewide average rainfall total stood at 5.14 inches, nearly 6 inches below normal and the second driest May 1-July 18 dating back to at least 1921. For north central Oklahoma, it was the driest such period since 1921 with an average total of 3.21 inches, 7.4 inches below normal. Southwestern Oklahoma fared the best since May 1 with an average total of 5.95 inches, still a deficit of 4.4 inches, for a dismal ranking of 10^th driest since 1921.

The drought impacts continue to mount. There are 29 county burn bans in effect as the vegetation that was allowed to thrive during the warm and wet early spring dries out, becoming fuel for wildfires. Reports of cattle sell-offs due to diminishing stock ponds and a lack of hay or pasture are becoming more numerous, and warm-season crop conditions show further deterioration. The USDA rated 91 percent of the state’s topsoils as being either short or very short of moisture, with a similar rating of 89 percent for the subsoils. State reservoirs have seen a steepening decline through the dry weather. Lake Altus-Lugert, an important irrigation lake for the cotton crop in the southwest, is down to 21 percent of its conservation pool. A part of Oklahoma City’s water supply chain upstream to the northwest, Canton Lake has faced steady declines and is now at 50% of its conservation pool. Several of the state’s largest reservoirs are between 80-85 percent of their conservation pools, such as Skiatook at 82 percent and Eufaula at 85 percent.

The outlook for relief is a bit bleak, at least in the short term. The Seasonal Drought Outlook released Thursday morning by the Climate Prediction Center calls for drought to persist or intensify over much of the United States, including Oklahoma, through at least the next couple of weeks. All indicators continue to favor above normal temperatures through August and the August-October period. Further heat would allow for continued drought intensification should rainfall remain scarce. Widespread triple-digit temperatures have returned to the state in recent days. The average temperature for July thus far is 2.5 degrees above normal, well on its way to becoming the 23^rd month out of the last 28 to finish warmer than normal. Oklahoma continues on a possible course towards its warmest year on record, dating back to 1895. The statewide average January-June temperature finished at a record 60 degrees, 5 degrees above normal and besting 2006’s 58.9 degrees. The mark for the state’s warmest year on record remains 1954’s 62.8 degrees.