Cold Fronts Tame August Heat

Tue, Sep 01, 2020

Three strong cold fronts brought the summer heat to its knees during August, but drought took advantage of a mostly dry month to proliferate across western Oklahoma. The far southeast was anything but parched, however, after several rounds of heavy precipitation and a brush with the outskirts of Hurricane Laura left it with nearly a foot of rain for the month. There were sporadic outbursts of severe weather during August. Straight line winds of 70 mph and greater were suspected in the derailment of 16 train cars in Ellis County on August 10, and the Oklahoma Mesonet site at Burneyville recorded a wind gust of 80 mph on the 16^th. Mother Nature saved the most exciting weather for last, though, with a strong cold front on August’s final day. The front kicked off several rounds of storms that brought widespread severe weather and flooding. Numerous water rescues of stranded motorists were reported with flash flooding across central and southeastern Oklahoma, and hail to the size of golf balls fell with many of the storms.

The triple dose of cold air during August brought Oklahoma’s statewide average temperature down 1.8 degrees below normal according to preliminary data from the Mesonet. The month finished at 79 degrees to rank as the 26^th coolest August on record, dating back to 1895. Heat was still present during August, owing to its summer roots. Temperatures soared into the triple digits at times, topping out at 110 degrees at both Camargo and Hollis on the 28^th. Oklahoma City recorded its first triple-digit temperature of the summer that day at 102 degrees. Heat index values indicated oppressive heat was even more widespread. Idabel’s heat index rose to 118 degrees on the 29^th. The Mesonet’s 120 sites recorded heat index values of at least 105 degrees 546 times during August. The state’s lowest temperature was 53 degrees at Cookson on the 19^th. Summer finished with a statewide average temperature of 80.1 degrees, 0.5 degrees above normal to rank as the 58^th warmest June-August on record. The first eight months of the year ranked as the 25^th warmest at 63.2 degrees, a degree above normal.

August was dry for the most part, but saved somewhat by the late-month storm system that brought flooding rains across central and southeastern Oklahoma. The statewide average total of 2.94 inches was just 0.01 inches below normal to rank as the 57^th wettest on record. That total belied the actual experiences across the state, however. The Panhandle fell 1.13 inches below normal for their 29^th driest August on record, while the southeast was 4.06 inches above normal for their fifth wettest. The far southeast was 4-8 inches above normal, bolstered by tropical rains from Hurricane Laura. Nevertheless, most of the state was somewhere between 1-3 inches below normal. The Mesonet site at Broken Bow led the month’s totals at 11.13 inches, and Blackwell brought up the rear with 0.49 inches. The summer finished at 9.55 inches to rank as the 55^th driest on record, 0.80 inches below normal. The January-August average total of 28.06 inches was 3.2 inches above normal to rank as the 21^st wettest such period on record.

The worst drought conditions continued across southwestern and west central Oklahoma. The U.S. Drought Monitor portrayed most of the western third of the state in moderate-to-severe drought intensity, with small areas of extreme drought centered on Harmon and Beckham counties. Severe drought also existed in northern Cimarron County. The Drought Monitor’s intensity scale slides from moderate-severe-extreme-exceptional, with exceptional being the worst classification. The chance for drought relief appears greatest in the main body of the state, according to the Climate Prediction Center’s (CPC) September drought outlook. The drought is expected to persist and possibly intensify where it currently exists in the Panhandle. The drought outlook is based partly on CPC’s September precipitation outlook, which sees increased odds of above normal precipitation in all but the Panhandle, where increased chances of below normal rainfall are indicated. The September temperature outlook shows increased chances for below normal temperatures across the eastern two-thirds of Oklahoma.