May Weather Brings Disaster to Oklahoma

Tornadoes and flooding battled it out for Oklahoma’s top weather headline during May 2019, with both combatants bringing mayhem and misery to the state. The scope and scale of the weather disasters prompted Gov. Kevin Stitt to declare a State of Emergency for all 77 counties. According to reports from the Oklahoma Department of Emergency Management, at least six fatalities and 118 injuries were attributed to the flooding and severe weather. Preliminary reports from the National Weather Service (NWS) office in Norman indicate at least 61 twisters struck Oklahoma during May, a number that is expected to rise as more damage areas are investigated. Of those 61 tornadoes, eight were considered “strong” on the Enhanced Fujita Scale, rated as EF2 or EF3. Combined with the 22 confirmed touchdowns during April, the 2019 total stands at 83. Oklahoma averages 23.2 tornadoes during May and 56.2 per year based on 1950-2018 counts. Two fatalities due to tornadoes were reported during May, both from a trailer park in the path of an EF3 tornado that briefly touched down in eastern El Reno. The total tornado deaths during 2019 rose to four according to NWS reports, all in mobile homes during EF3 tornadoes.

Flooding was the most widespread and damaging of the weather hazards during May, with entire communities seemingly engulfed in flood waters at times. Historic rains in Oklahoma and upstream in Kansas swelled creeks and rivers, and overflowed reservoirs and dams across the state. The flood waters did not discriminate as both urban centers and rural areas were inundated. Voluntary and mandatory evacuations were required downstream of several reservoirs due to water releases and fear of dam failures. Extensive flooding was occurring along the Arkansas River’s path through Oklahoma from the Kansas to Arkansas borders. The river crested near or above record levels along its route through the state. Flooding along the river in Tulsa was the worst that city has seen since 1986 as levee systems designed to protect low lying areas were threatened by the rising water. The small town of Moffett in Sequoyah County was completely swamped by flood waters, forcing its evacuation. Braggs in Muskogee County was surrounded, isolating it from the outside and forcing air evacuations. The swollen Cimarron River swept away homes as it undercut the river’s banks. Hundreds of roads were closed throughout the state due to high waters, and an untold number of stranded motorists required water rescues due to flash flooding.

According to preliminary data from the Oklahoma Mesonet, the statewide average rainfall total was 10.48 inches, 5.66 inches above normal to rank as the third wettest May since records began in 1895. The total also earned fourth place on the list of wettest calendar months in Oklahoma. Tops on that list was May 2015’s 14.44 inches, followed by October 1941 and May 1957 with 10.75 inches and 10.54 inches, respectively. North central Oklahoma’s average of 12.2 inches was 7.84 inches above normal, ranking it as the wettest calendar month on record for that part of the state. Central, northeastern, and west central sections saw their second wettest Mays on record. Most of the heftiest rainfall totals occurred along that corridor from west central through northeastern Oklahoma. The NWS cooperative observer site at Pawnee led the state with 22.52 inches, although there was a report of 24.69 inches by a volunteer observer near Talala. At least 24 NWS sites broke their all-time May rainfall mark. Nineteen of those sites broke their all-time wettest calendar month marks as well, including seven sites whose records date back over 100 years. The Mesonet site at Talala recorded 19.6 inches. Of the 120 Mesonet sites, 66 recorded more than 10 inches of precipitation, while all but six received at least 5 inches. The Kenton site received 2.13 inches of rain during the month for the lowest total, but that was still 0.07 inches above normal. The climatological spring – March 1 through May 31 – ended as the fourth wettest on record with a statewide average of 17.16 inches, 6.04 inches above normal. The first five months of the year were 6.23 inches above normal at 20.74 inches to rank as the fourth wettest such period on record. The northeast experienced its wettest January-May on record with an average of 28.2 inches, 11.16 inches above normal.

The excessive rains and associated cloudiness kept high temperatures 2-3 degrees below normal, although the surge of warm, moist air from the Gulf of Mexico had the opposite impact on low temperatures. The clouds and rain won out, however, and the statewide average temperature finished at 66.7 degrees, 1.5 degrees below normal to rank as the 34^th coolest May on record. The season’s last freeze occurred on May 22 when Eva reached a low of 32 degrees. Eva recorded the only other sub-freezing temperature of the month with 31 degrees reported on May 10. Altus and Beaver grabbed the state’s top reading of 93 degrees on the 28^th and 16^th, respectively. Spring’s statewide average of 58.2 degrees ranked as the 37^th coolest on record, 1.1 degrees below normal. The first five months of 2019 ended almost a degree below normal, the 54^th coolest on record.

Dry conditions were but a memory for the state by the end of May. The June precipitation and temperature outlooks from the Climate Prediction Center (CPC) indicated greatly increased odds of below normal temperatures and above normal precipitation for much of the state. Given the wet, cool forecast, CPC’s U.S. Monthly Drought Outlook for June did not foresee any drought development within the Southern Plains or Oklahoma.