May Sees Numerous Severe Weather Days

Known as the state’s most active severe weather month, May tried to live up to that moniker with several extended periods of threatening weather. Although it didn’t quite match some of the more ferocious Mays since the beginning of the decade, it was still quite lively nonetheless. At least one instance of severe weather was reported somewhere in the state on 16 of the 24 days between May 8 and May 31. The National Weather Service published a preliminary count of 19 tornadoes during May, four short of average for the month. That total could rise with further investigation, however, including the possibility of several weak tornadoes on the month’s final day in central Oklahoma. The preliminary count for the year thus far stands at 49. May 9 was the most violent day with at least 12 tornadoes being reported. That total included several significant tornadoes across south central Oklahoma that left two dead and several others injured. The two fatalities, both 76 year old males, occurred near Katie in an EF-4 monster that churned through Garvin County and near Connerville in an EF-3 tornado. The Sulphur Mesonet site recorded a wind gust of 88 mph associated with those storms, and softball size hail fell near Wapanucka in Coal County. 


Despite the active weather, May ended drier than normal across much of the state. Data from the Oklahoma Mesonet estimate a statewide average of 4.12 inches, 0.70 inches below normal and the 51st driest May since records began in 1895. As is customary for convective precipitation, however, the fortunes of differing areas of the state varied dramatically. Far southern Oklahoma received 5-8 inches while west central Oklahoma totaled 1-2 inches. In fact, much of the state saw rainfall totals drop from 1-4 inches below normal. May rainfall totals from the Mesonet ranged from 12.39 inches at Cookson to less than an inch at two Panhandle locations. Despite the disappointing rainfall totals, the climatological spring season (March-May) ended as the 31st wettest since 1895 with a statewide average of 12.34 inches, about an inch above normal. Again, some areas fared better than others over the season with south central Oklahoma seeing its 11th wettest spring while west central sections experienced their 55th driest. Those same variations were exhibited in the year to date rainfall statistics as well with the 24th wettest January-May on record for south central Oklahoma and the 35th driest for west central sections. Overall, the first five months of the year were about an inch below normal at 13.88 inches.


May was unusual not only for its lack of rainfall, but also for its lack of warmth. According to preliminary data from the Oklahoma Mesonet, the statewide average temperature for the month was 65.9 degrees, 2.3 degrees below normal to rank as the 21st coolest May since records began. None of the 120 Mesonet stations observed a triple-digit high temperature during May. The month’s last freeze – and lowest temperature of the month – was recorded at Boise City with 31 degrees on May 2. The highest temperature was 99 degrees at Altus on May 10. Despite the cool May, the spring season was the 25th warmest on record with a statewide average of 60.7 degrees, 1.4 degrees above normal. The first five months of the year exceeded normal by 2 degrees, the tenth warmest January-May on record.


The June outlooks from the NWS’ Climate Prediction Center (CPC) call for increased odds of below normal temperatures across all of Oklahoma and above normal precipitation across southern Oklahoma. Those outlooks are based upon forecasts for heavy precipitation and the associated lack of sunshine during the first week of June according to CPC forecasters. The strong El Niño that impacted weather across the globe, including the enhanced rainfall amounts of 2015 in Oklahoma, has all but ended. Forecasters at CPC now conclude the equatorial pacific waters will enter neutral conditions for a few months before quickly transitioning to La Niña during the summer and then strengthen through this fall and winter. While there is no indication yet of the strength of this La Niña, possible impacts include drier and warmer than normal weather from late fall through mid-spring 2017.


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