The Amazing Rains of May: Photos and Stats

Now that May has mercifully drawn to a close, and the south-central states are drying out and cleaning up, we can take full measure of what an incredibly, destructively soggy month it was, especially for Texas and Oklahoma. Both states obliterated their rainfall records for any calendar month going back to 1895. While the rains quickly doused a multiyear drought (see Figure 3 below), the flooding killed at least 31 people, with 6 others missing as of Monday night, and inflicted at least $1 billion in damage, according to estimates from the insurance broker Aon Benfield. Below are a few memorable images from the past month—but first, some numbers:


Figure 1. Top-ten wettest months in the statewide averages for Oklahoma and Texas. The May 2015 values are preliminary. Data courtesy Gary McManus and John Nielsen-Gammon, the state climatologists for OK and TX respectively, from a database maintained by NOAA’s National Centers for Environmental Information (formerly the National Climatic Data Center).


As Figure 1 shows, the totals for both TX and OK in May exceeded the previous records by more than 30%, truly a phenomenal outcome. In fact, the gaps between the #1 and #2 outcomes are far larger than the gaps between #2 and #10! Texas state climatologist John Nielsen-Gammon (Texas A&M University) came up with a back-of-the-envelope estimate for how often you would expect such an extremely wet month in his state: about every 2000 years, assuming the climate of the past century were to persist. For more on the science behind recurrence intervals such as this and how they’re produced, see our post from last Saturday. Interestingly, no other single month appears on the top-ten wettest lists for both Texas and Oklahoma—another sign of how unusually widespread and persistent this event was.

The rains of May made weather history on a local scale as well. WU weather historian Christopher Burt assembled the preliminary list below of some cities that notched their all-time wettest months in May, including their periods of record (POR).

ARKANSAS
Ft. Smith: 19.85” (previous record 15.02”, June 1945; POR began 1882)

COLORADO
Colorado Springs: 8.13” (previous record 8.10”, May 1935; POR began 1894, with some data back to 1871)
La Junta: 7.38” (previous record 6.27”, Aug. 1916; POR began 1910)
Eads: 9.25” (previous record 8.60”, July 2014; POR began 1907)
Ft. Morgan 10.46” * (previous record 9.98”, Apr. 1900; POR began 1896)
(*Ft. Morgan data are from a CoCoRaHS station and not official)

OKLAHOMA
Oklahoma City: 19.48” (previous record 14.66”, June 1989; POR began 1891)
Lawton: 20.47” (previous record 16.67” ,June 2007; POR began 1912)

TEXAS
Wichita Falls, TX: 17.00” (previous record 13.22”, May 1982; POR began 1897)
Childress, TX: 13.21” (previous record 12.05”, May 1941; POR began 1897)

Burt adds: “The wettest location in the Oklahoma Mesonet was Lane, with an amazing 28.17”. If official, this would smash the previous OK state monthly precipitation record of 23.95”, set at Miami in May 1943.”

Bob Henson



Figure 2. Rainfall in May 2015 was far above all previous Mays in the Oklahoma City climatological record, as shown in this trace of cumulative totals achieved day by day. Image credit: Patrick Marsh, @pmarshwx.


Figure 3. The definition of Weather Whiplash: portions of Texas and Oklahoma went from the most extreme category of drought--"Exceptional"--to no drought whatsoever in just four weeks. A five-class improvement in drought in such a short period of time is bound to lead to serious flooding.


Figure 4. Sunlight filtered through clouds and rain casts a copper glow on flooded field near Lubbock, TX. The city saw a spectacular, drought-quenching series of storms in late May, although the month’s 12.12” of rain fell short of May 1941 (12.69”) and September 1936 (13.93”). Image credit: Jason Davis.


Figure 5. In Oklahoma City on May 23, a truck powers its way through high water--and serves a good example of what to avoid when behind the wheel during heavy rain. As little as two feet of water can sweep most vehicles off the road, and it only takes a few inches of water to obscure a road that might be washed out. (Jim Beckel/The Oklahoman via AP.


Figure 6. Canoes replaced motor vehicles on a road near Bear Creek Park in west Houston on May 30. Interpolation from rain gauges suggests that upwards of 13” of rain fell in 24 hours over one part of southwest Houston. Widespread flooding inundated large parts of the urban area. Image credit: AP Photo/David J. Phillip.


Figure 7. In northeastern Oklahoma, water poured through the Robert S. Kerr Lock and Dam along the Grand River on May 30 at the rate of 349,000 cubic feet per second, or about four times the average flow rate over Niagara Falls. Image credit: Tulsa District, U.S. Army Corps of Engineers.


Figure 8. Mike Graf stands on the foundation of his home near Wimberley, TX, on Stone Canyon Street after it was completely swept away by the Blanco River in the flood on Saturday night, May 23. "It's only things," he said. The flooding killed at least 8 people along the Blanco River, with several others still missing, and destroyed dozens of homes in and near Wimberley. Image credit: Jay Janner/Austin American-Statesman via AP.


Figure 9. This campground at Kaw Lake, in north-central Oklahoma near Ponca City, wasn’t getting much use on June 1. Image credit: wunderphotographer CReese.


Figure 10. The calm after the storm: a photo taken on Memorial Day, May 25, after the flooding had peaked at Bastrop, TX. Image credit: wunderphotographer Kiowa63.