Flooding swamped parts of the Southeast over the weekend, with as much as a foot of rain falling in western North Carolina. At the same time, the Mississippi River continued its long-lasting assault on communities along its banks. Near St. Louis, the crest over the weekend was second highest on record.
Just the latest high-water news, during what has seemed like a never-ending parade of storms.
During May, a stormy pattern, headlined by widespread flooding in the nation’s heartland and a two-week swarm of tornadoes, boosted the nationally-averaged precipitation to the second highest level on record for the month. The 4.41 inches was 1.5 inches above normal, only trailing 2015’s 4.44 inches, according to the National Oceanic and Atmospheric Administration.
The substantial May total helped pushed the most recent 12-month output for the Lower 48 states to the highest level in 125 years of record-keeping (since 1895): 37.68 inches. It easily topped the previous record 12-month total of 36.20 inches set just last month.
Following a wet 2018, flooding of 2019 burst onto the scene in the central U.S. during mid-March, when snow-melt and heavy rain inundated parts of Nebraska and Iowa. Since then, flash flooding and river flooding have engulfed large portions of the Plains and Midwest as well as the Corn Belt.
But the deluges have fanned out from this region at times, including Houston last week, and now the Southeast.
Until the rains arrived this weekend, parts of the Southeast were facing the sudden onset of drought thanks to a persistent dome of sinking air that produced both extreme heat and excessively dry conditions in late May.
Aside from that, the Lower 48 has mostly seen record low drought coverage this spring, tied to the record 12-month rainfall. The 37.68 inches averaged over the nation since last June is a whopping 7.73 inches above average.
The magnitude of the rainfall is likely related to the presence of El Niño, the episodic warming of waters over the tropical Pacific Ocean which tends to increase storminess in the southern U.S. Yet this last 12-month rainfall average bests prior records coming out of the strong El Niño winters (1972-73 and 1982-83) by more than two inches.
While it is likely that the weak El Niño is intensifying rainfall over the Lower 48, increases in heavy rain events are also among the most anticipated and well-documented impacts from climate change.
May was characterized by warm extremes in the Southeast and simultaneously cold extremes in the north-central. Such a contrasting pattern, which may become more common in a warming world, breeds storminess.
In the short term, there’s some good news for the flood-weary. A less active pattern is expected for the next week or so in the central U.S. After that, a stormy pattern may try to resume by the latter portion of June.