Flooding continues in Louisiana in wake of 1,000-year rains
Last week, more than two feet of rain fell in northwest Louisiana and portions of Arkansas and Texas, transforming the landscape into raging rivers and newly formed lakes.
Several thousand homes have been flooded in Louisiana, where rivers have reached all-time record highs, in some cases rising to the height of power lines. The rains were so heavy that one meteorologist referred to the event as a "rain bomb" on Twitter.
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NASA's precipitation tracking satellite, known as the Global Precipitation Measuring mission, or GPM, captured the narrow bullseye of heavy rainfall.
The rains resulted from a stuck weather pattern that featured an unusually strong upper level low pressure system that acted like a pump, pushing an atmospheric river of moisture from the tropics toward the southern U.S.
Once the moisture got there, it encountered a stalled frontal boundary, which forced the air to rise, cool and condense into clouds and heavy precipitation.
This process continued over the same area for more than three days.
In some cases, the return period of the rains that fell near Monroe, Louisiana, and other communities is just 1-in-1,000 years, meaning that in an individual year there is just a 0.1% chance of such a heavy rainfall event occurring.
The Bayou Dorcheat at Lake Bistineau, for example, has been at record high levels since at least March 12.
The bulge of floodwaters coursing southward, which the National Weather Service is calling a "flood wave," is causing flooding downstream.
The Sabine River near Deweyville, along the southwestern Louisiana border with Texas, has also exceeded its all-time record high.
The flooding has killed at least four people, and President Obama has declared a major disaster in Louisiana, freeing up federal aid to flow to the region.
Detailed attribution studies have not yet been conducted to determine if human-caused global warming influenced the likelihood of or the severity of this extreme weather event.
However, many studies published during the past several years have shown that heavy precipitation events are becoming more common and severe in some parts of the world, as global warming adds more moisture to the atmosphere.
In addition, some climate scientists think global warming may be tilting the odds in favor of long-duration weather events.
A new, comprehensive report from the National Academy of Sciences released on March 11 shows that climate science has advanced to the point where the frequently-made caveat that no single extreme event can be tied to climate change is invalid.
The report states:
In the past, a typical climate scientist’s response to questions about climate change’s role in any given extreme weather event was “we cannot attribute any single event to climate change.” The science has advanced to the point that this is no longer true as an unqualified blanket statement.
A study published on March 7, for example, showed that extreme precipitation events are increasingly common worldwide.
Andrew Freedman is Mashable's Senior Editor for Science and Special Projects. Prior to working at Mashable, Freedman was a Senior Science writer for Climate Central. He has also worked as a reporter for Congressional Quarterly and Greenwire/E&E Daily. His writing has also appeared in the Washington Post, online at The Weather Channel, and washingtonpost.com, where he wrote a weekly climate science column for the "Capital Weather Gang" blog. He has provided commentary on climate science and policy for Sky News, CBC Radio, NPR, Al Jazeera, Sirius XM Radio, PBS NewsHour, and other national and international outlets. He holds a Masters in Climate and Society from Columbia University, and a Masters in Law and Diplomacy from The Fletcher School at Tufts University.
