The Planet

Hurricane Harvey Has Dropped So Much Rain, The National Weather Service Had To Make A New Map

by Tod Perry

August 29, 2017

If there’s one word that’s been used most frequently to describe Hurricane Harvey’s impact on southeast Texas and southwestern Louisiana it would be “unprecedented.” It’s been labeled a “once-in-500 years storm,” and the governor of Texas said that after everything has blown over, residents will have to find a “new normal.” The National Weather Service — no stranger to extreme weather events — has said the storm is “unprecedented and all impacts are unknown and beyond anything experienced.” 

The amount of rain that has deluged southeast Texas is so unheard of, the National Weather Service created new color charts to “effectively map it.” 

The old scale the service used ranged from 0.1 inch to 15 inches and used 13 colors from light green to purple. Hurricane Harvey has forced it to change its dark purple color to denote 15-20 inches and then adds two more shades to mark 20 to 30 inches and 30 and more. 

For some perspective, as of Tuesday morning, Harvey has dropped over 49 inches of rain on Houston. That’s just three inches shy of the all-time U.S. rainfall record of 52 inches in 1952 by Hurricane Hiki in Hawaii. According to meteorologist Ryan Maue, current rainfall totals across southeast Texas are now in the range of 14 to 15 trillion gallons. 

One reason for the unprecedented storm could be new weather pattens created by climate change. There is a well-established physical law, the Clausius-Clapeyron equation, which states that a hotter atmosphere holds more moisture. “The waters of the Gulf of Mexico are about 1.5 degrees [Celcius] warmer above what they were from 1980-2010,” Sir Brian Hoskins from the Grantham Institute for Climate Change told the BBC. “That is very significant because it means the potential for a stronger storm is there, and the contribution of global warming to the warmer waters in the Gulf, it’s almost inevitable that there was a contribution to that.” 

Share image via National Weather Service/Twitter.

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Hurricane Harvey Has Dropped So Much Rain, The National Weather Service Had To Make A New Map