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NOAA: D.C.'s Blizzard Measurement Accurate

August 14, 2017
By David Dishneau, The Associated Press
A weather observer at Reagan National Airport lost a snow-measuring device during the January blizzard but still accurately recorded a snowfall total that was lower than in nearby Washington, the National Oceanic and Atmospheric Administration said Thursday.

The report resolves questions about why the 17.8-inch measurement from the Jan. 22-23 storm was so much lower than the 21-to 26-inch readings taken in the District of Columbia. Those questions, along with previously known errors in snow measurements elsewhere, prompted the agency to review January blizzard data from eight locations from Washington to New York.

Their findings substantiated the Reagan National total; invalidated a Newark, New Jersey, record; and resulted in a new record for New York's Central Park.

The report upholds the practice of measuring snowfall with 2-foot-square white boards, checked every six hours. But it recommends attaching flags to the boards so they can't get lost in the snow. That's what happened at Reagan National, as first reported in January by The Washington Post.

"While the observer could not locate the snow measurement board for several hours during the afternoon of January 23, proper measuring procedures were followed," the report reads. It says the unidentified observer "took particular care to measure the snow and ensure accuracy of the snowfall totals."

He used an approved alternate method of measuring snow depth from the ground to the top, and then subtracting his last measurement to determine the new snowfall amount, Andy Horvitz, National Weather Service meteorologist and co-leader of the blizzard review team, said in an email.

Although the resulting snowfall total was lower than those in Washington, it was close to totals from other nearby sites in northern Virginia, the report says.

"Snow measurements are extremely difficult to take because precipitation is inherently variable, a problem compounded by strong winds and compaction during a long duration event," National Weather Service Director Louis Uccellini said in a statement. "Still, it's important that we scrutinize questionable measurements and reject those that scientists deem invalid to ensure the public's continued confidence in the U.S. climate record.'"

Horvitz said checking a board more frequently than every six hours can inflate the measurement by not allowing for standard compaction. The report says that's what happened at Newark Liberty International Airport, where weather observers took hourly measurements to improperly calculate an all-time record snowfall of 28.1 inches. The review team found that the observers may have been measuring snowfall improperly since 1996.

"A separate team will investigate the best course of action to determine the accurate snowfall total and, as appropriate, amounts may be changed," the report says. The Newark observers have been retrained on proper procedures, the agency said.

The report says a 26.8-inch storm total reported by the National Weather Service for New York's Central Park will be changed to an all-time record 27.5 inches. The error stemmed from miscommunication between the Central Park Conservancy, which correctly measured the snowfall, and the weather service's New York forecast office, the report says.

The blizzard dropped more than 40 inches of snow in some areas and set or tied 25 all-time, one-day snowfall records, Horvitz said.

He said several of the report's 11 recommendations apply nationwide.

Copyright 2016 The Associated Press. All rights reserved.

Image: In this Jan. 23, 2016, file photo, despite adverse weather conditions, people visit New York's Central Park as a large winter storm enveloped the East Coast.(AP Photo/Craig Ruttle, File)