Домой United States USA — Science What went wrong with Charlotte’s snow forecast?

What went wrong with Charlotte’s snow forecast?

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NewsHubHundreds of thousands of Charlotte-area residents who went to bed Friday night, expecting to see snow-covered yards Saturday morning, awoke instead to a crust of ice over an otherwise-barren landscape.
The National Weather Service predicted snowfall of 4-8 inches across Mecklenburg County, but less than an inch was on the ground at Charlotte’s official reporting station, Charlotte Douglas International Airport, when daybreak arrived.
What went wrong?
“Storm shifted northwest at last minute,” WBTV meteorologist Al Conklin tweeted to one area resident Saturday morning. “It happens. It’s weather.”
Or, as Conklin told viewers, “Weather is not a perfect science.”
Charlotte’s loss was the northern Piedmont and foothills’ gain. Places like Statesville, Hickory and Lenoir, where 3-5 inches were expected, instead got double that amount.
The busted forecast was similar to a storm in February 2015, which was expected to bring 4 or more inches to Charlotte – and didn’t. In both cases, the rain-snow dividing line was 25 to 50 miles farther north than predicted.
Meteorologists base much of their forecasts on computer models. Those are programs that take atmospheric data, add in results from past events, and produce forecasts.
Earlier in the week, computer models showed a major winter storm affecting the Carolinas. The models also showed cold air from an arctic mass reaching the Carolinas before the precipitation arrived.
By late Thursday, one model – the North American (or NAM) – began predicting the low pressure system would cross Florida near Jacksonville. That is farther north than other models were forecasting. In addition, the NAM showed colder air not arriving as quickly as the other models showed.
Throughout the day Friday, the NAM stuck to its guns, showing a lot of rain and sleet for places like Charlotte and Raleigh. The other models predicted heavy snow.
Charlotte’s TV meteorologists began preparing residents by late Friday afternoon, cautioning that snowfall totals south of the city could be much less than earlier predicted.
On Saturday morning, meteorologists like Conklin and the National Weather Service’s Trisha Palmer noted that the cold air was playing catch-up with the precipitation to the southeast of I-85.
As Palmer noted, “I’m guessing that probably half of the residents across the area are happy with us right now, and the other half not so happy.”
The air finally got cold enough for a final area of precipitation from the storm to fall as snow Saturday morning in Charlotte. But the overall impact of the system was far different than expected.

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