Every decade, the National Oceanic and Atmospheric Administration releases a new analysis of average temperature and precipitation values across the country. The data is used to compile 30-year normals.
You’re probably most familiar with this data thanks to your local TV weatherperson. They’ll say something like today’s high temperature was much higher than normal. Or a big rainfall event will help with drier than normal conditions.
It’s information that can help you figure out what to wear before heading out the door – but it has a whole host of other, more long-term uses as well.
“They’re utilized by many economic sectors around the country to make decisions for time periods in the future when we don’t know what the weather’s going to be,” says Micheal Palecki with NOAA’s National Centers for Environmental Information – the group responsible with compiling the information to create those new normals. The uses range from helping utilities determine cooling and heating days and even retailers in figuring out when to put winter coats on racks in stores.
Palecki says the data largely aligns with what scientists have been saying for some time now – earth continues to experience a warming climate.
That includes the U.S, where most of the country saw air temperatures increase by anywhere from a quarter to a whole degree Fahrenheit over the last decade. There was one exception to that, though.
“The north central U.S. – North Dakota, South Dakota, parts of Minnesota and Montana – are in fact, have normals that are a little cooler this time around than the previous 30-year period,” explains Palecki.
He says the new data shows precipitation totals have also increased for the eastern and central part of the country, but the southwest was drier.
The information is pretty complex, Palecki says – much more than a simple average.
“If you take 30 June 1st’s and add them up and divide them by 30, you’re likely not going to get the same number that we get because we are adjusting and fixing the data for various problems," he says. "And also, we’re making sure that the daily averages when you add them up for a month correspond with the monthly averages.”
Those problems include things like missing data or changes in observation times.
Here in Virginia, the new normals lined up pretty closely with national trends – according to Phil Hysell with the National Weather Service in Blacksburg.
“Generally speaking, we saw a slight uptick in average temperatures and a pretty significant uptick in average annual precipitation. And snowfall totals for the year on average went down as well," he explains. "Now, that certainly wasn’t the case at every site, but generally speaking, most of the sites in Virginia saw those trends.”
He says putting the data together takes a large network of information.
“All of the data that the National Center for Environmental Information uses to calculate these normals come from local climate sites, from local weather stations, from volunteer weather observers – the co-op data program. From the CoCoRaHS observers – the Community Collaborative Rain, Hail and Snow Network," explains Hysell. "So, it’s all local data that we receive – we quality control it – and then it’s sent up to the national level to create these normals.”
Hysell adds the newest data was also used to help compile another recently-released set of normals – those used to project the number of tropical systems each year. Those projections show 14 named storms per year will be the new normal – an increase of two over the previous average. Officials say warmer ocean temperatures are partly to blame for that jump.
