New "normals" give an updated look at weather patterns

The yardstick for comparing temperature and precipitation to what is “normal” for South Dakota has changed thanks to an updated set of long-term averages.

That means watchers’ scale for normal precipitation anticipates more rainfall than before at many locations across the state, a South Dakota State University expert said, while normal winter low temperatures are not as severe in many places.

Dennis Todey, South Dakota state climatologist for the South Dakota Cooperative Extension Service, said the change takes effect starting in July 2011 in many agencies that use weather data. Weather forecasters and others who track weather data will start using a new set of 30-year averages updated for the period 1981 to 2010.

“The take-home message for most people is that with any kind of a program that is comparing to some sort of an average, those numbers are going to change now. Just be aware of that and make sure that if you need to compare to some sort of average that you are getting the most current set of data involved looking at those averages,” Todey said.

Todey explained that the official averages that are used by the federal government and any kind of federal program are the 30-year averages that are calculated by the National Climatic Data Center, updated every 10 years.

“Previously, we compared everything to the 1971 to 2000 averages,” Todey said. “The National Climatic Data Center has done very quick work this year and done the calculations on the previous data. As of July 1 they released the new version of the 30-year averages, or the ‘normals,’ as they’re officially called, from 1981 to 2010.”

The National Climatic Data Center has installed the new averages on their weather and climate products. The National Weather Service will be installing them on their products starting in July. South Dakota State University’s state climate office will install them as soon as possible so that people can compare weather data to those normals.

Todey said once his office has had a chance to look more closely at the new normals, he’ll also have a better idea of how the 30-year averages are shifting around the state. But already the state climatologist has a pretty good idea about some of the general trends.

“I fully expect we’ll see some changes upward in precipitation, that averages will become higher than they were before. I did have a chance to look at the Brookings station and it did show a fairly big increase in Brookings, but we’ve not had a chance to look at those in detail across the state,” Todey said.

Todey’s initial expectation is that 30-year average temperatures will also change.

“The changes that we know we have seen are changes upward in minimum temperatures, especially in winter.”

Todey will know more once he’s had a chance to look at the data, but he notes that the 1970s are dropping out of the 30-year average, and there were several cold winters then, compared to several more mild winters in the past decade. Summertime highs may have eased downward as well in at least parts of the state.

“Summer temperatures are cooler for some stations, but not much change for others.”

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Citation: New "normals" give an updated look at weather patterns (2011, August 2) retrieved 15 October 2019 from
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Aug 02, 2011
If it is an "Historical Average" that is to be used for comparison, then why would only a segment of the Historical record be used as the baseline?

I don't get it. Has the NWS been adjusting the baseline every thirty years or so for the past 150 years? This seems more than just a touch Brave New World-ish.

Someone please help me out here...

Aug 03, 2011
Extract from NCDC.."Why does NOAA produce Normals?
NOAA's computation of climate Normals is in accordance with the recommendation of the World Meteorological Organization (WMO), of which the United States is a member. While the WMO mandates each member nation to compute 30-year averages of meteorological quantities at least every 30 years (1931 - 1960, 1961 - 1990, 1991 - 2020, etc.), the WMO recommends a decadal update, in part to incorporate newer weather stations. Further, NOAA's NCDC has a responsibility to fulfill the mandate of Congress "... to establish and record the climatic conditions of the United States." This responsibility stems from a provision of the Organic Act of October 1, 1890, which established the Weather Bureau as a civilian agency (15 U.S.C. 311)." http://www.ncdc.n...ENORMALS

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