tag:blogger.com,1999:blog-6168620747792092240.post5474389486522415472..comments2024-03-27T15:09:59.039-06:00Comments on Wasatch Weather Weenies: As Close to "Normal" as It GetsJim Shttp://www.blogger.com/profile/15799757451626876963noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-6168620747792092240.post-38817704401260629652013-10-13T15:07:19.163-06:002013-10-13T15:07:19.163-06:00I was originally going to comment on this topic be...I was originally going to comment on this topic before I got to the bottom, so I will tag on.<br /><br />I learned within the past year that technically "normals" and "averages" are not synonymous, despite some people using them interchangeably, and/or assuming that a normal is the same thing as a 30-year average.<br /><br />A "normal" is a statistic created by the National Climatic Data Center. They are listed in the daily NWS climate reports and are thus widely used. Yes, they are based on the most recent 3 decades of data, but it is not a simple average. The data (especially temperatures) go through an adjustment process, of which I don't know the details, just that it is supposed to make the data more "representative." Sometimes the differences can be more significant than one might expect.<br /><br />Throw in the possibility of using a period of record average (which can be easily accomplished if one has access to the ACIS interface), and you create quite a challenge when someone asks "What is the average number of 90 degree days per year in X City?" It could be 13 (NCDC "normal"), 15 (pure 30-year average), or 20 (period-of-record average). :-\<br /><br />Also I'd speculate that the 30 year number allows one to compare different station's normals in an apples to apples context, in addition to being the magical statistical (n=30) threshold. It wasn't too long ago that many stations didn't have much more than 30 years of reliable data as well.Andrewhttps://www.blogger.com/profile/00048073965784367130noreply@blogger.comtag:blogger.com,1999:blog-6168620747792092240.post-77628943022924174682013-10-13T14:00:32.717-06:002013-10-13T14:00:32.717-06:00Ultimately, it is simply a protocol recommended by...Ultimately, it is simply a protocol recommended by the World Meteorological Organization. This is probably more than you want to know: http://www.ucar.edu/communications/quarterly/winter0809/normal.jsp<br /><br />My guess is that most of the time you these days you are seeing the 1981-2010 average. The NWS would do well to include such information in anything that includes an average statistic so that we know for sure.<br /><br />JimJim Shttps://www.blogger.com/profile/15799757451626876963noreply@blogger.comtag:blogger.com,1999:blog-6168620747792092240.post-62134389385533119402013-10-13T12:56:59.966-06:002013-10-13T12:56:59.966-06:00Thanks for a good post. One of the things that has...Thanks for a good post. One of the things that has always bothered me about our use of "averages" is that, as you note, the "average" temperature listed on the TV and in newspaper is the 30-year average. Obviously this custom skews recognition of climate change. Is this 30-year norm worldwide practice? Has there ever been a discussion among meteorological professionals that you all should lobby the media to, say, provide both the 30-year average (calling it that by name) but also, say, the 20th-century average? Also, when did 30 years become the definition of "average"? Thanks! Derek Hoffhttps://www.blogger.com/profile/13788619739997805477noreply@blogger.com