NWS "record period" vs "normal period"

[coriolis]

I keep records of the weather observations at this location on a big honking speadsheet with charts and graphs. My primary source is the NWS daily climate report.

They list record highs and lows over a period from 1895 to the present, but for what they call "normal" they use a period from 1971 to 2000. It would be easy enough to calculate averages from the larger data set. Why do they take a smaller data set which would be inherently less representative and call it "normal?"

[wall_cloud]

From a state climate office website:

Climatologists define a climatic normal as the arithmetic average of a climate element such as temperature over a prescribed 30-year interval.� The 30 year interval was selected by international agreement, based on the recommendations of the International Meteorological Conference in Warsaw in 1933. The 30 year interval is sufficiently long to filter out many of the short-term interannual fluctuations and anomalies, but sufficiently short so as to be used to reflect longer term climatic trends. Currently, the 30-year interval for calculating normals extends from 1971 to 2000.

So in reply, I would say that the 30 year climatology is actually MORE representative, since it doesn't include observations that occured maybe 100 years ago. Ob sites move, surrounding conditions change and our "normals" change slightly as well.

Even normals calculated based on the entire observation history would not classify as "normal". Average would be a correct term, but average isn't normal by any stretch. Personally, I hate the term normal when applied to temperatures.