WRAL WeatherCenter Blog

Not so much a question as a statement about the drought coverage. I think that it is very misleading to say that the rain fall is actual versus normal. The normal is actually an average over time. Sometimes it is higher and sometimes it is lower. To say that we are 9 inches of rain below normal is really 9 inches below the average.

Posted April 5, 2008

MIKE MOSS SAYS:      Ron,    There may just be a matter of semantics involved there. As it happens, "normal" in this case is just the word agreed upon by climatologists to distinguish the 30 year average of monthly or yearly precipitation, with the averaging period ending with the most recent "zero" year. So, "9 inches below normal" at this time means "9 inches below the average amount for the same periof of time during the years 1971-2000." Using this climatological definition of normal distinguishes this particular value from an almost endless array of other possible averages (5-year average ending last year, a 10-year average ending on the last "five" year, and so on).

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