Watching weather reports over the years, you’ve no doubt heard the words “normal” and “average,” but what exactly do they mean?
First, let me show you how to get the daily climate report so that you can see the day’s normal and actual temperature. Let’s say you want to know what the day’s high and low were, or if they were above or below “normal,” perhaps whether any records were challenged, maybe what the high wind gust was, or you may wish to know any number of other climate stats for the day, including rainfall and snowfall.
Well the most complete daily climate report for Aroostook County is issued for Caribou, and to access it, all you have to do is google on “NWS CAR CLI”. Click the top item in the resultant list. Once you’ve done that, in column 2 you will see Bangor highlighted. Simply click down to Caribou, which is just below it, and then in column 4, click “go’. The full report for the preceding day is usually issued by 1:30 a.m. or so. There is a same-day preliminary report issued around 4:30 p.m. each day, but a daily climate record officially runs midnight-to-midnight, so you need to wait until that 1:30 a.m. release to get the official daily climate report.
Ok, back on the report itself, you will see the words “normal value” in the fifth column from the left. When you see these terms, “normal high,” or “normal low” (or normal anything for a date), that is the same as saying “the average” high/low/etc. Normal equals average in a daily climate report.
But, again, what is meant by normal (or average)?
These are simply values based on a 30-year period of daily observations, smoothed out to display such things as the warmest and coldest times of the year. For example, the averages tell us that at our coldest time of the year, Caribou’s average high is 19 degrees, and the average low is 0. The current period we use for calculating our normals is 1981-2010. It is recalculated every 10 years, so the next 30-year period will be 1991-2020.
Knowing the averages is very handy if you like to keep a weather diary, as it allows you to know whether you’re experiencing typical weather or unusual weather for that time of year.
Other than normals, there is one more climate reference point which is very important, and that is “period of record.”
At Caribou, weather records began being kept in 1939. On Friday, October 7th, 2016, Caribou had a record high of 76 degrees. The correct way to say that is to say that the 76 degree high for that date was the warmest on record. Some people erroneously say “warmest ever.” Seventy-seven years worth of data versus “ever” are two very different things!
Before I close this week, I’d like to invite you to tune in at 6 p.m. on both November 9th and 10th, as I’ll be delivering my winter forecast. I plan to address three main areas: prediction of total snowfall for the period Nov 1st – April 30th, whether the snow during the heart of winter will have good “staying power,” (something that for much of The County was sorely lacking last winter). And finally, I’ll also be giving my energy usage projections for this winter as compared to last winter, measured by Heating Degree Days. I have written of those previously, and if you didn’t read that column, it’s an easy term to search online, and it’s handy to know. Heating Degree Days.
Oh, and what is our normal snowfall? At Caribou it is 108.7”.
Ted Shapiro holds the Broadcast Seal of Approval from both the American Meteorological Society and the National Weather Association. An Alexandria, Va. native, he has been chief meteorologist at WAGM-TV since 2006. Email him at tshapiro@wagmtv.com.
