(WKBN) – Each day, most meteorologists talk about the weather and how it will impact your life in the days ahead. They also compare the current weather, or the weather for tomorrow, with an average or normal weather condition.
What do normal and average mean?
Let’s take a look at these two words when used in meteorology. Are they the same?
The definition of Average: If you look “average” up in the Merriam-Webster dictionary you will find a series of definitions of what it means. Going down the list of definitions you will need to stop at 2a to find the one that relates to the use in meteorology. 1a: a single value (such as a mean, mode, or median) that summarizes or represents the general significance of a set of unequal values b: MEAN Sense 1b; 2a: an estimation of approximation to an arithmetic mean.
So, the average when used in weather is an approximation to an arithmetic mean. What does that mean?
Let’s do an example. The high temperature on a given day was 77°F. The low temperature on that same day was 45°F. The math needed to find the average is to add the numbers together and then divide by the number of entries. Example from our given day: 77+45=122; 122/2= 61. So, the average temperature on this given day was 61°F.
This can be used with any type of weather including temperatures, rain, snow, wind, etc.
The definition of Normal: If you look ”normal” up in the dictionary, you will find a series of definitions. Going down the list, you will need to stop at “3a:” to find the one that relates to the use in meteorology. 1a: conforming to a type, standard, or regular pattern: characterized by that which is considered usual, typical, or routine; b: according with, constituting, or not deviating from a norm, rule, procedure, or principle
2: occurring naturally; 3a: approximating the statistical average or norm
So, the weather definition of normal is approximating the statistical average or norm. What does that really mean? Let’s think of this in weather terms.
Normal in weather is the long-term average of a meteorological parameter, according to the National Weather Service definition. We already learned what an average is earlier in this article.
An example of this would be “temperatures are normal today” as a meteorologist tells you the weather on television.
In weather, the normal is produced by taking the average parameter data over a 30-year period. In statistics, the number of 30, or higher, is used because a number below 30 can create more significant variation.
So, the normal in meteorology is the number that is an average over a 30-year period. The normal period is updated every 10 years. We are currently in the normal period from 1991 through 2020. We will not see a new normal until 2030 is finished. It will come out in 2031.
A normal is an average of a parameter (temperature/precipitation/wind) over a 30-year period.
The normal helps indicate what kind of climate an area is in.