I have to say I am a big fan of October weather. It is, after all, a transitional month, which often leads to an interesting variety of weather – from the remnants of summer warmth during a classical spell of Indian Summer weather to the crisp, deep blue of a chilly October afternoon, complementing the reds, oranges, and golds that paint the hillsides and valleys.
October often teases snow-lovers with the first flakes of the year, and leaves of a coating of the white stuff about once every five years or so, more often over the higher elevations, again a lovely contrast to the autumn foliage lingering in the valleys below.
These changeable conditions require an active weather pattern, as we alternate from high pressure to low pressure, accompanied by the passages of weather fronts. This smorgasbord of weather reminded me of one of my favorite systems for forecasting, developed more than a century ago. The earliest listing I can find is from Professor Edward B. Garriott, the Chief of the Forecast Division of the U. S. Weather Bureau in the late 1890s. This has been copied in countless publications, to the point that its origins have been nearly obscured. Nevertheless, the table above works as well today as it did over one hundred years ago.
I first found this table in one of my first forecasting books, “The Golden Guide to Weather,” by Lehr, Burnett, and Zim, first published in 1957. You may have also seen it in the “Old Farmer’s Almanac”, though it seems to have disappeared from there in recent years.
The primary tool in this forecasting method is the barometer, measuring the atmospheric pressure. The pressure on the table is divided into four categories; above 30.20 inches, which is fairly high, between 30.00 and 30.20, or moderately high, less than 30.00 inches, or moderately low, and below 29.80 inches, which is quite low. Atmospheric pressure, which results from the density of the air, directly influences the generally rising or sinking motions in the atmosphere. Beneath high pressure, air tends to sink, which in turn causes the air to warm and dry out. Notice on the table that the higher pressure readings are associated with fair weather. Lower pressure indicates an upward motion to the air, lifting what moisture is available, which then forms clouds and eventually precipitation. Correspondingly on the table, you can see the connection with lower pressure and storms. You can often see this relationship on an actual barometer, with the lowest pressures labeled as “stormy,” not as low “rain,” climbing up to the middle range, when “change” would be more likely. As the pressure increases, it goes from “fair” to “very dry.”
The other factor on the table is the wind direction. Winds coming from the south or east come to us from the ocean, and generally from warmer locations, and so they often indicate stormy weather approaching. By contrast, westerly winds travel to us from the middle of the continent and usually deliver drier air.
This method of forecasting utilizes some very basic, foundational scientific principles – making measurements or observations, and then recording the effects or results. In this way, it shows the state of weather forecasting in the late 1800s. An article in the publication “Monthly Weather Review” from May of 1897 highlights the forecasting table, along with,
“Weather wisdom, gained by an observance of local atmospheric signs and conditions, has been possessed by man from time immemorial. Much of this wisdom has been embodied in proverbs which possess considerable merit for the sections and localities in which they originated. In farming communities, sayings regarding the wind, the temperature, the clouds, and evidences of atmospheric moisture have been handed down from generation to generation.”
In other words, this table, along with old weather sayings and proverbs, was the forecasting system of its day. However, meteorology was on the cusp of a dramatic revolution. By the late 1800s, telephone and telegraph communication permitted weather observations over large regions to be compiled and analyzed, which lead to creating weather maps, showing areas of higher and lower pressure, the wind directions, and the types of weather. Science was also gaining a deeper understanding of the workings of the atmosphere, which explained why differences in pressure, temperature, wind, and moisture created different types of weather. This meant the weather could be turned into numbers, which could be calculated, yielding a prediction of future conditions – forecasting. The biggest challenge was making tremendous volumes of calculations in a timely fashion. At first, it took longer to calculate the forecast than it took for the weather to happen. This finally changed with the development of computers, leading to the modern forecasting methods of today.