Weather forecasting

“ Buchan concludes that over the ocean terrestrial radiation is more powerful than solar radiation in causing those vertical disturbances in the equilibrium of the atmosphere which give rise to the thunder-storm.
CHAPTER XXXV WEATHER-FORECASTING
To foretell with any degree of certainty the state of the weather for twenty-four hours is of immense [Pg 117] advantage to business men, tourists, fishermen, and many others. The weather is everybody’s business. And the probabilities of accurate forecasts are so improving that all are more or less giving attention to the morning meteorological reports. ”

“ There are probably many people among us, well above the illiterate level, who have no clear idea as to what constitutes a scientific weather forecast. The distinguishing feature of such a prediction, apart from the fact that it is made by a trained meteorologist, is that it is, in all cases, based upon a weather map.
The forecasting machine is a big one, with its human gear spread over a wide territory. Eventually it will be spread over the entire globe, and then we shall have better forecasts. ”

“ There are clear cases that fall into one or another discipline—the question of how likely it is that it will rain tomorrow is clearly a question for weather forecasting, while the question of how the Earth’s changing axis of rotation contributes to ice ages is clearly a question for climatology—but many questions will be of interest to both disciplines, and there is bound to be significant overlap in both topic and method. ”

“ The prediction or foretelling of the weather which may be expected to prevail at any station or in any district is weather forecasting.
Weather forecasts are usually made on our daily weather maps for 24 hours in advance. It is by no means an easy thing to make accurate weather forecasts. Careful study and much practice are required of the forecasters of the Weather Bureau before they are permitted to make the official forecasts which are printed on the daily maps and in the newspapers. ”

“ It represents conditions which are not to be expected in every cyclone which appears on our weather maps. If all cyclones were exactly alike in the weather conditions around them, weather forecasting would be a very easy task. ”

“ The Weather Bureau does not possess on its books the record of any two days when the weather was duplicated over the United States."
"You mean that every day's weather map is different?"
"As different as every human face," the Forecaster replied, "and to those of us who have done much forecasting, it is as easy to see from the map when the weather is going to be peaceful or stormy as it is to tell whether a man is smiling or scowling. But let us look at these three charts closely, and you will see just why Fred was right. ”

“ But, apart from every aid furnished by cosmic meteorology to that of our individual planet, the extension of the international simultaneous weather-reports will, we believe, ultimately afford the data requisite for approximately forecasting some main features of the seasons. A single example (the great heat of last October on the eastern side of the United States) will illustrate the possibility of attaining in some degree this long-desired object, which, like an ignis fatuus, has eluded the pursuit of men for so many ages. ”

“ Forecasting Weather The prediction of weather at some future time is based upon an understanding of weather processes and observations of present conditions. Thus, when there is a certain sequence of cloud types, rain usually can be expected to follow. If the sky is cloudless, more heat will be received from the Sun by day, and more heat will be radiated outward from the warm Earth by night than if the sky is overcast. If the wind is from a direction that transports warm, moist air over a colder surface, fog can be expected. ”

“ At the present time, when weather prophecies have come to form a recognized part of our complex social machinery, it would be ungrateful to omit noticing that Hooke was the first to propose a scientific system of meteorological forecasting. ”

“ That we live in an age of great intellectual acumen, and that he is indeed a wise prophet who can even dimly outline the possibilities of the next century, is fitly shown by the development of meteorological science during the recollection of the present generation; although one must admit that in the making of weather forecasts, valuable as they are, we have not advanced beyond the partly empirical stage. ”

“ Thus, before meteorology passed from an “art” to “science,” many individuals learned to interpret certain atmospheric phenomena in terms of future weather, and to make reasonably accurate forecasts for short periods into the future.
With the establishment of weather observation stations, continuous and accurate weather information became available. As observations expanded and communication techniques improved, knowledge of simultaneous conditions over wider areas became available. This made possible the collection of “synoptic” reports at civilian and military forecast centers. ”

“ There is not a profession, or trade, or handicraft in society which is not at every turn more or less influenced by the weather, and compelled to act upon some kind of weather-forecasts. No sooner had the Weather Bureau commenced its daily publication of "Probabilities" or "Indications," in 1870, than "whole troops of practical applications" of the data sprang into existence. It will be so with the international bulletin and charts of simultaneous meteorology. ”

“ The cooperative observer can do much to aid in establishing definite facts on which predictions may be made. Among them and of first importance is establishment of the direction of rain-winds. These, as has been shown, are easterly winds, but conditions of topography may change the real direction to one that is apparent. The apparent direction should be established for each month in the year. In every community there are weather-wise people who possess valuable information that they have not recorded. ”

“ By preserving the weather map each day and noting the movements of the Highs and the Lows, any intelligent person can make a fairly accurate forecast for himself, always remembering that the Lows, as they drift towards him, will bring warmer weather and sometimes rain or snow, and that as they pass his place of observation the Highs following in the tracks of the Lows will bring cooler and fair weather, except during periods of extreme summer heat, when the Lows bring showers that cool the parched earth ”

“ It is evident, therefore, that a complete knowledge of the weather conditions in any part of the world, which it is understood carries with it the ability to make correct forecasts, can never be obtained unless the weather conditions in every other part are known. ”

“ It is the expectation of the meteorologist that some day he will be able to accurately forecast the weather for weeks and months in advance. What a wonderful conservation of human energy would result if it were possible to tell the farmer when the great corn and wheat belts would have abundant rain during the next growing season, or when droughts would parch and wither the vegetation ”

“ Charts are then prepared for distribution, showing the direction and force or the wind, the barometrical pressure, the temperature, and the atmospheric conditions generally. The comprehensive idea which the Office thus acquires of what Nature is doing over a considerable portion of the earth's surface, enables it to accomplish two useful pieces of work—to forecast the weather for the next twenty-four hours, and, if necessary, to warn particular localities to look out for squalls. ”

“ If when it falls the temperature rises, and the air becomes more charged with moisture; then wind, rain (or snow) may be expected from the S.E., S., or S.W.
Exceptions to these rules occur when a Northerly wind with wet (rain, snow, or thunderstorm) , is impending, previous to which the barometer often rises (but only on account of the direction of the coming wind) , and thus deceives those who from the rising are led to look for fair weather. ”

“ These governmental bureaus usually pursue both Climatology and theoretical meteorology in addition to their daily practical work of telegraphy, forecasting, and publication of charts. Although, of course, in most cases, the so-called practical work absorbs the greater part of the labour and the funds, yet everywhere it is recognized that research and the development of a correct theory of the motions of the atmosphere are essential to any important progress in the art of forecasting. ”

“ Weather prediction must be far more precise than climate prediction in order to be interesting. However, it also need only apply to a timeframe that is many, many order of magnitude shorter than climate predictions. Meteorologists are interested in predicting with relatively high accuracy whether or not it will rain on the day after tomorrow. Climatologists are interested in predicting--with roughly the same degree of accuracy--whether or not average precipitation will have increased in 100 years. ”

“ Whence it follows that the most important problem of meteorology is the investigation of the causes and consequences of the disturbance of indifferent equilibrium of the atmosphere, and the weightiest problem in weather prediction is the investigation of the geographical origin or extraction of air currents pursuing their course above us toward the pole. ”

“ It must occur to everyone to adopt the intermediate view that, on the one hand, the local vertical circulation, with its clouds, rain, hail and snow, and evolution of latent heat, and, on the other hand the waves and whirls in the general circulation, mutually contribute toward our storms and fair weather. It only remains to allot to each its proper importance in any special case.
Undoubtedly aerial billows, and the clouds that must frequently accompany them, exist everywhere in the earth’s atmosphere. ”

“ The most popular and profitable use to which meteorologic observations can possibly be put would be, if it is practicable, to forecasting in part the character of coming seasons—whether the next winter will be mild or severe, or the approaching summer wet or dry. ”

“ The tendency, at present, among those who are desirous of forming a scheme of weather prediction, is to seek the origin of our weather-changes in changes of the sun's condition, and, by determining the laws of the solar changes, to ascertain the laws which regulate changes in the weather. ”

“ We have generally found country folk more reliable about the immediate future of the weather than the falling or rising of the barometer, for local conditions are often an important factor in the case and modify the barometer’s forecast. ”

“ Showers undoubtedly occurred in conjunction with Post’s experiments, but conditions favoring their occurrence were plainly indicated on the current daily weather maps, and they had been duly forecast by the Weather Bureau.
The professional rain-maker does not generally resort to the expensive process of bombarding the clouds. ”

“ Happily, our meteorologists are at length beginning to define with growing clearness and confidence the laws which underlie and regulate the complicated and ever varying phenomena which we call the weather, and many of these laws, like most natural laws, are beautiful in their simplicity. Although ‘weather wisdom’ is as old as history itself, the science of the weather or meteorology is a growth of the last few years. The weather wisdom of our forefathers may in the light of present knowledge be divided into sense and nonsense. ”

“ In framing official predictions of the weather the daily synoptic and isobaric chart is the chief evidence relied upon.
To forecast with any degree of accuracy requires considerable experience, a knowledge of the distribution of the normal local climatic elements, and a due appreciation of the significance of the varying features of atmospheric systems and the degree to which they are affected by latitude, longitude, the seasons of the year, and, at times, even by the prevailing conditions of the land surface over which the atmospheric systems are passing. ”

“ Man is so profoundly affected by weather changes from day to day that all civilized countries have established weather services. Observers taking regular weather records are stationed at thousands of different places in all parts of the world, and the observations which they makexii are used by meteorologists in preparing daily weather maps and forecasts, and in studying the conditions of temperature, winds, and rainfall. In the United States alone there are about 3000 of these observers. ”

“ This bold step brought meteorologists face to face with a quite new problem. From the air pressure, the temperature, the moisture, and the winds observed at a certain hour of the day at various spots and telegraphed to a central station, they had to infer the next probable state of weather. So, leaving aside the great problems of atmospheric circulation, they directed their attention to the changes of weather rather than to the causes of the changes. [2] For this purpose purely empirical laws were of great value. ”

“ This extension of forecasting doubtless will be accomplished as the result of further study of solar impulses which disturb the orderly processes of the earth’s atmosphere and initiate storms, combined with a comparative study of meteorological data. We may be laying the foundation of a great edifice which shall adorn the civilization of future centuries. ”