United States Weather Bureau

“ The weather forecast made by the United States Weather Bureau for the Washington-Pittsburgh area for the period 11:30 a.m. to 7:30 p.m. was available to the pilot prior to take-off and the record shows that the forecast, together with sequence weather reports, was examined by the crew prior to preparation of the flight plan. The forecast predicted that overcast to occasionally broken clouds would exist from the mountains eastward, with scattered showers through the mountains and some mild thunderstorms in the afternoon. ”

“ The weather map of the United States is based on simultaneous observations made at about 150 stations in different parts of this country, besides several coöperating stations in Canada, Central America, Mexico, and the West Indies. At each of our stations, whose48 location may be seen on any weather map, the Weather Bureau employs one or more observers, who, twice a day, at 8 A.M. and 8 P.M., “Eastern Standard Time,” make regular observations of the ordinary weather elements, i.e., temperature, pressure, humidity, wind direction and velocity, precipitation, cloudiness, etc. ”

“ The ranchmen in the West, with thousands of cattle under their charge; the trainmen in charge of cattle trains; the engineers of large buildings, such as hotels, stores, and office buildings, who must have their fires hotter in cold weather,—these and many more watch, and are governed by, the cold-wave forecasts of our Weather Bureau.
Mean Annual and Mean Monthly Isothermal Charts.—We have thus far considered isothermal charts for the United States only, based on the temperature observations made at a single moment of time. ”

“ It was demonstrated that the two were in reality one storm, and that its path could have been ascertained and the fleet forewarned in ample time to reach safety.
In order to intelligently predict the weather for even a small section of the country it is necessary to know the conditions that exist over the whole United States, and over as much of the rest of the world as possible. The Weather Bureau receives observations from one hundred and fifty-four stations. ”

“ Whoever knowingly issues or publishes any counterfeit weather forecast or warning of weather conditions falsely representing such forecast or warning to have been issued or published by the Weather Bureau, United States Signal Service, or other branch of the Government service, shall be fined under this title or imprisoned not more than ninety days, or both. ”

“ For New England, the circuit center is Boston. All messages are received at this office, and from here transmitted to the next office, which is New York, and from New York to the next center, until the news is transmitted to the coast. The wires are open from 8:00 until 9:30 A. M. The western offices follow the same procedure until the weather indications are received by all stations. Immediately the preparation of the map is begun and they are mailed to interested parties by the Weather Bureau Stations of the United States. ”

“ Since 1871 a still more careful analysis of the United States daily weather maps has shown that it is necessary to consider the fact that the winds on the west side are colder and drier than those on the east side of the storm center. ”

“ New Hampshire has the record for the largest hailstones seen here so far; they were 4 inches in diameter and weighed 18 ounces, and were 121⁄2 inches in circumferences.
RAINFALL There are records in Japan of where rain has reached 30 inches in twenty-four hours; in India where it has reached 40 inches in twenty-four hours.
The average rainfall in the United States is 35 inches.
There are certain places in India where the yearly rainfall averages over 470 inches; whereas other regions of India show less than 4 inches. ”

“ Another weather type, often noted during our winter in the central and eastern United States, and strongly contrasted with both of the preceding conditions, is that which brings us a warm, damp, southerly wind, frequently accompanied by heavy rains. As these damp winds blow over snow-covered surfaces they become foggy and the ground is said to “smoke”; the heavy rain rapidly melts the snow; slush and mud make bad walking; rivers and brooks rise rapidly, perhaps overflowing their banks; low-lying places become filled with standing water. ”

“ The ground is frozen all the year round below a slight depth over wide areas. The extremely low temperatures are most trying when the steppes are swept by icy storm winds (buran, purga) , carrying loose snow, and often resulting in loss of life. In the North American interior the winter cold is somewhat less severe. North American winter weather in middle latitudes is often interrupted by cyclones, which, under the steep poleward temperature gradient then prevailing, cause frequent, marked and sudden changes in wind direction and temperature over the central and eastern United States. ”

“ 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. ”

“ Local Winds In addition to the winds of the general circulation and those associated with migratory cyclones and anticyclones, there are numerous local winds which influence the weather in various places. The most common are the land and sea breezes, caused by alternate heating and cooling of land adjacent to water. The effect is similar to that which causes the monsoons, but on a much smaller scale, and over shorter periods. By day the land is warmer than the water, and by night it is cooler. ”

“ It was then discovered that a certain type of weather map preceded such failures of the forecaster. One who is interested in gaining early knowledge of the approach of a cold wave to the United States should watch not only for the appearance of abnormally high barometer readings, from the stations of the Canadian Northwest, or from Montana and North Dakota, but especially for a crescent-shaped Low, with one horn of the crescent touching Lake Superior and the other extending into the middle Rocky Mountain region, at about Colorado. ”

“ Unfavorably dry spring weather also prevailed west of the Rockies, ensuring below-normal summer runoff in most Western river basins.
March: Record-setting warmth in March followed a nearly nationwide cold snap from mid-January through February. Monthly temperatures averaged at least 10 degrees F above normal at several sites across the central one-third of the Nation, while cooler-than-normal weather was confined to the Northeast and scattered locations in Florida and along the Pacific Coast. ”

“ Introduction Weather is the state of the Earth’s atmosphere with respect to temperature, humidity, precipitation, visibility, cloudiness, and other factors. Climate refers to the average long-term meteorological conditions of a place or region. All weather may be traced to the effect of the Sun on the Earth. Most changes in weather involve large-scale horizontal motion of air. Air in motion is called wind. This motion is produced by differences of atmospheric pressure, which are attributable both to differences of temperature and the nature of the motion itself. ”

“ As the warm front passes, the temperature rises, the wind shifts clockwise (in the Northern Hemisphere) , and the steady rain stops. Drizzle may fall from low-lying stratus clouds, or there may be fog for some time after the wind shift. During passage of the warm sector between the warm front and the cold front, there is little change in temperature or pressure. ”

“ Here is advice that will help you protect yourself and your family against the hazards of winter storms--blizzards, heavy snows, ice storms, freezing rain, or sleet.
• KEEP POSTED ON WEATHER CONDITIONS. Use your radio, television and newspapers to keep informed of current weather conditions and forecasts in your area. Even a few hours' warning of a storm may enable you to avoid being caught outside in it, or at least be better prepared to cope with it. You should also understand the terms commonly used in weather forecasts:
--A blizzard is the most dangerous of all winter storms. ”

“ It is believed that a further discussion of meteorological phenomena on a broad basis, by means of International Weather Charts, both in daily and monthly form, must eventually result in important and fundamental discoveries. It is gratifying to American pride to know that in this international task of outlining the geography of the air, the United States has liberally provided the labor and means for presenting these ten years' meteorological data in such tabular and geographical forms as to render them available for study by all. ”

“ A sudden and rapid fall indicates a sudden downpour and high winds, or both. In summer a thunder-storm is preceded usually by a drop in pressure.
Wind Indications of Weather Conditions.—Throughout the eastern half of the United States [2] winds with a westerly element—northwest, west, and southwest winds—indicate fair weather. Winds with an easterly element—northeast, east, and southeast winds—indicate unsettled weather, rain or snow.
A straight north wind is apt to be a clear- weather wind. “The north wind driveth away rain.”—Prov. ”

“ 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. ”

“ Of course, that's not nearly all that the Weather Bureau has to do with snow. In the northern states, especially of the Pacific Coast, snow surveys are of great importance. The Weather Bureau often sends men to determine the amount of snow that has fallen over a given area, in order to find out how much water may be expected. This is needed in flood forecasts and irrigation projects. Some of our men, boys, can tell you thrilling tales of their expeditions on snow-shoes up snow-covered slopes where there is never a trail. ”

“ 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. ”

“ Each of these the Weather Man has to study when he makes a forecast, but, in the United States, his work is aided by the fact that weather always travels eastward and that the storm follows regular tracks, sharply outlined, like Indian trails across the country."
"Roads in the air?" queried Fred.
"Yes, my boy," the Forecaster answered, "regular roads in the air. There used to be an old saying: 'American weather is made at Medicine Hat.' In a sense this was true, for about sixty per cent of the storm areas—'lows' or region of low barometric pressure—come from the Canadian Northwest. ”

“ Ever-increasing knowledge regarding them makes possible a continually improving weather service. However, the ability to forecast is acquired through study and long practice, and therefore the services of a trained meteorologist should be utilized whenever available. ”

“ 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. ”

“ Therefore, the best LOP’s for a fix may not all be from the very nearest stations.
The user should also be aware that the propagation speed of Loran changes with time as well. Temporal changes may be seasonal, due to snow cover or changing groundwater levels, or diurnal, due to atmospheric and surface changes from day to night. Seasonal changes may be as large as 1 μsec and diurnal changes as large as 0.2 μsec, but these vary with location and chain being used. Passing cold weather fronts may have temporary effects as well. ”

“ 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. ”

“ 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. ”