The most important development in marine meteorology in recent years has been the rapidly increasing use of radiotelegraphy, both by marine observers in transmitting reports of observations to shore and to other ships, and by meteorological institutions in issuing weather bulletins and storm warnings to vessels at sea. The first regular undertaking in this line was carried out under the auspices of the London Daily Telegraph in the year 1904. This newspaper arranged with some of the leading transatlantic steamship lines to furnish weather reports by wireless from their vessels, and these reports were published in its columns for several months. The following year the United States Weather Bureau began, in a tentative way, the collection of wireless weather reports from off-shore vessels, and similar undertakings were soon afterward launched in other parts of the world, but for some years such reports were of little practical value, owing to the limited range of wireless communication.
A SHIPBOARD WEATHER MAP
Vessels off the American coast can make their own weather maps every night, using data supplied at fixed hours by high-power radio stations (shown by stars on the map), together with radio reports from other vessels. Letters near stations are the code letters used in wireless bulletins to describe the stations. Vessel reports are indicated by names. Arrows show direction of wind and the force on the Beaufort scale (shown by the number of feathers). Besides data for constructing maps, the radio stations issue forecasts and storm reports for each of the numbered zones shown off the Atlantic coast and over the Gulf.
At the present time wireless reports from ships on the Atlantic enable the forecasters on both sides of that ocean to extend the areas of the weather maps on which their predictions are based, and reports from ships are also received to a limited extent by forecasters on our Pacific coast as well as in the Far East, India, and elsewhere. In this country such reports have been especially valuable in indicating the movements of West India hurricanes, and thus have helped to solve the problem of protecting the vast tonnage that has been attracted to Caribbean waters by the opening of the Panama Canal. The reciprocal process of transmitting weather intelligence to vessels by wireless bulletins, broadcasted at certain hours every day by high-powered radio stations, has made much more progress. Such bulletins include information concerning the current and prospective weather, winds and storms over specified ocean areas, as well as reports of observations made at a number of land stations, from which it is possible for vessels at sea to construct their own weather maps. They are thus enabled to take advantage of favorable winds and to avoid unfavorable winds and storms. Wireless weather reports from other vessels help to piece out these shipboard maps.
The meteorological services of all civilized countries adjacent to the sea display signals along their coasts to announce the coming of storms dangerous to navigation. One of the earliest devices used for this purpose was the “aeroclinoscope,” a form of semaphore formerly employed by the meteorological service of Holland. The position of the arm of the semaphore indicated the region in which the barometer was low; i. e., the storm center. In the British Isles, in the middle of the last century, Admiral FitzRoy introduced the use of canvas cones and “drums” (i. e., cylinders), which, seen from any direction, have the appearance of solid triangles and squares against the background of the sky. The British later abandoned the drum and used the cone only, pointing up or down for northerly or southerly gales, respectively. The American storm flag—red with a square, black center—was adopted by the United States Signal Service (the predecessor of the Weather Bureau) in 1871. This signal was subsequently amplified by the addition of red and white pennants to show the expected direction of the wind at the beginning of the approaching storm. Most countries use lanterns for night storm signals. In the year 1909 a uniform system of signals, consisting of cones by day and lanterns by night, was recommended for use in all countries by an international commission which met in London.
In spite of this recommendation some thirty or forty different systems of daytime storm signals are now in use in different parts of the world. On the China coast an elaborate system of signals, consisting of cones, balls, diamonds, and squares displayed on a mast and yardarms, indicates the existence of a typhoon anywhere in the neighboring seas, together with its location and movement.