Charles Fitzhugh Talman

That it behooves a sailor to be weather-wise has always been admitted, but there was a time, almost within the memory of men now living, when neither seamen nor landsmen had the remotest conception of the benefits that a systematic study of the meteorology of the sea was capable of conferring upon the maritime world. The man who first grasped the importance of such a study and translated his ideas into facts was the American naval officer, Lieutenant Matthew Fontaine Maury.

During his brief career at sea Maury became impressed with the meagerness of the information then available concerning the winds and currents that aid or hinder the voyages of sailing ships. When, in consequence of an accident that incapacitated him for shipboard duties, he was assigned to service in Washington, he began to explore the old logs of naval vessels, filed in the Navy Department, for notes on meteorological conditions, and eventually developed a plan of securing regular observations from both the Navy and the merchant marine. The result of this undertaking was the publication of the famous Wind and Current Charts, which revolutionized navigation throughout the world.

The practical value of these charts, of which 200,000 copies were distributed to the masters of merchant vessels of all nationalities, was promptly recognized. By taking advantage of the favorable winds and currents shown on the charts, and avoiding those that were unfavorable, mariners were able to reduce the average time of a sailing voyage between the Atlantic and Pacific ports of the United States by forty days. The money value of the charts to vessels sailing from the United States to South America and the Far East was estimated at $2,250,000 per annum. British shipping on all seas is said to have benefited to the extent of $10,000,000 per annum. Neither was the utility of the charts limited to the saving of money. The following episode is cited in Maury’s biography:

“When the San Francisco, with hundreds of United States troops on board, foundered in an Atlantic hurricane, and the rumor reached port that she was in need of help, everyone looked to Maury as the only man in the country who could tell where to find the drifting wreck. To him the Secretary of the Navy sent for information. He at once set to work and showed how the wind and currents acting upon a helpless wreck would combine to drift her ‘just here’, pointing to a spot on the chart, and making a cross mark with the blue pencil he had in his hand. Just there the relief was sent, and just there the survivors of the wreck were picked up. This was an incidental result of his study of winds and currents.”

A further outcome of Maury’s enterprise was the holding, at his suggestion, and by invitation of the United States Government, of an International Maritime Conference, which met in Brussels in 1853, and worked out a world-wide plan for meteorological observations at sea. The work thus begun has since been carried on by the leading maritime nations of the world. In the United States the duty of gathering weather reports on a uniform plan from vessel masters has been intrusted, at different times, to the Hydrographic Office, the Signal Service, and the Weather Bureau. It is now performed by the last-named institution, through its Marine Division, but the Pilot Charts and books of sailing directions (“Pilots”) in which the compiled information is published, are issued by the Hydrographic Office of the Navy.

The modern successors of Maury’s Wind and Current Charts are, especially, the Pilot Charts for the different oceans issued monthly in Washington, and the monthly charts of similar character published by the British and German governments. Apart from these periodical publications, valuable collections of meteorological charts for oceans or smaller marine areas have been published by the British, German, Dutch, Indian, Japanese and other authorities.

The value of such publications has not been lessened by the gradual substitution of steam for sails on ocean-going vessels. While wind is no longer all-important, it is a factor in determining the speed, and hence the earning capacity, of all classes of ocean shipping, and the same is true of marine currents. Fog and drifting ice are, in general, more serious obstacles to steamers than to sailing ships. A glance at one of the Hydrographic Office Pilot Charts will suffice to show that these publications are indispensable to the mariner. On these charts we find, first of all, in the center of each five-degree square of latitude and longitude a “wind rose” showing the frequency of the winds that have been observed in that region from each of the cardinal points, and their average force from each direction. On the charts will also be found the routes recommended for full-power and low-power steamers and sailing vessels, lines of magnetic variation, tracks of storms in past years for the month in question, location and force of currents, average limits and prevalence of fog for the month, recent information about drifting ice and derelicts, descriptions of storm signals, and an abundance of other information of vital importance to the seaman.

OCEAN WEATHER MAP PREPARED FROM VESSEL REPORTS

JAN. 11, 1913, GREENWICH MEAN NOON

U. S. Weather Bureau

Solid black lines are isobars. Arrows fly with the wind, the center of the arrowhead marking the position of the vessel, and the number of feathers denoting the force of the wind on the Beaufort scale. Shading of the head shows degree of cloudiness.

Most of the material used in the preparation of the charts above described is obtained from a great corps of volunteer marine observers, who enter their observations at stated hours in forms provided for the purpose and send these records to the establishment in charge of the work at the end of each voyage. The forms furnished by the United States Weather Bureau prescribe only one regular observation a day, to be taken at Greenwich mean noon. Each observation shows the position of the ship, the direction of the wind, the force of the wind on the Beaufort scale, the height of the barometer, the readings of the dry-bulb and wet-bulb thermometers, the temperature of the water at the surface, the state of the weather, and the kind, amount, and movement of clouds. In order to check the accuracy of the barometric readings, the observer is instructed to read his barometer at prescribed hours on three successive days when in port and send the readings to the Weather Bureau. On receipt of these readings the Bureau compares them with those of the nearest meteorological station, and then mails the observer a “barometer tag,” showing the results of the comparison and the error of his instrument. Besides keeping up these routine observations, the observer keeps a record of fog encountered at any hour of the day and makes detailed reports on storms. Many marine observers also report observations at stated hours by wireless telegraphy.

The enormous fund of information thus collected over the ocean is applied to several purposes besides the construction of Pilot Charts. Our Weather Bureau and certain foreign meteorological institutions prepare daily charts, showing approximately the instantaneous conditions over great oceanic areas, especially the North Atlantic. These maps are analogous to the daily weather maps published for land areas, but the drawing of each map is, necessarily, delayed for several months after the date to which it refers, in order to allow time for the receipt of as many reports as possible from ships at sea. As a rule such charts are prepared in manuscript only, but, though they cannot be distributed after the manner of ordinary weather maps, they are valuable for studies in the institution itself on the movements of storms and other atmospheric processes. They also enable the meteorological officials to answer inquiries concerning the winds and weather that have prevailed over a particular part of the ocean on any specified date. Such inquiries come from vessel owners, underwriters, and others, and the replies are frequently used as evidence in admiralty suits.

In the case of one series of such maps—viz., the daily synoptic charts of the North Atlantic, begun by Niels Hoffmeyer, of Copenhagen, and now prepared jointly by the Danish Meteorological Institute and the Deutsche Seewarte, in Hamburg—the charts have actually been published and sold, though they are so costly that the number of sets in libraries throughout the world is probably small. These remarkable charts present daily pictures of the winds and barometric pressure over the North Atlantic Ocean and the adjacent continents from 1873 to 1876, and from 1880 down to a recent date.

From what we have already said it will be seen that the marine observers cooperating with the United States Weather Bureau and kindred institutions abroad are all contributing toward the great task of recording the history of the weather over the oceans from day to day and assembling data that can be digested in the form of marine climatic statistics and used as the basis for many scientific investigations. This concerted undertaking does not, however, constitute the whole scope of marine meteorology. Every intelligent mariner finds it necessary to acquaint himself with the laws of the winds, indications of coming storms, means of determining the proximity of icebergs, the systems of storm signals used in different countries, the method of constructing weather maps from wireless bulletins, etc. He ought, in short, to become an accomplished meteorologist.

One of the classic problems of the navigator is that of handling his ship in a violent cyclonic storm, especially a tropical hurricane. The reader will recall that a cyclone, besides traveling as a whole at a rate of several hundred miles a day, consists of a system of winds rotating around the center. The result of this double motion is that the winds on one side of the center are not only more violent than those on the other, but they are also so directed as to drive a vessel running before the wind, across the storm track ahead of the advancing center, while those on the other side tend to drive a vessel to the rear of the storm. The two halves of the storm area are accordingly known as the “dangerous” and “navigable” semicircles, respectively. While this simple statement sets forth the fundamental facts involved, the actual problem is complicated by many features, such as the fact that the winds do not blow in circles, but more or less spirally, that the area of the storm cannot be readily determined, that two storms may occur in close proximity to each other, etc.

The accompanying diagram, published by the United States Hydrographic Office, represents a cyclonic storm in the northern hemisphere, the circles being isobars, or lines passing through places at which the same barometric pressure prevails (indicated in inches), and the arrows indicating the direction of the winds. The diagram is thus explained:

“For simplicity the area of low barometer is made perfectly circular and the center is assumed to be ten points to the right of the direction of the wind at all points within the disturbed area. Let us assume that the center is advancing about north-northeast, in the direction of the long arrow, shown in the heavy full line. The ship a has the wind at east-northeast; she is to the left of the storm track, or technically in the navigable semicircle. The ship b has the wind at east-southeast and is in the dangerous semicircle.***A vessel hove to at the position marked b, and being passed by the storm center, will occupy successive positions in regard to the center from b to b4, and will experience shifts of the wind, as shown by the arrows, from east through south to southwest. On the other hand, if the storm center be stationary or moving slowly and a vessel be overtaking it along the line from b4 to b, the wind will back from southwest to east, and is likely to convey an entirely wrong impression as to the location and movement of the center. Hence it is recommended that a vessel suspecting the approach of proximity of a cyclonic storm should stop for a while until the path of the center is located by observing the shifts of the wind and the behavior of the barometer.”

The movement of the winds around the storm center shown in this diagram is that of cyclones of the northern hemisphere; i.e., contrary to the direction of the clock hands. In the southern hemisphere they blow in the opposite direction around the center.

By observing the rise or fall of the barometer, the shift of the winds, and the state of the sea and sky, the experienced navigator is generally able to lay down on a chart the approximate position of the storm center and steer his vessel so as to avoid danger. Various devices, known as “storm cards,” “cyclonoscopes,” etc., have been used to aid in the process of locating a storm from shipboard observations. In the Far East mariners use for locating typhoons an ingenious combination of the storm card and the aneroid barometer, called the “barocyclonometer,” an invention of the Rev. J. AlguÉ, director of the Philippine Weather Bureau.

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.

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.