coasts, passing generally to the northeast. The rainfall is less than in the preceding month. MAY is as a rule a pleasant month. There are but few southeasterly gales. Northwest winds prevail north of Cape Mendocino. Occasionally high north to northwest winds blow steadily for several days along the coast. Gales are rare, and when they do occur are of moderate intensity. JUNE is as a rule a pleasant month. Areas of high pressure may move from the California coast northward through Oregon and Washington. Winds are as a rule from the west or northwest. Rainfall is scant south of Cape Mendocino. More or less fog prevails along the coast. JULY is generally a pleasant month. High northwest winds prevail along the coast of Oregon and northern California. There is also much fog in the afternoon at the entrance to San Francisco Bay, and much fog prevails along the coast. AUGUST is usually a quiet month. Storms are infrequent. Rainfall is very light along the coast, especially south of Cape Mendocino. Fogs are frequent on the California coast. Strong north to northwest winds prevail along the entire coast. August averages the most fog of any month of the year. SEPTEMBER is a quiet month. Occasional storms occur toward the close of the month and rainfall is heavier on the Oregon and Washington coasts. The winds are generally from the northwest, and much low fog prevails close to the shore. OCTOBER marks the beginning of stormy weather. Occasional disturbances with high southeasterly gales may be expected from the Straits of Juan de Fuca south to Point Reyes. Rainfall is heavier and fog is less frequent except south of Cape Mendocino. NOVEMBER is a stormy month. Southeast gales are frequent, increasing in severity toward the close of the month. This month marks the beginning of the rainy season in California. DECEMBER is a stormy month. Southeast gales are frequent and winds from 40 to 60 miles an hour may occur with these storms. The rainfall is heavy along the entire coast. Low-lying fogs frequently occur in the morning along the coast, but are much less frequent than in summer. Smoke from forest fires occurs during July, August, and September in Puget Sound and Georgia Strait and at times extends a considerable distance seaward, southward and northward of Cape Flattery. At times it is a serious hindrance to navigation and has been known to prevent it entirely in Puget Sound. In recent years its prevalence has considerably diminished, some seasons being entirely free from it. It is cleared away by rains. STORM WARNINGS Storm warning are displayed by the United States Weather Bureau at numerous places on the coasts of the United States and the Great Lakes. Small craft warning.-A red pennant indicates that moderately strong winds that will interfere with the safe operation of small craft are expected. No night display of small craft warnings is made. Northeast storm warning.-A red pennant above a square red flag with black center displayed by day, or two red lanterns, one above the other, displayed by night, indicate the approach of a storm of marked violence with winds beginning from the northeast. Southeast storm warning.-A red pennant below a square red flag with black center displayed by day, or one red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the southeast. Southwest storm warning.-A white pennant below a square red flag with black center displayed by day, or a white lantern below a red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the southwest. Northwest storm warning.-A white pennant above a square red flag with black center displayed by day, or a white lantern above a red lantern displayed by night, indicates the approach of a storm of marked violence with winds beginning from the northwest. Hurricane, or whole gale warning. Two square flags, red with black centers, one above the other, displayed by day, or two red lanterns, with a white lantern between, displayed by night, indicate the approach of a tropical hurricane, or one of the extremely severe and dangerous storms which occasionally move across the Great Lakes and Atlantic coast. The following are the storm warning display stations within the limits covered by this volume: Marine reports are telegraphed from the following points on the Pacific coast, under an arrangement with the Merchants' Exchange, San Francisco, Calif., the reports being prepared by agents of the exchange or by captains of coasting vessels: Honolulu, Hawaii. Surf, Calif. Brandon, Oreg. Willapa Harbor, Wash. Raymond, Wash. Westport, Wash. The supervision of radio communication in the United States, including the Hawaiian Islands, is controlled by the Federal Communications Commission. Time signals.-Radio time signals are sent daily from the United States naval radio stations at San Francisco (Mare Island), Calif. (call letters NPG) and Honolulu, Territory of Hawaii (call letters NPM). These are rebroadcast from Arlington, Va. (call letters NAA). For the latest information as to time, frequency in kilocycles, and type of emission see H.O. No. 205, Radio Aids to Navigation, issued by the Hydrographic Office, United States Navy. As indicated in the table below, the time signal consists of the transmission of dots (.) and the omission of the dots (0) for various seconds preceding the hour signal. The hour signal is the beginning of the transmission of a dash (-) of 1 second duration. This is followed by the letters VA. In the event of an error occurring in the signal, another time signal will be transmitted 1 hour later. Hydrographic information, weather reports, and other information of benefit to shipping are sent out from these stations. RADIOBEACONS The United States Lighthouse Service operates radiobeacons in or near the area covered by this volume at the following places: Los Angeles Harbor Light Anacapa Island Light Point Arguello Light Point Sur Light San Francisco Lightship Farallon Light Point Arena Light Blunts Reef Lightship Cape Blanco Light 72870°-34- -2 Cape Arago Light (under construction Columbia River Lightship Grays Harbor Light Umatilla Reef Lightship Swiftsure Bank Lightship Race Rocks Light Smith Island Light Point Wilson Light For details as to frequencies, geographic positions, signals, and thick and clear weather transmission, see Pacific Light List of the Lighthouse Service or Hydrographic Office Publication No. 205. These radiobeacons are intended for the use of vessels equipped with radio compasses. While the use of radiobeacons should not lead a mariner to neglect other precautions such as the use of the lead, etc., during thick weather, the bearings will greatly reduce the dangers incident to navigation in the fog. The bearing of the radiobeacon may be determined with an accuracy of approximately 2° and at distances considerably in excess of the range of visibility of the most powerful coast lights. The apparatus is simple and may be operated by the navigator without the assistance of a radio operator or with the knowledge of the telegraph code. The radio direction finding apparatus consists of a radio receiving set, similar in operation to those used for radiotelegraph or radiotelephone reception, and a rotatable coil of wire in place of the usual antenna. By rotating the coil the intensity of the signal received from the transmitting station is made to vary, and by noting the position of the coil when the signal is heard at its minimum intensity, the bearing of the transmitting station is readily obtained. It is important to note that the bearing of an incoming radio wave is subject to errors not unlike the deviation of the magnetic compass. Those using radio direction finding aboard ship are cautioned to bear these errors in mind and to keep the radio compass calibrated at all times. This may be done during clear weather by comparing the bearing obtained with the radio compass with the bearing as obtained by visual methods in general use. All radio bearings are subject to what is called "night effect", a variable error sometimes experienced near nightfall and sunrise. The uncertainty due to this cause may be lessened by taking repeated radio bearings. The signals from the radiobeacons have definite characteristics for identifying the station, and bearings may be obtained with even greater facility than sight bearings on visible objects. At some of the stations the radio and sound signals are synchronized for distance-finding purposes. Caution in approaching lightships on radio bearings.-Radiobeacons placed on lightships provide very valuable leading marks in approaching the coasts and ports. Consequently nearly half of the radiobeacons on the Atlantic and Pacific coasts of the United States are located on lightships. Several recent incidents, however, show that serious risks are incurred by masters of steamers using radio bearings to set courses directly or nearly so for the lightships, without suitable precautions. Recently an Atlantic liner in approaching Nantucket Lightship in a dense fog, found the radio bearings so accurate that the steamer scraped the side of the lightship and carried away the antenna yards; the other signals of the lightship were not heard in time to permit the course to be changed to pass clear; also the crew of the lightship did not hear the steamer's fog warning whistle in time to give any special counter warning. Later this lightship was run down and sunk by another liner under similar circumstances. It is of the greatest importance, in using radio bearings for approach, that at a sufficient distance before reaching a lightship, the course be set to pass safely clear. Radio bearings themselves offer a convenient means of checking this, by methods well known in ordinary navigation. The navigator may check his position when steering to pass to one side of the lightship, by taking successive radio bearings and using these with the intervening distances run, to ascertain the distances off from time to time. Radio cross bearings may also often be used. Soundings should not be neglected, as a few soundings in connection with a radio bearing or a chain of soundings themselves usually give an excellent position. See Soundings and Echo Soundings in appendix, page 339. A general description of this method of navigation and the instruments required is given in Lighthouse Service publication, Radiobeacons and Radiobeacon Navigation, which may be obtained from the Superintendent of Documents, Washington, D.C., price 15 cents. RADIO DIRECTION-FINDER STATIONS United States naval direction-finder stations will furnish radio bearings to mariners of all vessels equipped with radiotelegraphic transmitters. While the use of these bearings should not lead a mariner to neglect other precautions, such as use of the lead, etc., during thick weather, these bearings will greatly reduce the dangers incident to navigation in the fog. the Accuracy of bearings.-The accuracy with which bearings can be taken depends on various conditions and, while bearings taken by a station can generally be considered accurate to within 2°, Government cannot accept any responsibility for the consequences of a bearing being inaccurate. In the case of bearings which cut the coast line at an oblique angle, errors of from 4° to 5° have been reported. Bearings obtained between about one-half hour before sunset and one-half hour after sunrise are occasionally unreliable. It is probable that the accuracy of a bearing is also affected if the ship's transmitting instrument is not adjusted to the correct wave length. Bearings signaled as approximate" or "second class" should be regarded with suspicion as being subject to considerable error. The maximum distance for 66 which bearings from these stations are accurate is 150 miles. Direction-finder stations used as radiobeacons.-A naval direction finder station when used as a radiobeacon, transmits upon request, its call sign for 45 seconds on 375 kilocycles (800 m). The following list of naval radio direction-finder stations will be of use to vessels navigating the approximate limits of this volume: Imperial Beach, San Diego, Calif. Point Arguello, Calif.1 Point Montara, Calif." The calibrated arc between 111° and 160° passes overland, and bearings in this sector should be used with caution. San Francisco Bay entrance group; master station, Point Montara. |