PILOT CHART OF THE NORTH ATLANTIC OCEAN

The following is a summary of information contained on this chart, and in order that certain items may be more readily identified, they have been numbered and a duplicate number inclosed in a circle placed on the chart as close to the item or feature as practicable:

FRONT

Month of issue.
Date of printing.
Foundation of chart.
[6]Explanation of symbols:
(a) Derelicts and wrecks.
(b) Drifting buoys.
(c) Icebergs and field ice.
(d) Radio stations.
(e) Magnetic variation.
(f) Ocean currents.
(g) Storm tracks.
(h) Prevailing winds and calms.
(i) Scale of wind percentages.
[20]Explanation of inset chart pertaining to normal reduced barometric pressure and normal temperature for the month.
[21]Inset chart showing isobars and isotherms for the month; also annual rate of change in the variation of the compass.
[1]Average conditions of wind and weather during the month.
[9]Local weather.
[4]U. S. storm-warning flags and explanation of use.
[19]Storm signals for Great Britain and France.
[22]Inset chart showing percentages of gales.
Storm tracks.
Wind roses graphically presenting average wind directions and percentages of calms and light airs.
Lines of equal magnetic variation for the epoch 1925.
[13]Lag in U. S. naval radio time signals.
[3]North Atlantic Lane Routes—United States.
[7]North Atlantic Lane Routes—Canada.
Various steamer routes.
Various sailing vessel routes.
Lines of equal fog frequency.
Current arrows.
Trade-wind limits.
Compass rose (true).
Magnetic equator.
Various drifts of derelicts and buoys.
[5]U. S. submarine warning flag.
[11]Communication via U. S. Coast Guard stations.
[12]Note to observers relating to Hydrographic Office publications and blanks for reporting information.
[15]H. O. publications obtainable at the Panama Canal.
[16]List of Branch Hydrographic Offices.
[17]Equator crossings in the North Pacific Ocean for sailing vessels.
Sources of hydrographic and meteorological information.
[14]Note regarding percentage of fog.
[2]Key to storm tracks shown on chart.
[10]Currents north of the Bahamas.
[8]Notes to observers.
[23]U. S. radio-compass stations.
[18]Note on counter equatorial current.

BACK

Fog at sea.

CURRENT REPORTS

On the Current Reports to the Hydrographic Office the set and drift should be the difference between the dead reckoning position (corrected for all known errors except current) and the position determined by astronomical or other fixes.

Blank forms and envelopes may be obtained from any Branch Hydrographic Office or from the main office in Washington.

DATE ON WHICH AN OBSTRUCTION IS SIGHTED

The attention of shipmasters is invited to the fact that it is very desirable to know the date when ice and other obstructions reported by radio from ship to ship were sighted. Many reports of this kind come to the Hydrographic Office bearing only the date of the radiogram and lacking the date when the obstruction was seen. Cooperation in supplying this additional fact will assist the work of this office and will be appreciated.

SPECIAL SUBJECTS FOR INVESTIGATION

The Hydrographic Office is pursuing the following special subjects of investigation and invites reports of the same from mariners:

Port facilities, great sea waves, ocean currents, ocean routes, and value and correctness of charts.

Information relative to and blanks for reporting the same can be obtained from the Hydrographic Office or its Branch Offices.

(From top of chart)

No. 1400
Price 10 cents

Founded upon the researches made in the early part of the nineteenth century by Matthew Fontaine Maury, while serving as a lieutenant in the United States Navy.

(From bottom of chart)

N. A.—NOVEMBER, 1927.
Printed October 15, 1927

Prepared from data furnished by the HYDROGRAPHIC OFFICE of the NAVY DEPARTMENT and by the WEATHER BUREAU of the DEPARTMENT OF AGRICULTURE.
[Legislative Act, June 17, 1910.]
Published at the HYDROGRAPHIC OFFICE under the authority of the SECRETARY OF THE NAVY Washington, D. C.

1 AVERAGE CONDITIONS OF WIND AND WEATHER OVER THE NORTH ATLANTIC OCEAN DURING NOVEMBER

Pressure.—Pressure continues only moderately high along middle latitudes, but the crest to the southwestward of the Azores has increased to 30.15 inches. Off the coast of the United States the isobar of 30.10 inches extends farther eastward into the ocean than in October. A belt of moderately low pressure, 29.90 inches, extends in low latitudes across the ocean into the Caribbean Sea. The Iceland Low continues to deepen and the isobar of 29.70 inches appears in the position occupied by the 29.80 line of the previous month.

Temperature.—The temperature has fallen 10° to 18° along the American coast and on the Gulf of Mexico except off central and southern Florida, and 3° to 8° over the British Isles and off western Europe. Elsewhere the changes have been unimportant. Sharp contrasts in temperature appear off the American coast, the temperature ranging from 30° in the Gulf of St. Lawrence to 75° at Key West. Along the northern trans-Atlantic routes the mean is from 45° to 55°. In the greater portion of the Caribbean Sea and east of it, between the 15th parallel and the Equator, the temperature is about 80°.

Westerly Winds.—North of the 35th parallel the winds are fresh, with greatest percentage from the westerly quadrants, although they shift considerably with the passage of cyclonic storms.

Northwesterly winds sweep the American coast from the Gulf of St. Lawrence to Hatteras. South of Hatteras they become northerly to northeasterly, merging with the trades south of Jupiter.

The Trade Winds.—West of the 30th meridian the northeast trades lie mainly between the 5th and 26th parallels, but east of that meridian they are farther north, and the southern and northern limits touch the African coast at latitudes 12° and 32° N., respectively. A pronounced type of these trades occurs between the Cape Verde and Canary Islands. In mid-ocean the trades are easterly, but again become northeasterly over the West Indies, the Caribbean Sea, and the Gulf of Mexico.

The southeast trades extend about 4° north of the Equator west of the 15th meridian. East of that meridian, in the same latitude, the winds become southerly, and in the Gulf of Guinea, south-southwesterly.

Gales and Calms.—With the approach of winter, there has been a moderate increase in the percentage of gales north of the 35th parallel, except near the Azores, where it is less than during October.

Gales are infrequent south of latitude 35° N., and only seventeen West India hurricanes have been observed during the 39-year period 1887 to 1925.

Calms are of highest percentage between the 5th and 10th parallels and northward along the African coast to the Canary Islands.

Fog.—The percentage of fog has diminished generally since October, although the area of highest percentage, 30 to 35 per cent of days, continues to the southeast of Newfoundland with little change. A light increase has occurred in the English Channel.

2 KEY TO THE NOVEMBER STORM TRACKS AS SHOWN UPON THIS CHART

No.DatesBegins near—

°

°

IOct. 24-Nov. 2, 191241 N.75 W.
IINov. 12–20, 19121280
III 19–21, 19124057
IV 6–10, 19135345
V 12–15, 19161180
VI 18–19, 19192278
VII 16–19, 19202486
VIII 28-Dec. 2, 19203480
IX 10–13, 19214068
X 9–14, 19241977
XI 10–12, 19244047
XII 5–7, 19254337

Tracks of other and older storms than those shown on this chart were published in previous editions. Positions given are at Greenwich mean noon.

ICE CONDITIONS

Navigation of the Strait of Belleisle by the trans-Atlantic trades ordinarily ceases about November 25, although the average formation of local ice is some two weeks later. In the River St. Lawrence the close of navigation occurs during the last week in November.

3 NORTH ATLANTIC LANE ROUTES—UNITED STATES

In accordance with the North Atlantic Track Agreement, the Hydrographic Office advises that the North Atlantic Lane Routes, agreed to in Oct. 1924, by the principal steamship companies, shown on this chart in full black lines are effective as follows:

TRACK CEASTBOUND.—Cross longitude 50° in latitude 42° from Sept. 1 to Jan. 31 inclusive.
WESTBOUND.—Cross longitude 50° in latitude 43° from Sept. 1 to Jan. 31 inclusive.

Vessels bound to or from United States ports calling at Halifax have the option of following either the Canadian or United States seasonal tracks to or from that port, passing 40 miles south of Sable Island westbound, and 60 miles south of Sable Island eastbound, when proceeding on U. S. tracks, or 20 miles south of Sable Island eastbound, when proceeding on Canadian tracks.

Vessels bound direct to Portland (Maine) may follow the Canadian Seasonal tracks.

NOTE.—The above routes are liable to alterations when, owing to abnormal ice conditions it is considered advisable by the steamship lines who are parties to the North Atlantic Track Agreement. Notice of these alterations will be published by the U. S. Hydrographic Office.

4 U. S. STORM WARNINGS.

N. W. WindsS. W. WindsN. E. WindsS. E. Winds“Hurricane” Warning

Flags 8 feet square. Pennants 5 feet hoist, 12 feet fly.

Storm Warning Flags.—A red flag with a black center indicates that a storm of marked violence is expected.

The pennants displayed with the flags indicate the direction of the wind: Red, easterly; white, westerly. The pennant above the flag indicates that the wind is expected to blow from the northerly quadrants; below, from southerly quadrants.

By night the approach of storms of marked violence is indicated by: Two red lights, one above the other, for winds beginning from the northeast; a single red light for winds beginning from the southeast; a red light above a white light for winds beginning from the southwest; and a white light above a red light for winds beginning from the northwest.

Hurricane Warnings.—Two red flags with black centers, one above the other, displayed by day, or two red lights with a white light between, displayed by night, indicate the expected approach of a tropical hurricane, or one of the extremely severe and dangerous storms which occasionally move across the Lakes and northern Atlantic coast. These warnings are displayed at 219 Weather Bureau stations on the Atlantic and Gulf coasts of the United States, and at the following places in the West Indies: Basseterre, St. Kitts; Aguadilla Central, Aguirre Central, Arecibo, Arroyo, Fajardo Playa, Guanica Central, Humacao Playa, Luiza (Canovanas Central), Mayaguez Playa, Ponce, San Juan, and Vieques Island, Porto Rico; Kingston, Jamaica; Puerto Plata, San Pedro de Macoris, and Santo Domingo, Haiti; Roseau, Dominica; St. Thomas, Virgin Islands of the U. S. A.; Grand Turk Island, Turks Islands; Swan Island; and Habana, Cuba.

Note.—The Weather Bureau stations at Cape Henry, Virginia, and the Philadelphia Maritime Exchange Station at Delaware Breakwater are equipped for day and night communication with passing vessels. The International Code is used by day and the Morse Code, flashlight, by night. Messages to or from vessels will be forwarded to destination.

SMALL CRAFT

Moderately strong
winds are expected

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.

5 U. S. SUBMARINE WARNING FLAG

The submarine distinguishing and warning flag is hoisted on the tender or parent ship of United States submarines to indicate that submarines are operating in that vicinity. It consists of a rectangular red flag with white center on which is the profile of a torpedo in black. Launches accompanying submarines also fly this flag.

Vessels seeing this signal should give the escorting vessel a wide berth and keep a good lookout for submarines.

6 EXPLANATION OF SYMBOLS.

DERELICTS AND WRECKS.—The name of the vessel is given, if known, and the symbol in red represents the reported rig and condition at the date set opposite to the position. The successive positions in which the derelict was sighted are joined by lines of dashes and the corresponding dates are indicated.

DRIFTING BUOYS.—These are shown in red color. The date when sighted is also given in red.

ICEBERGS FIELD ICE.—These symbols with date represent ice of previous month. When numerous bergs are reported by one vessel along a given track the date and position of the first and last one only are graphically shown, and the number of bergs is written on a line joining them.

RADIO STATIONS.—Represents various governmental stations. The U. S. naval radio stations operate to various distances. Communication with most of them can be relied upon by all vessels for 100 nautical miles at least.

MAGNETIC VARIATION.—The lines of equal magnetic variation for every degree for the epoch 1925 are shown by lines of fine dots in black.

OCEAN CURRENTS.—The yearly average set of the stream and drift currents is shown by small black arrows.

STORM TRACKS.—The several red lines indicate the individual paths followed by the centers of the more severe cyclonic storms that have occurred during the corresponding month in past years. (See table in another column.) The successive positions of a storm center at Greenwich mean noon are indicated by small circles with their corresponding dates.

PREVAILING WINDS AND CALMS.—The wind rose, in blue color, in each 5-degree square shows the character of the winds that have prevailed within that square. The wind percentages north of latitude 30° were concentrated upon eight points; south of latitude 30° upon sixteen points. The arrows fly with the wind. The length of the arrow, measured from the center of the circle on the attached scale, gives the number of times in each 100 observations that the wind has blown from or near the given point. The number of feathers shows the average force of the wind on the Beaufort scale. The figure in the center of the circle gives the percentage of calms, light airs, and variable winds.

For Example: The attached wind rose should be read thus: In each 100 hours the wind has averaged as follows: from N. 32 hours, force, 4; from NNE. 20 hours, force 3; from NW, 18 hours, force, 2; calms, light airs, and variables, 30 hours.

SCALE OF WIND PERCENTAGES

7 NORTH ATLANTIC LANE ROUTES—CANADA

In accordance with the North Atlantic Track Agreement, the Hydrographic Office advises that the North Atlantic Lane Routes to Canada shown in full black lines are effective as follows:

TRACK “F”

From May 16 to the Opening of Belle Isle Route and to November 30 When Not Using the Belle Isle Route

Eastbound.—Steer from a position 25 miles south of Cape Race on a course 10 miles south of the Great Circle track until approaching Fastnet, Inishtrahull, or 19 miles south of Bishop Rock.

Westbound.—Steer from Fastnet, Inishtrahull, or 10 miles south of Bishop Rock, on a course 10 miles north of the Great Circle track until approaching Cape Race, then steer a course to pass 10 miles south of Cape Race, thence to the St. Lawrence.

TRACK “G”

From the Opening of the Strait of Belleisle to November 14

Eastbound.—Steer from Belle Isle on a course 10 miles south of the Great Circle track until approaching Fastnet, Inishtrahull, or 10 miles south of Bishop Rock.

Westbound.—Steer from Fastnet, Inishtrahull, or 10 miles south of Bishop Rock on a course 10 miles north of the Great Circle track until approaching Belle Isle.

Note.—Vessels bound to or from U. S. Ports FROM OR TO THE NORTH OF IRELAND have the option of following the Canadian Seasonal Track “F” passing 40 miles south of Sable Island WESTBOUND, thence to position south of Nantucket, and EASTBOUND from position 40° 10′ N. in 70° 00′ W. to position 60 miles south of Sable Island.

8 TO ALL OBSERVERS

Many letters to observers acknowledging reports of marine data are returned to the Hydrographic Office on account of wrong or insufficient address.

It is realized that mariners change their addresses frequently and their mail in consequence is frequently delayed and sometimes lost; but the office is anxious to get letters of acknowledgment through to each observer, and to accomplish this it requests observers to indicate plainly in reports where acknowledgments should be sent.

Should any observer fail to receive an acknowledgment of information furnished this office, he may be sure that it is due to faulty address, as every report is acknowledged.

9 LOCAL WEATHER

For extended remarks on wind and weather along the more important coasts, see the Sailing Directions published by the U. S. Hydrographic Office.

10 CURRENTS NORTHWARD OF BAHAMA ISLANDS

In the angle between the Gulf Stream and the Bahama or Antilles Current, and the Bahama Islands to approximately latitude 30° N., currents setting southward have been experienced.

11 U. S. COAST GUARD STATIONS

All U. S. Coast Guard Stations on the Atlantic and Pacific coasts are equipped for signaling by the International Code, the Semaphore Code, the Occulting or Flashing-Light Code, and the International Morse Code (Wigwag). On the Atlantic coast those stations north of Cape Hatteras, with few exceptions, and on the Pacific coast those stations near lines of communication, are prepared to transmit messages of passing vessels either by telegraph or by telephone and telegraph combined.

12 NOTE TO OBSERVERS.

Hydrographic Office Publications.—To those mariners who contribute marine data relating to this or other publications of the Hydrographic Office, the Pilot Charts, Notice to Mariners, and Hydrographic Bulletins are given in exchange free of cost. In American ports in which a Branch Hydrographic Office is established mariners of every nationality should call for them in person and receive in addition the latest information regarding charts, sailing directions, dangers to navigation, etc. All services free. Office hours 9 a.m. to 4.30 p.m. To other American ports and to foreign ports the Pilot Charts will be forwarded by mail upon application to the Hydrographic Office or to the nearest Branch Hydrographic Office. In such cases state clearly for which ocean and for which months they are desired and the post-office address to which they should be sent.

Other Places of Supply.—The above-named publications and observers’ blanks will also be furnished upon application to the Harbor-master at Manila and the American Consular Offices in the leading seaports abroad.

Marine Data Reports.—These should be handed or mailed promptly upon arrival in port to the nearest Branch Hydrographic Office, or to the Main Office, in the franked envelope supplied for that purpose. At places outside of the United States or its possessions such communications may be handed to the American Consul who will mail them free of cost.

Observer’s Address.—Mail for captains and officers of the merchant marine is frequently returned because the ship has sailed from the port named in the address. Those who desire their Pilot Charts, Notices to Mariners, and Hydrographic Bulletins to reach them regularly should make arrangements to have their mail follow them, or else give the Hydrographic Office an address at which such mail will be held for them until they return.

13 LAG IN U.S. NAVAL RADIO TIME SIGNALS

The U. S. Naval observatory during the year 1925, determined the lag of the Annapolis and Arlington signals to be about nine hundredths of a second (.09). The error of the time signal is generally less than one-tenth of a second (.1).

14 FOG.

The dotted blue lines show the percentage of days on which fog was observed in November from 1901 to 1906, inclusive.

15 HYDROGRAPHIC OFFICE PUBLICATIONS OBTAINABLE AT THE PANAMA CANAL

By authority of The Governor of The Panama Canal some of the duties of the Branch Hydrographic Offices are performed by the Captain of the Port at Cristobal and the Captain of the Port at Balboa. Reference charts and sailing directions may be consulted at these offices, and shipmasters may receive the Pilot Charts, Notice to Mariners, and Hydrographic Bulletin in return for marine and meteorological data reports. Observers’ blanks and comparisons of navigational instruments may be obtained at the same time. Neither of these offices maintains a regular mailing list for the distribution of publications; such mailing lists are maintained at the Branch Hydrographic Offices along the United States coasts (see addresses elsewhere on the chart) and at the main office, Washington, for the benefit of those shipmasters and officers who contribute data regularly.

Sale of Hydrographic Office Publications.—The Captain of the Port of Cristobal, Canal Zone, is an agent for the sale of Hydrographic Office publications. Applications should be made to the Captain of the Port at Cristobal or at Balboa.

16 BRANCH HYDROGRAPHIC OFFICE ADDRESSES

Boston, Mass.

14th Floor, Customhouse

New York, N. Y.

Rooms 301–302, Maritime Exchange, 78–80 Broad St.

Philadelphia, Pa.

Main Floor, The Bourse Building

Baltimore, Md.

Room 123, Customhouse

Norfolk, Va.

Room 16, Customhouse

Savannah, Ga.

First Floor, Customhouse

New Orleans, La.

Room 215, Customhouse

Galveston, Tex.

Room 301, Customhouse

San Juan, P. R.

Federal Building

San Pedro, Calif.

Immigration Building, San Pedro

San Francisco, Calif.

Merchants’ Exchange

Portland, Oreg.

Room 407, Customhouse

Seattle, Wash.

Room 408, Lowman Building

Duluth, Minn.

Room 1000, Torrey Building

Sault Sainte Marie, Mich.

Room 10, Federal Building

Chicago, Ill.

Room 481, Post Office Building

Detroit, Mich.

7450 East Jefferson Ave.

Cleveland, Ohio

Rooms 406–408, Federal Building

Buffalo, N. Y.

Room 345, Post Office Building

HYDROGRAPHIC INFORMATION OFFICE

Honolulu, T. H.

Room 219, Federal Building

17 EQUATOR CROSSINGS FOR SAILING PASSAGES IN THE PACIFIC OCEAN.

This table gives the data for ships north bound in the Pacific from Cape Horn or west coast of South America, for the United States.

Month of crossing.Longitude
of crossing.		Lose SE.
trades.
Prob. lat.		Enter NE.
trades.
Prob. lat.		Lose NE.
trades.
Prob. lat.
January114° 00′ W.5° 00′ N.8° 00′ N.27° 00′ N.
February113° 30′ W.3° 30′ N.6° 30′ N.26° 00′ N.
March113° 30′ W.5° 30′ N.8° 30′ N.27° 00′ N.

Vessels bound from Cape Horn to the line during the above months will meet the SE. trades (in longitude 90° W.) as follows: January, 29° S.; February, 28° S.; March, 26° S.

18 NOTE.

Between 25° to 50° W and 5° to 10° N the current sets to the eastward from July to December.

19 STORM SIGNALS

GREAT BRITAIN

A black cone point upwards indicates that a gale from NW., through North, to SE. may be approaching. A black cone point downwards indicates that a gale from SE., through South, to NW. may be approaching.
Three lights of like color suspended from the corners of a triangle replace the cone at night.

FRANCE

Gale from NW’d.Gale from SW’d.Hurricane.
Gale from NE’d.Gale from SE’d.

20 EXPLANATION OF INSET CHART.

The inset chart below shows the normal reduced barometric pressure and the normal temperature of the atmosphere for the month, and the annual change in the variation of the compass.

Isobars are shown by full and dashed blue lines; isotherms by dotted blue lines.

Any wide departure from the normal pressure shows some disturbance and may indicate a coming gale.

21 ISOBARS AND ISOTHERMS FOR THE MONTH.

Readings of mercurial barometers must be corrected to 32° F. and to standard gravity, by the tables given below, in order to compare them with the pressures shown on the inset chart. Aneroid barometers require no correction for gravity.

To 32° Fahrenheit.To standard gravity
Att. Ther.Corr.Lat.Corr.
°In.°In.

40

−.08

0

−.06

50

−.06

10

−.06

60

−.06

20

−.06

70

−.11

30

−.04

80

−.14

40

−.01

90

−.17

50

+.01

The red lines show the annual change in the variation of the compass. The direction of movement of the north end of the magnetic needle is indicated by E. or W.

22 GALES.

The figures in the center of each 5-degree square show for the month of November the percentage of days (i. e., the number of days in each hundred) upon which winds of force 8 and over have been recorded at some point within the given square during the eleven-year period 1897–1907.

23 U. S. RADIO-COMPASS STATIONS

Information relative to the methods for obtaining radio-compass bearings from the U. S. radio-compass stations situated on the U. S. Atlantic, Gulf, and Pacific coasts, together with a list of such stations, formerly printed on this chart, will be found in H. O. Publication No. 205 of 1927, “Radio Aids to Navigation”; price, 75 cents.

Transcriber’s Note: