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originate and die out far from the mainland and hundreds of miles from the West Indies. The storm area varies from about 100 miles to 500 or more miles in width, with a comparatively calm center some 10 or 20 miles in diameter. This center is an area of lowest atmospheric pressure around which the wind blows in a more or less circular course (spirally) in a direction contrary to the hands of a watch. In some respects the center, or "eye" is the most dangerous part of the hurricane and is therefore a region especially to be avoided; for, although the air movement within it, if any, is usually light and fitful, the seas in this area in most cases are very heavy and confused, rendered so by the shifting violent winds surrounding it. The storm-field advances in a straight or curved track, sometimes with considerable speed, at other times at a very slow rate. The highest rates of progression usually occur when the storm moves northward or northeastward over the United States, or in middle or higher latitudes over the ocean. The average speed is about 12 or 15 miles an hour.

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Hurricanes form over a wide range of the ocean between the Cape Verde and the Windward Islands, over the western part of the Caribbean Sea, and in the Gulf of Mexico. While some move northward in the beginning, especially those that originate southeast of Bermuda, the majority take a westerly to northwesterly course. these some curve gradually northward, either to the eastward of or above the larger islands of the West Indies, then turn northeasterly or easterly near to or at a considerable distance from the Atlantic coast of the United States. Others pass over or south of the greater islands and enter the Gulf of Mexico, thence curve northward or northeastward and strike some part of the east Gulf coast or continue to the westward and strike the west Gulf coast. Tracks of hurricanes are shown on the pilot charts of the North Atlantic Ocean and Central American waters, published monthly by the United States Hydrographic Office.

The hurricane season is likely to begin in June and close with November. The months of greatest frequency are August, September, and October. Hurricanes are most likely to be severe during August and the early half of September. During all the months of the season, however, the possibilities of encountering an intense storm are sufficiently great to warrant the mariner in keeping careful watch of the weather elements while in these waters. Information concerning Hurricane Warnings issued by the United States Weather Bureau is contained in this volume under Radiotelegraphic Weather Broadcasts (p. 18).

Signs of approach. One of the earliest signs of a hurricane is the appearance of high cirrus clouds which converge toward a point on the horizon that indicates the direction of the center of the storm. The snow-white fibrous mares' tails appear when the center is about 300 or 400 miles distant. Another usual early indication is a long, heavy swell propagated to a considerable distance, sometimes two or three days in advance, when there is no intervening land to interrupt it. This swell comes from the general direction in which the storm is approaching. There is usually a slight rise of the barometer at the outset, followed by a continuous fall. In front of the storm, if it is advancing in some westerly direction toward the observer, the winds blow from a northerly point (northeast, north, or northwest);

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if in some northerly direction toward the observer, they will blow from an easterly point (southeast, east, or northeast). A further indication is a rough, increasing sea. If one or more of these signs be wanting, there is little cause for anticipating a hurricane.

As the storm center approaches the barometer continues to fall; the velocity of the wind increases and blows in heavy squalls, and the changes in its direction becomes more rapid. Rain in showers accompanies the squalls, and when closer to the center the rain is continuous and attended by furious gusts of wind; the air is frequently thick with rain and spume drift, making objects invisible at a short distance. A vessel on a line of the hurricane's advance will experience the above disturbances, except that as the center approaches the wind will remain from the same direction, or nearly so, until the vessel is close to or in the center.

Distance from center.-The distance from the center of a hurricane can only be estimated from a consideration of the height of the barometer and the rapidity of its fall, and the velocity of the wind and rapidity of its change in direction. If the barometer falls slowly and the wind increases gradually it may be reasonably supposed that the center is distant; with a rapidly falling barometer and increasing winds the center may be supposed to be approaching dangerously near.

Practical rules.-When there are indications of a hurricane, vessels should remain in port or seek one if possible, carefully observing and recording the changes in barometer and wind and taking every precaution to avert damage by striking light spars, strengthening moorings, and if a steamer, preparing steam to assist the moorings. In the ports of the Southern States hurricanes are generally accompanied by very high tides, and vessels may be endangered by overriding the wharf where moored if the position is at all exposed.

Vessels in the straits of Florida may not have the sea room to maneuver so as to avoid the storm track and should use every endeavor to make a harbor or stand out of the straits to obtain sea room. Vessels unable to reach port and having sea room to maneuver should observe the following rules:

When there are indications of the near approach of a hurricane, sailing vessels should heave to on the starboard tack and steamers remain stationary and carefully observe and record the changes in wind and barometer so as to find the bearing of the center and ascertain by the shift of wind in which semicircle the vessel is situated. The safety of the vessel often depends on heaving to in time.

Bearings of center.-Facing the wind, the storm center will be 8 to 12 points to the right; when the storm is distant it will be from 10 to 12 points, and when the barometer has fallen five- or six-tenths it will be about 8 points.

A line drawn through the center of a hurricane in the direction in which it is moving is called the axis or line of progression, and facing in the direction of its path the semicircle on either side of the axis is called, respectively, the right hand or dangerous semicircle and the left hand or navigable semicircle.

To find in which semicircle the vessel is situated:

If the wind shifts to the right, the vessel will be in the right hand or dangerous semicircle with regard to the direction in which the

storm is traveling, in which case the vessel should be kept on the starboard tack and increase her distance from the center.

If the wind shifts to the left, the vessel will be in the left or navigable semicircle. The helm should be put up and the vessel run with the wind on the starboard quarter, preserving the compass course, if possible, until the barometer rises, when the vessel may be hove to on the port tack, or if there is not sea room to run the vessel can be put on the port tack at once.

Should the wind remain steady and the barometer continue to fall, the vessel is in the path of the storm and should run with the wind on the starboard quarter into the navigable semicircle.

In all cases act so as to increase as soon as possible the distance from the center, bearing in mind that the whole storm field is advancing.

In receding from the center of a hurricane the barometer will rise and the wind and sea subside.

TIDES AND CURRENTS

Tide tables for the Atlantic Ocean are published in advance annually by the Coast and Geodetic Survey, price 25 cents. This volume supplies full tidal data for the east coast of North and South America, the west and north coasts of Africa, and all of Europe.

It contains a table of full daily predictions of the times and heights. of high and low waters for certain reference stations along the coast, with full explanations for the use of this table. The use of table 2 of the Tide Tables should be known to every navigator. By means of this table the predictions given for the reference ports are extended so as to enable one to obtain the predictions for each day for a large number of other stations.

The effect of strong winds, in combination with the regular tidal action, may at times cause the water to fall below the plane of reference of the chart, mean low water. The water may also rise about the same amount above mean high water, due to similar causes.

Caution. In using the Tide Tables, slack water should not be confounded with high or low water. For ocean stations there is usually but little difference between the time of high or low water and the beginning of ebb or flood current; but for places in narrow channels, landlocked harbors, or on tidal rivers the time of slack current may differ by two or three hours from the time of high or low water stand, and local knowledge is required to enable one to make the proper allowances for this delay in the condition of tidal currents. To obtain the times of slack water, reference should be made either to figures given for various places in this volume of the Coast Pilot or to the Current Tables.

Current Tables for the Atlantic coast of the United States are published in advance annually by the United States Coast and Geodetic Survey. This volume, which sells for 10 cents per copy, includes the daily predicted times of slack water and the times and velocities of strength of flood and ebb for certain reference stations and a table of current differences and constants by means of which corresponding daily predictions may be readily obtained for numerous other places. These tables also include current diagrams for six bodies of water along the coast which show in a graphical

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form the velocities of the flood and ebb currents and the times of slack and strength over a considerable stretch of the channel of these waterways.

CURRENTS, CAPE HENRY TO KEY WEST

From our present information the indications are that, except during northerly and northeasterly winds, a current of about 0.5 knot, setting northeastward with the trend of the coast, may be expected outside the 10-fathom (18.3 m) curve as far north as Cape Hatteras, and that it increases offshore toward the axis of the Gulf Stream.

Strong currents are produced by the wind along the coast in northeasterly and southerly gales, reversing or greatly accelerating the normal current. Their strength and set depend on the direction, strength, and duration of the gale. A table showing the direction and velocities of the currents that may be expected with winds of given strength is given on page 37.

The following is a more detailed statement of the currents along the coast:

Latitude 37°05' N., longitude 75°41′ W. (off the entrance to Chesapeake Bay). The tidal current here is only very slightly rotary and appears to turn counterclockwise. The strength of the flood current occurs about one hour after flood begins at Chesapeake Bay Entrance and sets 265° with a velocity of about 0.3 knot. The strength of the ebb current comes about one and one-half hours after ebb begins at Chesapeake Bay Entrance and sets 85° with a velocity of about 0.3 knot. Since the current is only slightly rotary, there is practically slack water at Cape Charles Lighted Buoy about two hours before ebb begins, and also about two hours before flood begins at Chesapeake Bay Entrance.

Diamond Shoal Lightship (off Cape Hatteras, N. C.).-The tidal current here is rotary, turning clockwise, but very weak, the velocity of the current at times of strength being less than a tenth of a knot. The currents encountered off Cape Hatteras are, therefore, nontidal and depend chiefly on the wind and on the Gulf Stream. Winds from the southwest, south, and southeast directions bring about the strongest currents, which set northeastward, a wind of 35 miles per hour bringing about a current of 114 knots. Winds from the northeast and northwest are only about 50 percent as effective in producing currents, a wind of 35 miles per hour from the northeast or northwest bringing about a southerly current of about 11⁄2 knot.

Cape Lookout Shoals Lighted Whistle Buoy (off Cape Lookout, N. C.). The tidal current here is rotary, turning clockwise. The strength of the flood current occurs about one hour after flood begins at Charleston Harbor Entrance and sets 275° with a velocity of about 0.4 knot. The strength of the ebb current comes about one hour after ebb begins at Charleston Harbor Entrance and sets 95° with a velocity of about 0.4 knot. The minimum currents before flood and ebb are about 0.2 knot. Since the tidal current here is weak, the currents brought about by the winds completely mask the tidal currents. general the current appears to set northeastward in the summer months and southward during the winter months, with an average velocity of about 0.3 knot.

Frying Pan Shoals Lighted Whistle Buoy 2 A. F. P. (off Cape Fear River, N. C.).-The tidal current here is rotary, turning clockwise.

The strength of the flood current occurs about one hour after flood begins at Charleston Harbor Entrance and sets 295°, with a velocity of about 0.3 knot. Strength of ebb comes about one hour after ebb begins at Charleston Harbor Entrance and sets 120°, with a velocity of about 0.4 knot. The minimum current before flood comes about two hours before flood begins at Charleston Harbor Entrance, setting southwestward with a velocity of about 0.2 knot. The minimum current before ebb comes about two hours before ebb begins at Charleston Harbor Entrance, setting northeastward with a velocity of about 0.2 knot.

Charleston Lighted Whistle Buoy C (off the entrance to Charleston Harbor, S. C.).-The current is rotary, turning clockwise. The strength of the flood current occurs about one hour after flood begins at Charleston Harbor Entrance and sets 265°, with a velocity of about 0.3 knot. The strength of the ebb current comes about one and three-fourths hours after ebb begins at Charleston Harbor Entrance and sets 95°, with a velocity of about 0.3 knot. The minimum currents before flood and ebb set southward and northward, respectively, with a velocity of about 0.2 knot.

Martins Industry (five miles east of the entrance to Port Royal Sound, S. C.).-The current here is rotary, turning clockwise. The strength of the flood current occurs about two and one-half hours after flood begins at Charleston Harbor Entrance and sets 285°, with a velocity of about 0.6 knot. The strength of the ebb current comes about one and one-fourth hours after ebb begins at Charleston Harbor Entrance and sets 105°, with a velocity of about 0.6 knot. The minimum currents before flood and ebb set southward and northward, respectively, with a velocity of about 0.2 knot.

Savannah Lightship (off the entrance to the Savannah River, Ga.).— The tidal current here is rotary, turning clockwise. The strength of the flood current occurs about one and one-half hours after flood begins at Savannah River Entrance and sets 295°, with a velocity of about 0.3 knot. The strength of ebb current occurs about two and three-fourths hours after ebb begins at Savannah River Entrance and sets 115°, with a velocity of about 0.5 knot. The minimum currents before flood and ebb are very small, setting southward and northward, respectively, with velocities of about 0.1 knot.

Brunswick Lighted Whistle Buoy 2 B (off the entrance to St. Simon Sound, Ga.). The tidal current is rotary, turning clockwise. The strength of the flood current occurs about one and one-half hours after flood begins at Miami Harbor Entrance and sets 295°, with a velocity of about 0.5 knot. The strength of the ebb current comes about two hours after ebb begins at Miami Harbor Entrance and sets 115°, with a velocity of about 0.5 knot. The minimum currents before flood and ebb set southward and northward, respectively, with velocities of about 0.1 knot.

THE GULF STREAM

The Gulf Stream sets eastward and northward through the Straits of Florida, and after passing between Fowey Rocks and Little Bahama Bank it continues northward and then northeastward, following the general direction of the 100-fathom (183 m) curve as far as Cape Hatteras.

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