Caribbean Sea. British Virgin Island
The British Virgin Islands, located N and E of the Virgin Islands of the United States, are comprised of Tortola, Virgin Gorda, Anegada, Jost Van Dyke, Peter Island, and about 35 smaller islands and cays.
Road Harbour, Sopers Hole and Gorda Sound are the three main harbors within the British Virgin Islands. There are no berthing accommodations for large ships in the group, except for Port Purcell in Road Harbour with 7.3m alongside. Other large ships must anchor in the roadsteads.
The demarcation line between the Virgin Islands of the United States and the British Virgin Islands runs N between Little Hans Lollik and Little Tobago, then through The Narrows between Saint John and Great Thatch Island, then around the E side of Saint John through Flanagan Passage between Flanagan Island and Pelican Inlet.
On approaching the British Virgin Islands from the N, Virgin Gorda will be the easiest feature to identify, rising in a clear, well-defined peak.
West of Virgin Gorda, Tortola will appear the next most conspicuous as its highest peak will be seen, as a flattened and elongated summit.
Jost Van Dyke can be identified by a number of rugged pointed peaks.
Winds—Weather.—The weather of the British Virgin Islands is ideal and is cooled 10 months of the year by the E trade winds. The islands have an average mean temperature of 26°C.
Fog, thunderstorms, and high humidity are almost unknown. Rainfall is moderate.
At Saint Martin E fronts cause rain at irregular intervals, mostly during summer. Hurricanes are a constant threat during June through November.
At Saint Christopher the average winds are from the E at a rate of 10 knots during the month of July, and 6 knots during the rest of the year.
At Antigua, the E to NE trades prevail with average speeds of 9 to 13 knots. The rainy season for the island is May through November.
The weather for Guadeloupe is generally healthful and tempered by trade winds. The island is subject to violent storms at times and hurricanes occur occasionally.
Rollers or ground swell in the area of the islands, frequently occur from October to May and sometimes continue for 3 or 4 days.
In general, they set in after a prevalence of E and SE winds. They also follow winds from the NE, especially when these winds are strong.
Rollers have been observed to break over depths of 16.5m between Tortola and Guana Island, close N.
The rollers appear to loosen sand, thus discoloring the water N of the islands as far as the edge of Virgin Bank.
In some places near the W end of Anegada, where the bottom is composed of fine sand, the formation of the banks is frequently changed.
Tides—Currents.—The average rise and fall of the tide is about 0.3m among the British Virgin Islands. The actual fluctuation of the water level consequently depends largely upon the winds and other meteorological conditions. The tide of the Atlantic Ocean side is chiefly semi-diurnal, whereas on the Caribbean side the tide is chiefly diurnal.
The currents among the islands are not well established by observations. An ocean current, which has an average rate of 0.2 knot and a direction varying from NW to N, prevails during all seasons of the year.
The SE tidal current is reported to predominate during the summer months from the middle of June to the middle of August. Near the commencement of this period the current has been observed to set for 8 days continually to the SE with unusual force.
The NW tidal current is reported to prevail during the months of September, November, March, and April.
Depths—Limitations.—Numerous reports and surveys indicate that shoal patches of small extent may be encountered on the banks covered by this sector. Deep-draft vessels, especially those drawing over 12m should remain outside the 100m curve where possible.
The British Virgin Islands are located on a bank, over which the depths are less than 200m, extending in an ENE direction for nearly 90 miles from the E end of Puerto Rico. Anegada is located close to its NE extremity, but the remainder of the group lie near the S edge of the bank.
Caution.—Vessels approaching the islands from the N should avoid the following banks:
1. Whale Banks (18°41'N., 64°43'W.), with a least depth of 18.5m.
2. Turtle Head (18°38'N., 64°46'W.), with a least depth of 11m.
3. Barracouta Banks (18°34'N., 64°52'W.), with a least depth of 20m.
4. Kingfish Banks (18°31'N., 64°40'W.), with a least depth of 14.5m.
Saba Bank, Barracuda Bank and the dangers extending E from St. Croix are the main dangers when approaching from S.