Caribbean Compass Yachting Magazine 2015

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Tradewinds and Windows: a Caribbean Wind Primer by Frank Virgintino SEPTEMBER 2015 CARIBBEAN COMPASS PAGE 24 What are These Tradewinds? The tradewinds of the Caribbean are the prevailing pattern of winds within the lower portion of the Earth’s atmosphere, found in the tropics near the Earth’s equator. Sailing vessels have used the winds for time on end and cruising sailors smile at their mention. They blow predictably from east to west. In the Northern Hemisphere, the winds blow predominantly from the northeast and from the southeast in the Southern Hemisphere. Owing to what is referred to as Hadley cell circulation, surface air flows toward the equator while upper airflow is towards the poles. How this affects Caribbean cruising sailors depends largely on the time of the year. During winter months, tradewinds are normally in the range of 15 to 20 knots. However, they are not consistent: at times they do not blow at all, while at other times they can blow at 30 knots or more for days on end. The winter trades are also dry and comfortable, having come from the African continent, passing over the Sahara Desert. During the summer months, the tradewinds are east-southeasterly and blow in the 15- to 20-knot range and are much more consistent. These winds are not dry, like the winter tradewinds, as the wind passes from the southeast and carries a great deal of moisture and humidity. They can also bring low-pressure systems that can develop into storms and even hurricanes. In general terms, you can sail around the Caribbean Sea during the winter months with tradewinds that are a joy to sail in with never a worry. Sailing north and south in the Lesser Antilles can be an experience without equal. Many other areas of the Caribbean Sea are easily routed, providing you are heading east to west. —Continued on next page WIKIMEDIA
— Continued from previous page One of the best strategies you can use to avoid sailing straight downwind is to crisscross the Caribbean Sea, on some type of reach. From any part of the Lesser Antilles, this makes for a good strategy. Coming from west to east is a greater challenge. The easiest way to effectively move against the prevailing wind is to employ strategies based on the idiosyncrasies of different areas. The first is to not try to come east on the south side of the Caribbean Sea. In the area of Colombia, the fetch produces very high seas, there is an adverse current, and the winds blow stronger in that area on the average. Even if you were to sail east from the ABC islands, you would still have to buck very strong winds and stronger than average adverse currents off the coast of Venezuela. If you move in close to Venezuela to try to reduce adverse current, you risk heightened danger from what has become a crime- and piracy-ridden coast. If you stand offshore, you will have stronger winds and higher seas to contend with. The best strategy to sail west to east in the Caribbean Sea is to utilize the southern sides of the islands of the Greater Antilles (Jamaica, Hispaniola and Puerto Rico). These islands have very considerable mountain ranges, with the Dominican Republic having the highest at over 10,000 feet. Cold air from the tops of the mountains descends (actually slides down like a river) after the sun sets and most often, if the tradewind has not been above average during the day, these katabatic winds will stall the tradewinds within three to five miles of the coast. In such cases you will find that if you use these winds after sundown, that there will be no “slog to windward.” In fact on many nights, you will sail east on a port tack in light offshore winds all the way to eastern Puerto Rico. Many cruising sailors arrive in the Caribbean Sea with the misconception that sailing is always a reach in moderate winds. That is not the case and to cruise the Caribbean, or any part of it, requires an understanding of methods to cope with the exceptions and intricacies of the trades. It is a matter of understanding and not a matter of force over nature. You can definitely fight the tradewinds but you cannot fight them indefinitely. When you reach a point where it is simply not fun anymore, consider that you might be doing something wrong. Understanding and insight are the keys to dealing with the forces of nature. Use the tradewinds to your advantage. The Caribbean Sea is a potpourri of winds. Some of the special wind movements that can be studied and used to one’s benefit include the following. Beware Northers Early in the tradewind season (November through March), north winds blow from North America, sometimes with a great deal of force. These winds can extend as far south as Colombia and as far east as the Virgin Islands. Skies become grey and clouds wispy. Temperatures drop. Most often these winds can stall the tradewinds. The north shores of the Greater Antilles can become very dangerous at times of strong northers. The entire distance from Cuba to the Virgin Islands can become a dangerous lee shore. This is one of the reasons, if coming from Florida or the East Coast of the US, I favor entering the Caribbean Sea through the Windward Passage. I can sail eastward — not on a lee shore in the Atlantic, but rather in a more “user friendly” sea: the Caribbean. In an area such as the waters around Colombia within 150 miles in any direction, tradewinds blow from the Lesser Antilles and a fetch of that distance creates higher than average tradewinds. When a strong norther interacts with such tradewinds, the area becomes virtually untenable and the winds are often referred to as “strengthened tradewinds” or “reinforced trades”. Those who want to cruise to Colombia and surrounding areas might well consider heading there in April when the season for northers comes to an end. It is also a good idea as Colombia is out of the hurricane zone and late season sailing in that area is a way to avoid that danger. Dealing with Squalls and Storm Cells During the normal tradewind season, there can be periods of bad weather. I am not referring to hurricanes, as those mega-storms are a special class unto themselves. —Continued on next page A typical Caribbean squall. When you see a rising cloud and falling rain, expect a burst of wind SEPTEMBER 2015 CARIBBEAN COMPASS PAGE 25
Page 1: C A R I B B E A N On-line C MPASS S
Page 4 and 5: SEPTEMBER 2015 CARIBBEAN COMPASS PA
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Page 32 and 33: BOAT PAINT & STUFF Time Out Boat Ya
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