Caribbean Weather - a very basic primer

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Continuous sunshine and balmy trade breezes, right? Well, not too far wrong.

There are two seasons, the dry and the wet, but they are not always well differentiated. During the dry season (February to June), there will often be weeks of clear sunny weather broken only by an occasional small rain shower. In the wet season (July until January) there will still be plenty of sunshine, but with more frequent showers and occasional rainy days with no sun. There is very little temperature difference between the seasons; you can expect 78 to 85F (25 to 29C) year round.

The winds nearly always blow from between northeast to southeast at 10 to 25 knots; calms are rare. The wind tends to strengthen around the northern ends of islands. Rain usually arrives in intense squalls that can be seen coming from afar. Sometimes these squalls have a lot of wind in them (40 knots or more); often they do not. There is no way to tell before they arrive. Infrequently, a squall or cold front can produce winds from the west, making the usual anchorages uncomfortable.

During the winter months, storms and cold fronts farther north sometimes produce swells that reach the Windwards. These northerly swells can make anchorages that are open to the north or west rolly and occasionally untenable. Few swells are really bad ~ but when they are, you have to be prepared to move to a calmer spot, even in the middle of the night. Swells have caused the demise of quite a few unattended yachts. Hurricanes also cause swells during the hurricane season. These swells may come from any direction, depending on the position of the storm.

In the winter season a big high-pressure area to our northeast is a dominant feature. When the isobars get tight, the wind increases and is sometimes very fresh (25-30 knots). We call these Christmas winds. This high pressure is offset by cold fronts that come down from the northwest. They almost never make it as far as the Windwards, but as they approach, we often get very calm and sunny weather followed by wind and rain, as their tail ends affect our area.

Visibility varies from an exceptional low of five miles to a high of over 50 miles. Extremely hazy days are caused by dust from Africa. Sometimes reddish traces may be found on the cabin and decks. On hazy days avoid dust stains when doing the laundry by wiping off the lifelines before hanging out the washing.

The hurricane season is from June to October (hurricanes have been known occasionally in November and very rarely in December). People now tend to talk of "named storms" only about half of which will reach hurricane strength. The months of June, July, and October only produce about one hurricane every three years for the whole western Atlantic, including the Caribbean Sea and Gulf of Mexico. During August and September the number is around five a year. Hurricanes frequently start well out in the Atlantic Ocean, often on the latitude of the Windwards, but then they usually swing north and pass through the Caribbean higher up. Very few hit the Windwards and sometimes years go by without one in this area, but it is essential to check the forecasts, especially in these days of rather active hurricane seasons. You can get weather on the radio, but it is hard to find consistently good forecasts.

It is probably easiest to go into an internet cafe and get the weather on the web. (We give links to several forecasts on doyleguides.com.) Cruisers nets are good for weather. The Grenada Cruisers net is on VHF: 68 at 0730, Monday to Saturday. You can occasionally pick up the weather part in the Grenadines.

Here are some terms you will hear on the radio and what they mean: "Intertropical convergence zone" affecting the area. This is not any kind of low, but you may get some rain squalls or cloudy weather. "Tropical disturbance," "tropical wave," and "upper level trough" are poorly organized weather systems associated with rain squalls of varying intensity. A "tropical depression" is an organized weather system with sustained winds of up to 35 knots and rain. Sometimes these can be very nasty and other times they turn out to be nothing. A "tropical storm," on the other hand, is definitely something to be avoided as it has lots of rain and sustained winds of 35 to 63 knots. Once the sustained winds become more than 64 knots, it is called a hurricane.

Hurricane winds can come from any direction, so be prepared to get out of the way or run for one of the hurricane holes: Cohe du Lamentin, Trois Ilets, or, better still, Cul de Sac Marin in Martinique; Rodney Bay Lagoon or Marigot Bay in St. Lucia; the mangrove swamp in Tyrrel Bay, Carriacou; and in Grenada, Port Egmont. Drive your boat aground bow first into the mangroves. Tie off to the biggest mangrove trees with all available lines (use at least ten). Put out two anchors astern, turn off all seacocks, remove all sails, awnings and biminis, leave the boat and find somewhere safe ashore.