When you think of a chart, you probably imagine a piece of paper with tons of numbers on it that tells you how deep the water is and where rocks are. This type of chart is known as a Nautical Chart, and these charts are very useful for navigating in a specific area. While Nautical Charts offer a very narrow view of the world, focusing on a small area of coastline and water, Pilot Charts offer a much broader view of an entire body of water.
Pilot Charts do not give information about depth and obstructions, instead they offer information about weather. Pilot Charts denote wind directions and strength, likelihood of encountering a gale, ice, or fog, as well as the typical direction and intensity of currents. Pilot Charts are about the weather what Nautical Charts are about the water.
Pilot Charts are organized by region and by month. Each month has its own weather patterns and needs to be represented on its own chart. When you look at a pilot chart, one of the first things that will jump out at you are these little wind roses placed all over the page.
Wind roses are set every 5 degrees and represent the average wind for that area via their arrows and feathers. The wind strength is denoted at the end of the arrow with the feathers according to the Beaufort scale. Each feather represents 1 force.
The arrow points into the wind, telling you the prevailing wind directions that month. The more often the wind blows from that cardinal direction, the longer the arrow will be. If the wind is particularly prevalent from one direction, it will be written on the arrow. In our example, Force 4 winds will blow from the NE 67% of the time. If it is not blowing from the NE, it will be blowing from the E. Looking at the rose, you can see that the winds tend to be Force 3 or 4 for the month of January.
The number in the middle of the rose represents the number of days that month with absolutely no wind.
If you are planning a cruise, choosing a route where the prevailing wind will be a broad reach with no becalmed days would prove ideal.
If your planned route follows along wind roses that look like this, you may want to look for another route. This wind rose denotes that 1 day out of the month may be becalmed, but otherwise the wind blows from any direction and very strongly. The average winds in this area are Force 5 and Force 6!
Aside from prevailing wind information, Pilot Charts denote average currents and their strengths using green arrows.
When choosing a route, try to find a course where you are not only on a broad reach, but also sailing with the current. The current can either be your friend or make the entire experience much less enjoyable. If the wind and current oppose each other, you can expect to encounter much larger seas!
Picking a route where you sail downwind and down current will make passage making much easier as well as much faster than if you choose a different route where you are fighting the elements as you voyage.
Below are links to PDF copies of pilot charts for the entire world. They are organized by ocean, and sub-organized by month. Clicking on the desired month will open the link to that pilot chart in a new window. Using these pilot charts, you can plan the best time and route for any ocean passage.