It’s seems like common sense, but we urge cruisers to lift their heads out of the plotters and augment what’s happening on the screens in front of them with some simple observations around your boat. Clouds are among the most visible indicators of weather and can often help predict thunderstorms, an approaching front, rain, or a squall.
Start by learning to identify cloud forms and how they may affect weather. This may feel like a kid’s school science project, but it’s a necessary first step. Although there are infinite shapes a cloud can take, the common classification system includes 10 types: cumulonimbus, cumulus, stratus, stratocumulus, nimbostratus, altostratus, altocumulus, cirrostratus, cirrocumulus, and cirrus. It’s important to learn the characteristics of each cloud type. Books such as Chapman Piloting offer a good overview and helpful pictures. Next, watch how clouds form in your area, determine whether they are increasing or decreasing in amount, and understand what shape they are taking. As a general rule, lowering or thickening cloud formations indicate wet weather is on the way. Then, begin to combine this information with other items such as barometric pressure and wind velocity.
As everyone knows, when a front passes through, there is a change in the current weather predictions. Technology such as Predict Wind are now wonderful tool to have on board and use, but you still want to be able to dissect what is happening around your boat in real time. For example, a cold front can be indicated in warm weather when clouds lower and cumulus clouds begin form high above. This is a result of warm air being displaced by approaching cold air. Also, altocumulus clouds, shown here, are usually an early warning sign that a cold front is coming. If it’s summertime or you’re in the tropics with warm, humid air, these clouds may turn into thunderstorms as the cold front approaches. Barometric pressure can also rapidly decrease and a squall line will often accompany the front.
As a warm-front approaches, clouds build up and the pressure falls. Cirrus clouds can first be seen, followed by cirrostratus, then altostratus and, finally, nimbostratus, which develop in the rain area. After the warm front has passed through, cumulus and/or stratocumulus clouds will form and begin to rise again.
You may wonder with all the technology inside of most pilothouses, does this all really matter? Yet our boats are designed to go far for long periods of time and self-sufficiency is a key element to this objective. Having more knowledge than less is certainly key to making this happen.