Sudden storms create unpredictable waves and seas that present a significant risk to recreational boaters. In the United States alone, there are approximately 100,000 thunderstorms each year. These and other rapidly developing or un-forecasted storms create havoc and navigational challenges everywhere they form. It goes without saying that the resulting waves, seas, and surf conditions have the potential to present great challenges to all skippers’ skills at the helm. In extreme cases sudden changes in weather can challenge the crew’s survival skills as well. Because boaters operate in this constantly changing environment, it is important for them to understand the dynamics of weather, and how the resulting forces impact a boat’s stability and maneuverability while underway in rough weather driven conditions.
Winds and Sea Breezes … Often times recreational boaters will set out on a cool and calm sunny morning expecting a relaxing journey. Then, and for no apparent reason, afternoon waters become so choppy that returning to port becomes an adventure. These changes are caused by the sun heating the earth faster than it warms the water. As the heated land air rises, the upward draft draws in the cooler sea air creating a sea breeze. However, at times a sea breeze can turn into a strong wind that creates choppy seas that can be challenging. This is especially true for small boats, paddle crafts, and personal water crafts. Sea breezes can become quite strong and cause very rough seas during colder months in waters with a long fetch.
Thunder and Lightning … THUNDERSTORMS …are dangerous, especially because they are accompanied by lightning. They develop and move quickly bringing strong winds that cause rough waves. Static on the ship’s AM radio is a sign that a thunderstorm may be in the area. LIGHTNING …All thunderstorms have lightning. It is created when opposite electrical charges are attracted to one another within developing storm clouds or between a cloud and the earth. Lightning is very dangerous. When you spot dark thunderclouds approaching the area head to a safe harbor if possible. While underway stay seated and avoid holding onto metal railings, hard top supports, or fish towers. JUDGING YOUR DISTANCE FROM THE STORM … You can measure your distance from a thunderstorm by observing a lightning flash then counting the seconds it takes for the thunder to arrive. Convert seconds to miles by dividing the total time by 5. 10 seconds/5 = 2 miles.
Waterspouts … Waterspouts are tornados that form over water, or tornados that move from land to the water. They are associated with severe thunderstorms, and are often accompanied by high winds and seas, large hail, and dangerous lightning. If you spot or encounter a waterspout move away. Navigate at a 90-degree angle away from where the waterspout appears to be happening. Usually waterspouts dissipate in 10 to 20 minutes, but they can last as long as an hour.
Fog … is a visible phenomenon made up of tiny water droplets or ice crystals suspended in the air that reduce visibility to less than 1000 meters. Some mariners view fog as a low cloud. Mist and haze are similar to fog but in their cases visibility is greater than 1000 meters. There are three types of fog, Advection, Radiation, and Inversion. ADVECTION FOG … is the most troublesome type of fog. This type of fog occurs when warm, moist air moves over colder surfaces on land or at sea. As the temperature difference between warm and cold areas increases, the fog becomes more dense which results in reduced visibility. RADIATION FOG… forms over land on calm, clear nights as the loss of radiated heat cools the ground. This phenomena causes the top of the fog bank to drop as the warmer surfaces are cooled. Radiation fog is a very common type of fog. It is the most prevalent during the fall and winter months. Radiation fog forms overnight as the air nearest the ground cools and stabilizes. The fog will begin to form at or near the surface of the water or land. It will then thicken as temperatures continue to cool. This fog will also increase in height overnight. While radiation fog can be thick, it is usually patchy. It is generally stationary and will dissipate as the sun rises. Radiation fog can be visible on satellite images.
INVERSION FOG …is a downward extension of a stratus cloud trapped under the base of a low-level temperature inversion. They are particularly prevalent off western coasts in tropical regions during the summer. In addition to reducing visibility, inversion fogs trap air pollution, accentuate loud surface noises, and can cause ice storms during cold months.
Ice … One of the most serious effects of subfreezing air temperatures at sea is the accumulation of topside ice. As the ice continues to accumulate it results in an increased weight being placed on decks, cabins, and masts. This accumulation of weight above the waterline results in the boat becoming increasingly unstable and may lead to capsizing.
Monitoring the Weather … Keeping a "weather eye" is a well-established mantra for mariners. It simply means pay attention to changes in weather or sea conditions, listen for “SECURITE” announcements, and monitor a weather APP.