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Weather preparedness tips from our friends at Boat U.S. Foundation

On the Water How-To

Photo:@donn.mt.406

As boaters, we have a deep appreciation for nature—it is, after all, what makes it all possible. Unfortunately, with all of its majesty also comes the unpredictably of weather. 

Fortunately, there are steps you can take to boat safely and get ahead of it.

Wind and current

A boat’s handling characteristics are affected by wind and current, no matter what type of hull and power combination it has. Keeping a course or maneuvering in close quarters may be straightforward on a calm day during a slack tidal current, but the boat may become quite ill-mannered when coping with a stiff crosswind or crosscurrent. Since bows on many power boats are higher than the sterns, they tend to fall off the wind when backing, despite anything that is done with the helm. So, in general, when operating a boat in large waves and high winds, head into the waves at a slight angle, and reduce your speed. This will help you maintain control, and avoid falling off of a wave, or having a wave break over your stern.

Hull type has the most effect on how a boat reacts to the current. Displacement-type hulls with considerable draft are affected by current to a greater extent than shallower-draft, lighter, planing-type hulls. Water is much denser than air, so a half-knot cross current may have more effect on a displacement cruiser than a stiff 15 to 20 knot wind.

On the other hand, given the same conditions, a planning-type hull with a high tuna tower could be more affected by wind than by current. Neither a displacement nor planing boat can ignore the wind current. Skippers of both will find one of them a major factor affecting the boat’s maneuverability. This becomes most apparent while running at low speed in close quarters.

Large ocean undulations, generated by distant storms and unrelated to local causes, are called swells. The surface of a swell may be perfectly calm, but it is usually textured by the wind into groups of tiny ripples called "catspaws." The ripples gradually build into waves.

As the waves travel quickly over a long fetch, the distance free of obstructions, each crest reaches higher above its trough. Increasing wind tears at the wave tops, revealing whitecaps and throwing off spume. When this heavy sea encounters shallow water, its energy can no longer be absorbed by the circular movement of water within each wave. The crests rise and break. Surf crashes ashore.

The same sea, meeting a current, will rear up, creating a rip, sometimes amplified by the narrowing funnel of an inlet. Over long fetches of shallow water, strong winds may create waves of moderate height, but with a viciously steep and short chop which is even more dangerous than ocean waves of greater size.

Both coastal and inland boaters are familiar with currents, the horizontal flow of water in a downstream direction. Currents are also found in open water where they range from huge, persistent ocean movements to the strong but short-lived undertow, or rip current, of a beach where surf finds its way back offshore. Ocean, lake and river currents respond to the push of prevailing winds. In addition, ocean currents are affected by variations in water density resulting from different levels of salinity and temperatures.

Regular, intermittent currents that respond to movement of the sun and moon are called tidal currents. Tides are the actual rise and fall in local water level as tidal currents force masses of water alternately against and away from shore. Incoming tidal currents flood, then ebb as they retreat.

Every current, regardless of its origin, has a set and a drift (speed). Set is the true direction toward which a current flows; drift is its speed. The speed of tidal currents and the height of the tides are so important to coastal navigation that annual tide tables and tidal current tables are published under government supervision.

Depending upon the bodies of water on which you boat, tides can have a major impact on your boating experience. Watch the tide charts or listen to tide reports in your area before you go boating. Going aground is never a good time.

Weather avoidance

Most commercial radio and television stations give marine weather broadcasts during the boating season, with updates several times a day. Other sources of weather information include NOAA, the National Weather Service, and other government agencies.

  • Make a habit of listening to your local broadcast beginning the night before you plan to go boating.
  • Get the most current forecast just before you set out.
  • Use the time-honored practice of scanning the horizon for changes in the wind, waves, water, and sky that signal developing weather patterns.
  • Purchase a small, inexpensive battery-operated weather radio, available at many retail electronics outlets.

NOAA Weather Radio operates continuously on the following frequencies:

162.400 MHz (channel 1)

162.475 MHz (channel 2)

162.550 MHz (channel 3)

NOAA broadcasts current weather conditions such as temperature, humidity, wave conditions, dew point, barometric pressure, wind speed and direction, and other weather information.

For more severe weather, NOAA uses the following descriptions:

Small Craft Advisory: Observed or forecast winds of 18 to 33 knots—Small Craft Advisories may also be issued for hazardous sea conditions or lower wind speeds that may affect small craft operations (there is no legal definition of the term "small craft").

Gale Warning: Observed or forecast winds of 34 to 47 knots.

Storm Warning: Observed or forecast winds of 48 knots or greater.

Tropical Storm Warning: Observed or forecast winds of 34 to 64 knots or higher associated with a tropical storm.

Hurricane Warning: Observed or forecast winds of 64 knots or higher associated with a hurricane.

Special Marine Warning: Observed or forecast winds of 34 knots or more associated with a squall or thunderstorm and expected to last for two hours or less.

 

Thunderstorms

Thunderstorms are created when warm, moist air rises, cools and condenses. It swells into mounds of thick, billowy cumulous clouds that quickly darken into the towering ominous-looking cumulonimbus clouds characteristic of thunderstorms.

Consider the formation of this thick, dark cloud an unmistakable thunderstorm warning, and head immediately for a safe anchorage. The sharper, darker and lower the front edge of the cloud, the more severe the storm. The anvil-shaped top of the storm cloud points in the direction that the storm is traveling.

You can determine the distance of an approaching thunderstorm by counting the number of seconds between the lightning flash and the thunder clap, and dividing by five. That will give you the distance in miles you are from the storm. Another handy tip that a thunderstorm is near is to tune your radio to any AM station. Thunderstorms will create static crackling on a station that would otherwise sound clear.

 

If a thunderstorm is approaching you

  • Make sure everyone aboard is wearing a life jacket.
  • Secure all loose gear, hatches or ports.
  • Determine your location and the best course back to shelter.
  • Keep a sharp lookout for the other boats and obstructions.

 

Once the storm hits

  • Try to take the first (and heaviest) gusts of wind on the bow, not abeam. Heading into the wind is the most seaworthy position for most small boats.
  • Approach waves at a 45-degree angle to keep the propeller underwater, to reduce pounding, and to provide a safer and more comfortable ride.
  • If there is lightning, unplug radios and all electrical equipment.
  • Stay low. Don't make yourself the tallest target. Keep away from metal objects that aren't grounded to the boat's protection system.

When lightning strikes

 

  • The best protection against lightning is avoidance. Lightning is random, unpredictable and very dangerous. Here are some tips to help you avoid lightning while on the water.
  • Head into shore well ahead of the turbulence.
  • Lightning can lash out for miles in front of a storm, and it can strike after a storm seems to have passed.
  • Look for tall clouds that have an anvil shaped top.
  • Approach waves at a 45-degree angle to keep the propeller underwater, to reduce pounding, and to provide a safer and more comfortable ride.
  • Stay low. Don't make yourself the tallest target. Keep away from metal objects that aren't grounded to the boat's protection system.
  • Thunderstorms generally move in an Easterly direction, so if you see a storm to the South or Southeast of you, by and large you can rest easy. If you see a storm to the West or Northwest of you – look out.
  • Turn off as much of your electronic equipment as you can, (unplugging equipment is even better) and try and stay in your boat's cabin if possible.

For more important boating tips and information, visit www.boatus.org .

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Weather preparedness tips from our friends at Boat U.S. Foundation
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