Marine Weather (from a Sailor's Perspective)

(Always Under Construction)

I am not a meteorologist, but as a sailor, I do recognize the importance of having an appreciation for the science.

Red Sky at Night, Sailor's Delight

In the mid latitudes, weather systems generally move from west to east. A red sky in the west, as the sun sets, indicates that the atmosphere between you and the sun is essentially clear.

If you can see through the atmosphere that is west of you, you are likely looking at high pressure and a stable air mass.

What you are seeing is very likely tomorrow’s weather.

The sky appears red because the shorter blue wavelengths are filtered out by the thicker atmosphere, while the longer red wavelengths are able to get through.

Red Sky in the Morning, Sailor take Warning

In the mid latitudes, weather systems generally move from west to east. A red sky in the west, as the sun sets, indicates a clear atmosphere between you and the sun.

On the other hand, a red sky in the east at sunrise suggests that the clear weather has passed and the odds are, that the not so nice weather is moving in from the west.

Just as with the sunset, the sky appears red because the shorter blue wavelengths are filtered out by the thicker atmosphere, while the longer red wavelengths are able to get through.

Marine Weather Services in Canada

The primary source of Marine Weather Services in Canada is the Department of Environment and natural resources. Marine forecasts are available for all of Canada’s coastlines and waterways at: https://weather.gc.ca/marine/index_e.html.

In addition to marine weather forecasts, the department also publishes a National Marine Weather Guide as well as Regional Marine Weather Guides geared to the different regions of Canada. These guides provide very valuable information about conditions that are unique to certain parts of the country.

Weather Concerns for Boaters

Visibilty (Fog)

Of utmost importance when out on the water is being able to see where you are going. Fog is one of the more significant weather hazards you will have to deal with.

Wind

Wind is described based on the direction from where it is blowing, i.e. a west wind is blowing out of the west. In marine forecasts, wind speed is expressed in knots (nautical miles per hour).

If you are a sailor, wind can be fun, particularly if there are no significant waves. If the wind blows for period of time, waves are generated. Two factors determine wave height. First, the length of time the wind has been blowing, and second, the amount of water (the distance) the wind has been blowing over. That distance is referred to as “Fetch”.

When heading out on the water, boaters should know what to expect from the wind. Check your local forecast before casting off.

Marine Weather Wind Warnings:

Strong Wind Warning – 20-33 kts

Gale Warning – 34-47 kts

Storm Warming – 48-63 kts

Hurricane Warning – Greater than 63 kts.

 

A Guide to Marine Weather in different regions of Canada can be found at: https://www.canada.ca/en/environment-climate-change/services/general-marine-weather-information/regional-guides.html. These publications are highly recommended.

Lightning

 

Lightning is almost always associated with thunderstorms. Lightning is powerful, unpredictable and dangerous. When it comes to weather phenomena, it is also a complex topic.

From a mariner’s perspective, the concern is with a significant buildup of energy in the atmosphere looking for a place to discharge or looking for the shortest and fastest way to ground. The ground is the water that your boat is sitting in. For a sailboat, the shortest way to the water (ground) is your mast (the conductor). From the top of your mast, lightning will instantaneously find it’s way to water (ground), using the best and most direct conductors.

If you are out on the water in a thunderstorm, the best advice is to stay low and away from the conductors.