Boating Course Weather. Canadian Power & Sail Squadrons. General As an operator of a small vessel you can not safely ignore the weather. Even an elementary knowledge of theoretical meteorology can add greatly to piece of mind, comfort, and competence while afloat.
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Canadian Power & Sail Squadrons
As an operator of a small vessel you can not safely ignore the weather. Even an elementary knowledge of theoretical meteorology can add greatly to piece of mind, comfort, and competence while afloat.
The object of this section is to provide a basic explanation of weather hazards and to describe marine weather forecasts and warnings, and how to obtain them.
Marine Weather Hazards Manual and The Wind Came All Ways – Owen Lange
These publications are available through Environment Canada’s Meteorological Service
This presentation is available for download from my personal web site. The address is:
Five Phenomena that can be hazardous to operators of small boats.
Wind – The atmosphere in motion. Measured in knots for marine use (1.15mph, 1.85km/h). Winds may be steady or gusty.
A gust is a sudden increase in wind speed of 10 knots or more, lasting only a few seconds.
Both gusts and squalls may also be accompanied by a change in wind direction.
In a similar manner, an approaching patch of darker, disturbed water on a windy day can reveal the approach of a gust or a squall when there may be no other clue to its presence.
An example would be a wind from directly astern. In this case the boat’s speed is subtracted from the true wind speed to give the apparent wind speed.
There is a very good article on the web relating to apparent wind, you can find it at the following address:
Sudden unexpected changes in speed or direction can cause problems however.
Marine winds are greatly affected by topography, and tend to follow the shore line.
Showers may be accompanied by gusts or squalls, whether or not a thunderstorm is occurring. When a shower approaches, prepare in advance for a short period of strong and gusty winds.
Note that the water will move at only about 3% of the wind speed.
Swell Waves – left over wind waves that have moved away from their source area.
Stronger winds require shorter fetches and durations to raise the same wave, and a storm force wind can produce 1-2m waves only a mile offshore in about 15 minutes.
Significant wave height is the average of the highest third of the waves
Most frequent wave height………0.5 X sig wave height
Average wave height……………..0.6 X sig wave height
One wave in 10…………………..1.3 X sig wave height
One wave in about 1000 …………1.7 X sig wave height
Maximum wave …………………2.0 X sig wave height
Waves moving into shallow water (depth less than 1.5 times the distance between adjacent crests) also shorten and break. Both conditions may be hazardous to small vessels.
Fog is cloud that forms at ground level. The term is commonly used to describe any reduction in visibility.
Requires clear skies, light winds and sufficient moisture, conditions most commonly found under a ridge of high pressure in the fall.
The air cools overnight and will become saturated given sufficient moisture.
Radiation fog is often thin and patchy and tends to form in, or flow into and fill low lying areas.
Dispersion usually begins as the sun warms the ground which then warms the air near the surface.
Horizontal movement of air.
80% of sea fogs are this type.
Contact with a cooler surface causes a moist air mass to cool below the dew point and fog will form.
Rain falls out of the warm air behind a warm front and into the cold air below.
This type of fog will dissipate when the front passes through.
Electrical discharge in the atmosphere accompanied by thunder.
Lightning does not often strike small vessels and when it does, usually electronic equipment is damaged, but rarely does anything major happen to the hull or crew.
A lightning strike is carried from the mast or antenna through heavy grounding wire to the keel or grounding plate, then to the water.
During a thunderstorm, stay clear of the mast or antenna, and of the wiring and rigging attached to them.
Avoid metal objects and hunch as low as possible in the centre of the cockpit or cabin.
Hail poses the same risks afloat as ashore. May do minor damage to boats if the hail stones are large enough. Can also cause eye damage if you look up when hail is falling.
Meteorological Service of Canada (MSC) produces marine forecasts for both coasts, nearshore and offshore, and for all the larger lakes of the country.
Where do we find information ?
How do we interpret the information ?
Weather information is available from:Television – The Weather NetworkAM Radio – 1130 CKWXInternet – Environment CanadaTelephone - Recoded MessagesVHF Radio
Issued at 0400, 1030, 1600 and 2130 hours
Forecast valid for 24 hours- updated if conditions change
“Securite, Securite” on Channel 16, Switch to WX or 21B
Light 0 to 11 knots
Moderate 12 to 19 knots
Strong 20-33 knots
Gales 34-47 knots
Storm 48-63 knots
Hurricane 64 knots or more
Victoria- WX 3, 21B
Comox- WX1, WX3, 21B
Tofino- WX1, WX2, WX3, 21B
West Coast Vancouver Island
Prince Rupert- WX1, WX2, WX3, 21B
North Coast, Queen Charlottes
WX 1 (162.55 MHz), WX 2 (162.40 MHz), WX 3 (162.475MHZ), 21B (161.65 MHz)
Continuous Marine Broadcast – Phone
Strong Wind Warning (20-33 knots)
Issued for Southern inner coastal waters between Good Friday and Rememberance Day.
Gale Warning (34-47 knots)
Hurricane Force Wind Warning
(64 knots or greater)
Monitor VHF Channel 16,
Switch to WX or 21B
Before Setting out:
Check current weather and sea conditions by contacting other vessels in your area of interest.
Obtain the latest marine forecast and warnings for your region.
Decide if you and your boat can navigate safely in the weather and sea conditions expected.
Monitor Channel 16 for announcements of CCG weather broadcasts.
Monitor the water ahead for signs of wind changes.
Note changes in wind speed and direction.
Recording all these observations in a log book is a good way of quickly building up a store of knowledge of your area.
When manoeuvring in a confined area at low speeds, turning into the wind will considerably reduce the amount of room required to make the turn, compared with turning downwind.
Approaching showers may include wind gusts or squalls. Rapid building of large cauliflower-shaped clouds indicate a possible thunderstorm within an hour or so.
The approach of dark, rolling, threatening clouds may herald a thunderstorm within the next few minutes.
Sometimes there is also a ring around the sun or moon that is observable before the clouds become too thick.
Consider if a change in the wind was forecast, or if it is a new development.
Consider if a change in wind was caused by some topographic feature altering the flow of the air. Is the altered wind direction now going to oppose a current?
An increasing swell usually indicates the presence of a large weather system in the direction from which the swell is coming, and it may be approaching.