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.

There are professionals whose job it is to collect, analyse, and interpret weather data and to disseminate this information to users.

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.

Publications that will be useful on the British Columbia coast Marine Weather Hazards Manual and The Wind Came All Ways – Owen Lange

Mariners Guide – West Coast Weather Services. These publications are available through Environment Canadas Meteorological Service These publications are available through Environment Canadas Meteorological Service

For those who wish further instruction in meteorology, the CPS Fundamentals of Weather is recommended.

This presentation is available for download from my personal web site. The address is: weathercat.ca

Weather Hazards Five Phenomena that can be hazardous to operators of small boats.

Wind Wind Waves Waves Poor Visibility Poor Visibility Lightning Lightning Hail Hail

Wind

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.

A squall is an increase in speed that lasts 2 minutes or more. Both gusts and squalls may also be accompanied by a change in wind direction.

A cats paw is the name given to the patches of ripples betraying the presence of slightly more wind on an almost calm day.

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.

Only apparent wind is felt on a moving boat. This is a combination of the wind and the boats movement.

An example would be a wind from directly astern. In this case the boats 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:

Wind without waves is usually only a problem when manoeuvring in a confined area. If a boat is well secured, it would take very strong winds to cause damage.

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.

Expect changes in the wind when leaving protected areas or when approaching prominent topographical features. (Local knowledge)

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.

Waves

Waves – Energy transferred from the air to the water. Note that the water will move at only about 3% of the wind speed.

Wind Waves – generated by the wind blowing over the water surface. Swell Waves – left over wind waves that have moved away from their source area.

Wind wave heights are directly related to the wind speed, time (duration) of the wind, and distance (fetch) it blows over the water in a straight line.

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.

Wave Trains 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

Wind waves may be superimposed on swell waves.

Waves that oppose a current, such as at a river mouth, have a shorter wavelength, are steeper, and break more often than waves that do not oppose a current.

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.

Poor Visibility

Fog Fog is cloud that forms at ground level. The term is commonly used to describe any reduction in visibility.

Radiation Fog Requires clear skies, light winds and sufficient moisture, conditions most commonly found under a ridge of high pressure in the fall.

Called radiation fog because it is caused by radiational cooling. The air cools overnight and will become saturated given sufficient moisture.

The winds must be light but not calm, a bit of mixing is required to form radiation fog, otherwise the condensation will result in heavy dew.

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.

Radiation Fog

Advection Fog 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.

This type of fog is usually widespread, deep and persistent. It may last for days and may not dissipate until the wind changes direction.

Frontal Fog Rain falls out of the warm air behind a warm front and into the cold air below.

When the air reaches saturation fog and or cloud will form. This type of fog will dissipate when the front passes through.

Frontal Cross Section

Lightning

Lightning 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 properly grounded mast or antenna provides a cone of protection which usually extends over the whole hull of a small vessel.

A lightning strike is carried from the mast or antenna through heavy grounding wire to the keel or grounding plate, then to the water.

Cone of Protection

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

Hail 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.

Weather Forecasts

Meteorological Service of Canada (MSC) produces marine forecasts for both coasts, nearshore and offshore, and for all the larger lakes of the country.

Marine Weather Forecasts Where do we find information ? How do we interpret the information ?

Weather information is available from: Television – The Weather Network AM Radio – 1130 CKWX Internet – Environment Canada Telephone - Recoded Messages VHF Radio

Forecast Regions

South Coast 03 - Fanny Island 03 - Fanny Island 21 - Sheringham Point 21 - Sheringham Point 22 - Tofino 22 - Tofino 23 - Estevan Point 23 - Estevan Point 24 - Nootka 24 - Nootka 25 - Solander Island 25 - Solander Island 26 - Quatsino 26 - Quatsino 27 - Sartine Island 27 - Sartine Island 28 - Pine island 28 - Pine island 29 - Herbert Island 29 - Herbert Island 30 - Egg Island 30 - Egg Island 31 - La Perouse Bank ( Weather Buoy) 31 - La Perouse Bank ( Weather Buoy) 32 - South Brooks (Weather Buoy) 32 - South Brooks (Weather Buoy) 33 - Cape Scott (MAREP Station) 33 - Cape Scott (MAREP Station) 61 - Chatham Point 61 - Chatham Point North, Middle and South Nomad Buoys not shown North, Middle and South Nomad Buoys not shown

Georgia Basin

Georgia Basin Weather Buoys and Stations 01 - Sentry Shoal (Weather Buoy) 01 - Sentry Shoal (Weather Buoy) 02 - Halibut Bank (Weather Buoy) 02 - Halibut Bank (Weather Buoy) 03 - Fanny Island 03 - Fanny Island 04 - Cape Mudge 04 - Cape Mudge 05 - Campbell River 05 - Campbell River 06 - Powell River 06 - Powell River 07 - Grief Point 07 - Grief Point 08 - Chrome Island 08 - Chrome Island 09 - Port Alberni 09 - Port Alberni 10 - Sisters Island 10 - Sisters Island 11 - Ballenas Island 11 - Ballenas Island

Georgia Basin Weather Buoys and Stations 12 - Entrance Island 12 - Entrance Island 13 - Merry Island 13 - Merry Island 14 - Pam Rocks 14 - Pam Rocks 15 - Point Atkinson 15 - Point Atkinson 16 - Sand Heads 16 - Sand Heads 17 - East Point 17 - East Point 18 - Kelp Reef 18 - Kelp Reef 19 - Discovery Island 19 - Discovery Island 20 - Race Rocks 20 - Race Rocks 21 - Sheringham Point 21 - Sheringham Point 61 - Chatham Point 61 - Chatham Point

Synopsis and Forecasts 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

Synopsis and Outlook Wind Speed Terms Light 0 to 11 knots Moderate 12 to 19 knots Strong knots Gales knots Storm knots Hurricane 64 knots or more

Synopsis and Forecasts- VHF Weather Channels Victoria- WX 3, 21B Strait of Georgia South Strait of Georgia South Howe Sound Howe Sound Juan de Fuca Strait Juan de Fuca Strait Haro Strait Haro Strait West Coast Vancouver Island South West Coast Vancouver Island South Comox- WX1, WX3, 21B South End of Texada Island to Northern Vancouver Island South End of Texada Island to Northern Vancouver Island Adjacent Mainland Adjacent Mainland

Synopsis and Forecasts- VHF Weather Channels Tofino- WX1, WX2, WX3, 21B West Coast Vancouver Island Prince Rupert- WX1, WX2, WX3, 21B North Coast, Queen Charlottes WX 1 ( MHz), WX 2 ( MHz), WX 3 ( MHZ), 21B ( MHz)

Synopsis and Forecasts- Sources Continuous Marine Broadcast – Phone Mt. Helmcken – Mt. Helmcken – Bowen Island/Mt Parke – Bowen Island/Mt Parke – Comox – South Area – Comox – South Area – Comox – North Area – Comox – North Area – Tofino – Tofino –

Marine Weather Information - phone Nanaimo or 8877 Nanaimo or 8877 Campbell River Campbell River Port Hardy Port Hardy Victoria , Victoria , Vancouver Vancouver Television The Weather Network The Weather NetworkInternet

ec.gc.ca/weatheradio

Marine Warnings Strong Wind Warning (20-33 knots) Issued for Southern inner coastal waters between Good Friday and Rememberance Day. Gale Warning (34-47 knots)

Storm Warning (48-63 knots) Hurricane Force Wind Warning (64 knots or greater) Monitor VHF Channel 16, Securite, Securite Switch to WX or 21B

Weather Procedures for Safe Boating 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.

Obtain tide and current information. Decide if you and your boat can navigate safely in the weather and sea conditions expected.

While Under Way Monitor Channel 16 for announcements of CCG weather broadcasts.

Periodically obtain weather information from Weatheradio Canada. Monitor the water ahead for signs of wind changes.

Note progressive changes in the sky, and monitor the direction the clouds are moving. Note changes in wind speed and direction.

Note changes in waves or swell. Recording all these observations in a log book is a good way of quickly building up a store of knowledge of your area.

Weather Tips Manoeuvring 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.

Clouds 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.

Cumulonimbus (CB) Base of the Cloud with Mammatus

Cumulonimbus (CB) with anvil top

The gradual thickening, and lowering, of clouds may foretell several hours of rain and poor visibility developing in one to three hours.

Sometimes there is also a ring around the sun or moon that is observable before the clouds become too thick.

Cirrostratus (CS) with complete halo

The appearance of a red sky or a rainbow may indicate deteriorating weather if it is early morning or improving weather if it is late in the day.

Wind 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?

Waves 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.

End