Transcript Boating Course Weather - Kilpatrick Road Weather

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
Mariner’s Guide – West Coast
Weather Services.
These publications are available
through Environment Canada’s
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
 Waves
 Poor
Visibility
 Lightning
 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 cat’s 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 boat’s
movement.
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:
http://johnellsworth.com/writing/nautical/understand_appwind/understand_appwind.html
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
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
21 - Sheringham Point
22 - Tofino
23 - Estevan Point
24 - Nootka
25 - Solander Island
26 - Quatsino
27 - Sartine Island
28 - Pine island
29 - Herbert Island
30 - Egg Island
31 - La Perouse Bank ( Weather Buoy)
32 - South Brooks (Weather Buoy)
33 - Cape Scott (MAREP Station)
61 - Chatham Point
North, Middle and South Nomad Buoys not shown
Georgia Basin
Georgia Basin Weather Buoys and Stations











01 - Sentry Shoal (Weather Buoy)
02 - Halibut Bank (Weather Buoy)
03 - Fanny Island
04 - Cape Mudge
05 - Campbell River
06 - Powell River
07 - Grief Point
08 - Chrome Island
09 - Port Alberni
10 - Sisters Island
11 - Ballenas Island
Georgia Basin Weather Buoys and Stations











12 - Entrance Island
13 - Merry Island
14 - Pam Rocks
15 - Point Atkinson
16 - Sand Heads
17 - East Point
18 - Kelp Reef
19 - Discovery Island
20 - Race Rocks
21 - Sheringham Point
61 - Chatham Point
Synopsis and Forecasts
Issued at 0400, 1030, 1600 and
2130 hours
Forecast valid for 24 hoursupdated if conditions change
“Securite, Securite” on Channel 16, Switch to WX or 21B
Synopsis and Outlook Wind Speed Terms
Light
Moderate
Strong
Gales
Storm
Hurricane
0 to 11 knots
12 to 19 knots
20-33 knots
34-47 knots
48-63 knots
64 knots or more
Synopsis and Forecasts- VHF
Weather Channels
Victoria- WX 3, 21B
 Strait of Georgia South
 Howe Sound
 Juan de Fuca Strait
 Haro Strait
 West Coast Vancouver Island South
Comox- WX1, WX3, 21B
 South End of Texada Island to Northern Vancouver
Island
 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 (162.55 MHz), WX 2 (162.40 MHz), WX 3 (162.475MHZ), 21B (161.65 MHz)
Synopsis and Forecasts- Sources
Continuous Marine Broadcast – Phone
 Mt. Helmcken – 250-363-6880
 Bowen Island/Mt Parke – 250-363-6492
 Comox – South Area – 250-339-0748
 Comox – North Area – 250-974-5305
 Tofino – 250-726-3415
Marine Weather Information - phone
 Nanaimo
-250-245-8899 or 8877
 Campbell River
-250-286-3575
 Port Hardy
-250-949-7148
 Victoria
-250-363-6717, 250-363-6492
 Vancouver
-604-666-3655
Television
 The Weather Network
Internet

http://www.weatheroffice.com
http://www.weatheroffice.pyr.ec.gc.ca/atadwxradio_e.html
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 cauliflowershaped 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