Whilst the forecasts are generally very accurate, they are not 100% accurate,
100% of the time. Just like your luck, the weather can change in an
instant! So, when necessary, check with other sources, such the
BOM forecast, your mates, and of course, what’s actually happening
When the weather is not as the forecast predicted, the tendency is to blame
the forecast. We'd like to suggest that the forecast is accurate as it possible can be, it's the
weather that changed!
Let's think about how a forecast is generated.
The first step is to collect real observations from around the globe so that
you can feed past weather and current weather into the computer model that
generates the forecast.
Weather observations are sourced from many places, such as the daily release of
a weather balloon which measures the air pressure a various altitudes.
(There's more to forecasting, than just sea level)
Other sources include ships which are part of a world data collection system
that take weather observations such as temperature, air pressure, wind
direction and speed and radio them in to a central collection point.
There are also weather buoys that freely float the currents of the ocean and
automatically radio their observations in. Similar concept on solid
ground - land based weather stations automatically collect weather data and
radio the information in - no human help required.
There will always be areas of the atmosphere where no local observations have
been collected. These areas are calculated using sophisticated
estimation systems to use surrounding observations to calculate what's going
on in the area without any observations.
The computer model then uses historical data, current data and local knowledge
to predict what the weather is most likely to do next - a forecast.
The forecasts are regenerated every 6 hours, and the graphs are updated here
moments later. The further out the forecast is (e.g. 7 days) the less chance it
has of being accurate due to the chaotic nature of weather.
How to read the Wind & Wave Forecast graph
Unlike the live graphs which represent part of a single day, the forecast
graphs cover 7 days.
Each "forecast" arrow is three hours apart from the previous arrow,
representing a forecast wind speed/direction and swell every 3 hours of the day
for 7 days in advance.
How to read the Wave Direction & Peak Period Forecast graph
Wave direction is the direction the swell is travelling. As every spot where
waves break has a unique coastline, it represents a general indicator of the swell direction
prior to being influenced by things such as groins, reefs, points and bays etc.
Peak Period is an estimate of the average time (in seconds) between peaks. As a general
indicator, the longer the period, the more powerful the swell. For example, 9-12 seconds may
indicate wind waves while powerful swells have a period longer than 15 seconds. Bigger periods will also
indicate faster moving swell. For example, a 2 metre swell @ 22 seconds can travel at over
twice the speed of a 2 metre swell @ 9 seconds.
Just like the other graphs, the centre of the arrow indicates the point where the value should be read from.
Each increment at the base of the graph is a 4 hour period, with the longer bar on the "day" axis indicating
How to read the Wind Forecast Graphs
Did you know that the arrow colours are reversible?
This site was originally built for Windsurfers & Kitesurfers - where strong wind is a good
thing, so green=strong wind.
If you fish or surf, then light wind is a good thing, so .. red=strong wind.
How to work out the Wind Speed
The most recent live reading is at the right hand end of the graph, and up to 12 hours history
extends towards the left - check out the time label at the bottom of each graph.
Arrows indicate the strength by their Height on the graph and the colour of the arrow:
Green Arrows indicate Strong wind, which is 17+ knots, 30+ Km/H, Force 5 or
This graph shows an 18 to 20 knot southwester around 1pm
Yellow Arrows indicate Moderate wind, which is 11-16 knots, 20-29 Km/H,
This graphs shows a 14 to 16 knot southwester around 2pm
Red Arrows indicate Light/No wind, which is 0-10 knots, 0-19 Km/H, Force 3 or
A 7 to 9 knot easterly around 8-9am
Brown Arrows indicate, um .. 'soil your dacks' weather.
A running joke here for years, we finally made them live. Nothing beats a solid
35+ knots, and to be out in it as a kiter/windsurfer is really exciting stuff, but without a doubt
there a moments when you might fill your shorts. Let alone if you're out in a small boat in these
Indicates wind 35 knots+
Table of wind speeds
||0 to 10 knots
||Force 3 or less
||11 to 16 knots
||Fresh & Strong
||Force 8 and above
The Middle of the arrow is where you
should read the wind speed from the scale at the sides. Picture the arrow as
being like a compass needle, where it rotates around a central point of
The Grey arrows
indicate the maximum gust during the 10 minute period.
Time of day is displayed along the
bottom of the graph.
The site was initially designed for Windsurfers,
so the colours use a Traffic Light type colouring, which may be the opposite of
your needs .. especially if you surf! You can reverse the colours in the graphs
by clicking here
For most locations, the wind strength and
direction is the result of a 10 minute average
How To Read The Wind Direction
arrows indicate the direction the wind is going based on North being at
the top of the screen and West being at the left.
This concept confuses some people first off, because they are expecting the arrows to
work like a weather vane and point towards the arriving wind.
It can also be confusing if you're looking at your computer monitor in a Southerly direction, as all the
directions will be reversed.
We had to choose whether the arrows were indicating where wind went, or where it came from.
We figured that most things in life, such street signs (e.g. one way signs), swell direction arrows and traffic cops all point in the direction
that something is going.
Pointing where the wind is going also makes good sense when the arrows are overlaid over a map (..see demo)
Take a "Northerly" wind, for example. "North" is at the top of the screen (as maps generally have their
northmost point at the top), and a "Northerly" is a wind that travels from the North to the South, so it is
drawn as an arrow that points down - that is, pointing from North to
Easterly Example: An easterly wind heads from the east (right side of
the screen) towards the west (left side of the screen), so the arrow is drawn
pointing to the left.
Sunrise & Sunset
The grey shaded area of the graphs indicate night time. The graphs are live 24 hours are day and always
display the most recent 8 hours of live wind data. You can also view yesterdays full 24 hour history by clicking
the "Yesterday" link located in the left hand menu.
The graphs below show the progress of an awesome West Australian seabreeze, and displays from Midnight to Midday
As illustrated by the grey gradient, Sunrise was at 5:32am
In the graph above, you can see the seabreeze arriving at 10:30 am where it shifts from a SE to a SSW.
The graph below is 8pm later the same day, and shows the previous 12 hours to 8am.
The grey gradient at the right indicates night is approaching (sunset was 7:32pm)
This particular day was an amazingly consistent 20 knot southwester which continued right through past midnight...interesting
change of direction from SSW to S once the sun went down...
All times are aligned!
||In the example graphs below, the wind graph at the top has readings every 10 minutes, whilst the graph underneath
The Time axis of all the graphs on the same page always align vertically.
We've drawn the red line over the graphs to show how the times line up.
This example shows two graphs at 12:30 pm. As the lower graph only reports on the hour, there is a gap to show the time since
the last report. The upper graph has data every 10 minutes.
Stations that report hourly will have a gap at the right hand side due to the lower reporting period,
and this makes it easy to verify the latest readings.
The red line shows how all the graphs times align.
How To Read The Tide Graphs
What causes a Tide?
Gravity! Water stays on our planet due to gravity. As the Moon orbits the Earth, it pulls the sea water
towards itself. The Sun provides a similar effect, and as our distance from the Sun changes during the year, this also
affects the tides.
Sophisticated algorithms are used to compute the tide levels based on the rotation of the Earth, and the
position of the Sun and the Moon, and our distance to the Sun.
Predicting tides also relies on knowledge of "harmonics". Hundreds of tide monitoring stations (which are usually mounted
on a jetty or other stable structure) measure the real water level. If a massive body of water is pulled
one way, then the other, and all the while bouncing of sea walls and beaches, you can imagine how it can affect the
calculations. So, from these real readings, the harmonics can be deduced which are then fed into the tide equations to
assist in predicting tides.
Tsunami's, strong wind, swell and storm surges will all affect the level of water experienced at your local spot.
What use is Tide information!?
The tide graphs are handy for surfers, windsurfers and kitesurfers - anybody
who likes to hit a wave now and again. Tides can have a huge effect on the swell.
A wave is caused by the shallowing of the ocean floor as a force of water approaches it. The only way "out" for the
energy in the water is up .. thus a wave is created. Thats why waves don't generally break in the open ocean, but do tend to break
over shallow areas of water such as reefs and beaches. Reef breaks can be some of the most powerful waves due to the sudden
change of depth.
This is where the tide comes into it...if there's a 2 metre swell and there's going to be a 1 metre high tide, then that's going
to take some of sting out of the swell, because there may be an additional 1 metre of water depth. (Remembering that the
reef/beach may not necessarily be at "mean sea level")
However, if it's low tide (say 10cm), then that 2 metre swell is going to be a lot more exciting!
You can't mention tides without mentioning fishing! Many fish become active on a change of tide .. the changing
currents can stir fish into life meaning they'll jump on your hook more readily. Because high tide adds extra
depth, it can change which areas fish can feed in - fish can head into areas that were inaccessible on a low tide.
The tide graphs are not for navigation
Using the seabreeze tide graphs to work out if your yacht can make it up the river where you need "at least
78 centimetres of clearance or it will run aground" is not recommended. For navigation issues, please use the official guides at
Bureau Of Meteorology, or for Western Australia, the
Coastal Data Centre
The "Live" tide graph is not from real observations
Thinking of heading out to go fishing or hit the surf and want to know what level the tide is up to?
The tide graph at the bottom of each page is plotted from the tide predictions and is there as a convenience
so you can see a close-up view of the tidal activity - it is not taken from real tide readings in the ocean.