Conditions

Weather

 “Everybody gonna paddle out together, any kind of weather, cause everybody’s OK.”      Xavier Rudd

You’ve got to love that kind of optimism, and it’s not far from the mark. There isn’t much that can keep you and your kayak off the water. In 2008, I managed to paddle for 41 days straight, unimpeded by the weather. Although  there are days when you’re better off keeping your Uggies on and staying inside to see what Bear Grylls is up to in the latest episode of Man vs. Wild. It is important to always check the forecast, and the likely impact of the weather on your plans. Strong winds, thunderstorms, and hail are not our friends and are best avoided.

Conditions

In a kit that has been created for schools, the Australian Bureau of Meteorology explains that “Weather is a description of what’s happening with the air, sun, rain and wind when you go outside.” As such, the current weather can be checked simply by getting off the couch and out of the house.

Making predictions is a little trickier, although meteorologists have identified consistent patterns that can help. These patterns are the basis of forecasts reported in daily newspapers, TV broadcasts, and on the internet. The Bureau of Meteorology, WillyWeather, and Weatherzone websites are all excellent sources of information about predicted weather .

Weather patterns are driven by the interaction of the sun, air, and water. They are also influenced by the rotation of the earth, both on its own axis and around the sun.

When the sun heats the surface of the earth in a particular place, the air above it rises. This reduces the air pressure at sea level and creates what is known as a low pressure system. When the air falls back down again, the pressure increases and creates a high pressure system. In an attempt to restore balance, Mother Nature moves air from areas of high pressure to areas of low pressure until both are equal. This movement of air is what we know as wind. The greater the difference in sea level pressure, the stronger the wind. For the purpose of illustrating these differences, meteorologists produce synoptic charts like this one from the Bureau of Meteorology. Lines called isobars connect points of equal pressure and are superimposed over a map of the relevant area, and high and low pressure systems are indicated by ‘H’ and ‘L’ respectively.

The wind doesn’t blow directly from a high pressure system to a low pressure system. Due to a phenomenon known as the Coriolis effect, the flow of air is deflected to the left in the Southern Hemisphere. This means that it moves anti clockwise around high pressure systems and clockwise around low pressure systems. Interestingly, the opposite occurs in the Northern Hemisphere. If you know the position of the prevailing system, you can also successfully predict the wind direction.

For longer range forecasts, it is useful to remember that pressure systems are not static. They move from west to east. It is therefore possible to forecast the weather by tracking their progress from that direction.

A complication in coastal areas is the “sea breeze” that springs up on summer days when the land becomes much hotter than the sea. When hot air above the land rises, cooler air from over the sea moves in to take its place. In eastern Australia you would naturally expect this to come directly from the east, but the Coriolis effect is at work again, deflecting the flow to the left. That’s why our sea breezes come from the north east. In the evening, the land cools and the wind subsides. In some cases, the land becomes cooler than the sea during the night and a gentle offshore breeze picks up. This wind is usually weaker than the sea breeze as the temperature difference is smaller.

Unsettled conditions and rain are usually associated with low pressure systems. The rising air carries water vapour, primarily in the form of evaporation from oceans, rivers and lakes. As it rises, it cools, and the water condenses into droplets which form clouds followed by rain, hail, and snow. If conditions are particularly hot and humid, the fast rising air can lead to a thunderstorm. Calm and sunny conditions are generally associated with high pressure systems. This is because the dry air is settling slowly back down to earth.

Tides

Anyone who has spent time at the seaside or beside an estuary will have noticed that the water level is not constant. It rises and falls on a regular basis. Particularly perceptive people will also have noticed that water is pushed into estuaries as the sea level rises and it is drained out of estuaries as it falls. The overarching term generally used to describe all of these processes is tides.

An excellent detailed explanation of the causes and effects of tides can be found on the National Oceanic and Atmospheric Administration (NOAA) website. There is a lot to take in if you want to completely understand the processes involved but for the purposes of planning paddling adventures on tidal waters in Australia, I have broken it down into the few things I think you might want or need to know.

Tides are driven by gravitational forces exerted on the world’s oceans by the Moon and the Sun, and centrifugal forces applied to the world’s oceans by the revolving Earth-Moon partnership and the Earth-Sun relationship. Gravitational forces draw the ocean towards the Moon and towards the Sun. Centrifugal forces send it to the opposite side of the Earth from the Moon and the Sun. Broadly speaking, the net effect of this is that water levels rise in those places that are on the same side or directly opposite side of the Earth from the Moon and the Sun, and they fall everywhere else. This sounds chaotic but the Moon is much closer than the Sun, so its forces are much stronger. The Sun’s forces generally only serve to enhance or diminish the effect of the Moon. As the Earth rotates on its axis 360 degrees every 24 hours, two bulges of water, which could be regarded as waves, move horizontally around the planet in synchronization with the position of the Moon. As a general rule, this creates two high tides and two low tides per day, usually just under 6 hours apart.

There are a small number of places in the world where the difference between high and low tide is virtually non-existent for one or two days a month. One of those is Adelaide in South Australia where the phenomenon is known as a dodge tide.

The height of the tide varies depending on the distance of the Earth from the Moon and the Sun, and the extent to which the forces exerted by the Sun enhance those of the Moon. The highest tides occur at New Moon when the Sun and the Moon are on the same side of the Earth as each other and Full Moon when they are on opposite sides of the Earth. These are called spring tides. The lowest tides occur when the Sun and the Moon are at right angles to each other. These are called neap tides.

The difference between high tide and low tide is known as the tidal range. A higher high tide will usually be accompanied by a lower low tide and therefore a greater tidal range. Greater tidal ranges result in faster tidal flows through channels and estuaries because there is more water moving in-between high and low tide. It is important to note that the speed of the tidal flow is not constant. It is slowest near high tide and low tide, and quickest at the mid-point between the two.

The speed of the tidal flow can also be affected by the shape of the land, above and below the water. In general, it will be quicker in narrow and shallow sections. Tide times for estuaries are always later inland than at the coast.

If you are planning on paddling in a tidal area, make sure to check the predicted time and height of the tides, and consider what effect tides might have on your chosen venue. Too much water may leave a fantastic beach submerged. Not enough could mean a portage is required or worse still, your day is cut short. In addition, the direction and speed of the tidal flow could either impede or assist your journey.

Tide predictions are published in a number of places. The Bureau of Meteorology, WillyWeather, and Weatherzone websites are all great sources of tidal information. There are also applications (“apps”) for smart phones. If you don’t have access to the internet, check in the local newspapers, watch the weather report on the television news, or pick up a tide chart from your friendly neighbourhood fishing shop or outdoor store.

Inland water levels

Some of Australia’s best paddling is on inland waterways. The water is fresh so there is no tedious boat washing at the end of the day, and the fishing is pretty good too. However, there is a not-so-small issue. Water levels cannot be predicted like they can in tidal areas.

In 1906, Dorothea Mackellar described Australia as a land “of drought and flooding rains”. That description seems more appropriate than ever as global warming exacerbates the impact of the El Niño Southern Oscillation (ENSO). Inland waterways are largely dependent on rain to keep them flowing, so periods of no rain and periods of excessive rain have dramatically different results. Dams and weirs constructed in many places also impact on the availability of water.

Luckily for people who want to go inland paddling, water levels are monitored. In Queensland, river levels are reported online by the Bureau of Meteorology, and the same is done for dam levels by the relevant water manager. Seqwater looks after south east Queensland, and SunWater handles the rest. In NSW, up to date information on water levels is published on the NSW Water Information website. If you want to be sure that there is just the right amount for your next inland adventure, take a look at what they have compiled about your chosen destination before you head off.

If you want to be sure that there is just the right amount for your next inland adventure, take a look at what they have compiled about your chosen destination before you head off.