DESTINATIONS - OUTDOORS HEALTH & SAFETY
Camping in rain or strong wind isn’t any fun at all. Knowing a bit about weather patterns can help in successful trip planning.
My old man was a weather fanatic. Every morning, he’d get up, wake the household by way of the mandatory, five-minute, heavy smoker’s hacking cough, then look out the kitchen window.
“It’s just started to rain,” was a typical announcement. “And it’s coming from the east.
“If from the East; three days at least,” he’d recite, while digging out his wellies and oilskin coat.
Another of his favourite doom-sayings:
“Wind before rain; soon fine again;
Rain before wind, your sails you mind”.
He was also obsessed by sunrises and sunsets:
“Red sky at morning; sailor’s warning.
Red sky at night; sailor’s delight.”
With that upbringing and sailing as a lifelong pursuit, watching the weather became second nature to me, but it’s surprising how little attention is paid to weather forecasts by many bush travellers.
Sure, most people usually don’t head for the ski fields without listening to a snow report and don’t go fishing in a tinny without looking up the wind and wave forecasts, but many travellers head off on a camping holiday without the faintest idea of likely weather.
The consequences of being in the right place, but at the wrong time can cause anything from a camper trailer sale to a family break-up. Even a cushy caravan or motorhome is somewhat claustrophobic after four days of constant rain and howling wind.
Broadly speaking, the time of year you’ve selected for your trip dictates where you should go, based on the likely weather conditions. As a general rule, you head north of the Tropic of Capricorn and to the Red Centre during the cooler months and turn south of the Tropic for coastal and mountain destinations
during the warmer months.
The most restricting annual weather pattern for Australian travellers is the Wet Season that hits the northern tropical areas during the southern summer.
Unless you plan to stay in the far north for The Wet and are prepared for lengthy travel restrictions due to flooding and cyclones, don’t go there at that time of the year.
The inland desert regions are no-go zones during the summer: temperatures can reach the 50s and even a minor vehicle problem can become life-threatening. As of 2009 the Simpson Desert tracks are closed during the hot months.
Conversely, Alpine regions that are snow-covered during winter are open during summer months.
Within that broad travel framework there are changing weather patterns to be aware of. In these days of laptops and wireless broadband it’s possible to consult long-range and short-range weather forecasts for most of the regions you’re visiting. The ‘BoM’ site (Australian Bureau of Meteorology) is an excellent source of weather data that’s updated regularly.
The most critical item on any weather site is the ‘warning’ information. Warnings are issued to cover weather extremes and are typically
strong wind, thunderstorm, frost, damaging hail, snow, ice and sleet warnings. There are also warnings of extreme heat and wind conditions that can provoke dangerous bush fires.
All these weather conditions should be noted and acted on by bush travellers.
Normally, strong wind systems blow themselves out in a day or two, so if you can postpone your drive you’ll have a safer journey.
Hail, snow, sleet and ice warnings should also make you reconsider a planned drive, until conditions improve.
Forecast temperature should be a guide to daily activity during a bush trip. If it’s going to be stinking hot, don’t plan a bush walk during the middle of the day: break up your activities so that you’re active when it’s coolest. Do a walk in the morning, drive during the hottest part of the day and walk again in the late afternoon.
The temperature forecast should indicate what clothing and supplies you’ll need for the day’s planned activities. In cold weather, combine the temperature forecast with the predicted wind chill factor when you’re planning what to wear.
As is made all too obvious every bushfire season, the day’s weather forecast is an excellent indication of bushfire risk, but many people ignore the warning. If you’re camped in a fire-prone area and the forecast favours wildfires, think about moving to a safer position.
Weather forecasters talk of ‘low’ and ‘high’ barometric pressure zones. Atmospheric pressure is the weight of the air above us, but we’re not conscious of it. However, variations in atmospheric pressure contribute to weather patterns.
Atmospheric pressure is measured on a barometer and its rate of change indicates the speed of a change in the weather. You hear of mariners monitoring the ship’s barometer and fearing the worst when the ‘glass is falling rapidly’.
Normal barometric pressure at sea level is 101,325 Pascals, or 101.3kPa, or 760mm (29.92 inches) of mercury, or 1 Bar, or 1013.25 millibars, depending on which measuring units you prefer.
The most common weather pattern charts are drawings of Australia, with curved lines that look like map contours; shorter,
heavier, curved lines with little shapes on the front of them and the letters ‘L’ and ‘H’. The drawings are known as synoptic charts.
The curved lines are called isobars and encase either the letter ‘L’, indicating a low barometric pressure zone, or ‘H’, indicating a high pressure zone. On some weather maps the isobars have barometric pressure numbers on them.
In the southern hemisphere the wind flows around a low pressure zone in a clockwise direction and around a high pressure zone in an anti-clockwise direction. So, when you see one of these zones on a synoptic chart you can visualise the wind following the isobars around the centre.
The spacing of the isobars gives a good indication of wind strength: the tighter the spacing, the greater the wind strength.
Wind strength is also indicated by a ‘wind barb’, which is a dot with a tail. The direction of the tail is the wind direction and the number of barbs on the tail indicates wind strength.
Almost always, the weather patterns move from west to east across Australia, so if you’re experiencing bad weather as the result of a ‘low’ in the area and you can see a ‘high’ moving towards you from the west, you can expect the weather to improve soon.
When high pressure and low pressure systems collide the result is a ‘front’. A warm front is shown on a synoptic chart as a dark, curved
line with little semi-circles on the leading edge. The semi-circles show the direction of the warm air flow. A cold front is also shown as a dark, curved line, but with little triangles on its leading edge. The triangles show wind direction.
Fronts usually indicate a change in wind speed and direction, with effects that vary from gentle breezes to gale force.
If you’re in an area where you can’t access a synoptic weather forecast chart you can have a stab at doing your own weather forecasting. Cloud observation is a great help.
A word of warning here, for followers of my Old Man’s ‘red-sky’ theorem: it works well enough in coastal areas, but in inland Australia it’s common to see red sunsets and sunrises that have no influence on the coming weather pattern.
‘Happy’ clouds are well-spaced, white cumulus that indicate stable weather. Usually there’s no rain, or at most, occasional showers.
If you see high-altitude cirrus clouds, streaked by winds, it can be a sign of a weather change in a day or two. However, in desert areas, high-altitude clouds are frequently seen, without any subsequent weather change. Winter rain in Australia’s parched inland seems to be less common than late-Wet or early autumn rain.
Cumulo-nimbus clouds that form later in the day house destructive forces. They build up to very high altitudes and often have anvil-shapes. These thunderstorm clouds can produce dangerous lightning, destructive hail and squalls.
Weather watching is fun and can make the difference between a safe, happy trip and a disastrous one.