The weather at Lake Keepit Soaring Club is always good… but then you'd expect us to say that.
The Australian summer is officially December to February but this big country covers such a range of latitudes that superb thermal flying is available in every month of the year, if you are prepared to travel.
In mid-summer in eastern Australia, the best conditions are mostly further to the south than Keepit though the temperatures can be a brain-frying 40ºC on the ground and the terrain fairly dull. The further north you go, the more humid the summers – until in Central Queensland the summer is the least favourable season for XC flying, with almost daily thunderstorms from mid-morning - and gliders generally stay in their mosquito infested hangars with only cane toads for company.
As summer turns into autumn, the prime XC region drifts north, into northern New South Wales and southern Queensland. By mid-winter in July where even warm days are a chilly 24ºC, the best flying in the country has reached Central and Northern Queensland, while the southern sites are shivering in European winter misery.The sweet spot on the map of this annual cycle is northern NSW, where good XC flying is possible 12 months of the year.
The summers might not be quite as extreme as in the south, and the winters not quite as consistent as the north, but it is possible to fly year-round in good to excellent conditions – and nowhere else can boast that.
There's one gliding club located right in this sweet-spot – and as you might have guessed, it's Lake Keepit Soaring Club. Conditions throughought the year are mostly cumulus with light winds, and the area provides an interesting mix of flatlands and low mountains. The club itself has a good range of club gliders and cabins for accommodation. What else do you want?
The location is also arguably the most picturesque in the country, with the airfield nestled next to the lake and adjacent to a large swathe of native bush. The wildlife is abundant – and in fact the greatest risk in flying at Lake Keepit is probably the chance of a mid-air with a pelican (know this has probably never happened) or bumping into a kangaroo on landing (on rare occasion, this has).
On average only 20-30 days are lost each year to weather. The January average is for 6 days with rain. However this is not your normal Northern European drizzle, it's more likely the occasional sun-shower under overdeveloped clouds or a late afternoon thunderstorm, often isolated to the high country.
The dominant feature influencing Australian weather is the belt of subtropical high pressure cells which transit Australia from the west to east, taking about a week to do so.
In the winter and early spring they tend to be about 30 degree south of the equator, somewhere near the NSW/Queensland border, and then progress southward and by summer can reach 40 degrees south, just to the south of the Australian mainland. Their centre is fairly stable, with a strong temperature inversion, being descending air from the tropics.
The anti-clockwise movement of air around a high pressure system (opposite to northern hemishphere) brings in a surge of fresh cold air on the eastern side. After the system has passed through, the wind swings around to the northeast and then north. The lower levels of air warm up creating what is usually a good temperature profile and improved gliding conditions. The days tend to get better until the arrival of the next high pressure system often preceded by a cold front.
These seasonal variations in the high pressure belt mean that Southern Queensland has good gliding weather in late autumn and spring. This pattern of superior weather moves south as the season progresses.
Higher ambient temeratures over the land mean that the air pressure is lower than over the ocean. The normal daily movement inland of cooler sea breezes plays a significant part in our gliding task planning as it virtually wipes out useful thermals in its area of influence.
Some gliding clubs in South Australia are affected by a sea breeze which follows the Murray River to the east of the Mr. Lofty ranges. Victoria is notorious for the Kilmore Gap, through which a flood of cold thermal destroying air pours on good gliding days. The Great Dividing Range running parallel to the NSW coast forms a dam holding back the cooler sea air. The lowest point is at Murrurundi at the head of the Hunter Valley. Here, on a typically thermally active day a river of cold air 10km wide floods inland.
It is split in two by the Liverpool Range to the south of Lake Keepit with one arm moving southwest towards Dubbo and Narromine and the other moving northwest up the Liverpool Range towards Gunnedah, 26 km to the west of Lake Keepit on the other side of the Carroll Range. The leading edge of these masses of maritime air form a convergence zone where the cold incoming air undercuts the warm inland air and is marked by good lift and active cumulus clouds.
Sometimes a sea breeze front can create remarkable gliding conditions but it is bad news if you have to traverse the cold air behind it to complete a task. At Lake Keepit we avoid this possible problem by tasking to the area likely to be affected first and coming home later from a different direction.
Lake Keepit is located with the Great Diving Range lying to the east and the expansive inland plains to the west. The unique position gives special gliding opportunities as well as interesting and varied country over which to fly. No wonder two current Australian champions learnt their skills here.
Overseas pilots, used to relying on cumulus clouds, rather than the more common blue thermals of dry inland Australia, will feel at home. The average cloud cover in January is 2 octas at 9.00 am and 5 octas at 3.00pm. When coupled with an average maximum temperature of 34ºC and 40% humidity, equates to an average cumulus cloud base of 8,000'.