Townsville is considered part of the dry tropics because it has much lower rainfall compared to regions to the North and South. The seasons are generally split into a wet and dry period for the tropical areas of Australia. November to April is the wet season, and May to October is the dry season. The dry season is dominated by South Easterly (SE) trade winds that are warm and dry. The average annual rainfall for Townsville is 1143mm, most of which falls in the wet season. The angle of the coastline provides shelter from the lift effect that produces rain all year round for the regions of North and South. high-pressure systems are dominant at this time. A High-pressure system is where the air is pushed away and circulates in an anti-clockwise direction over vast areas of the country, sometimes the size of the entire country. Some high-pressure systems have a deformity in the circulation called a ridge. Often a ridge will appear along a coastline and act as a buffer to keep the rain away from crossing the coast.
During the wet season, the high-pressure systems make way for low-pressure systems that include circulating air regions in a clockwise direction or lengths of the atmosphere where air pools. Circulating low-pressure systems generally form at the end of these troughs where the air curls around the back.
These can develop into tropical low storms or intensify into tropical cyclones over water. Inland troughs form where hot, humid air is thrust into the atmosphere creating a breeding ground for storm activity. Storms reach upper levels of the atmosphere where wind directions change and guide them. Sometimes they stay along the trough, sometimes they move away, and generally towards the East. Often troughs extending a frontal system to the South will form along the Great Dividing Range of Australia, where Westerlies push against the mountains and are thrust up into the atmosphere, creating short-lived storms. This is the orographic lift. One side of a mountain is generally greener than the rain shadow side. Townsville is surrounded by mountains and, commonly, the rain shadow where the populated areas are, thus referred to as the Townsville Dome.
A trough called the Monsoon Trough that sits along the equator during the dry season will drift South towards the top of Australia. This is generally the start of the wet season and will pulse North and South 3 or 4 times during the wet season. Typically, a cyclone will only form along the Monsoon Trough at a point where air can curl around the end of the trough. The monsoon trough pools hot, humid air from the equator, which increases the rain intensity over the Northern regions of Australia. Where a trough crosses the coast, be it the monsoon or other, air will converge to one location on the coast. This will combine cool-dry and warm-humid air, which increases the lift and thus increases rainfall.
The Ross River Dam is one of two main water supplies to Townsville. In 2019 Townsville saw the dam reach levels above 100% and the Dam went into automated action. You can read more about how the water levels are controlled on the EAP page listed below.
The Dam Filler game is a board game aimed at explaining the Dome that so many people talk about when it comes to Townsville's weather. In fact, the dome effect is felt in many locations and so the key learning in the game applies to multiple locations around Australia and indeed the world. While this is an educational game, it is educational as you play, and you will be having fun while you play!
Purchase your copy of the Dam Filler game from the Tobruk Kiosk or check out rhe video and order from the gift shop.
Further Reading
Australian Bureau of Meteorology: http://www.bom.gov.au/climate/data-services/education.shtml
Townsville Emergency Action Plan: https://www.townsville.qld.gov.au/water-waste-and-environment/water-supply-and-dams/ross-river-dam
Ross River Dam: https://m.youtube.com/watch?time_continue=6&v=L5PwMRWLB1I&embeds_euri=https%3A%2F%2Fwww.townsville.qld.gov.au%2Fwater-waste-and-environment%2Fwater-supply-and-dams%2Fross-river-dam&feature=emb_logo
Credits
Thanks to all those who helped make this project possible, including:
Australian Bureau of Meteorology (http://www.bom.gov.au/aviation/data/education/glossary.pdf) for educational terminology and educational content (http://www.bom.gov.au/climate/data-services/education.shtml)
Orographic lift image https://commons.wikimedia.org/wiki/File:Rain_Shadow_Effect_caused_by_Orographic_Lift.png
All synoptic drawings were hand-drawn by Andrew Brown
Andrew Brown for his knowledge of weather patterns and knowing how to make clouds fun
Lachlan Robertson for structuring and brainstorming game ideas in earlier iterations of the game
All our play testers who helped us see our game become a reality!
Maps courtesy openstreetmap.org for the map of Townsville
Map of Australia https://commons.wikimedia.org/wiki/File:Australia_location_map.png
Wally’s weather community for supporting the development of the game
All game content is © 2022-2023 copyright to Instructional Engineer