Meteorologists normally only name weather systems that threaten significant impacts over a large area – think hurricanes, or the massive winter ‘nor’easters’ that batter the Atlantic US and Canada. Hector is an exception: a simple thunderstorm, named not for his power, but his dependability.
Hector forms over the Tiwi Islands, off the coast of Darwin in Australia’s Northern Territory, so reliably that you can set your watch by him. Nearly every afternoon during the build-up and rainy seasons, September through to March, Hector appears at 3pm.
His clockwork consistency is the result of a local microclimate, created by sea breezes and the Tiwis’ pyramid-like topography.
The islands are surrounded by tropical marine air. In the morning sunshine, dry air over the land warms faster than the humid air over the sea. As the dry air heats up, it expands, creating a pocket of low pressure above the islands that sucks the marine air onshore as afternoon sea breezes.
These sea breezes rush in from all sides. When they converge at the peaks, they have nowhere to go but up, carrying moisture from the seas with them. As the column of air rises, it cools and condenses, forming water droplets and clouds, and injecting instability into the atmosphere that quickly builds into a deep convective storm. Hence Hector’s nickname: Hector the Convector.
He was named by World War II pilots, who used his hulking cumulonimbus thundercloud as a navigation beacon when flying between Darwin and Papua New Guinea.
According to the Australian Bureau of Meteorology, Hector is one of the most consistently large thunderstorms on the planet, regularly reaching over 19km (12 miles) high — and occasionally punching into the stratosphere.
He’s also one of the most well-studied. Thunderstorms tend to be unpredictable, short-lived beasts. It’s difficult to pinpoint just where they’ll pop up, but since the 1980s scientists have been exploiting Hector’s extraordinary reliability to probe the mechanics of storm formation and investigate phenomena including lightning and updrafts.
This article is an answer to the question (asked by Dawn Greer, via email) 'What is Hector the Convector?'
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