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The sticky, humid weather that has beset Sydney over the past week will transform into heavy rain and thunderstorms on Saturday afternoon.
Severe weather warnings have been issued by the Bureau of Meteorology, with concerns about flash flooding as a trough of low-pressure systems merge with exceptionally high humidity, producing slow-moving thunderstorms for Sydney and south-eastern NSW.
Sydney could receive between 70 and 100 millimetres of rain on Saturday evening into Sunday morning, bureau meteorologist Tristan Sumarna said.
“It depends on whether the thunderstorm forms in a certain location and stays in that location for an extended period of time,” he said, warning the outcome could be similar to the storm last month in Sydney, when 111 millimetres fell within about three hours at Lidcombe.
“We’ve got a very similar setup to that today, with a moist, northeasterly flow and a sort of southerly change, stopping around the Sydney coast. Depending on where that stops, we may see heavy to locally intense rainfall in the basin.”
While the rain may seem like it could rinse out the humidity that Sydneysider’s have no doubt experienced all week, Sumarna said the moist air would continue to linger.
“We will still see a broad easterly regime for the next couple of days, into early next week, and that will continue to ring a lot of that moist air from the Tasman Sea to the Sydney region, keeping the relative humidity higher than what we’d like it to be,” he said.
A monsoon tracking around the Northern Territory is the reason Sydney has been dealing with an accumulation of humid air, Sumarna said. The only way to cut it is by a strong cold front coming through.
“All of this tropical moisture is connected to Queensland and the Northern Territory. An active monsoon with previously multiple tropical lows across northern Australia has meant that … it has been drawing an ample amount of moisture from the tropics towards NSW,” he said.
“For the humidity to go away, we do need quite a strong cold front to bring a westerly wind change to the region, and that helps to flush out the humidity. But currently we don’t seem to have that on the forecast until around later next week, which is a little bit uncertain at this stage.”
Earlier on Saturday, Orange recorded 33 millimetres of rain in one hour around noon, with East Kangaloon recording 53 millimetres in one hour during the afternoon.
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