News National Thunderstorm asthma warning as severe weather heads north
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Thunderstorm asthma warning as severe weather heads north

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A storm made from multiple weather systems dropped by the Melbourne Cup before heading north. Photo: AAP
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Asthma sufferers have been warned to take extra care as a storm front sweeping across NSW could trigger serious breathing problems in some people.

A clash of hot and cold weather systems threw up an instant flood in Victoria on Tuesday that turned the Melbourne Cup into a mud bath, brought trains to a standstill, and blew out the power to 30,000 homes and businesses.

That extreme weather is expected be felt through NSW and southern Queensland on Wednesday, with fears that high levels of pollen in the air could trigger asthma and respiratory conditions as the storms approach.

“Thunderstorms cause pollen grains to explode and release fine particles which can be inhaled deeply into the lungs, causing even more people to wheeze and sneeze,” NSW Health’s Richard Broome said in a statement on Tuesday.

The warnings come after 3600 people presented to hospitals in Melbourne with breathing problems following storms in 2016. At least nine deaths were linked to the event.

“Anyone with diagnosed asthma should carry their asthma medication with them at all times during this high-risk period,” Dr Broome said.

Tropical waters from the Indian Ocean

The New Daily asked the Bureau of Meteorology’s extreme weather forecaster and meteorologist Dean Narramore to explain where the water came from Tuesday, and what caused it to be dumped in such violent fashion.

He said that most of the water was picked up by warm air off the Indian Ocean, and to a lesser degree off the Coral Sea. The water was then carried – by winds from the north-west – at higher altitudes of between five and eight kilometres.

The BOM national radar on Tuesday afternoon. Image: Bureau of Meteorology

“The air at this height is also much colder than the warm moist air at the surface, and this leads to the atmosphere becoming unstable,’’ Mr Narramore said.

As this upper trough travelled south, down and across Western Australia, and into southern Australia, the winds up top were blowing off in different directions, bringing up warm air from the bottom.

“The diverging winds in the upper levels produces uplift,” he said. “Think of the atmosphere as a cylinder: When you’re taking air away from the top, it’s replaced by air from the bottom.”

A cold front travelling north

Meanwhile, a cold front from the south west had picked up a small amount of moisture off the Southern Ocean. It was travelling north.

When these two systems clashed, it led to strong uplift of the warm, moist air at the surface – which was further enhanced by the instability up top.

Said Mr Narramore: “It’s this convergence of the cold front from the south and the warm surface air from the north, in combination with all the moisture in the mid and upper levels of the atmosphere that has produced the great downpour that has flooded Melbourne, and is continuing to occur as it moves on.”

So what’s next?

On Wednesday, the front from the south west will take a firmer hold in South Australia, Victoria and Tasmania – “as more and more cold air comes up from the south behind the front in the south-westerly winds”.

Mr Narramore said Tasmania will get snow down to 700 metres, and Victoria down to 1000 metres. In the meantime, the rain-heavy upper trough that soaked Melbourne will be pushed up through NSW and into southern Queensland.

“The cold front coming from the south is meeting and lifting all the warm air ahead of it,” he said. “And this will lead to all the rain and storms in NSW and Queensland tomorrow (Wednesday).”

The rain will be heavy but sadly too brief to affect the drought.

Ghost in the radar

While a look at the BOM national radar on Tuesday showed some of what Mr Narramore was describing, apparently it pays to have a meteorologist on hand to explain what’s true and what’s not.

On the radar, there appeared to be rain in play around Broome – and The New Daily asked if this was part of the big clash of multiple weather systems.

In fact, there was no rain in that part of Western Australia. Mr Narramore said the inversion of cold air on the ground, overlaid by warm air, was misread by the radar and created an illusion of rain activity.

He said if you checked the satellite imaging, you’d see there was no cloud.

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