Where have all the cyclones gone, and will they come back?
WHERE have all the cyclones gone?
If you were one of the millions of Australians who sweltered through the relentless heat of the season dubbed the "angry summer" by climatologists, you would be forgiven for not noticing the tropics have been unusually quiet this year.
More than 200 weather records tumbled across Australia this summer, according to the Climate Council, and, just six days into autumn, Cyclone Blanche brought with her yet another, when she became the first of the season to make landfall.
Blanche crossed the northern coast of Western Australia as a category two storm on March 6, the latest a cyclone has made landfall in Australian history, according to the Bureau of Meteorology.
It was just the third tropical low that has formed into a cyclone this season, which began on November 1, well down on the long-term season average of 11.
It is the second consecutive year Australia's cyclone count has been chronically low.
Last year, there were just three for the entire season, itself a record for the quietest cyclone count in the country's history.
That, however, did not particularly surprise scientists at the bureau.
They had tipped before the season began that numbers would be low, due to the ongoing effects of an El Nino weather pattern that brings dry air, which is not conducive to the formation of a high-energy cyclone.
This year, on the other hand, the low numbers have blindsided them.
Dr Andrew Watkins the manager of climate prediction services at the bureau, said scientists are, at present, trying to get to the bottom of exactly what happened.
He said it has also attracted intrigue from international meteorologists, with visitors from the United States and the United Kingdom travelling to Australia to try to work out just what is going on.
"This year, we're not in an El Nino, we were heading into a neutral pattern, so we were saying it would be an average to above average season," Dr Watkins said.
"We would have expected 11 or above and to only have three so far is fascinating.
"We're fascinated by why this season has been so benign."
They have a few theories, Dr Watkins said, and are presently crunching the data to get to the bottom of it.
"There are several theories and at the moment the data is pouring in from satellites and everywhere," he said.
"We have here or four ideas and we want to test each one of them out.
"Many people just think tropical cyclones form over warm water, which is true, but there are other factors, a few things need to come together to form a cyclone.
"They are quite amazing things that don't form that easily. Maybe something strange is happening with one of these factors."
But could it be a sign of things to come?
In other words, could it be the impact of climate change is already being felt?
In the Climate Council's Cranking up the Intensity: Climate Change and Extreme Weather Events report released earlier this year, the independent body predicted that in coming years, due to rising temperatures, cyclones would get less frequent but those that formed would be higher in intensity.
Dr Watkins said that did not appear to be the case this year, as the cyclones that had formed had been fairly weak.
But he said "basic physics" governed that climate change would increase the intensity of cyclones in the future.
"For each degree of warming there is about seven per cent more moisture in the atmosphere, so there is more moisture now than, say, 50 years ago," he said.
"In reasonably simple terms, the warmer it gets, the more steam comes off the water and the warmer the atmosphere, the more moisture it can hold."
He said it naturally followed that the amount of rain each cyclone brought would be higher, and thus the cyclone more intense.
It does not, however, explain this season's anomaly.
"Being perfectly honest, climate change is a factor in most of our climate science these days but in terms of tropical cyclones you couldn't put this season down to climate change," he said.
"More generally though, the projections are for fewer tropical cyclones but when we do get them, they will potentially be more intense, just not this year."
What it may have caused, however, is the drenching rains that have bucketed down relentlessly on Australia's north and west this summer, as the east sweltered.
The Northern Territory has had one of its wettest wet seasons in recorded history, and could also be on track to smash the rainfall record of 141 days set in 2011.
Dr Watkins said the rain was due to unusually active monsoonal troughs, which had stretched far further south than usual.
He said unlike the lack of cyclones, the highly active monsoon season could potentially be explained by climate change.
"There may be some of that increased moisture in the atmosphere at play there," he said.
"The monsoon trough has been very active and a lot further south than normal.
"Western Australia has had lots of rain, particularly up in the Kimberley but, at times, it has drawn right down the coast to south west West Australia.
"Ravensthorpe (southern WA) had its record rainfall for February before Valentines Day.
"That was again related to moisture coming down from tropics, so it has certainly led to some interesting times."
But it seems it's not just Australian scientists the always unpredictable Mother Nature is perplexing this season.
"The whole southern hemisphere is having one of its quietest cyclone seasons on record," Dr Watkins said.
"Everywhere is missing out. It may be there has been quite a change in the Indian Ocean, though, that said, at the start of the season there was no reason to believe the season would be particularly weak.
"But the weather gods have stepped in and we are diagnosing as we speak to try and understand it better."