Tuesday, October 14, 2014

No chance of an average cyclone season?

Cairns Post: 2014-15 tropical cyclone outlook: only one cyclone to cross Australia’s east coast
THERE’S good news for people living in cyclone-prone areas of Australia, with fewer tropical cyclones predicted this season.
The report then goes on to cite a 66% chance of fewer cyclones than normal/average in Australia predicated on near El Nino climate conditions over recent months, before quoting a Bureau of Meterology (BOM) spokesman:
In past El Niño years, there has been at least one cyclone to cross the Australian coast, he said, warning that even one can cause significant damage and be potentially fatal.
"At least one" does not appear to be exactly the same thing as "only one"? This has all been based on the 2014–15 Australian Tropical Cyclone Outlook. There has been some modelling uncertainty over the probability of an El Nino event for some months now.

The BOM have been careful to quote only probabilities, not predictions, unlike the media reports. The 66% chance of fewer than average cyclones is balanced by a 34% chance of more than average cyclones. Which makes me wonder what happened to the probability of just an average number of cyclones?

Never mind the BOM probabilities above are for Australia which is broken down into five regions, the probabilities are even more average for FNQ and the Coral Sea:
The eastern region outlook indicates a near average tropical cyclone season is most likely (42% chance of above average, 58% chance of below average. About a quarter of tropical cyclones in the eastern region make landfall. Forecast accuracy in this region is low.
So it all looks pretty average to me!?!

Note:  There are on average 25% fewer cyclones each season in the northern region than there are in the eastern region. Perhaps this could explain at least some of why it is valid for risk based property insurance premiums to be cheaper in Darwin than they are in Cairns!

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