Yasi — the super cyclone that isn’t so unusual
For all the other Christine Milne’s out there, who think coal mining causes cyclones, the empirical evidence inconveniently declares that super-cyclones have been hitting Queensland regularly for the last 5000 years.
As usual, it’s the name-callers who cling to 100 year time-frames and deny the long term evidence, while we “cherry-picking denialists” gravitate towards long term studies based on real observations. (The evidence lies in an obscure industry newsletter called Nature.) The way researcher, Jon Nott, describes it, things have been unusually quiet in our high CO2 world for the last few decades, but cyclones used to be a lot worse, and “worse” is coming back.
Thanks to The Australian for putting together a very timely piece about the historical pattern of cyclone activity.
[Johnathon] Nott is an expert on the incidence of super cyclones. By analysing ridges of broken coral pushed ashore by storm surges, he has catalogued the incidence of super-cyclones over the past 5000 years.
In a paper published in the scientific journal, Nature in 2001 his research shows the frequency of super-cyclones is an order of magnitude higher than previously thought.
Nott’s work puts into perspective current debate about whether climate change is responsible for the extreme weather events in Queensland.
Over recent centuries, massive cyclones have been relatively common. And after an extended period of relatively little activity their return is overdue regardless of rising global temperatures.
The BOM talks about the PDO without saying P.D.O but this is the closest I’ve seen them come (maybe I’ve missed it) to seriously talking about the major role the PDO (Pacific Decadal Oscillation) plays.
According to a paper by BOM Queensland weather forecaster Jeff Callaghan, the frequency of severe land-falling tropical cyclones had declined to low levels in recent decades in line with the El Nino weather patterns. Callaghan’s analysis shows that landfalls occurred almost twice as often in La Nina years as they did in El Nino years and that more than one [super] cyclone only ever hit land during La Nina years.
Callaghan says it would be imprudent to suppose the low number of tropical cyclones crossing the coast in recent decades would continue and planning should reflect the possibility of a rapid return to higher landfall rates.
Callaghan’s research confirms Nott’s analysis that tropical Australia is overdue for a dramatic intensification of cyclonic activity, regardless of whether there is a climate change signal in what is happening now or not.
Indeed Nott warned back in 2001 that a super cyclone was coming, and to their credit, the ABC–Catalyst show let the public know. The last super-cyclone was in the early 1800′s, so if there is a 200 – 300 year frequency, we appear to be right on target. What effect did all those emissions have again?
What the longer term records show, however, is that the frequency of extreme cyclones follow a predictable long-scale pattern.
“What the record shows is we go through extended periods, hundreds of years, of high activity and extended periods of little activity,” Nott says.
“The past 100 to 150 years has been very quiet in Queensland in terms of what happened in the past. The couple of hundred years prior to that were very active.”
According to shorter term decadal scale-that uses a 10-year cycle- Queensland can also expect a big increase in the number of severe cyclones.
The Interdecadal Pacific Oscillation indicates the tropical north is due to emerge from a three-decade period of low cyclonic activity and return to the conditions of the 50s, 60s and 70s.
From Roger Pielke’s blog
Andrew Bolt did a good analysis of the blame-man-kind-for-cyclones trick.
Nature 413, 508-512 (4 October 2001) | doi:10.1038/35097055; Received 20 February 2001;
As far as this super-cylone research goes below, if the storm surge didn’t rise to the 4m category, then Yasi wasn’t the super cyclone of the Nott studies, and the next big one is still coming.
Great news — so far — no lives lost.
I watched the coverage on the ABC last night. Significantly none of reported wind speeds I saw even came close to the forecast 300km/hr. The largest one was 138 km/hr. Presumably things must have slowed down more than expected. (Otherwise the ABC TV coverage was an endless repetition of Anna Bligh, Premier of QLD, being a newsreader and weathergirl, interspersed with “webcam” shots of the same three square meters of haggard palm fronds in Townsville).
*Max recorded wind gusts so far don’t seem to be over 185km/hr.
The Australian compares Yasi to Katrina. (Remember this story was written yesterday, and printed last night).
Pick of the Comments
Lawrie #10 writes:
During one of our many droughts I watched storms build and felt sure we would get some welcome rain. Then a southerly would hit and the storm would just blow away.
Last night on a talkback show they were talking of Yasi striking the coast at the top of the tide. A fisherman rang and said it wouldn’t happen. He said “every fisherman knows that the cyclones slow down to let the high tide flow out. He went on to say thay Yasi was supposed to cross the coast at a certain time but was now delayed by at least an hour.” I wonder if he is right and if he is, whether any of our experts will take notice of just a fisherman.
Ken Stewart #12 comments:
Maximum wind gust recorded at landfall (at Lucinda) was 185kmh- a far cry from 290kmh. Lucinda is about 70km from Mission Beach where Yasi crossed. And have a look at this:
See how the wind was bucking around? Looks close to the eye to me.
I told a mate on Tuesday not to get too excited about this week’s 6 o’clock disaster porn. Having seen alot of cyclone and hurricane time-lapse I knew Yasi would fizzle. Anything tracking greater than 60 degrees along the coast meets too much swell resistance. Those that track between 30 to 45 degrees amplify with a suction effect from coastal swell. You see this happen around Florida regularly.
Yasi was driven by prevailing winds almost perpendicular to the coast. Which, means about an hour or two of high tides, alot of beachside destruction but, not a whole lot of precipitation.
For wind speeds: See also Ken Charles Warren, #34 #35 #36.
Page edited on 15-Oct-2012. The “update” was moved lower in the text.