* Below is a guest post written by Ken G, a long-time Darwin resident and media/IT professional. Ken discussed his ideas not only with Darwin “storm chaser” enthusiasts but with Darwin residents who went through Cyclone Tracy. It’s a keen amateur perspective on a frightening weather event but well worth reading in my opinion.
Cyclone Yasi was a big and scarey storm system. Media and politicians continue to refer to it as a Category 5 cyclone with winds nearing 300 kmh near its centre, the largest cyclone ever to hit a populated area in Australia. But is that really true? A fairly obscure story on Australian Geographic website points out that “the full force may never be known because there are no gauges where the monster storm made landfall” and an engineer interviewed on last Friday’s 7:30 Report suggested that available data indicated Yasi was probably a small to medium Category 4 system with winds a bit over 200 kmh. But that’s just about the full extent of any questioning of Yasi’s actual strength and destructive force. What does the evidence actually tell us?
Don’t get me wrong; it did seem like it was going to be a very large event and government authorities were well justified in taking the steps they did to encourage residents to take it very seriously. Looking at the Bureau of Meteorology site and at the radar images you could see this was a very nasty storm that was going to hit the coast. Moreover, even if it WAS “only” a small-medium Category 4 cyclone that’s still a very large storm with frightening and lethal destructive force.
A number of observations sites did register very high wind readings (Lucinda Point 185km/h) and some stopped working after the main part of the storm hit them. What we are unable to see from these observations is the estimated wind speed of 290 to 300 kilometres per hour. How is the Bureau of Meteorology estimating these wind speeds? If you look at the observations for Finders Reef, less than 90km south of the cyclone at 11.30 pm the night of the cyclone we see wind gusts to 109km/h but the Bureau of Meteorology and the US navy weather site was showing a estimated wind speed of 125knt or about 230km/h for the similar location. If these higher wind speeds are correct then why are the ground stations getting the wind speed so wrong? Should we be relying on these ground stations for information?
“US Navy Weather site”: http://www.nrlmry.navy.mil/tc_pages/tc_home.html
“Flinders Reef” Bureau of Meteorology Observations
“Lucinda Point” Bureau of Meteorology Observations
Maximum Recorded wind speed 185km/h at Lucinda Point
However, we need to be a little careful here. Lucinda Point is around 80 kilometres as the crow flies from Mission Beach where apparently the centre of Yasi’s eye made landfall, and maximum wind speeds tend to drop off quite rapidly as one moves away from the centre of a cyclone. In a typical cyclone maximum wind speeds are experienced within about 20 kilometres of the edge of the eye. Yasi’s eye was apparently about 80 kilometres in diameter and so we would expect Lucinda to be just outside the area where maximum wind speeds were experienced. Thus this reading does suggest that Yasi was a Category 4 system, and quite possibly a significant one with destructive wind gusts well into the 200 km/h plus zone.
The physical evidence of destruction in the path of this cyclone is also interesting as most of the damage does not appear to support the 300 km/h estimated wind speeds quoted by the Bureau of Meteorology and media.
If you look at images of the destruction of Darwin after cyclone Tracy (a large category 4 cyclone as stated by the Bureau of Meteorology) you will see not only 80% of all buildings destroyed but the total lack of vegetation left in its path. You might explain the discrepancy between Tracy and Yasi in terms of destruction of the built environment by the fact that Building Codes are so much more rigorous today than they were in 1974, but it seems highly unlikely that they’re growing trees more cyclone-hardy than they were 36 years ago. This is not just trees stripped of their leaves but the trees no longer there and the almost total destruction of all utilities for a city of 40,000 people at that time.
(Tropical Cyclone Tracy is arguably the most significant tropical cyclone in Australia’s history to hit a significant populated area. It accounted for 65 lives, the destruction of most of Darwin and profoundly affected the Australian perspective to the tropical cyclone threat.
The media has played this current cyclone up so much that is almost impossible to get a true picture of what has happened. The media statements like “the destruction was like an atomic bomb” is so incorrect, go to Hiroshima and have a look at the museum and look at the images, Cyclone Yasi was nothing like an atomic bomb. Go to the Darwin museum and have a look at the Tracy exhibition, look at the videos of people and the destruction after Cyclone Tracy and see the total despair that cyclone brought to Darwin.
If we are to believe the media hype Cyclone Yasi was and is a category 5 severe storm that has wreaked havoc from as far north as Port Douglas and south to Mackay when in fact Dunk Island through to Tully experienced the full force of this cyclone and came out with building, trees and water damage on a scale far less than that of Tracy, and certainly not the enormous loss of life that the media was predicting only the night before.
To leave the impression that much of North Queensland’s coast experienced a category 5 cyclone is incorrect and belittles the people of Dunk Island, Mission Beach and the Tully region that lived through this storm.
I feel for the people that have gone through this event and fear for their safety should an actual category 5 cyclone hit. After reading an article on the web from someone that was in Tully the night of the cyclone and his statement of 300km/h winds I have to wonder, I am sure it felt like 300km/h winds to him but is this scientific data that can be relied on?
As someone that lives in Tropical Australia and every year face the cyclone season it would be good to have true and accurate information from the Bureau of Meteorology and not the hype of the media to make informed decisions about your own safety. It would be good to find out exactly how the Bureau of Meteorology predicts the wind speed for these events and what place the ground observation stations play in this. Can we rely on the Bureau of Meteorology for true and accurate forecasting of these extreme weather conditions or are they simply too underfunded to do this job with any accuracy and allow the media to take control? As someone has said the Bureau of Meteorology is usually 100% correct for yesterday’s weather so will they now correct history and tell Australia what the actual wind speed and the true category rating of Cyclone Yasi?
Why is that important? The engineer interviewed on last Friday’s 7:30 Report explained it quite well. Houses in both North Queensland and the Northern Territory are required to be engineered to withstand category 4 cyclones. But there’s a huge difference between 200 km/h winds (the strongest gusts in a smallish Category 4 cyclone) and 300 km/h winds. Winds around 300 km/h actually exert forces on buildings that are twice as strong as at 200 km/h, so that a house engineered to withstand the former may well not survive the latter. If people living around Innisfail, Tully and Mission Beach are left with an erroneous understanding that their houses withstood a Category 5 cyclone (as most did), it may well be much more difficult next time a large cyclone threatens to persuade them to evacuate their homes and save their lives. Media hyperbole may end up being a contemporary version of the boy who cried wolf once too often.