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No need for Category 6

Dr Sushil K Sharma
Monday, March 12, 2018

TEACHING meteorology or even climate sciences to politicians and lay persons so they stop making wild generalisations, speculations and inaccurate assertions is an uphill battle in the present climate of climate change activism.

Some bend the truth to suit their purposes, whatever it may be. Often they do not realise the damage they cause.

An inaccurate assertion or wild generalisation, made many times over, often is taken as a fact by lay persons and especially by our younger generation of students, who in our nation are extremely poor in the sciences. The majority of the students graduating from secondary schools have no knowledge of physics as this subject is conveniently ignored as a choice.

In a community generally weak in the sciences, as a result of the above shortcomings for over three to four decades, people need to be very careful as to how they talk about climate variability and change issues not only in our community but also regionally and internationally in meetings, conferences and workshops.

The climate change lobby is seriously in breach on many occasions, when they use emotion rather than scientific evidence to support their arguments. It has almost become a hot potato where we are in danger of our community just shutting-off completely from the mono-tone rhetoric we hear day-in day-out from some quarters without any scientific evidence.

Thus for just an example, when a public figure keeps saying that "cyclones are getting stronger and stronger and more frequent" publicly and the media keep reporting these ambiguities; then our people take all these "information" as scientific facts. However comments like these, are not evidence-based and there is considerable damage and scientists have to spend many hours to correct these mistakes.

There is a great need not only for our secondary and tertiary students to attempt to study and learn meteorological and climatological sciences as part of education and training towards disaster and human preparedness and mitigation studies for our vulnerable region.

This given the vulnerability of our people to weather and climate variability and change issues we face and the fact that our people and in particular our politicians, planners, disaster management teams are at the forefront of decision making on many relevant issues in these fields — it is suggested that they need to upgrade their educational qualifications and professional skills or seek the support of special expert advisers.

If this is done then we will not have embarrassing situation for politicians trying to play the role of scientists, as shown in the erroneous comments and facts cited below in a daily newspaper as reported recently, where a politician not only is making major mistakes, but is totally fooled for relying on "hearsay" information, and is not standing on clear footing of his own reliable scientific knowledge.

New Zealand government Climate Change Minister James Shaw told Radio NZ: "The MetService experts tell me that it (Winston, which smashed Fiji in 2016) had much stronger winds than the 230kmh upper limit of a category 5 cyclone.

"Tropical Cyclone Gita hit Tonga with sustained winds of over 230kmh and gusts of up to 278kmh.

"It's just that the international cyclone rankings don't go higher than Category 5. The only reason it wasn't a Category 6 cyclone is because we don't have a Category 6, but we might need one in the future."

The learned minister is incorrect in a number of ways. Firstly there is no upper limit in a Category 5 Severe Tropical Cyclone system for the Australian/Fiji region as stated and neither is the figure of 230 km/h stated anywhere in the WMO manuals. Quite simply all the above the statements are incorrect.

To clarify this point it should be noted that the Category 5 systems in our region, as per the WMO approval and technical manuals, have 10-minute sustained winds of over 200+ km/hr and maximum momentary gusts of over 280+ km/hr.

Severe TC Winston passed directly over Vanuabalavu, where a national record wind gust of 306 km/h (190 mph) was observed. This wind gust was clearly covered by the Category 5 scale, which states that in a Category 5 system, we can expect momentary gusts of over 280+ km/hr.

Severe TC Winston reached its peak intensity on February 20 with 10-minute winds of 280 km/h (175 mph) and a pressure of 884 hPa, shortly before making landfall on Viti Levu. Here again the Category 5 Scale clearly states that 10-minute sustained winds can be over 200+ km/hr.

Using the 50 per cent rule, we can speculate that the gust was around 320 km/her (280+140 = 320) This is also covered by the over 280+ km/hr gusts figures as stated.

While passing just south of Tonga, Gita was a Category 4 system (10-min 160-199 km/her winds with 225 to 279 km/her wind gusts) according to the official warnings from the Fiji Meteorological Service, which have responsibility of forecasting system in that part of the world. Only after the 10-15 km/hr westward passage of Gita for about the following 24-36 hours, did the system intensify further becoming a Category 5 system.

Gita, with estimated 10-minute sustained winds of 200 km/hr (108 knots, 124 miles per hour) gusting to 300 km/hr (162 knots, 186 miles per hour), remained relentless showing no sign of recurving towards our expected climatological path, of an initial south westerly to southerly and then a south easterly quadrant later.

Thus it should be noted that STC Gita was a relatively weaker system compared with Winston. The minister is again in error for suggesting it passed Tonga as a Category 5 system.

He also suggested that: "It's just that the international cyclone rankings don't go higher than Category 5. The only reason it wasn't a Category 6 cyclone is because we don't have a Category 6, but we might need one in the future."

We should note Gita was a cyclone on the lower end of the Category 5 scale (where the minimum threshold is for sustained winds of 200+ km/hr with momentary gusts of 280+ km/hr) and no insinuation should be made that it was eclipsing the Category 5 scale at the other end - where there is no maximum cap; in any way and that had we could have expected a Category 6 to be used, if such a category existed.

Also alarming people especially by suggesting that we may be in the need of a new Category 6, lacks credibility and is based on speculation and false inference, lacking data scrutiny, meteorological and climate science.

* Dr Sushil K Sharma BA MA MEng (RMIT) PhD (Melb) is a WMO accredited professional meteorologist. He is an associate professor of Meteorology at the Fiji National University. This opinion is his and not of the FNU or this newspaper.

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