BOM Caught Out Hyping Results Again

Cyclone Marcie was a terrible storm. It has been reported as “Cat-5” which is the top of the cyclone/ hurricane scale.

The devastation, though widespread has not been as severe as you might have been expected.

The BOM was forecasting that the cyclone would become Cat-5 and of course the media ran with that, but in the event, as far as we can measure these things it made landfall as a Cat-3.

So it the BOM doing to cyclones what it has been doing to temperature records? Are they being re-categorised to march the global warming mantra of “more extreme weather”?

Of course if we believe that Rockhampton and Yeppoon survived a Cat-5 and it was only really a Cat-3 will that lead to relaxed building standards and complacency that could be fatal when a real Cat-5 storm comes.

Sigh! I used to be a real fan of science untll it became just another propaganda vehicle.

From Jo Nova:

Category Five storms aren’t what they used to be

The facts on Cyclone Maria: the top sustained wind speed was 156 km and the strongest gust 208 km/hr. These were recorded on Middle Percy Island in the direct path before it hit land and apparently rapidly slowed.  The minimum pressure recorded after landfall was 975Hpa. BOM and the media reported a “Cat-5″ cyclone with winds of 295 km/hr. To qualify as a Cat 5, windspeeds need be over 280km/hr. The UN GDACS alerts page estimated the cyclone as a Cat 3.

The damage toll so far is no deaths (the most important thing), but 1,500 houses were damaged and 100 families left homeless. It was a compact storm, meaning windspeeds drop away quickly with every kilometer from the eye, so the maps and locations of the storm and the instruments matter. See the maps below — the eye did pass over some met-sites, but made landfall on an unpopulated beach with no wind instruments. It slowed quickly thereafter. The 295 km/hr wind speed was repeated on media all over the world, but how was it measured? Not with any anemometer apparently — it was modeled. If the BOM is describing a Cat 2 or 3 as a “Cat 5″, that’s a pretty serious allegation. Is the weather bureau “homogenising” wind speeds between stations?

What will happen when Australians living in cyclone areas have to prepare for real Cat 5s? How much respect will Australians have for the BOM (and the ABC) if they find out that supposedly dispassionate and impartial scientists have been hyping weather events to score political points? Will the BOM issue any clarifications and corrections?

What does a Cat 5 mean anymore?

The headlines are still calling Marcia a “Cat 5″ cyclone three days later. But today there are many questions about that, and very different debates have broken out on the old media and the new. On the mainstream media, Premier Annastacia Palaszczuk is already defending the BOM after the Marcia “surprise”. But she is talking about the sudden escalation of a Cat 1 or 2 up to a 5, and whether the BOM gave residents enough warning. On the Internet people are asking why it was called a Cat 5. As Jennifer Marohasy points out, the top speeds recorded showed the cyclone was a Category 3. “Middle Percy” was under the path, and out to sea.

There is a weather station on Middle Percy, and it recorded a top wind speed of 156 km/h, the strongest gust was 208 km/h, and the lowest central pressure was 972 hPa. This raw observational data is available at the Bureau’s website and indicates a category 3 cyclone.

As commenters unmentionable and Ken recorded here, none of the observed wind-speeds came remotely close to being Cat 5. By strange coincidence, two guest authors here, Ken Stewart and TonyfromOz, live north of Rockhampton and both “walked in the eye” last Friday. I’ve spoken to both this morning, and fortunately their houses and families are OK, though still without electricity.

The US Navy’s Joint Typhoon Warning Centre was tracking the cyclone and, like me, noted the surface observations from Middle Percy Island. The US Navy had been estimating wind speeds based on the Dvorak modelling method. This method is considered much less reliable than aircraft reconnaissance, with surface observations (from anemometers and barometers) historically the ultimate measure of a tropical cyclone’s wind speed and central pressure. For example, in the case of Cyclone Yasi, a barograph at Tully sugar mill recorded a minimum central pressure of just 929 hPa, and this is the value in the final report from the Australian Bureau of Meteorology confirming that Yasi was a category 5 system.

In the case of Marcia, the US Navy acknowledged that their Dvorak estimates were higher than the surface observations from Middle Percy Island. In particular their real time “warning”, no longer available on the internet, noted an “intensity of 110 knots” based on the anemometer on Middle Percy. This corresponds with the highest wind gust recorded on Middle Percy Island as Marcia passed over. The maximum sustained wind speed, however, never exceeded 156 km/h, and the central pressure was never less than 972 hPa. This makes Marcia a category 3 based on the Australian system, and only a category 2 based on the Saffir-Simpson Hurricane Wind Scale.

Yet the bureau continued to report the cyclone, not as it was, based on the surface observations, but as they had forecast it in a media release the previous day: “Tropical Cyclone Marcia to reach Category 5 system at landfall”.

Full story here

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