Larry strikes Australia

Tropical Cyclone Larry roared onto the coast of eastern Australia Sunday near the town of Innisfail as a major Category 3 hurricane with sustained winds of 118 mph and gusts to 180 mph. Although no deaths or serious injuries were reported, Larry caused tens on millions of dollars in damage to structures and crops in a part of Australia unused to seeing severe tropical cyclones. Innisfail is a popular jumping-off point for tourists heading to the Great Barrier Reef, and Larry will be a severe blow to the economy. The reef itself suffered a direct hit from the cyclone, but the extent of damage is unknown.

Larry may be the strongest tropical cyclone in recorded history to hit the east coast of Australia. The north coast and west coast of Australia are more prone to major hurricanes, and just last year Tropical Cyclone Ingrid hit Croker Island in the Gulf of Carpenteria off the northern coast of Australia as a Category 3 hurricane of strength similar to Larry.


Figure 1. Tropical Cyclone Larry at landfall in Australia.

As bad as Larry was, the media coverage I saw yesterday on several news web sites was over-hyped. All of the major media reports I saw called Larry a Category 5 storm with winds up to 180 mph, and one report said it could become "Australia's Katrina". What they didn't mention was that Australian tropical cyclones are ranked by the Australian severity category, a one to five ranking system based on the maximum wind gusts of a storm. A storm that has wind gusts in excess of 174 mph (280 km/h) is classifed as a Category 5. In the U.S. Saffir-Simpson scale that we are familiar with, the strength of a storm is based on the sustained winds, not the gusts. Tropical Cyclone Larry at landfall had 118 mph sustained winds, which made it a low-end Category 3 storm on the Saffir-Simpson scale--Category 3 sustained wind speeds range from 111 to 130 mph. Larry's lowest pressure was 925 mb (same as hPa, hecto-pascals, which the Australians use as their pressure unit). Katrina at its maximum intensity had maximum sustained winds of 175 mph, with gusts to 215 mph, and a minumum pressure of 902 hPa (mb).

The Southern Hemisphere tropical cyclone season runs November through April. The waters in the Southern Hemisphere oceans have reached their peak temperatures, and are now starting to cool. There is another storm, Tropical Cyclone Wati, that is near the Australian Coast in the same region as Larry stuck, but Wati is expected to recurve out to sea and weaken over the next three days.

Jeff Masters