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Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.Category 4 Ita Nearing Australia
Dangerous Category 4 Tropical Cyclone Ita is nearing landfall in Australia’s Queensland state. Maximum sustained winds estimated by the Joint Typhoon Warning Center were 155 mph at 18 UTC on Thursday, just 1 mph below the threshold of Category 5 strength. The Australia’s Bureau of Meteorology estimated that Ita had a central pressure of 930 mb at 18 UTC. Satellite loops show a moderate-sized tropical cyclone surrounded by an intense eyewall with very cold cloud tops. Radar loops from Cairns, Australia show spiral bands from Ita are already bringing heavy rains to the coast. With moderate wind shear of 10 - 15 knots and ocean temperatures near 28°C, Ita should be able to maintain Category 4 strength until landfall occurs Friday evening local time in Australia. The center of Ita is likely to pass very close to Cooktown (population 2,400) as a major hurricane, and near Cairns (population 143,000) as a weakening Category 1 storm. Ita will likely be the strongest tropical cyclone to hit Queensland since Category 4 Tropical Cyclone Yasi hit on February 2, 2011. Yasi killed one person and did $3.6 billion in damage.
Figure 1. Visible satellite image of Ita taken at 21:32 UTC (5:32pm EDT) April 10, 2014. Image credit: NOAA/SSD.
Ita passing close to location of world-record tropical cyclone high water mark
Storm surge is a huge concern from Ita, and the cyclone is passing just east of the location of the world record high water mark from a tropical cyclone: the 13 - 14.6 meters (43 - 48 feet) from Australia's March 5, 1899 Bathurst Bay Cyclone. That Category 5 storm was a monster, with sustained winds in excess of 175 mph, and a central pressure between 880 and 914 mb. Mahina killed at least 307 people, mostly on pearling ships, and was the deadliest cyclone in Australian history. The eyewitness account of Mahina's record storm surge was provided by Constable J. M. Kenny, who journeyed to Barrow Point on Bathurst Bay to investigate a crime on the day of the storm. While camped on a ridge 40 feet above sea level and 1/2 mile inland, Kenny's camp was inundated by a storm wave, reaching waist-deep. On nearby Flinders Island, fish and dolphins were found on top of 15 meter (49 foot) cliffs. However, an analysis by Nott and Hayne (2000) found no evidence of storm-deposited debris higher than 3 - 5 meters above mean sea level in the region. They also cited two computer storm surge simulations of the cyclone that were unable to generate a surge higher than three meters. Indeed, Bathurst Bay is not ideally situated to receive high storm surges. The Great Barrier Reef lies just 20 - 40 km offshore, and the ocean bottom near the bay is not shallow, but steeply sloped. Both of these factors should conspire to keep storm surges well below the record 13 - 14.6 meters reported. The authors concluded that the actual surge from the Bathurst Bay Cyclone may have been 3 - 5 meters. The observed inundation at 13 meters elevation, plus the observation of dolphins deposited at 15 meters above sea level could have been caused by high waves on top of the surge, they argue. Waves on top of the surge (called "wave run-up") can reach five times the wave height at the shore for steeply fronted coasts like at Bathurst Bay. Since waves in the Bathurst Bay Cyclone could easily have been 3 meters, 15 meters of wave run-up on top of the surge is quite feasible. Since wave run-up doesn't count as surge, the status of the 1899 Bathurst Bay Hurricane as the world record holder for storm surge is questionable. However, the event is certainly the world record holder for the high water mark set by a tropical cyclone's storm surge, an important category in its own right.
Figure 2. Satellite image of Bathurst Bay, Queensland Province, Australia. The record 43 - 48 foot storm surge wave occurred on Barrow Point, marked by an "x" on the map above. Image credit: NASA.
Figure 3. Track of the 1899 Bathurst Bay cyclone. Bathurst Bay is located at the point where the 914 mb pressure is listed. Image credit: Whittingham, 1958.
References:
Nott, J, N. Hayne, 2000: How high was the storm surge from Tropical Cyclone Mahina?", Australian Journal of Emergency Management, Autumn 2000.
Anonymous, 1899, The Outridge Report--The Pearling Disaster 1899: A Memorial", The Outridge Company, 1899
Whittingham, 1958, "The Bathurst Bay hurricane and associated storm surge", Australian Meteorological Magazine, No. 27, pp. 40-41. Scanned and put on-line courtesy of John McBride.
Jeff Masters
Figure 1. Visible satellite image of Ita taken at 21:32 UTC (5:32pm EDT) April 10, 2014. Image credit: NOAA/SSD.
Ita passing close to location of world-record tropical cyclone high water mark
Storm surge is a huge concern from Ita, and the cyclone is passing just east of the location of the world record high water mark from a tropical cyclone: the 13 - 14.6 meters (43 - 48 feet) from Australia's March 5, 1899 Bathurst Bay Cyclone. That Category 5 storm was a monster, with sustained winds in excess of 175 mph, and a central pressure between 880 and 914 mb. Mahina killed at least 307 people, mostly on pearling ships, and was the deadliest cyclone in Australian history. The eyewitness account of Mahina's record storm surge was provided by Constable J. M. Kenny, who journeyed to Barrow Point on Bathurst Bay to investigate a crime on the day of the storm. While camped on a ridge 40 feet above sea level and 1/2 mile inland, Kenny's camp was inundated by a storm wave, reaching waist-deep. On nearby Flinders Island, fish and dolphins were found on top of 15 meter (49 foot) cliffs. However, an analysis by Nott and Hayne (2000) found no evidence of storm-deposited debris higher than 3 - 5 meters above mean sea level in the region. They also cited two computer storm surge simulations of the cyclone that were unable to generate a surge higher than three meters. Indeed, Bathurst Bay is not ideally situated to receive high storm surges. The Great Barrier Reef lies just 20 - 40 km offshore, and the ocean bottom near the bay is not shallow, but steeply sloped. Both of these factors should conspire to keep storm surges well below the record 13 - 14.6 meters reported. The authors concluded that the actual surge from the Bathurst Bay Cyclone may have been 3 - 5 meters. The observed inundation at 13 meters elevation, plus the observation of dolphins deposited at 15 meters above sea level could have been caused by high waves on top of the surge, they argue. Waves on top of the surge (called "wave run-up") can reach five times the wave height at the shore for steeply fronted coasts like at Bathurst Bay. Since waves in the Bathurst Bay Cyclone could easily have been 3 meters, 15 meters of wave run-up on top of the surge is quite feasible. Since wave run-up doesn't count as surge, the status of the 1899 Bathurst Bay Hurricane as the world record holder for storm surge is questionable. However, the event is certainly the world record holder for the high water mark set by a tropical cyclone's storm surge, an important category in its own right.
Figure 2. Satellite image of Bathurst Bay, Queensland Province, Australia. The record 43 - 48 foot storm surge wave occurred on Barrow Point, marked by an "x" on the map above. Image credit: NASA.
Figure 3. Track of the 1899 Bathurst Bay cyclone. Bathurst Bay is located at the point where the 914 mb pressure is listed. Image credit: Whittingham, 1958.
References:
Nott, J, N. Hayne, 2000: How high was the storm surge from Tropical Cyclone Mahina?", Australian Journal of Emergency Management, Autumn 2000.
Anonymous, 1899, The Outridge Report--The Pearling Disaster 1899: A Memorial", The Outridge Company, 1899
Whittingham, 1958, "The Bathurst Bay hurricane and associated storm surge", Australian Meteorological Magazine, No. 27, pp. 40-41. Scanned and put on-line courtesy of John McBride.
Jeff Masters
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