Cyclone Mahina

Cyclone Mahina was the deadliest cyclone in recorded Australian history, and also potentially the most intense tropical cyclone ever recorded in the Southern Hemisphere. Mahina struck Bathurst Bay, Cape York Peninsula, colonial Queensland, on 4 March 1899, and its winds and enormous storm surge combined to kill more than 300 people.

While the Australian Bureau of Meteorology, which is the Regional Specialised Meteorological Centre of the basin, estimates Mahina's peak central pressure to be 914 hPa, the World Meteorological Organization is currently considering an application from Queensland scientists and researchers to have this value upgraded to 880 hPa, based on data from post-storm analysis. This would officially make Mahina the most intense cyclone recorded to have hit the Australian mainland, and the most intense tropical cyclone recorded making landfall anywhere in the world, as well as the most intense tropical cyclone ever recorded in the Southern Hemisphere, a title currently held by Cyclone Winston. Cyclone Mahina also produced the largest storm surge on record, generating a 13-metre-high (43-foot) surge.

Impact
Tropical Cyclone Mahina struck Australia on 4 March 1899, with a likely minimum central pressure of 880 hPa. Mahina ranks among the most intense cyclones ever observed in the Southern Hemisphere and almost certainly as the most intense cyclone ever observed off the Eastern states of Australia in recorded history. Clement Lindley Wragge, Government Meteorologist for Queensland, pioneered the naming of such storms and gave this storm its name, Mahina.

Storms of such intensity occur extremely rarely. Scientists identified two other Category 4 or 5 super-cyclones that struck Australia, in the first half of the 19th century, from their effects on the Great Barrier Reef and the Gulf of Carpentaria. This same research shows that on average, such super-cyclones occur in the region only once every two or three centuries.

A pearling fleet, based at Thursday Island, Queensland, was anchored in or near the bay before the storm. Within an hour, the storm drove much of the fleet ashore or onto the Great Barrier Reef; other vessels sank at their anchorages. Four schooners and the manned Channel Rock lightship were lost. A further two schooners were wrecked but later re-floated. The fleets lost 54 luggers, and a further 12 were wrecked but re-floated. People later rescued more than 30 survivors of the wrecked vessels from the shore; however, the storm killed more than 400 people, mostly non-European immigrant crew members. A depiction of the schooner Crest of the Wave in the storm was later sketched in a painting.

A large storm surge, reportedly 13 m high, swept across Princess Charlotte Bay and then inland about 5 km, destroying anything left of the Bathurst Bay pearling fleet and the settlement.

An eyewitness, constable J. M. Kenny, reported that a 48 ft storm surge swept over their camp at Barrow Point atop a 40 ft-high ridge and reached 3 mi inland, the largest storm surge ever recorded. However, reviewing the evidence for this surge, some scientists modeled a surge only 2 m to 3 m in height, based on the official 914 hPa central pressure. They also surveyed the area, seeking wave-cut escarpments and deposits characteristic of storm events, but found none higher than 5 m. Of the 48 ft surge, they suggested an incorrectly cited ground level or an involvement of freshwater (rain) flooding. A later study considers this conclusion likely premature and questions the barometer reading as unreliable and not representative of the actual lowest pressure. This subsequent study also examined new evidence of exceptionally high storm surge and inundation.

The cyclone continued southwest over Cape York Peninsula, emerging over the Gulf of Carpentaria, before doubling back and dissipating on 10 March.

Casualties
The exact number of casualties is not known, as many deaths were not recorded. Estimates range between 307 and 410.

In September 1899, the Queensland Marine Department published a list of 247 known fatalities. The Queensland Registry of Births, Deaths and Marriages has 283 registered deaths attributed to the cyclone, including 250 on pearling ships. One of the pearling fleet owners estimated another 30 people not officially registered as crew were killed and not reported to the Cooktown Registrar. Eleven crew members of the ship Sagitta were killed.

Around 100 Aboriginal Australians were killed but not recorded, as Aboriginal people were not counted as part of the population at the time. They had tried to help shipwrecked men, but the back surge caught them and swept them into the sea. Only eight Aboriginal people were recorded among the casualties, all of whom died on shore.

The Queensland Historical Atlas reported the death toll as "307 pearl divers and sailors and an unreported number of Aborigines".

Aftermath
People found thousands of fish and some sharks and dolphins several kilometres (miles) inland, and the storm embedded rocks into trees and bushes. On Flinders Island (Queensland), people found dolphins on the 15.2 m cliffs; however, this finding does not necessarily indicate a surge of this height; on this exposed site, wave run-up readily can produce these results even within the more modest calculated surge.

At Cape Melville, survivors erected a memorial stone to "The Pearlers" lost to the cyclone, naming 11 Europeans but only citing "over 300 coloured men" for the other seamen. The Anglican church on Thursday Island, Queensland, also commemorates this disaster.

Barometric pressure estimates
Contemporary reports vary considerably in the reported lowest barometric pressures. The pressure recorded on the schooner Olive reasonably consistently show her lowest pressure recorded: 29.60 inHg to 29.10 inHg or between 29.00 inHg and 29.10 inHg. In a further variant, "during the lull in the hurricane, the barometer on the Olive recorded" 29.70 inHg to 29.10 inHg.

Most sources record the schooner Crest of the Wave observation as 27 inHg. More modern reports of an 18 inHg observation on a vessel in the eye of Mahina are unrealistic (the most intense tropical cyclone, Typhoon Tip, had a central pressure 260 hPa higher).

One author accepted the 29.1 inHg report from the Olive and the 27 inHg report from the Crest of the Wave, seemingly unaware of the discrepant reports. He estimated the track of the cyclone from the damage reports, placing it directly over the position of the Crest of the Wave. The Olive to the north missed the centre. The separation between these schooners explains the difference between their respective pressure measurements. He calculated the centre pressure, standardised for temperature, as 914 hPa.

A study in 2014 found that the actual lowest pressure of the storm was around 880 hPa, based upon modeling of meteorological variables needed to induce the potentially world-record-setting surge height of 13 m. This surge closely matches new evidence on storm depositions and accounts actually reported to two other captains, and in a letter from an eyewitness to his parents, of a reading of 26 inHg. This study considers the apparently third-hand report of 27 inHg an unreliable measurement made possibly five hours prior to passage of the eye.

In comparison, the tiny Cyclone Tracy devastated Darwin in 1974, with a central pressure of 950 hPa. Barometric pressure this low at mean sea level also likely caused Cyclone Mahina to create such an intense, phenomenal, claimed world-record storm surge that was not immediately known afterward.

Popular culture
In 2008, Ian Townsend published The Devil's Eye: a novel as a historical fiction novel based on Cyclone Mahina. The novel was developed as part of his research fellowship at the State Library of Queensland.