The ghost of cyclones past

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Holiday makers generally put up with a lot of over­ crowding at seaside camping grounds, but last summer, when offered the chance to share their tent sites with a couple of decaying tropical cyclones, thousands thought discretion the better part of valour.

Cyclone Fergus, the first notable meteoro­logical tourist of the summer, brought torrential rain and damaging winds to parts of the North Island between Christmas and New Year. There was no loss of life, in part because of timely warnings about the ferocity of the storm.

Following close on the heels of Fergus, Cyclone Drena caused more wind damage but brought less rain. The combination of wind and extremely high tides caused millions of dollars’ damage at Thames, and a man was electrocuted when he grasped a fallen power line in order to pull himself up a bank.

During the summer the Pacific was influ­enced by a weak La Nina event which caused the flow over the North Island to be from the north-east more often than normal. This helped steer Fergus and Drena over the North Island, as well as causing persistent humid weather in Auckland.

Tropical cyclones form over the warmer waters of the South Pacific Ocean from November to early April in the presence of high-level anticyclonic outflow and low-level vorticity associated with outbreaks of thunderstorms in the South Pacific Convergence Zone

As they move away from the tropics and over colder waters, tropical cyclones weaken and lose much of their characteristic structure. In particular, the narrow ring of cumulonimbus clouds known as the “eye-wall,” which produces heavy rain and is surrounded by the relatively small area of maximum winds, breaks up and weakens.

For two tropical cyclones to form in the tropics close together in space or time is not unusual. However, for two to take such similar paths as Fergus and Drena when they leave the tropics is rare, although not without precedent.

In the ten cyclone seasons The Weekly News told the tale of destruction in 1936. 

Before this one, the low centres of four decaying tropical cyclones passed over New Zealand, while another five, such as Bola in 1988 came close enough to affect New Zealand’s weather. In addition, another three contributed to record floods in parts of New Zealand because of the warm moist tropical air their wind systems brought over the country, even though their centres of lowest pressure stayed well away from the land.

In a small number of cases, the remnants of a degenerating tropical cyclone combine with a trough of low pressure in the mid-latitude westerlies to produce a deep depression surrounded by a very large area of damaging winds and heavy rain. Such an event is most likely to occur in the second half of summer, or in autumn, when the sea surface temperatures are highest, allowing the tropical cyclones to maintain intensity for longer as they move south.

This happened with Cyclone Bola, which flooded Gisborne and Northland in March 1988, and with Cyclone Gisele, which sank the Wahine in April 1968. It also happened with an unnamed tropical cyclone that crossed the North Island on February 2, 1936.

Although this last event seems to have largely passed from popular memory, it may well have been the most destructive storm to have hit the North Island this century. It formed south of the Solo­mon Islands at the end of January and re-developed as an intense mid-latitude depression when it met up with a cold front over the North Tasman Sea.

As the cyclone crossed the country, the North Island sustained heavy rain in most areas, bringing most of the major rivers into flood. The Mangakahia River in

Northland rose 19 metres at Titoki. Kaitaia’s main street flooded a metre deep, and one man was drowned when a house was washed away.

In Whangarei, almost 300 mm of rain fell in 24 hours, and floodwaters raced through the business district, tearing up footpaths and entering buildings. Gelignite was used in an unsuccessful attempt to clear driftwood piled against Victoria Bridge, which carried the road to Whanga­rei Heads, where several cottages were blown down.

At Waitangi, the water rose two-and-a-half metres in 20 minutes, forcing eight men sleeping on the floor of the Tung Oil Company’s cookhouse to take refuge on the roof. When the struc­ture began to move they clambered into a tree overhanging the cookhouse, which was later carried away by the flood. A train was marooned by washouts near Kaikohe, and 60 passengers had to spend the night in the carriages.

Torrential rain fell on the until increased pressure carried away the obstacle and an enormous body of water swept down the river bed, carrying away a large bridge and damaging four kilome­tres of road. Both banks of the river were swept clean of soil and vegetation.

One observer saw rimu and kahikatea trees borne along by the torrent rear up when their roots or branches caught against some obstacle, and topple end over end with a crash that could be heard for miles. When the water subsided he picked up 40 dead trout and counted hundreds of eels killed by the rushing timber and large boulders carried along by the flood.

In Hawkes Bay, the Tukituki River flooded the settlement of Clive, cutting the road and rail link between Napier and Hast­ings and drowning 1500 sheep in stock yards. The Tukituki also broke its bank at Waipukurau, drowning thousands of cattle and sheep and forcing the evacuation of 70 houses.

Roads and railways were inundated by floods and undermined by washouts, bridges were destroyed, and slips came down in their thousands all over the North Island. Near Stratford the main trunk line was blocked by more than a dozen slips, the biggest of which was 500 metres long and full of trees.

In the Wairarapa, the Ruamahanga flooded farmland, cutting off Martinborough, and the Waipoua flooded several streets in Masterton. At Kopuaranga, just north of Masterton, a 14-ton traction engine disappeared into a river normally only a metre deep, and still had not been found several days later. At

Castle Point, the sea washed away the sandhills and invaded houses 100 metres inland.

Wind associated with the cyclone lashed the country from Picton to Kaitaia. Palmerston North was among the hardest hit towns. Houses lost roofs, chimneys were blown over, the grandstands of the A & P Association, the Awapuni Racecourse and the sportsground were demol­ished, and a man was killed when he was blown off his roof as he tried to repair it. A train was derailed near Makerua when the last two carriages and the guard’s van were caught by the wind and thrown down a bank.

At Longbum, the Anglican church was demolished and scattered over the road and railway line. A horse on a nearby farm was cut in half by a flying sheet of corrugated iron. Three huts next to the railway station were blown over. One somersaulted three times with the occu­pant rolling about inside with a heavy stove. His wife had just stepped outside when the but lifted and toppled over, missing her by a foot. She was blown into a clump of willow trees and had to be extricated by the stationmaster.

The Feilding Aero Club hangar was blown away and the two planes inside destroyed. In true Twister style, a motorist on the main road near Te Matai was chased by a large corrugated iron tank that raced across the paddock towards him. It jumped the fence, but luckily only struck his car a glancing blow.

Buildings were also blown down in Taranaki and in the Bay of Plenty, and the wind wrought havoc in orchards all over the North Island destroying a large portion of the crop. In Wairoa apples and pears were seen flying horizontally for some distance from the trees. Crops like maize, wheat, and oats were flattened from

Marlborough to Northland, haystacks blew away in many places, and, in Pukekohe, potato plants were sheared off at ground level.

In Auckland, 40 boats were sunk or driven ashore in the Waitemata Harbour and several more in the Manukau Harbour. In Wellington, disaster was only narrowly averted when the interisland ferry Rangatira steamed into rocks near the mouth of Wellington Harbour. After 20 minutes stuck fast she was able to reverse off the rocks, then turn and back slowly up the harbour. Taking water in through gaping holes in her bow, her propellers were half out of the water by the time she grounded next to the Clyde Quay wharf, and her forward lower passenger decks were awash.

At the height of the storm, trees were uprooted from ridges in the Tararua Ranges and thrown into the valleys. Trampers described whirlwinds twisting the crowns of trees around until all the branches splintered off.

Just as Drena followed Fergus last summer, so the great storm of February 1936 was followed by another decaying tropical cyclone in March, which affected a smaller area of the North Island, but caused more damage in some places.

Although accounts of the effects of cyclones last summer concentrated on death and injury to people, and damage to property, there was one story about the impact on wildlife. Orni­thologists visiting the gannet colony at Farewell Spit as Cyclone Drena passed by witnessed the combination of high sea levels and big waves inundate almost 90 per cent of the nests, drowning the chicks as the adults flew off.

One doughty chick was washed off its nest four times, but climbed back on, and was still there when the ornithologists left.

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