Saturday, December 23, 2006

Armidale's Hail Storms

Photo: Armidale after the storm, nineMSN.

Yesterday, 23 December 2006, a major hail storm hit the eastern edge of Armidale, the University city in the centre of New England's Northern Tablelands.

The twenty minute storm left a trail of destruction in its wake, with homes unroofed, windows smashed, cars damaged, trees stripped of foliage and glass from broken windows strewn about the streets.

Around 1,000 homes as well as other property including the local exhibition centre were damaged. The city has been declared a natural disaster area.

Photo: Gordon Smith, Armidale Exhibition Centre after the storm.

Hail storms are a relatively common feature of Tabeland's weather. Usually they do little damage. However, this is the second if somewhat smaller major storm to hit Armidale in the last ten years.

The story that follows is largely drawn from Peter Burr's story on Australia's severe weather. I have put in the link here, although I notice that there are problems in accessing it. I appear to be drawing from a cache copy.

On the afternoon of 29 September 1996 most Armidale residents were in doors, many watching the Rugby League grand final.

A storm had been building to the south west. By lunch time the sky became darker with storm clouds building to the sound of distant rumbling thunder. Just before 2pm an initial storm arrived with rain and small hailstones - around 10 millimetres diameter. The rain stopped at 2.30pm but intermittent thunder continued.

While no Armidale residents knew it, there had been no storm warning, a huge cumulonimbus storm cloud or a supercell had been building.

Inside this cloud massive updraughts were sweeping tiny particles of dust and ice up into the higher reaches where supercooled droplets of water were waiting to freeze onto them upon impact creating small hailstones. These hailstones were then falling to the lower levels before again being caught in the updraughts.

At 3pm this supercell approached the city from the south-west - a dark menacing cloud with an unusual colour described by many said later as orange or pink. The thunder increased and light rain started falling.

At 3.23pm the first of the hailstones fell on the city. At this stage the stones were 10 to 20 mm in diameter. They fell for about two minutes, then stopped briefly.

A roaring sound was then heard from the south-west. Unfortunately for Armidale, after making many trips up and down the hailstones circulating in the giant cloud had become bigger than golf balls and, too heavy to remain aloft, had started plummetting to the ground.

The huge hailstones made a deafening sound on roofs, and as they hit roads and hard surfaces they bounced several metres back into the sky. The wind started gusting from the south-west which was devastating for thousands of south and west facing windows - the sound of breaking glass accompanied the roaring of the hail. At 3.30pm it was all over.

The city had been extremely unlucky. Thunder storms are not unusual - the city averages 56 such storms annually - but severe hail is unusual. In this case, nearly all the major hail was dropped directly on the city itself.

The damage was astonishing. Eighty per cent of city buildings had been damaged, many severely, while some 3,000 cars received hail damage, creating a damage bill of over $A200 million, making it in insurance terms the third largest disaster in Australia's history.

In the longer term the effects were not all bad. The need to repair the damage created a building boom that lasted several years, leaving the city (always attractive) with a refurbished feel.

Photo: Gordon Smith, after the storm. This photo shows the scene in Armidale after the last storm as the combination of warm ground with the cold air and water creates mist. As Gordon notes, the scene now looks very pretty and peaceful, but the mist hides the storm damage.

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