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Tornadoes in Western Australia

One of Australia's most famous Tornadoes and one of the most beautiful tornadoes ever captured on film.

A brief summery of the Northam Tornado by David A. J. Seargent MA Ph.D. FRAS.

Northam (WA) 21 December 1977. A series of 18 colour Photographs obtained by P.J. May and C.J. Crane of the Northam research Station (about 80 kilometre's northeast of Perth) depict both the frightening power and exquisite beauty of this tornado. So spectacular was the tornado that its portrait made the cover of the 1980 edition of Climate of Australia but also featured on the cover of the October 1979 issue of the American meteorological journal Weatherwise, a rare honour for a non American tornado!

An article in the same edition of Weatherwise describes the Northam tornado as "one of the most beautiful tornadoes ever filmed" - the purple tinged storm clouds, golden wheat fields in the foreground and the dense sheath of red dust filling the lower portions of the funnel must surely have provided a remarkable spectacle and one which, thankfully, was unsullied by injury to persons and property as the tornado remained in open country throughout its life.

At the time of the tornado, a pronounced low-pressure trough lay in a NNE-SSW direction across the Northam area with some evidence of a localised low-pressure system or mesocyclone just south of the station and within the troughline. Surface winds appeared to be converging around Northam at the time (a common antecedent condition found in major US tornadoes) and high air temperatures (40 degrees Celsius at the time of the tornado) resulted in strong convection and generally added to the unstable atmospheric conditions. To cap it off (literally) a well defined westerly jet stream was evident aloft, at 15 kilometre's. The degree of storm development was, however, somewhat modified by the low humidity of the lower levels and, although thunderstorms developed and moved in from the east during the afternoon, they do not appear to have been particular severe.

Nevertheless, one obviously proved sufficient to spawn the tornado, just prior to 3 PM. Typical of the more violent tornadoes, the funnel extended from a rotating wall cloud at the base of the storm, indicating a general circulation within the parent storm on a scale significantly larger than the tornado itself. Probably because of the relatively low humidity, the condensation funnel remained quite small and apparently did not protrude very far below the cloud base. The vortex column was rendered visible by the large amount of red dust spiralling almost to the base of the parent storm. In the early stages, this dust sheath revealed up to five concentric hollow shells in the lower part of the vortex, a phenomenon possibly related to the particle-size distribution and general complexities of the helical flow dynamics. Similar shells have been reported in waterspouts and in other tornadoes such as the one at Port Headland on 17 December 1975, and even in large dust devils. Rotation of the Northam tornado, in common with most Australian and other Southern Hemisphere tornadoes, was clockwise.

The tornado appeared to the north west of the storm's precipitation shafts and seems to have been moving further away from them, as was apparent by the funnels increasing tilt with height, to the south or south east. It was conjectured by R.E.Peterson et al. That the tornado was being propelled away from the rain area by the gust front or cool air outflow from the shower.

During the course of the tornado, an interesting feature became more and more apparent, namely, the airflow within the vortex grew increasingly turbulent. At first, this turbulence was confined to the base of the dust sheath, where the dust took on the form of a "roll" surrounding the foot of the funnel and possible asymmetry's in the flow were suspected. Later this turbulent section extended for some distance upward along the funnel in a spiral and highly turbulent column. Detached inflow-bands of dust were recorded on the right edge of the vortex column.

The path length of this tornado from initial touchdown to final dissipation was about six or seven kilometre's. Fortunately, it did not encounter any man made structures although it did pass rather close to a house and made short work of a group of large gum trees lying a little more than halfway along its track.

Yet, the tornado was a severe one comparable, according Peterson et al. In their Weather wise paper, to the Great Bend (Kansas USA) tornado of 31 August 1974. From a film of this storm, wind speeds as high as 306 kilometre's per hour were deduced, implying that the velocity of Northam's winds may have been of a similar magnitude. It would seem, therefore, to have been an F-3 / T-7 force tornado, which is consistent with the uprooting of the large gum trees standing in its path.

A tornado caused a police alert at Northam before it skirted the town and dissipated late yesterday. The spiralling pillar of red dust and debris was seen by hundreds of people as it approached the town. A traffic patrolman, Paul Zegar, of Beverley, who was travelling towards Northam on the York road, first reported it to the Northam police. The Northam police set out in the direction of the storm but the tornado crossed the road about 30km from the town and blew out as it headed towards Goomalling. It was not seen in that town. The tornado was deep red against thick, black thunderclouds.
Little Rain: One of the policemen who left Northam for the storm area said that the swirling funnel of wind cut through bush and paddocks. It brought little rain. Power lines along the York road were strewn with debris in the wake of the tornado. No reports of damage were received last night. A spokesman for the weather bureau in Perth said that there were more tornadoes in WA than most people realised. The red colour of the tall pillar could have been due to reflection or refraction of light from the setting sun. It was probably a tornadic squall associated with thunderstorm activity.

I found it very interesting that even back in 1977 the BOM was saying we get far more tornadoes then people realised. The first five pictures below show the small condensation funnel and wall cloud. The other five photos show the main tornado. Certainly beautiful pictures aren't they. They are also great evidence for those that say we don't get real tornadoes in Australia.

These photos are used with exclusive permission by the owners and may not be reproduced in anyway without given permission from Inflow Images or the owners.