Paraparap Tornado
9th January 2000

The video sequence commenced at 15.41:54AEDST and terminated at 15.42:27AEDST (33 seconds). In this series of studies, cloud base features together with the deveopment of the dust tube are analysed. The video sequence was filmed from approximately 60kms north northeast of the Paraparap district. (VicRoads Country Directory p77H6)

Figure 5a

This frame shows distinctive base features and the intensification of the dust tube. A study of the location on the 11^th January 2000, showed numerous ploughed paddocks and gravel quarries. It is apparent that the vortex has passed over a dry ploughed paddock, allowing dust to enter the circulation thus allowing the tube to become visible. The main base features are very interesting, and rotation is discernible. The hole is probably caused by dry air incursion from the surface and this may account for the evaporation of the base. A surprising feature is the rapidity of the vertical motion of the dust along the tube (it would be possible to roughly work out the speed of ascent and estimate the vertical wind speed).

Figure 5b Simplified sketch of developing dust tube.

Figure 6a

Dust continues to be injected along the vortex tube and has almost reached the cloud base. There is an angled "cone" lowering to the left of the "hole". Together with the "hole", this feature was rather persistent.

Figure 6b

Figure 7a Extracted video frame of dust tube developing under the flanking line.

The dust tube has now connected to the base features. The small cone lowering is probably a funnel. The "hole" in the base is still a feature as dry surface air is drawn into the circulation along the vortex tube. The tornado is attached to the large cumulus congestus, which slopes to the left at a distinct angle. The lower vertical extent cumulus to the right is slightly south of the tornado.

Figure 7b

Simplified sketch of developing dust tube.

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