The Paraparap tornado is a good example of a non-severe thunderstorm tornadic event. The positioning of ASWA spotters on this day has allowed the rare interception of such an occurrence, allowing the very nature of the event to be studied in detail.

The occurrence of this tornado was videoed and photographed. There are also reliable on-ground witnesses near to the area with good descriptions.

There were a number of criteria present on the day to satisfy the possibility of a tornadic occurrence in a non-supercell storm profile. The lapse rate in the lower 3km was extremely steep and potenitally superadiabatic, there was also present a significant mid level dry layer which may have enhanced updraft potential. Strong lapse rates also existed between 500hPa and 300hPa. A modified Lifted Index for the Geelong area showed the 'LI' at -4.9 which equates to the potential for tornadoes. Although speed shear was rather weak there was sufficient backing of the airflow profile between the surface and 300hPa, returning relatively strong helicity. The presence of a surface trough provided a favourable convergence line and with strong local updrafts enhancing low level convergence and concentrating pre-existing vertical vorticity (Davies, Jones & Brooks et al 1993) There was also a local sea-breeze operating near to the Paraparap district.

From the evidence shown in the report, both visual and atmospheric profile analysis, it is concluded than an F0 strength tornado occurred over the Paraparap district. It produced minimal damage but provided a unique opportunity to study the event in detail.

The report has been written by Clyve Herbert (ASWA Victoria). Infield photographs and video were taken by Jane ONeill. The assistance of the Severe Weather section of the Bureau of Meteorology, Melbourne in providing data has been invaluable.

Witness statement

Sounding YMML (94866) 0Z & 12Z 9/1/2000

Geelong Airport AWS Observations 9/1/2000 0Z - 0530Z

Geelong Airport modified trace (CAPE) - courtesy Anthony Cornelius (ASWA - Queensland)

500hPa analysis

300hPa analysis

Hodographs - 12Z 8/01/2000, 0Z 9/01/2000, 12Z 9/01/2000

We would like to thank the following people and organisations for their contributions to this report:
Ray Kollmorgen & Tony Bannister, Severe Weather Section (Melbourne), Bureau of Meteorology.
Anthony Cornelius - ASWA Queensland for the analysis of CAPE at Geelong Airport
Lindsay Smail - Geelong Weather Services, ASWA Victoria for his assistance in completing the report.