Paraparap Tornado 9th January 2000
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| Perceived Storm Motion From a visual observation, cirrus outflow from the anvil moved with the upper steering flow. This visual observation confirms the data available from the Melbourne Airport sounding at 1100AEDST, that is, cirrus moved from a direction of ~250deg, however the active multi-pulses showed storm motion to the right of the mean geostrophic flow with a tendency for new cells to favour development on the west-southwest flank. Type of "Thunderstorm" From a visual aspect, the storm was a small high based multicell. Each new pulse merged with a glaciated anvil area. On two occasions, visual and video analysis showed each pulse to be a vigorous if somewhat small identity. The tornadic pulse approaching maturity at 1540AEDST is capped by pileus, confirming the strong upward displacement at that level (see Figure 3). It is possible to identify the level of pileus from the sounding which shows a more humid layer at 6800m. Atmospheric Indices Soundings taken at Melbourne Airport at 1100AEDST did not show an abnormally low Lifted Index (LI). The LI was calculated at +1.58 which returns a forecast of 'showers probable'. The total - totals (TT) analysis returns a reading of 48, which conforms to scattered moderate thunderstorms. Interestingly, the Energy Index (EI) is rated at -0.49, which converts to 'scattered severe thunderstorms possible'. These calculations were based on a maximum surface temperature of 28C. With actual maxima reaching 32-33C over the Paraparap district (31.9C officially at BoM Geelong Airport AWS), a modified Lifted Index of -4.9 was obtained (see Figure 3). A rating of -4.9 equates to a 'possibility of severe thunderstorms with a risk of tornadoes'.
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