Re: Australian tornado climatology and information / Bulahdelah Tornado Report 1/1/1970

Michael Thomas,

You mention of the parameters being sketchy for the day. What do you feel was lacking in this storm outbreak?

I think your previous post above cover things well. I meant to suggest that I was confirming the difficulty to gather sufficient information to achieve a sufficient profile for the time the storm occurred. Was there an increase in the windshear profile. Given the dynamics, were the old profiles and 're-analysis accurate' for so long ago given the lack of data.

I guess what I look for are:

- instability and steep lapse rates. The delta H7-H5 temperature difference > 19C is a rule of thumb for violent tornadoes. Was this the case on this day?

- inflow - one would require to know the pre-storm environment but at least the low level profile was favourably directional

- mid-level moisture profile being dry to enhance clean structure and less upper level loading in terms of precipitation. This should overly deep moisture to 700hPa. Together, with upper level windshear can lead to classic supercell profiles.

- existance of boundaries can assist and this region particularly further south extending to the region west of Bulahdelah have natural boundaries. Were there other outflow boundaries on the day

- upper trough short wave passing through to break a lower level cap

Seriosuly though, the lower level wind shear is the most common missing ingredient that differs between the US and Australia regularly. I feel that deep moisture can also be an issue - the lack of dryline dynamics also tends to be present here.

Whenever we have had ingredients in place, tornadoes occur. Population density or not, someone sees a tornado under the intense storms on the day.


Jimmy Deguara