The Bulahdelah tornado report written by B.W. Shanahan at the Bureau of Meteorology is now online.
—> PDF link
An interesting read. 55 knots from the NNE at 850 from the Coffs Harbour sounding – not bad lol
Plug a bit more boundary layer moisture into that 9am plot and you'd end up with a rather high CAPE figure.
David Croan replied in an email:
Definitely Michael, I'd say richer moisture would, given those 22 degree dewpoints at noon near Taree, would have advected down so the 16 dewpoint at noon is off. From the model there is not a great deal of 500mb cooling between 0 and 6z, not sure how accurate that is, but the very strong CAP was breached so something changed through the day in addition to just heating. Very dynamic system, those winds 3pm at Coffs …wow –0-3 SREH would have been high end, and presume 0-1 km too if we had that information.
It seems Australia is a tipping point with these sorts of systems. We have had nothing really like this in the last 13 years, in fact it is getting horribly boring here as far as chasing. Was the fact that this Brisbane and then Sandon tornadoes occurred soon after just a coincidence, or does it reflect subtle shift in longer term patterns. Always hopeful it will tip back in favour of more intense upper systems with this sort of surface cyclogenesis, in the warm season of course. We must be overdue surely!
then Jimmy Deguara responded:
Yes to me the 850 winds and moisture are the key ingredients to low bases and inflow dominant structure. The upper level cooling would have been in place further west at the least. Nevertheless, so long as you have uplift and some lifting mechanism and great shear we are business.
and Michael Thomas
From what I see, there appears to be some pretty big differences between the wind profiles given in the report versus the reanalysis. In the reanalysis, the 850 mbar winds are in the 20 to 30 knot range over the Northern rivers/mid-North Coast whereas in the report the 850 mbar winds much stronger at Coffs Harbour (55 or 60 knots at 3 pm?). I also suspect that the LI's were considerably lower than shown in the reanalysis given that dew points were in 20 to 22 C range with 500 mbar temps around -12 to -14C. How would you rate this outbreak to a classic US setup (with the limited information available)?
