Helicity

[Stuart Robinson]

I just looked at the RUC for tornado parameters - notice the 1000m/s of helicity NE of Katrina

http://www.rap.ucar.edu/weather/model/ruc0...hr_sfc_sreh.gif (http://www.rap.ucar.edu/weather/model/ruc03hr_sfc_sreh.gif)
(above link will update)

[Jeff Snyder]

Yes, strong low-level shear (0-1km and 0-3km SRH) are pretty common with hurricanes. That said, the size and intensity of the storm certainly result in a larger-than-normal area that will "experience" this strong low-level shear. With insolation commencing in some locations ahead of and to the right of the hurricane, instability will icnrease through the day for many locations ahead of and to the right of the storm -- there is actually a pretty good chance of a pretty good tornado event from this hurricane.

[HAltschule]

The helicity values are real....and real scary. I think you're right. A significant tornado event may be about to unfold. As such, SPC has a MOD risk of SVR...which in itself is uncommon for these events.