Finally! Rotating severe weather possible in the Southern Plains!
It looks like the fall season has finally arrived, as a strong cut-off upper-level storm system is forecast to eject across the Great Plains today. Moisture will definitely not be a problem, with lower 70 dewpoints pumping northward to central Oklahoma by afternoon, giving rise to CAPE values around or a little above 2000 J/kg across central and southern OK ahead of the cold front. A typical problem with these cut-off systems is maintaining a sufficiently strong low-level jet near the boundary, and having the shear vectors properly align with the given storm motion for tornadoes. However, while rather difficult to forecast, the
ingredients often do come together for tornadoes over a very localized area with these compact, circular systems, and we have had luck with them in the past. Thus, we'll be keeping a close eye from here in Norman and will likely chase regardless of what happens, especially since we really haven't had anything to chase for a few months.
As usual, the RUC model looks a little aggressive with the instability values in the warm sector of this system, but I figured an optimistic point of view was needed here after the recent storm chasing drought. We still think the RUC is typically best at handling the low-level wind fields, and more favorable low-level shear for tornadoes is forecast by the RUC over central/southern OK than both the NAM and GFS. Another limiting factor for tornadoes that is indicated by all models is the orientation of the surging cold front being roughly parallel to storm motions, which would mean storms may have trouble remaining discrete supercells. This could support a rapid transition to a squall line, but either way we'll have some powerful severe storms to drive into! We'll try and have live streaming video going for this event, so be sure to check out the LIVE page above for some real-time video, storm reports, and chat!
http://www.tornadovideos.net/component/content/article/1-latest-news/1029-finally-rotating-severe-weather-possible-in-the-southern-plains
