Outbreak forecast w/o high risk

[Bryce Stone]

I will be the first to admit that I don't have the background in meteorology that many of you have. My speciality is the English language. That's why I am asking this question: what happened with this event?

As of right now, only one tornado appears on the SPC storm reports page and no tornado warnings are out. Meteorologically speaking, why did the risk of tornadoes not verify? While I'm overjoyed that a potentially very deadly nighttime tornado outbreak in the deep south didn't occur, I'm really curious about why it didn't. Any thoughts?

 

[Dave Gallaher]

Sunday chase

I will be chasing out of the Tennessee Valley on Sunday. ATM (4:00am central) full moon offers visible reference on 850/500mb shear as holes in each cloud deck reveal the juice is moving.

If anyone is interested in helping with nowcast, it would be appreciated. I have cell phone and NOAA radio, no laptop.



Dave Gallaher
Huntsville, AL

 

[Jeff Snyder]

I will be the first to admit that I don't have the background in meteorology that many of you have. My speciality is the English language. That's why I am asking this question: what happened with this event?

As of right now, only one tornado appears on the SPC storm reports page and no tornado warnings are out. Meteorologically speaking, why did the risk of tornadoes not verify? While I'm overjoyed that a potentially very deadly nighttime tornado outbreak in the deep south didn't occur, I'm really curious about why it didn't. Any thoughts?

I put the reason on the widespread nature of the storms and the meager instability... The best shear remained in MS most of the afternoon and evening, but the good moisture wasn't able to make it very far into that state. As such, surface-based instability remain very limited. Additionally, there were numerous/widepsread storms, which resulted in numerous cell collisions/interactions (I saw a couple of nice supercells killed by this). The outflow created by the numerous thunderstorms likely enhanced the cool-side of the boundary, making it more difficult for the instability and moisture to head northward into MS/AL. A deep low would have helped strengthen the southerly flow and likely would have resulted in the Gulf moisture and instability making it farther into MS/AL. The only location that looked pretty good all evening was southern LA, though storms failed to initiated there. The couple of supercells that did look decent on radar and were tornado warned in MS likely faced a very stable near-surface layer (again, lots of outflow from nearby / previous storms) which made tornadogenesis very difficult.

 

[Mike Johnston]

Jeff, does the fact that the area of interest was so close to the coast itself have anything to do with your analysis? Having lived within a few miles of the coast of South Carolina, it seemed like many times severe forecasts failed to verify just along the coastline. I know onshore flow itself can sometimes serve as lifting mechanism, but is there a natural moderating mechamism at work in the lower- or mid-levels or something in close proximity to the coast? Yesterday, it just appeared that helicity was practically non-existent in the southernmost areas of the forecast where the juice was coming in.