Tornadoes and Outflow Boundaries

[Andy Wehrle]

Is it safe to say that an isolated area of early morning thunderstorm activity is somewhat of a good thing in an area that is 'primed' for potential severe weather/tornado development later in the day because of the possibility of developing outflow boundaries? I've always thought that you wanted a severe weather area primed up and not filled up with any type of convection for fear of atmosphere disruption or stabilization.

It all depends on whether the atmosphere can recover following the early convection. If you can get several hours of clearing/heating with one or two outflow boundaries that are well-defined enough to track in real time, it should be a good day for you (as a chaser) given other conditions being favorable.

In fact, I can't recall a major tornado day in Wisconsin that didn't have some garbage MCS move through between 6 AM and 11 AM...but I also know of plenty of potentially big days that weren't because the sky never cleared out in time...or it did but subsidence in the wake of the impulse associated with the earlier convection kept the potentially supercellular "second round" from ever forming.

Sometimes, if other conditions are favorable enough, tornadoes can happen along outflow boundaries even with little clearing and only small pockets of recovering instability. I think this is what happened on June 12, 2008, when skies remained mostly overcast, yet cluster-embedded "training" thunderstorms became supercellular and produced numerous, although short-lived and weak, tornadoes.

 

[Justin Wiley]

Thanks a lot guys. That pretty much answered everything. Interesting stuff that I can now add to my brain.