Around 4:15 Saturday afternoon, the Storm Prediction Center issued a Tornado Watch that included most of our counties here in Central Texas.  But between that time and the time the watch was cancelled shortly before 9 pm, nothing happened.  We remained storm and rain-free in Central Texas.  This often leads to people asking, "Why was a watch issued when there were no storms?"

First, we need to think about the reason a watch is issued.  A Severe Thunderstorm or Tornado Watch is issued when conditions in the atmosphere are favorable for the development of severe or tornadic storms.  What does that mean?  Usually, it's a combination of factors including high instability (lots of heat and humidity), the presence of surface frontal boundaries (like cold fronts or drylines), and some upper-level forcing (think jetstream).  We had all of those ingredients Saturday afternoon.  But so often in meteorology, it's not cut-and-dry.  The atmosphere is a huge, complex system - a system in which a temperature change of as little as 1 degree can mean the difference between having thunderstorms or not.  It's hard enough to measure those finite details of our atmosphere, let alone predict them.

What specifically happened Saturday? We certainly had a lot of heat and humidity in place, but it turns out we probably didn't have enough. We had a layer of warm air aloft - called a "cap" - that prevented storms from developing.  In order to have thunderstorms, one of two things must happen.  Either the cap has to weaken on its own (through a variety of different processes), or the air near the ground must be heated enough to allow it to rise above the layer of warm air aloft.  (Sound complicated? It is. That's why we meteorolgists go to school and get paid the big bucks!  Okay, maybe not the "big" bucks...)  On Saturday the cap held its own, and cloud cover prevented our temperatures from warming enough to overcome the cap.

So was the Storm Prediction Center justified in issuing the watch?  In my view, absolutely yes.  The conditions were ripe for thunderstorms, and had any developed they likely would have become severe very quickly.  It just so happens that sometimes one ingredient doesn't quite come together, and it happens to be the one ingredient that prevents thunderstorms from forming.  And I think the Storm Prediction Center would probably share my view that it's better to err on the side of caution when it comes to severe weather potential.  After all, I think it's better to issue a watch, make sure people are prepared, and see nothing happen (as long as that doesn't happen too often) than to not issue a watch, see storms develop, and know that people are unprepared.  Your thoughts?