More on the Monsoon...

So I'm looking out the office window at a wall of water falling from the sky, ducking each time the thunder rattles the plate glass and praying for a prolonged power outage. A particularly fun monsoon storm - hitting as it should right at the point where the afternoon heat was becoming opressive. I'm betting, however, that although I can't see past the gray curtain, that somewhere in town someone is basking in the glorious sun, wishing it would just go ahead and rain already. How can this be? How is that it can be pouring midtown and be scorched and parched in Oro Valley, just a 15 minute drive away?


In a nutshell, it all has to do with how the storms form themselves. Unlike winter storms which blow in on the face of a large-scale weather front, blanketing miles of land with gentle (if sometimes annoyingly persistent) rains, summer monsoon storms are built on-site, one at a time, by a combination of factors more complex than the plot of Lost. Here, does this diagram help?





Yeah, didn't think so. I kinda found it facinating but not very helpful, too. Basically, a summer thunderstorm has a pretty short lifespan. Heat is sucking in all this moisture, it's hitting the landforms all around Tucson (the Santa Catalina Mountains, the Rincon Mountains, the Santa Rita Mountains, even the Tucson Mountains, the Tortolitas and the Sierritas to name just a few). Because the air has to go somewhere, it goes up and we get that whole convective thing going. However, by creating different gusts, rain and movement, the storm sort of seals itself off by changing the very conditions that created it. So it becomes a self-supporting, evolving moster (above). Then it bounces around, not unlike a pinball hitting various kinds of bumpers and obstacles - sometimes even getting swatted back onto the playing field by another, older storm. From beginning to end, the average summer thunderstorm goes from developing to waning in about 40 minutes. Meanwhile, across town, the heat is at it again, only on a different slope in a different part of town. Maybe this one is a gusher, maybe it just fizzles when it gets over a piece of land that the first storm doused and cooled down (now the moisture's on the ground instead of the air, so it can't continue to fuel the storm). It's all a really cool puzzle. Click the weather underground link on the sidebar if you're really into this. You can look at weather stations all over town and see how variable the conditions are.


Now, then there's the storm events like the one on July 31, 2006 that flooded the Santa Catalinas (including Sabino Canyon) as well as slamming the Galiuro Mountains hard. This was not technically a monsoon storm. You wann know more? Well... then I guess you'll have to come back!

This is from the 1983 flood that changed the way Tucson deals with floods...