Ah, the Monsoon!

Alaska has the aurora borealis, Florida has hurricanes, Denver has winter blizzards, the mid-west has tornadoes and California has earthquakes, forest fires, debris flows, Santa Ana winds and Arnold Schwarzenegger. So what does a supposed barren wasteland like Arizona have to compete with such natural wonders?

Easy: the Monsoon.

Photo by Gene Rhoden

A two to three month long string of hot, humid weather punctuated by often spectacular, occasionally dangerous, always refreshing thunderstorms. Clouds blow into town like wild-west gunfighters: raising dust, cracking with thunder and pelting the land with bullets of water and (sometimes) ice... Then, just as quickly, they're gone, leaving a wake of cooler temperatures, broken tree limbs and muddy stream crossings. It's the reason the Sonoran desert is so much more awesome than the Mojave, it's the key to the existence of the saguaro and the mesquite bosques, and it's the ultimate reward for those who are able to withstand the onslaught of summer from May until July. Snowbirds just don't know what they're missing.


Now, over the years I've been asked a lot of questions about the monsoon. As the Queen of Useless knowledge and a 5th generation Arizona native, people seem to think I must be a repository of information about the nature of weather 'round here. Well, they're right - although I don't claim to be able to predict it. It is the very nature of the monsoon to be unpredictable, and by that I don't mean in the sense of a flaky friend or an unexpected plot twist, I mean 'not able to be predicted'. Those guys on tv are making educated guesses, and I kind of feel sorry for them. Talk about an impossible job.

Monsoon storm over the Rincon Mts.

First piece of important information is that the proper terminology is, indeed, 'the monsoon'. Storms that occur during this time might be called 'monsoon storms' or 'summer thunder storms' or 'hellacious squalls'. There are some who will call the whole season, or any individual storm within it 'the monsoons' - but they are losers. The term 'monsoon' actually refers to the change in wind patterns that brings warm, wet air from the south (either the Gulf of Mexico or the Gulf of California) - not the storms associated with it. This information will help you look super nerdy at parties, and you can always win points calling in and correcting radio dj's who will undoubtedly use the word completely wrong.

So, in a nutshell what happens is it gets freaking hot in the deserts of Mexico and Arizona (and to a lesser degree New Mexico, Nevada and Texas) over the summer, this hot air rises (explained: According to statistical mechanics, where air has greater kinetic energy it has a greater probability to occupy a higher gravitational potential than less energetic air. That is, the system tends toward maximal entropy ......from here). The rising hot air creates a vacuum of sorts, which sucks cooler, moister air from around it - primarily from the oceans to the southwest. Now you've got this cool swirling mass of cooler, moister and thus less stable air over your hotter than hell desert floor. The massive convection current continues and pretty soon that wet air is forced up to where it condenses into rain and viola. Rain. Moisture falling from the sky. Water in the air. 'round these parts, it's a pretty unusual thing... It brings out the worst in people (more on that later).

Interestingly enough, the existence of the monsoon in Arizona wasn't even a universally held truth until the 1990's. It seems that the relatively low population in the area and the respectively low cost of damages associated with these storm systems had created very little interest in finding out why it suddenly gets so rainy in the desert Southwest in late summer. Locals had called this a monsoon forever, but scientists were split. Many thought those dirty-toed Arizona hicks were just tryint to be cool with their talk of "tropical" weather patterns. You see (to get back to semantics and word history - one of my faves) the word 'monsoon' comes from the Arabic word "mausim" which means "season" or "wind-shift". This is because the first recognized monsoon was so much more obvious than ours. In the Indian sub-continent the change in wind pattern is triggered by the heating of the Thar desert. Again, it causes moist, cooler air to be sucked off of the ocean, which is uplifted by the base of the Himalayas, and bam. Rain. Rain like we never even seen before. This process alone is the root of Wendy's #3 life maxim: never live in Bangladesh (not that the monsoon is all Bangladesh has going against it, but it's enough).

The Indian subcontinent (not to make it feel inferior or anything...)

So, folks here were like - yeah, same thing happens here in Arizona - just without the cows floating by. So a climatological study was begun to determine if the pattern was the same, and, as I discussed earlier, a similar pattern was discovered - though the distance of the uplift from the ocean (Sierra Vista ain't exactly coastal), the smaller bodies of water involved and the less dramatic uplift (the Catalinas vs the Himalayas - I know who'd win) make our monsoons a little less wet and scary than those in India. Thank goodness, because I wouldn't want to be living in Tucson if it looked more like Dhaka.


Now, there's a lot more information about monsoons that I'd love to share with you - however because I actually do have a job I'm supposed to work at, and because some of you actually work for a living, too - I'll break this into a series. Today was just monsoon basics. Look for more cool monsoon info tomorrow... Or, if you can't wait, here's a good source that knows almost as much as me (not to mention, it's not half as entertaining).