A Little Bit About Monsoons

Usually when people talk about monsoons, you think of India. But did you know that southern Arizona around the Tucson Basin is one of the only true monsoon weather patterns to occur outside of India? (The definition of monsoon is "seasonal wind shift".) Both areas experience a seasonal wind shift, both occur in the summer, and from the south. Both areas occur in warm climates, with large, warm bodies of water to the south-southwest and southeast–-the Indian Ocean near India, and the Sea of Cortez and Gulf of Mexico for Arizona. Both areas also have large mountain ranges to the north (India's Himalayas, and our Sky Islands), which interrupt the moist southerly air flow, thus dumping more precipitation.

Sometimes a lot of precipitation.

Microbursts sometimes occur during monsoon storms. (A microburst is a very localized column of sinking air, producing damaging winds at the surface that are similar to tornadoes--the term is defined as affecting an area 2.5 miles in diameter or less and are capable of generating wind speeds higher than 168 mph.) They generally are formed by precipitation-cooled air rushing to the surface, but they perhaps also could be powered from the high speed winds of the jet stream deflected to the surface in a thunderstorm. Every monsoon we have multiple microbursts which uproot trees and snap wooden telephone poles as if they were toothpicks.

And, of course, there's the danger of flash flooding. Even if we stay dry in the valley, it could have rained in the mountains, and gravity does the rest. We have what's called a "stupid motorist law"--if someone drives past barricades or enters a low-lying area that has "do not enter when flooded" signs, and they have to be rescued, they have to pay $2,000 for their rescue. People who do this with children in the car are also charged with child endangerment. It's that serious.

But it's spectacular, too. We actually have water in our rivers...