Most folks probably don't associate the word "monsoon" with the American Southwest. Well, we have one - it's our life giving summer thunderstorm season from late June through mid September, when we in southeastern Arizona receive 2/3rd to 3/4th of our annual rainfall. Unfortunately, it's also when receive the side effects - violent lightening thunderstorms:
And microbursts, a very localized column of sinking air caused by a small and intense downdraft of heavy, wet and cool air sinking down into the lighter dry, warm surface air. This is an illustration of what it looks like:
And this is what it can do:
And haboobs, intense dust storm carried on an atmospheric "gravity current" - when a thunderstorm storm collapses and begins to release precipitation, strong wind gusts outward from the storm,pushing a wall of dust:
While the thunderstorms are spectacular from a distance, they are dangerous closeup. And we don't care much for the microbursts and we especially don't care for the haboobs, but we sure appreciate the rains. Especially these little guys:
That's a Chiricahua (Cheer-uh-kaw-wuh) Leopard Frog - frogs that actually live in the desert. I live near the Willcox Playa (ply-yah), a dry lake bed in central Cochise County, the southeast corner of Arizona. In the wetter climate of previous centuries the playa (ironically, the Spanish word for "beach") was a shallow year round lake, and the frogs thrived. In the current dry climate the playa only has shallow water during the monsoon. But the frogs adapted, burrowing deep underground and hibernating 9 months out of the year, surfacing to live, play and reproduce during the monsoon. I live in a pretty rural area on a 10 acre property. Normally when I take the dogs for a walk in the evening it's eerily quiet. During the monsoon it sounds like the soundtrack of the movie 'Creature from the Black Lagoon', with thousands of frogs chirping away.
Follow me over the orange squiggle for a more in depth discussion of America's Monsoon.
Most associate "monsoon" with torrential tropical downpours. What it actually means is seasonal reversing wind accompanied by corresponding changes in precipitation. The term was first used in English in British India. Normally the winds in India blow from the north and northwest, bringing in dry air. In the summer the wind flow reverses, blowing from the south and southwest, bringing in moisture laden air from the Bay of Bengal and Arabian Sea in the southwest, bringing heavy rainfall to the area. And that's very similar to what happens in the American Southwest. Normally our winds blow from the west and northwest, bringing in dry air from the eastern California and western Arizona deserts. In the summer a high pressure system normally sets up in the four corners area and the clockwise rotation draws up moist air from the Gulf of California, Mexico, and even as far east as the Gulf of Mexico:
How much rain? The average annual rainfall in Tucson is just over 11". Tucson is at an elevation of 2,600'. Cochise County is high desert, with an elevation of just over 4,000' for most cities, so we get a bit more rain, and annual average of 12-13". The average monsoon rainfall for Tucson is around 6", while most cities in Cochise County average 8-10". But the southwest Monsoon rain storms are usually very localized - it can sunny and dry in one place while 10-20 miles away is having a heavy downpour.
When that heavy a rain falls on the desert soil it runs off into low lying areas and washes (dry creek beds that only flow in heavy rain), creating localized flooding.
While it may be only a few inches of water flowing over a road, it's flowing swiftly and the road surface is very slippery. So every monsoon season we get a number of not so intelligent folks who think it's nothing and try to drive across it and end up like this:
Cars and trucks make lousy boats, don't try it!
June is the worst month in Arizona, hot and dry. It's in the high 90s to low 100s here in Cochise County, 100s in Tucson, and hundred teens in Phoenix (one of the several reasons I don't do Phoenix). But then we know it's only weeks until the onset of Monsoon, dramatically cooling things down. And overnight the desert turns green. Cacti bloom:
And desert wildflowers bloom:
And my leopard frogs come out to play.
Happy Hump Day!