Desert Moonsoon Thunderstorms!

August 19, 2010 by taha 

One of my favorite things about the summer here in the desert is our monsoon thunderstorms! Yes, believe it or not, we have moonsoon storms here. Many people associate “monsoon” with the storms that blow through India and wreak havoc with flooding and high winds. The word monsoon is actually derived from the Arabic word “mausim” which means season or wind-shift. The monsoon thunderstorms created here in the Sonoran Desert are a result of that shifting of wind that takes place as we move into the summer season.

During our winter, the wind flows primarily from the west or northwest from California and Nevada. As summer approaches, the winds shift to a southerly or southeasterly direction and moisture is brought up from the Pacific and Gulf of Mexico and dropped right in our lap! This seasonal shift generally occurs (on average) around the beginning of July (average date is July 7th to be exact) and generally ends mid-September (September 13th on average). In the past, the start of the season was defined as 3 consecutive days of dew points averaging 55 degrees or higher. It was always fun taking bets on when that was going to happen! In 2008, however, the National Weather Service actually established a set season starting June 15th and ending September 30th (similar to how a hurricane season is defined-although I believe the hurricane season goes through October 15th).

The thing I find unique and quite spectacular about the monsoon storms we get are the dust storms that precede the actual rain. The thunderstorms are not always accompanied by a dust storm but when they are, it is quite an impressive sight. The way the dust storm is created is that the typical monsoon thunderstorm has a front that pushes air downward quite forcefully. This air then hits the ground and is forced out and upward before the storm cell. This creates a gusty front which in turn kicks up large quantities of dust and sand that then creates a wall of dust. This wall of dust is actually called a haboob. Yes, we do chuckle everytime we hear that word. It’s just one of those funny words I guess. Well these haboobs, or walls of dust, can exceed over 3,000 feet in height!  Can you say “airport delays”?

Anyway (airport delays or not), once the excitement of the initial winds and haboob pass, the rain starts. These storms are often accompanied by heavy rains. We sometimes receive over 2.5 inches of rain in one storm! That is over 1/3 of our annual rainfall average. Wow! Now the flip side of this coin is the fact that rains that fall that fast cannot be absorbed by the desert quickly. So we do run the risk of flash floods and since most of our roads weave in and out of washes, drivers do have to use caution when out and about during and shortly after one of these storms. The washes are the area of the desert floor that siphon off the excess water and no, we cannot avoid having our roads run through them.  Most of the year it is not a problem.  During the monsoon storms you cannot drive through these washes if you see water running through them. Even if the water appears shallow, you cannot tell if a wall of water is, in fact, making its way down to your location that very minute.  If the road has caution signs up or is blocked, don’t try to save time by going around the signs even if it appears there is no water in the wash at the moment.  They are there for your safety.

Here in Arizona, we actually have a Stupid Motorist Law in place here for those individuals who put themselves at risk by entering these flash flood areas and subsequently getting stuck in the wash. This law means the motorist that requires rescue can then be charged for the cost of that rescue service due to placing him or herself in harm’s way (not to mention risking the safety of the rescue team!). The other safety measure worth knowing when it comes to driving in a dust storm, is if visibility becomes too poor to see and you must pull off the road, be sure to shut off all of your car’s lights and do not rest your foot on the brake. Motorists behind you will see your tailights and may think you are in a travel lane and proceed to follow you and hit your parked vehicle. They typically cannot see any better than you!

If you happen to be out hiking when one of these storms approach, be sure to separate yourself from your trekking poles (you know those metal lightning rods you hold in your hands?) and be sure that your group does not huddle together. Try to keep at least 50 feet apart from each other and if no shelter can be found, assume the lightning position (sitting on a backpack or some other object to separate you from direct contact with the ground). Do not sit under or near a tree, wire fencing, in an open field, by poles or bodies of water. Also, do not enter any nearby washes as these may become quickly flooded. The best safety precaution you can take is to check the weather forecast before going out on a hike at all!  With a little bit of planning ahead and knowing what safety measures to take, you too can enjoy the amazing show that our monsoon thunderstorms provide us each season!

I remember years ago when we first moved here to the valley (from New England) how funny it was to hear everyone get sooooo excited about the rain. It could be a slight drizzle and the evening headline on the news was STORM HITS THE VALLEY! Really? Well after all these years of living here, wouldn’t you know, I now get excited to hear that we have a “storm” coming. The storms don’t always pan out, but when they do, it is a spectacular sight to see!  And we are often given the opportunity to witness beautiful rainbows during our summers here in the desert such as the one shown in the photo with this posting.  We saw this rainbow just yesterday during our most recent “weather event” as the news stations like to say.  So if you are new to the Arizona desert, put aside the fact that it is sweltering here during the summer and know that with that summer heat comes some of the most beautiful and amazing feats of nature that you may not have the opportunity to see in any other part of the world!

If you would like to learn more about this beautiful desert we call home, just call us at Take A Hike Arizona   (480-634-8488) and we will be more than happy to take you out on a hike to experience, explore and enjoy this great area we live in!

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