Boyce Thompson Arboretum- Monsoon Thunderstorms

Arizona Monsoon Thunderstorms

Yes, there are monsoon thunderstorms in the desert.  In fact, the monsoons we think of in India are because there is a desert west of the ocean where their monsoons form up.

Here in Arizona our winter weather generally comes from the west and north – California and Nevada.  In the summer our weather generally comes from the south and southeast – from the Gulfs of California and Mexico and the Pacific Ocean. Tucson gets about 12 inches of rain a year.  July and August are the rainiest with about 2.5 inches of rain each month. April, May, and June are the driest months with about .2 inches of rain.  The other months get about an inch of rain.  The southern part of the state gets more rain while the northern part does get some snow.  The western part, such as Lake Havasu City and Yuma, get about 3-4 inches of rain a year.

Here the summer is humid.  Our humidity lately has been from 40% to 65%.  That makes the 90-to-110-degree afternoons muggy.  It also sets into motion the meteorological singularity of monsoon thunderstorms. For them to occur the humidity needs to be high for 3-4 consecutive days.  The heat from the earth and the strong southern winds bring moisture into Arizona that cause the thunderstorm formation.  The storms usually last from 30-60 minutes.  The rain can be slight – you can count the individual drops on a concrete patio.  The rain can also be a deluge, very, very heavy, have hail, and in between. The thunder and lightning can be spectacular to watch, from inside a structure or vehicle.

When there are several days in a row of possible monsoon thunderstorms the temperatures are cooler.  When Picket Post Mountain was obscured by the mists it was only in the 60’s and 70’s.  I had to dig out my long-sleeved t-shirts.

Sometimes, as the thunderstorms begin to form, the air in front of the thunderstorm will fall to the ground.  Then we have dust storms in valleys or large flat lands before where the thunderstorms may occur. These are called haboobs, from an Arabic word habb which means wind.  Thus, haboobs are windstorms. The term monsoon comes from the Arabic word mausim which means the turning of the wind, which is how monsoon thunderstorms are formed.  It was first used by the British in India to describe their large thunderstorms.

Arizona’s law holds the individual responsible.  This means you will be charged for the cost of rescue if you did not observe the posted signs or drove around barriers into a flooded area.

Don’t drive into standing water.  It is common for roads to have signs telling you to not drive into water as the road drops 6-10 feet in a dip.  That dip, after a monsoon thunderstorm, may be full of water.  People here know that the thunderstorm doesn’t have to have been near the dip.  Water isn’t easily absorbed by the land so much of it runs off, eventually ending up flowing very swiftly through that dip which could be many miles away. Most vehicles are floated by a foot of water and carried away by only 2 feet of rushing water.

Also, don’t drive into a dust storm. Pull off the road as far as possible, turn off your engine and lights and take your foot off the brake so people coming from behind don’t think you are a vehicle in motion.

After the monsoon thunderstorm the dry creeks will be swift and full flowing.  Then things change! Towns like Miami, also hit by the Telegraph fire, where the burn scar was dry hard land covered by ash that kept the ground from absorbing what little it might have, had flash flooding that took days to clear major roads of mud and rocks.

After the monsoon thunderstorms the desert becomes green!  Everything, ocotillo, creosote, and other desert plants green up and many bloom again.  Besides the flora, fauna also changes.  Insects, arachnids, snakes, and more seek drier ground or, as the garter snake in the video, they drown, rather like earth worms that come up to the surface after a rain in the mid-west, much to the delight of the robins. 

The cloud formations before can foretell the rain that might come.  I think the clouds are even more spectacular after the possibility rather than actual thunderstorms. 

I can’t narrate all the information about turkey vultures in the space of the video and I really don’t want to compromise the beauty of their flight.  So, here is the information about turkey vulture.  I saw more of such flights after the monsoon thunderstorms than at other times here.

Turkey vultures fly on thermal air currents.  A group of vultures is called a committee.  I shan’t comment on what that might indicate about the purpose or outcome of a committee as we think of a committee. The video of such a group soaring on the thermal air currents is called a kettle. When eating a group of turkey vultures is called a wake.  They have no feathers on their head.  This keeps their head clean when they reach into dead animals to eat and helps to radiate heat from their bodies. They don’t get sick from eating dead animals because if it’s too old they won’t eat it and because their stomach acid is so strong it kills any disease their meal might have.  Oh, and don’t get one angry at you, they’ll vomit on you.  You don’t want to smell that I’m told.