Experiencing The Monsoon

Reminder:  You can enlarge any of the photos in this blog by clicking on it.  Click again for a full-screen image.

I often get asked questions about our summer weather from people who don’t live year-round in southern Arizona.  Most frequently, I get asked: (1) How hot does it get? (2) Isn’t it really a “dry heat” that doesn’t feel all that bad? and (3) What is the Monsoon?

The answer to the first question is that it gets very hot here in summer.  We’ve had over forty days of 100+ degree temperatures so far this summer and it’s still only July.  Yesterday afternoon, while driving around, I noticed that my car thermometer read 106 degrees.  As for it being a “dry heat,” well, true, humidity is lower here than in many eastern states and that makes the temperatures feel relatively lower than the equivalent temperatures back East.  But, candidly, how many 106-degree days are there in New York or Washington, D.C.?  The bottom line is that hot is hot, and when it consistently gets above 100 it is and feels extremely hot.  Not many people that I know here are particularly active outdoors in the midday July and August sun.

Now, as to the third question.   The word “monsoon” is taken from Arabic and it refers to a shift in the wind pattern.  If you look at a map you’ll see that southern Arizona is actually pretty close to the Gulf of California.  During July and August the winds here frequently shift, allowing moist air from the gulf to infiltrate our local desert.  That raises the humidity (making everything feel much hotter!) and it increases the possibility of thunderstorms developing.  Thunderstorms in these parts are a relatively common phenomenon during the summer months and they account for about one-half or more of our total annual rainfall.

They can be massive and intense, almost unbelievably so.  It’s not beyond question to get a couple inches of rain in an hour or less from one of these storms.  They are often accompanied by sudden temperature drops, high winds, hail, and lightning and thunder.  These storms can produce significant, if brief, local flooding.  It may sound unbelievable, but people occasionally drown in flash floods produced by these storms.

The other day, Ned Harris and I went storm chasing in the Sulphur Springs Valley in extreme southeastern Arizona.  The area lies about 75 miles from our home and is a high, flat plain situated between mountain ranges.  It is ideal for chasing and observing storms.  One can see the storms from a long way off — tens of miles — and watch as they develop and intensify.

Beginning at about 11 yesterday morning we watched a storm starting to build over a distant mountain range to the east of the valley.

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In this first photo, which I’ve rendered in black and white, the storm appears as a growing cloud over the mountains.  The power of the storm is emphasized by the fact that it already dwarfs the mountains underneath it.  Those mountains rise to above 5,000 feet; the storm is easily five or six times the height of the mountains.  The dark area at the storm’s base is a wall of rain that is just beginning to crest the mountains.

I took the second photo from the edge of a corn field about an hour later.

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The storm has become truly massive, extending for ten miles or more along its base.  Additional storms were forming alongside the first storm and they appeared to merge with it.  The dark shield of rain is now clearly visible at the storms’ bottom.  At this point Ned and I could seen lightning flashes.

We lingered for about 1/2 hour and I took this third photo.

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The storm had crested the mountains and had begun to slide westward into the valley.  The rain shield had grown and appeared as a solid black wall.  This was one gigantic storm!

Ned and I drove back to Tucson.  The storm and several others associated with it followed us back.  By the time we returned, at about 3:30 in the afternoon, the skies east of town were as dark as they had been in the Sulphur Springs Valley.  Late yesterday afternoon and last night, Tucson experienced one of the most intense episodes of monsoon storms of the summer so far.

Photos taken with a Canon 5DS-R, 16-35mm f4 L zoom IS lens.  All photos taken at M setting, ISO 125, f10 or f11 @ 1/80.


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