Monsoons! Well, almost... 25 June 2008

Happy days are here again! The monsoons have arrived! Well, technically; sort of; not really - take your pick, depending on your version of the definition for "monsoon."

I heard on the local news recently that the "official" start of the monsoon season in Arizona has now been "set" as June 15 each year. That's new, however, and I don't like it. The monsoons aren't really a season as defined by equinoxes and whatnot. No, the monsoons are the result of an annual, large-scale shift in wind patterns, bringing moist tropical air north from Mexico. And just like any other defined weather phenomenon, why take the science out of it?

The old definition: when the dewpoint remains above 54ºF for 3 consecutive days, the monsoons have started. Monsoon-style thunderstorms become semi-regular before those 3 days pass, but at least something measurable like a dewpoint convinces us that the rains are finally here to stay.

Regardless of the technical definition, my own personal excitement peaks when I see this:


Big, dark clouds building over Tucson! This picture was taken from my roof in central Tucson, looking east towards the Rincon Mountains (7AM on June 25).


AND...




RAIN!! Reaching down from the sky and touching the Tucson Mountains, at the western edge of the city (7PM, same day).


I live for the monsoons each year, so needless to say I get all riled up whenever I see the first real signs of the season approaching. The North American Monsoon heralds a kind of "second spring" in southeastern Arizona. Now is when many grassland sparrows and other desert and semi-desert birds will breed again, and many will breed for the first time this year (Botteri's and Cassin's Sparrows being a good example). Every plant returns to a vibrant shade of green; reptiles, amphibians, and some mammals emerge from their burrows; birds sing anew. All of our flora and fuana wait expectantly for this each year, and I completely understand. :)

Bring on the rain!
John Yerger


P.S. - In case you're interested, NOAA has a monsoon website packed with enough info to satisfy the weather nerd in all of us: http://www.wrh.noaa.gov/twc/monsoon/dewpoint_tracker.php.

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