Though autumn is normally a time that witnesses increasingly drier weather, a sort of rain lottery exists for southern Arizona. With the monsoon losing steam as temperatures and humidity levels fall, the chances of an errant Pacific hurricane remnant increase dramatically. Late September into about mid-October presents our best window of opportunity to cash in on this liquid gold.
Despite the destruction wrought by various hurricanes in Baja California and Sonora, most that reach us are much diminished. When it’s predicted that a hurricane will come our way, we are most likely to get a Category 1 or 2, which would mean winds from about 74 m.p.h. to 110 m.p.h. – likely to cause moderate to extensive local damage. Fortunately, most hurricanes are downgraded to tropical storm systems by the time we make their acquaintance, thus delivering varying amounts of rain without the wholesale ruination normally associated with a full-scale hurricane. On September 7 and 8, 2016, I recorded 3.8” of rain from remnants of Hurricane Newton as it climatically spent itself in our area.
After hurricanes have delivered the brunt of their force south of the border, the Sea of Cortez sometimes funnels them our way with variable results. Duds are certainly possible with little or no rain. We’ve all seen the projected tracts of hurricanes towards their tail end with a variety of scenarios possible. So too with our weakened versions. Will they veer towards Yuma or New Mexico for example? Will they cause flooding or high winds? These and other questions often go unanswered until the eleventh hour.
When we do get a glut of rain from a hurricane or its remnants, then the local flora and fauna can be swift to respond. Plants soak up the moisture in their roots and may flower more profusely or for the first time. Entire species may be enticed from the soil to complete their life cycle in autumn. Last November I even gawked at Mexican Poppies – normally a spring plant – in Organ Pipe, which were teased out of the soil by a soaking October rain.
Many members of the Aster family flower in fall but will do so in greater profusion when gifted a deluge from the south. When we experience such a sopping autumn look to our grasslands, woodlands, and deserts for a third, and often unexpected, blooming period.
Normally trumped by our spring and summer blooms, autumn blossoms are much rarer and sometimes dependent upon Pacific storm systems as much or more than they are the monsoons. I have been fortunate to witness autumnal fields of asters, fleabanes, sunflowers and others in the San Rafael grasslands for example. These fragrant and winsome fields boosted butterfly populations by providing a late season source of nectar.
Invertebrate populations in general can benefit from the surplus rain, as grasshoppers and other species extend their life into or hatch out during autumn. They in turn – along with the surplus of seeds and other plant parts – furnish food for birds, mammals, replies, and amphibians.
Lastly, a tropical system in autumn may accrue positives in our parched state with limited water supplies, as well as tree and wildlife populations ravaged by drought. Critically important for our collective well-being, our waning aquifers and waterways will certainly benefit. The level of Patagonia Lake may rise or even fill, given the swelling of its feeder stream, Sonoita Creek. Increased flow in the creek and other local water conduits is essential to support and preserve our acclaimed biodiversity.
Thus, while the forecast of a hurricane or tropical storm may well send a shiver of nervousness down my spine, I have also realized the not inconsiderable benefits of tropical storm remnants over the years in our Sky Islands region.
Vincent Pinto and his wife, Claudia, run RAVENS-WAY WILD JOURNEYS, their Nature Adventure & Conservation organization devoted to protecting the unique biodiversity of the Sky Islands region. Visit: www.ravensnatureschool.org