BY MIKE MAGEE

On September 25, 1939, Southern California woke with fear of The Lash of St. Francis or El Cordonazo on the horizon. The term refers to northwestern tracking, cyclone-laden storms that can hit the western shores of Mexico and California most commonly around the Feast of Saint Francis, on October 4th. This one made landfall at San Pedro, California.

The calamity that day in Southern California was a rare event, the only one of its kind in the 20th century. The last one to hit, prior to this was in San Diego on October 2,1858. The Earth’s rotation normally assures that such cyclones in this region move from east to west, and out to sea. But the 1939 storm was the exception, and the big problem was the rain, some 5 1/2 inches over a 24-hour period (though the town of Indio, in the Coachella Valley of Southern California’s Colorado Desert region experienced 7 inches and buried the valley in 4 feet of water. Forty-five died on land, and 48 perished at sea. One positive – the storm marked the end of a 1-week heat wave where Los Angeles reached 107 F degrees and claimed 100 lives.

History repeated itself 84 years later this weekend, with a memorable “Lash” on the backend of a summer heat wave. The human, economic, and ecological tolls remain to be calculated. But one thing is for certain, global warming has arrived, and with it the production of both heat and water and a new, all too familiar meteorological phenomenon, the “atmospheric river.”

NOAA defines “atmospheric river” this way: “Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. While atmospheric rivers can vary greatly in size and strength, the average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. Exceptionally strong atmospheric rivers can transport up to 15 times that amount. When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.”

To be clear, these drenching above-ground collections of water are generally a blessing because they provide most of the much-needed precipitation to California’s dry areas and replenish the water cycles in the region. But as the Earth has warmed, they more frequently represent “too much of a good thing”, and are now responsible for 90% of California’s flood damage.