Hurricane scientist Nick Grondin explains how Hurricane Hilary, with help from El Niño and a heat dome over much of the country, could bring dangerous flash flooding, wind damage and mudslides to the U.S. Southwest.
What the Southwest does see fairly regularly are the remnants of tropical cyclones, storms that continue on after a tropical cyclone loses its surface circulation. These remnant storms are more common in the region than people might think.
A study led by atmospheric scientist Elizabeth Ritchie in 2011 found that, on average, about 3.1 remnant systems from tropical cyclones affected the U.S. Southwest each year from 1992 to 2005. That’s a short record, but it gives you an idea of the frequency.
Typically, the remnants of tropical cyclones don’t go beyond California, Nevada and Arizona, though it wouldn’t be unprecedented. In this case, forecasters expect the effects to extend far north. The National Hurricane Center on Aug. 18 projected at least a moderate risk of flooding across large parts of Southern California, southern Nevada and far-western Arizona, and a high risk of flooding for regions east of San Diego.