DENVER — Deserts aren’t supposed to get much rain, but Tropical Storm Rosa is flipping the script.
Rosa will make landfall Monday evening on Mexico’s Baja California.
This is Tropical Storm Rosa. The storm's interaction with Baja is weakening Rosa and that trend will continue. This is a large supply of moisture that will make its way into Colorado throughout the week. Denver's highest rain chances come Wednesday and Thursday.#cowx pic.twitter.com/nGstEUK4sZ
— Matt Makens (@MattMakens) October 2, 2018
The storm — which was recently downgraded from hurricane status — will douse Baja with 3 to 6 inches of rain, with some spots getting up to 10 inches, the National Hurricane Center said.
As it moves northeast, Rosa will also dump 2 to 4 inches of rain on much of Arizona, with up to 6 inches in the Arizona mountains.
The storm will also impact southeast Utah and southwest Colorado.
While much of southwest Colorado — including Durango, Ouray and Telluride — are under a flash flood watch, most of the state could receive moisture from the storm’s remnants.
This might include the season’s first snowfall for many mountain communities by the weekend.
In the Denver area, chances for showers are best toward the end of the workweek.
— NWS Grand Junction (@NWSGJT) October 1, 2018
Historically, it’s unusual for the Southwest to get pummeled by a hurricane or tropical storm. But “these events have begun to increase in recent years,” Norman said.
Research indicates global warming contributes to tropical storms getting “more intense, bigger and longer-lasting, thereby increasing their potential for damage,” said Kevin Trenberth, senior scientist at the National Center for Atmospheric Research.
While there might not be a direct link between global warming and the recent increase of severe storms in the Southwest, “it is possible that this could be a side effect of climate change,” Norman said.
“Warmer oceans are allowing eastern Pacific storms to reach higher latitudes,” he said. “This was not the case earlier. It was quite rare for an eastern Pacific storm to even reach Baja California, and this now becoming more common.”