It's rare for a tropical depression to hit Arizona, but that's exactly what's likely to happen early happen early next week as Hurricane Rosa's remaining energy tracks across the Desert Southwest, delivering flash flooding risks.
The National Weather Service has already issued flash flood watches for Monday and Tuesday for western Arizona into southern and eastern Nevada, southeastern California and Utah, including the cities of Phoenix, Flagstaff, Las Vegas, and Salt Lake City.
Rosa is expected to take a direct path over Phoenix on Tuesday, approaching late Monday with rain. The National Weather Service in Phoenix noted in a tweet that only "ten tropical cyclones have maintained tropical storm or depression status within 200 miles of Phoenix since 1950! Katrina (1967) was a hurricane within 40 miles of the AZ border."
How much rainfall will Rosa bring to Desert Southwest?
The latest National Hurricane Center models predict 2 to 4 inches of rainfall, with isolated amounts up to 6 inches in the Mogollon Rim of Arizona. Other areas of the Desert Southwest including the central Rockies and the Great Basin are likely to get 1 to 2 inches, with isolated totals up to 4 inches possible.
For those out of flash flood risk, Rosa's rain may be a blessing since the region is drought-stricken.
"Although flooding is a very serious concern, some of this rainfall will likely be beneficial since the Southwest is currently experiencing drought conditions. According to the U.S. Drought Monitor, just over 40 percent of Arizona is experiencing at least extreme drought, the second highest category," weather.com reported.
First, Hurricane Rosa's path leads to landfall across the Baja California peninsula of Mexico. Rosa, still at hurricane strength Sunday morning with maximum winds of 85 miles per hour, is 385 miles south of Punta Eugenia, Mexico and moving north at 12 miles per hour. The storm is encountering cooler waters in the Pacific and therefore powering down. Thus, it's expected to make landfall in Mexico at tropical storm strength in the afternoon or evening on Monday.
Rainfall across portions of Mexico could be heavy, posing a significant flooding risk.
"Rainfall totals of 3 to 6 inches are expected from Baja California into northwestern Sonora, with up to 10 inches possible," weather.com reported.
Rosa will then track north across Mexico as a tropical storm before reaching the Arizona border in the early morning hours Tuesday as a tropical depression, which will then track up through Arizona and into southern Utah by late Tuesday night.
"The main hazard expected from Rosa or its remnants is very heavy rainfall in Baja California, northwestern Sonora, and the U.S. Desert Southwest," the National Hurricane Center said. "These rains are expected to produce life-threatening flash flooding and debris flows in the deserts, and landslides in mountainous terrain."
