Satellite view of Hurricane Rosa, 28 September 2018. Graphic: The Weather Channel

By Linda Lam
28 September 2018
(The Weather Channel) – Hurricane Rosa rapidly intensified in the eastern Pacific, but its greatest impact will likely be as a weak tropical storm or depression bringing a threat of flash flooding to the southwestern United States early next week.
Rosa became a hurricane Wednesday morning in the eastern Pacific Ocean just under 500 miles south-southwest of Cabo San Lucas, Mexico.Rosa rapidly intensified into a major hurricane Thursday afternoon and is now a Category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale. Rapid intensification is defined as an increase in maximum sustained winds of at least 35 mph in 24 hours or less. Rosa has nearly doubled that rate of intensification. Rosa is the seventh Category 4 hurricane of the 2018 eastern Pacific Hurricane Season, tying the record recently set in 2015.Rosa will soon run out of warm water – fuel for hurricanes – and will begin to weaken on Saturday, but not before it finishes its rapid intensification phase on Friday. Gradual weakening is expected this weekend due to lower sea-surface temperatures, drier air and increasing vertical wind shear.Rosa is now turning more toward the north in response to an upper-level trough, or southward dip in the jet stream, that will be approaching the southwestern United States.

Projected Path and Intensity of Hurricane Rosa, 28 September 2018. Graphic: The Weather Channel

It is expected to weaken to a tropical storm, possibly a depression, before reaching the northern Baja California Peninsula Monday. […]Despite its weakening, deep tropical moisture from Rosa is likely to result in widespread rainfall, triggering flash flooding in parts of Arizona, southeast California, southern Nevada, Utah, and perhaps northwest New Mexico and parts of western Colorado next week. [more]

Hurricane Rosa, a Category 4 Storm Well Off Baja California, Will Be Desert Southwest Flood Threat Next Week