NASA measures southwestern U.S. record rainfall

Moisture pumping into southern California and the Desert Southwest from the remnants of hurricane Delores has caused record July rainfall. Data from the Global Precipitation Measurement (GPM) mission core observatory was used to estimate the rainfall.

Dolores formed over the weekend of July 11 and 12 about 175 miles (275 km) south-southwest of Manzanillo, Mexico. The storm moved north-northwest and on July 17, moisture associated with the storm began streaming to the northeast over Baja California, mainland Mexico and southern Arizona. As the storm continued moving to the north-northwest over the open waters of the Eastern Pacific Ocean, that stream of moisture moved north over southern California and Arizona.

Data from NASA's Integrated Multi-satellitE Retrievals for GPM (IMERG) were used to estimate the extreme amount of rain that fell from the remnants of former Hurricane Dolores. This analysis included data collected from July 13 to July 20, 2015. Rainfall that would not have been as significant in other areas of the United States had an extra impact in bone dry areas of California. Rainfall totals were estimated by IMERG to be over 268 mm (about 10.6 inches) in some areas of California.

This rainfall may provide some drought relief to the state of California that has been in the grip of exceptional drought conditions. Heavy flooding caused an interstate 10 bridge collapse on Sunday July 19, 2015 forcing closure of this main roadway between Southern California and Phoenix, Arizona.