Heavy Mountain Rainfall and Flooding Across Southeast Arizona: January 26-28, 2008

摘要

This event stemmed from a persistent longwave trough off the west coast of the United States. This trough allowed tropical moisture into Arizona from the ITCZ. Precipitable water values in the source region were about 2 inches (during the event precipitable water values were 1-1.25 inches over Arizona). Given the warm nature of this system, snow levels were very high for most of the event, staying above the mountaintops. A strong south-southwesterly low level jet with 30 knots at 850mb and 50-60 knots at 700mb caused immense moisture convergence and orographic lift, not only against the Mogollon Rim, but also on the Catalina Mountains where over 8 inches of rain fell. Not only was orographic lift a major part of this event, but also rain shadowing. Tucson International Airport was heavily shadowed by the Santa Rita Mountains, where only 0.04 was recorded for the whole event. Most of the Tucson Metro, outside the mountain rain shadows, had between a one quarter and one half inch of rainfall. Safford, which is in a rain shadow from the Pinaleno Mountains, had slightly more rainfall at 0.14 inches.