Oceanic Influences on Pacific Storm Track Activity and Southwest United States Precipitation from 1915-2011

The Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO) exert influence on the position and strength of storm tracks through ocean interactions with the atmosphere. This study utilizes a comprehensive set of satellite and in situ data from 1915-2011 to show how the IPO and AMO may have influenced and are related to historical December-January-February storm track activity (STA) and precipitation (snow) over the north Pacific and southwest US (SWUS). SWUS river basin water supply for people, agriculture and energy production throughout the year is predominantly dependent on snowpack depth and by changes in ocean conditions across multiple time scales.

Positive STA and precipitation anomalies are strongly related to positive (warm) IPO phases across datasets and time periods while negative (cool) IPO phases are not as robustly linked to specific anomalous conditions. Additionally, we find some evidence for STA-precipitation relationships with time and region dependencies. While continued global change could cause a mean poleward shift in STA and precipitation patterns in the future, there is as yet little indication of such a shift in observational data. Moreover, the interannual to interdecadal variability discussed in this study will continue to be important to water resource managers throughout the region.