The Pacific Decadal Oscillation is a climate variability pattern that cycles over decades. An indicator of the phase is sea surface temperature. In the warm phase the eastern Pacific Ocean is warm and the western Pacific Ocean is cool. In the cool phase, the western Pacific is warm and the eastern Pacific is cool. Right now, the eastern Pacific is very cool. Also, notice the equatorial Pacific is cool with La Nina in place.
The Pacific Decadal Oscillation Index represents the degree of PDO variability. With the current cool conditions, the November 2011 measurement of the PDO Index is the lowest it has been since 1961. The PDO INdex in November was -2.33. It has been mostly negative since 2005.
While a number of factors affect Arizona’s climate, a cool or negative PDO Index is typically associated with drier than normal conditions across the southern United States. This seems to fit our current dry pattern.
The chance for snow on Sunday is evaporating.