San José State University Department of Economics Thayer Watkins
Silicon Valley & Tornado Alley  The North Pacific Oscillation:
Theory and Observation  The concept of the North Pacific
Oscillation refers to a theory that there are two states of
meteorological conditions and circulation regimes for the North
Pacific. According to the theory the North Pacific stays in one
of those states for a period of time and then shifts to the
other. The National Oceanic and Atmospheric Administration
(NOAA) has compiled two relevant indices: the WP (Western
Pacific) Index and the EP/NP (Easter Pacific and Northern
Pacific) Index. If the ocean behaved strictly as the theory
suggests the tabulation of the the indices would look something
like this:  The actual histograms (tabulations of frequencies)
look like this.  The data for these histograms are for the
period January 1950 to October 2009. Some data for the EP/NP
index for a few months were not given. These months for the
EP/NP Index were left out of the tabulation.  The