A retraction that occurred in February 2006 triggered transition to a negative PNA pattern that lasted for six weeks. Analysis of this event reveals that anticyclonic wave breaking facilitated the transition by systematically redistributing the upper level potential vorticity (PV). Prior to retraction, negative PV anomalies were located upstream and downstream of the West Pacific jet. Evidence is presented that these two features eventually merge to form a high-amplitude ridge that ultimately breaks anticyclonically in the midlatitude East Pacific. The sources of the initial negative PV anomalies associated with this evolution are discussed, with particular consideration given to the phase of the Madden-Julien Oscillation and the role of a Sudden Stratospheric Warming event that occurred three weeks prior to the onset of the retraction. Analysis of the jet's evolution in EOF1/EOF2 phase space reveals that the jet is initially extended and northward-shifted (EOF1+, EOF2+). It proceeds to shift southward (EOF2+ → EOF2~) and then retract westward (EOF1+ → EOF1-) for several days before shifting even further southward (EOF1-, EOF2-). The meridional shifting and zonal retracting occur sequentially rather than simultaneously. Evidence of other retractions in the EOF phase space is presented that suggests this evolution is anomalous.