Extremely anomalous water mass properties, with deviations as high as 35 si
gma, were observed in the thermocline during January 2001 at the Hawaii Oce
an Time-series site north of Oahu. The spatial distribution of the anomalou
s waters is consistent with a submesoscale vortex with radius similar to 15
km, possibly a remnant of a mesoscale eddy. The most plausible source loca
tion of the anomalous waters is offshore of Mexico near Baja California. Gi
ven the southwestward subtropical gyre circulation, it is unlikely that the
se waters were transported directly westward to Hawaii. Unusual northward t
ransport of Equatorial Waters along the North American coast during the 199
7-98 El Ni (n) over tildeo event, and subsequent transport southwestward in
the core of a California Undercurrent eddy is more plausible. El Ni (n) ov
er tildeo modulation of eddy transport and diffusion of water mass properti
es may substantially impact the mean distribution of properties in the Nort
h Pacific subtropical gyre.