A deep, nonlinear warm eddy advecting water that was also anomalously salti
er, lower in oxygen, and higher in nutrients relative to surrounding waters
was observed in moored current and temperature measurements and in hydrogr
aphic data obtained at a site similar to 400 km off the coast of northern C
alifornia. The eddy was reproduced using a nonlinear quasi-geostrophic mode
l, initialized by an iterative procedure using time series of 2-day average
d moored current measurements. The procedure demonstrates how a data assimi
lative technique synthesizes and enhances the resolution of a relatively sp
arse data set by incorporating time-dependence and model physics. The model
forecast showed significant skill above persistence or climatology for 40
days. Our hypothesis, that the eddy was generated at the coast in winter an
d subsequently moved 400 km offshore by May, is consistent with the eddy mo
vement diagnosed by the model and with the observations and coastal climato
logy. The model evolution significantly underpredicted the temperature anom
aly in the eddy owing in part to unmodeled salinity compensation in trapped
California Undercurrent water. Together, observations and model results sh
ow a stable nonlinear eddy in the California Current System that transporte
d water and properties southwestward through the energetic eastern boundary
region. Coherent features such as this one may be a mechanism for property
transfer between the eddy-rich coastal zone and the eddy desert of the eas
tern North Pacific Ocean.