Among the normal modes calculated in a barotropic model of the world ocean is a Kelvin-like wave on the west coast of North America, whose period is 15.6 hours. On the California coast this wave has a phase speed of about 140 m s-1. If its amplitude is scaled to 50 cm at La Jolla (the M2 tide there), the 15.6-hour mode has a stored energy of 1.7¿1017 J, about one fourth the global energy of the M2 tide. With the same scaling power the wave is between 3¿1011 and 4¿1011 W. The possibility is discussed that this mode is an important elements of the M2 tide, but definite conclusions require a complete model synthesis which has not yet been made.