Short period modulations of less than one month are studied for M(2) t
idal waves in water level records taken from the Gran Canaria Island S
helf off the island's east coast). From the relation ship among modula
tions with low frequency oscillation observed in this zone (Bruno, 199
3), a mechanism based on non-linear interactions of meteorological low
frequency oscillation and M(2) signal is proposed. This interaction e
xplains a large amount of residual semidiurnal Variance in the water l
evel data.