CDO

Hi

I am new in cdo and I want to get some ideas about calculating EOFs of significant wave height.
The model (WW3) has provided long-term outputs of significant wave height in 3-hourly intervals for 31 year. When I try to calculate EOFs using following commands;

cdo eoftime,3 Hs_2000.nc out1.nc out2.nc

I get warning that:
cdo eoftime (Warning): Missing Value Support not Checked for this Operator!
cdo eoftime (Warning): Does not work with changing locations of missing values in time.

I get same warning when I proccess the data for anomalies first:
cdo sub Hs_2000.nc -timmean Hs_2000.nc anom_2000.nc
cdo eoftime,3 anom_2000.nc out1.nc out2.nc

cdo eoftime (Warning): Missing Value Support not Checked for this Operator!
cdo eoftime (Warning): Does not work with changing locations of missing values in time.

any ideas about this warnings or work around significant wave height is highly appreciated.

cheers
Ali