How to calculate weather window or wave persistence statistics?

I would like to calculate wave persistence statistics such as the expected duration that wave height would remain below a certain height threshold, which is useful for planning marine operations.

I have a long time series of hourly wave height and period measurements, but I don't know the standard approach to use the data to calculate the weather window. Can anyone recommend a good article or book which explains the method? There must be a good classic reference out there but I haven't found it.

 

Check out the National Weather Service. They should be able to give you that information.
http://www.weather.gov/