Beyond my knowledge to say why this is sometimes missing in the summary information, but look further down and you'll see there was another entry with wave heights missing in the summary info.

However it is still observing the wave height if you look at the current readings at the top, and if you page down to the bottom, to the detailed wave summary, where you'll notice that the waves have started to become steep. Wait until they become very steep. The sea conditions tha these buoys tell us about can be really amazing to comptemplate. You should have seen what the buoy south of Dauphin Island recorded last year for Ivan - really large, steep waves.

I wasn't tracking hurricanes then but I was visiting my cousin at the Jersey Shore when I saw on the news a strong hurricane was south of the MS coast. I was able to get a couple hours on the computers at the local library and get on the internet to search for and relay some information to my brother during the evening she made landfall. They had some trouble getting me to leave at 9pm! I vividly remember finding the NHC and NOAA sites and looking at the Mobile radar image, wondering when in the sam hill Ivan was going to make that bend to the right that they were talking about, and spare MS from destruction. The next morning I went back and checked the buoy info. Wow it was impressive. There was only one newspaper that I knew of that picked up on the info as well and noted the one exceptionally large (average) wave height of over 50 feet, which I also noted in an email to my brother:

"The buoy south of Dauphin stopped measuring waves from 3pm to 10pm...I think the waves were too extreme to measure...but came online after that and measured average wave height of 52.5 ft at 7pm"