I'm no guru, but I've always tried to relate swell explanations with actual experiences. Correct me if I'm wrong, but wasn't the last significant East long period swell that we experienced Hurricane Danielle back in 2010? I was also expecting closeouts with buoys reporting 14-15 second periods, but it wasn't too bad.
We get a handful or more of these type of East swells every year, mostly in the Fall or Spring.
it's been my humble observation that there are two different approaches to surf forecasting between the two. Swellinfo focuses on windspeed and direction to determine whether you're going to get green, blue or red. They do also indicate wave height, but it doesn't indicate whether or not it's going to be a good or bad day. Surfline tends to give you an overall assessment based on overall quality and so a day that comes out as blue on swellinfo might be listed as fair to good on surfline because the waves are good/big despite the windů on the other hand, a green forecast from swellinfo might be poor on surfline because the way of quality or wave height is lacking. Since out here on the left coast we do not get an actual surf report from this particular website, a more comprehensive eyes-on forecast is going to be over on surfline. Also, often surfline will have a general forecast for the day, but the individual surf report from the guy out in the field is sometimes different. Forecasting is just prediction.