Merrimack River Mouth Swell ForecastUnited StatesMAEssex CountyMerrimack River Mouth1-Day3-Day5-Day Graph Plots Open in Graphs Swell Height and Direction Forecast NOAA WaveWatch III Swell Period Forecast NOAA WaveWatch IIIMerrimack River Mouth swell forecast issued today at 12:41 am. Next forecast at approx. 12:41 am.Get an account to remove ads