Figure 7. Hourly averaged water levels, referenced to Mean Sea Level, for the Portland, ME tidal station for the month of February 2010. Predicted tidal elevations are represented by the blue line, while observed hourly averaged data is represented by red "+" signs. The difference between the observed and predicted water levels (marked by green "x" signs) is considered to be "surge." The high surge event occurring between February 25 and 26, 2010 is shown in the black outlined box (see Figure 8). It is also important to note the spring tide variation in the tidal range from about 12 feet (+6 ft down to -6 ft) at the start and end of the month, to the neap-tide variation of about 8 feet (+4 ft down to -4 ft) in the middle of the month. Storm surge during a period of larger tides can more easily flood low-lying coastal areas as opposed to days with smaller tidal ranges. Data courtesy of NOAA's Tides & Currents website.
Last updated on April 30, 2012