The timing of storm events with respect to the phase of the astronomical tide is extremely important. When a storm surge coincides with a spring high tide, the resulting total surge can be many times more devastating than the surge alone. A moderate event at low tide can become the storm surge of record at high tide.
An example situation was Hurricane Gloria, which moved along the Delaware and New Jersey coasts making landfall on Long Island, NY, at 1100 EST on 27 September 1985. The observed storm surge at Sandy Hook, NJ, had a peak value of 7.5 ft and occurred near low tide (1.0 ft). As a result, the total measured water level was 8.5 ft, corresponding to just 3.5 ft above normal high tide.
If the storm surge had occurred 4.5 hours earlier to coincide with high tide (5.0 ft), the peak surge value would have been 12.5 ft. The differences in levels of damage resulting from an 8.5-ft versus a 12.5-ft surge level can be considerable, and the only difference between the two scenarios was a 4.5-hour difference in time of occurrence.