Response to email question about storm surges.
The term “storm surge” has been unadvisedly expanded to frequently mean any rapid onslaught of water during rising high tides related to a cyclonic system
A true storm surge is pretty much a one-time deal, arriving with the initial onslaught of a storm. It can be slightly likened to an icebreaker effect, whereby a cyclone literally shoves a wall of ocean water out in front of it, most obvious as it makes landfall.
The height of a storm surge is determined by the size and intensity of the cyclonic system; the bigger and stronger, the larger the surge.
The forward speed of a storm also enhances a surge’s impact on land. The faster it’s moving forward, the more pronounced the wall of water it pushes ahead.
Hurricane Sandy is obviously a crawler, not the best storm surge producer. That’s why I’m wondering if some of the current “surge” forecasts are actually predictions of higher than usual tides, based on progressive high tides.
While Sandy will definitely bring along some serious surginess, I think the far larger flood factor will be from tide stacking.
Tide stacking is when a series of large, storm-driven high tides jam into the bay before previous tides have a prayer of draining out. It’s essentially an accumulative flood tide. The entire piggybacking process is often jumpstarted by a true storm surge. Each post-surge high tide is closer to a tidal surge.
I heard one TV meteorologist say, “The combined effect of these storm surges will cause serious flooding.”
In reality, he’s talking tidal surges and stacking, as opposed to consecutive storm surges, technically impossible.
By the by, storm surges have been known to push through bay regions then move far up rivers and creeks. They do NOT arrive like tidal bores or tsunamis, in a matter of seconds. However, within just half an hour they can usher in the equivalent of a normal six-hour tidal rise. What’s more, storm surges will easily override existing high tides. A five-foot storm surge arriving during an occurring five-foot high tide quickly escalates a normal tide to dangerous levels.