"Spring tide" could boost Irene's storm surge

NAGS HEAD, N.C. - Hurricane Irene is forecast to be barreling up the East Coast of the United States at a time when high tide levels will be above average, according to the National Oceanic and Atmospheric Administration.

Steve Gill, a chief scientist with NOAA's National Ocean Service, told CBS News that Sunday night's new moon and the "spring tide" that comes with it will result in one of the highest tide ranges of the year.

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"The range of tide is going to be higher than normal, and the storm surge is going to ride upon that higher range of tide," he said. "The conditions are going to be such that it's going to be the worst possible timing."

A "spring tide" occurs during each new and full moon, named not for the season but for the "jumping" of the tides. The sun and moon's slightly stronger gravitational pull on the Earth at this time results in lower-than-usual low tides and higher-than-usual high tides. Coupled with Irene's storm surge, a spring tide-influenced high tide could mean more coastal flooding in some areas.

The impact on tides will vary from location to location. At The Battery on the southern tip of Manhattan, for example, this weekend's spring tide will add an extra foot to the average tide range.

"It all has to do with the timing," Gill said. "If it makes landfall at the time of those high tides, that's going to make a difference."

NOAA has posted tidal information for cities within Hurricane Irene's forecast path on its website, taking into account the spring tide.

"People need to look at those tide tables and then look at what the forecast is for the storm," said Gill, "and when it is passing them and if it's near high tide ... look out."