By Margie Plunkett
The moon flexed its strength in September, pulling tides a half foot to a foot-and-a-half higher as it swung through its perigee.
The lunar perigee, when the moon’s orbit takes it closest to the Earth, occurred near the time of the Sept. 18 new moon, causing the higher than normal seas, according to Robert Molleda, meteorologist with the National Weather Service in Miami.
The moon’s power over the tides is usually strongest during the new and full phases, when the positions of the moon and sun are aligned, he explained. The effect is amplified as the moon’s gravitational pull becomes more influential when the orb draws closer to the Earth. And the tides are higher at the spring and fall equinox.
In Briny Breezes, the tidal waters rose into some streets near the Intracoastal. “We have these every spring and every fall, and fall is usually the highest,” Town Council President Sharon Kendrigan said.
The water comes across the street and up to Kendrigan’s second step. “There’s no damage, it comes in and goes out,” she said. The town discourages cars from driving through the brackish water, in part to prevent damage, she said. In addition, she said, at 10 miles an hour, they have a wake.
The seas have subsided now; they were down to within a half-foot of expectations by late September, according to Molleda.
The next lunar perigee is Oct. 13, which alone can mean tides of one to six inches higher, depending on local geography, according to NOAA. The closest new or full moon is Oct. 18.
The combination by itself will cause higher waters, but can become a critical influence when other weather that affects tides — such as a hurricane —is present, Molleda said.
The perigean-spring tides came into play earlier this summer, causing some minor flooding when seas were running higher up and down the Eastern U.S. coast, from Maine to Florida, according to an August report by the National Oceanic and Atmospheric Administration.
The moon wasn’t the primary reason behind those tides, which were up to 2 feet higher than expected, mainly in the mid-Atlantic, in June and July, according to the report. NOAA scientists said the event was caused by persistent northeast winds and a weakening Florida current transport, a current that feeds into the Gulf Stream, although they still needed further study.
Comments