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Sandy already producing a record storm surge
The National Weather Service in Atlantic City, NJ said that isolated record storm surge flooding already occurred along portions of the New Jersey coast with this morning's 7:30 am EDT high tide cycle. As the tide goes out late this morning and this afternoon, water levels will fall, since the difference in water levels between low tide and high tide is about 5'. However, this evening, as the core of Sandy moves ashore, the storm will carry with it a gigantic bulge of water that will raise waters levels to the highest storm tides ever seen in over a century of record keeping, along much of the coastline of New Jersey and New York.
The peak danger will be between 7 pm - 10 pm, when storm surge rides in on top of the high tide. The full moon is today, which means astronomical high tide will be about 5% higher than the average high tide for the month, adding another 2 - 3" to water levels. This morning's 9:30 am EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.9 on a scale of 0 to 6.
However, the destructive potential of the storm surge was record high: 5.8 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed since 1969, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003.
Sandy's storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' and a storm tide of 9.5' above MLLW to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy's storm surge is expected to be 10 - 12' above MLLW. Since a storm tide of 10.5' is needed to flood the subway system, it appears likely that portions of the NYC subway system will flood. The record highest storm tide at The Battery was 10.5', set on September 15, 1960, during Hurricane Donna.
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2280
The peak danger will be between 7 pm - 10 pm, when storm surge rides in on top of the high tide. The full moon is today, which means astronomical high tide will be about 5% higher than the average high tide for the month, adding another 2 - 3" to water levels. This morning's 9:30 am EDT H*Wind analysis from NOAA's Hurricane Research Division put the destructive potential of Sandy's winds at a modest 2.9 on a scale of 0 to 6.
However, the destructive potential of the storm surge was record high: 5.8 on a scale of 0 to 6. This is a higher destructive potential than any hurricane observed since 1969, including Category 5 storms like Katrina, Rita, Wilma, Camille, and Andrew. The previous highest destructive potential for storm surge was 5.6 on a scale of 0 to 6, set during Hurricane Isabel of 2003.
Sandy's storm surge will be capable of overtopping the flood walls in Manhattan, which are only five feet above mean sea level. On August 28, 2011, Tropical Storm Irene brought a storm surge of 4.13' and a storm tide of 9.5' above MLLW to Battery Park on the south side of Manhattan. The waters poured over the flood walls into Lower Manhattan, but came 8 - 12" shy of being able to flood the New York City subway system. According to the latest storm surge forecast for NYC from NHC, Sandy's storm surge is expected to be 10 - 12' above MLLW. Since a storm tide of 10.5' is needed to flood the subway system, it appears likely that portions of the NYC subway system will flood. The record highest storm tide at The Battery was 10.5', set on September 15, 1960, during Hurricane Donna.
http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2280