Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 3:46 PM GMT on April 15, 2007
Water levels are starting to rise along the Atlantic coast from New Jersey to Maine, as the Nor'easter of 2007 prepares to enter its explosive deepening phase. At 2pm EDT, the center of the storm was over North Carolina, with a central pressure of 987 mb. Winds over the ocean are starting to rise significantly. Sustained winds of tropical storm force--44 mph, gusting to 50--were observed at 2pm EDT just south of Long Island at Ambrose Light. The storm is expected to move northeastward and cross out to sea off the Delaware coast this evening, and rapidly intensify to a central pressure of 975 mb as it tracks up the coast of New Jersey and passes directly over New York City.
Figure 1. Tidal levels observed at The Battery in New York City as of 2pm EDT Sunday April 15. Note that water levels were two feet above normal at the time, but it was low tide. High tide tonight (near 00 GMT, or 8pm EDT) will see significant coastal flooding. The Battery is located on the southern tip of Manhattan Island. Image credit:NOAA Tides and Currents website.
Water levels at The Battery in New York City were two feet above normal at 2pm, but coastal flooding had not yet occurred, since it was low tide. The tidal range at New York City is six feet today, and some of the highest tides of the year are expected tonight and Monday, due to the arrival of the new moon. When the Sun, Earth, and Moon all line up (which happens during each new moon and full moon), the highest high tides of the year occur. The strongest winds of the 2007 Nor'easter will affect New York City during high tide tonight at 7:30pm. The expected 3-4 foot storm surge in western Long Island Sound near New York City would match the levels seen there in the "Perfect Storm" of October 31, 1991 (Figure 2), and the March 13, 1993 Storm of the Century. The worst coastal flooding in recent years in New York City occurred during the December 11-12 1992 Nor'easter, which damaged as many as 20,000 homes and forced almost 2,000 people to take refuge in emergency storm shelters. Storm surges of 4 feet were recorded near New York City (Figure 3), and 5.5 feet in western Long Island Sound. Some computer models are forecasting a 4-6 foot storm surge over Long Island Sound tonight, and it is possible that the flooding levels seen in the December 1992 Nor'easter will be exceeded. The timing of the peak of this surge with the high tide cycle will be critical, as will the exact track of the storm. If the storm does track directly over New York City tonight, the relatively calm winds near the center may allow some of the storm surge to flow out of Long Island Sound.
Figure 2. Tidal levels observed at The Battery in New York City during the "Perfect Storm" of October 31, 1991. This storm brought the second highest storm surge to New York City observed in recent years.
Figure 3. Tidal levels observed at The Battery in New York City during the Nor'easter of December 11-12, 1992. This storm brought the highest storm surge to New York City observed since tidal record began at The Battery in 1966.
The same storm also brought heavy snow to Kansas and baseball-sized hail to Texas Saturday, and more severe weather is occurring today across the region where the cold front is passing. However, the main story of this storm will be coastal flooding in the Northeast, and wind damage from tropical-storm force winds. Freshwater flooding from the storm's 3-5 inches of rain could also cause localized flooding problems.
Tune in tonight, I'll have an update, and there will also be a separate update on the East Coast Winter Storm blog.
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