The history of high-water levels (storm tide) in Wilmington, North Carolina since 1935. Prior to Hurricane Florence, the highest storm tides were during Hurricane Matthew in 2016 and Hurricane Hazel in 1954. Note that sea level in Wilmington has risen by close to 8 inches since Hazel struck. The red line marks a water level that has a 1% chance of occurring per year: a 1-in-100-year event. Florence’s water level fell above this line, making it a rarer than 1-in-100-year event. Graphic: NOAA / NWS / MDL

Dr. Jeff Masters
14 September 2018            

(Weather Underground) –  Hurricane Florence was only a Category 1 storm on the Saffir-Simpson wind scale when it struck, but the hurricane’s massive wind field brought a huge storm surge to the coast that broke all-time high-water records as much as 65 years old. Two of the three tide gauges on the south coast of North Carolina that have long-term records going back to 1954 or earlier (Beaufort and Wilmington) had those records fall on Friday, and the other station (Wrightsville Beach) notched its third highest water level on record. Long-term storm surge records like this are very difficult to break, and speak to how large and dangerous Florence’s storm surge has been. The threat from Florence's surge is not over yet, either--the National Hurricane Center was warning on Friday night that Florence's storm surge could still bring water levels up to 12 feet above ground in eastern North Carolina.

The largest storm surges reported on Friday from Florence were in New Bern and Emerald Isle, North Carolina, where water levels reached 10.1 feet and 7.0 feet above ground, respectively, according to the National Hurricane Center. New Bern, a city of about 30,000 residents, saw significant storm surge flooding after the Neuse River overflowed its banks and swept into the town. Craven County spokeswoman Amber Parker told ABC News that some people were trapped on their roofs. "I would say certain areas of New Bern are very desperate," she told the network. At least 200 people had been rescued on Friday morning, with another 120 people still awaiting rescue as of 10:30 a.m. Friday morning in New Bern, city spokeswoman Colleen Roberts told the Associated Press.

A record 1-in-100-year high water level at Wilmington, NC

The record for all-time highest water level at Wilmington, NC, where records extend back to 1935, fell on Friday. At 3:30 pm EDT, the water level (storm tide) reached 3.60’ above the high tide mark (Mean Higher High Water, or MHHW), beating the all-time record of 3.48’, set on 8 October 2016, during Hurricane Matthew. In third place is the 3.47’ water level set on 15 October 1954 during Hurricane Hazel. The water was pushed in by Florence’s unrelenting onshore winds, which were sustained at 48 – 64 mph during the period 8 am – 8 pm EDT Friday. According to data from NOAA, the new record water level rated as more than a 1-in-100-year event (less than a 1 percent chance of happening in a given year). As of this writing (8 pm EDT), the storm surge was still rising, and stood at 4.9 feet. Since low tide was approaching, though, water levels (the storm tide) had fallen below the record high mark.

A record-high water level observed at Beaufort

The history of high-water levels (storm tide) in Beaufort, North Carolina since 1953. Prior to Hurricane Florence, the highest storm tide was during Hurricane Hazel in 1954 and Hurricane Ione in 1955. Note that sea level in Beaufort has risen by close to 8 inches since Hazel struck. The red line marks a water level that has a 1 percent chance of occurring per year: a 1-in-100-year event. Florence’s water level would have been a 1-in-100-year event had it occurred in 1954, but now is closer to a 1-in-50-year event. Graphic: NOAA / NWS / MDL

Friday morning at 3:24 am EDT, a storm surge of 5.51 feet was recorded at the Beaufort, NC gauge. Fortunately, the tide was receding rapidly at that point, but the storm tide (the combination of the surge and tide) still set an all-time water level at the gauge near 2 am: 3.74’ above the high tide mark (Mean Higher High Water, or MHHW). According to NOAA, this broke the previous all-time water level record of 3.39’ above MHHW set on 15 October 1954, during Category 4 Hurricane Hazel (and tied on 19 September 1955 during Category 2 Hurricane Ione). Note that sea level in Beaufort has risen by about 0.7 feet since the time of Hazel, largely due to human-caused climate change, and Florence would not have been able to break Hazel’s record without it. [more]

Florence’s 1-in-100-Year Storm Surge Breaks All-Time Records

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