Figure 1. AVHRR visible satellite image of Hurricane Hugo taken on September 21, 1989. Hugo had intensified to a formidable Category 4 hurricane with 135 mph winds.
On Isle of Palms, a barrier island adjacent to Sullivan's Island, the mayor and several police officers were sheltering in a 2-story building which lay at an elevation of ten feet. As related in a story published in the St. Petersburg Times, they heard the following bulletin on the radio at 10:30pm the night Hugo made landfall:
"The National Weather Service has issued a storm surge update. It appears that the storm surge will be greater than anticipated. It is now expected to reach a height of 17 to 21 feet."
"Mom didn't raise an idiot," said the one cop with the most sense, and he convinced the others to get off the island. They left the island by driving at 5 mph through horizontal sheets of rain and hurricane-force wind gusts over the Ben Sawyer Bridge, which connected Sullivan's Island to the mainland. As they crossed onto the bridge, they passed over a large bump--the bridge and road bed were at different levels. Not good. While crossing the bridge, they could feel it swaying and straining, and heard the sound of metal, twisting and grinding and breaking. They made it, but only barely--minutes later, the hurricane tore the center span of the bridge from its connection on both ends, leaving it a twisted ruin in the bay.
Figure 2. The Ben Sawyer Bridge connecting Sullivan's Island to Charleston, South Carolina, after Hurricane Hugo. Image credit: NOAA Photo Library.
Hugo's storm surge
In McClellanville, on the coast thirty miles northeast of Charleston, between 500 - 1100 people took refuge at the designated shelter for the region, Lincoln High School. Lincoln High is a one-story school, mostly constructed of cinder block, located on the east side of Highway 17, and was believed to be at an altitude of twenty feet. McClellanville is about 4 - 5 miles inland from the open ocean, but lies on the Intracoastal Waterway, so is vulnerable to high storm surges. Near midnight on the 21st, a storm surge of twenty feet poured into Bulls Bay just south of McClellanville, and funneled into the narrow Intracoastal Waterway. Water started pouring into the high school and rose fairly rapidly. Within minutes, people were wading around up to their waists, the water still rising. In the school cafeteria, many refugees gathered on a stage at one end, putting children up on tables. The elevated stage kept them above water; others floated in the water. Another group was in the band room, which had a much lower ceiling than the cafeteria. They had to stand on desks and push out the ceiling tiles for more breathing room, as the water rose within 1 - 2 feet of the ceiling. Fortunately, Hugo's storm surge peaked at that time, at about 16 - 17 feet (Figure 4), and the people sheltering at Lincoln High were spared.
Figure 3. Estimated storm surge (height above ground) as estimated by NOAA's storm surge model, SLOSH. McClellanville (upper right) received a storm surge estimated at 16 - 17 feet.
According to Dr. Stephen Baig, the retired head of the NHC storm surge unit, the back-story is this: To build Lincoln High School, which lies at an altitude of ten feet, the local school board used the same plans that were drawn up for another school that is west of Highway 17, and that IS at 20 feet elevation. Not only the same plans, the same set of working drawings. Those working drawings showed a surveyed elevation of 20 feet above datum (probably NGVD29). Apparently Lincoln High was constructed either without benefit of elevation survey or the plans were not annotated with its site elevation. When the Red Cross inquired as to its utility as an evacuation site, whoever looked at the plans saw the surveyed elevation at 20 feet. That is what the Red Cross published. That is why the school was a designated shelter. Since that near-tragedy, the Red Cross requires a new elevation survey for every potential storm shelter. I think that at the time this was discovered all the designated shelters also were re-surveyed, just to be sure that no similar Lincoln High problems were waiting to happen.
Only one person died from Hugo's storm surge, a woman who sheltered in her mobile home that got struck by the surge. Her death was one of only ten deaths that have occurred due to storm surge in the U.S. in the 35 years between 1969 - 2005 (after the 100+ storm surge deaths due to Hurricane Camille of 1969, and before the 1000+ storm surge deaths due to Hurricane Katrina). This amazingly low death toll can be attributed to four factors:
1) Greater understanding of the storm surge and better storm surge forecasts issued by the National Hurricane Center, thanks to such tools as the SLOSH storm surge model.
2) The excellent job NWS/NHC/FEMA and state and local Emergency Managers have done educating the public on the potential surge they can expect.
3) The success local government has had making evacuations of low-lying areas work.
4) Luck. The 20+ storm surge deaths on the Bolivar Peninsula in 2008 from Hurricane Ike and the 41 storm surge deaths in New York and New Jersey from Hurricane Sandy show that there are still plenty of stubborn, unlucky, or uneducated people who will die when a significant storm surge hits a low-lying populated coast. To illustrate, I'll present an email sent to me from a resident in the Florida Keys during the Keys evacuation order for Hurricane Ike in 2008: I hate to bother you again, but we live on Marathon in the Florida Keys on the Atlantic side, and my husband says that if we see water coming up from storm surge and have an inch of water in our house, that we can outrun the storm surge in our car. Can you please tell me if there is any way this can possibly be true? P.S., I don't know of anyone who lives down here who is planning on evacuating for Ike. Everyone says they are staying. My response: You are right to be skeptical of your husband's idea. Once the surge begins, it typically rises very quickly. If you wait until the water is an inch high before trying to outrun the surge, the odds are that the surge will rise to over a foot high before you get your car out of the driveway. If the water is a foot high, the typical 10 - 15 mph speed of the storm surge's current has enough force to sweep a car away. The Keys have only one road out, and the storm surge will likely be moving perpendicular to the road, cutting off the only escape route well before the hurricane arrives. One of these days, there are going to be a lot of people who fail to evacuate caught and killed in the Keys by the storm surge from a major hurricane.
Kudos and links
I thank Ken Bass for providing the details on the Lincoln High storm surge near-disaster. Ken has written a very readable book about a fictional Category 4 hurricane hitting New York City.
Hurricanes-blizzards-noreasters.com has a web page with links to tons of Hurricane Hugo stories. Included are links to YouTube videos of a "Rescue 911" episode that interviewed survivors of the Lincoln High storm surge scare. The show also did a re-creation of the event.
Our Historical storm surge page has SLOSH model storm surge animations of Hurricane Hugo's landafall, as well as of 39 other famous hurricanes.
My favorite disaster relief charity, Portlight, recommends this 47-minute video documentary about Women's Stories of Reconstruction after Hurricane Hugo hit McClellanville South Carolina in 1989.
If you've never read my story of flying into Hurricane Hugo, do it. Twenty-five years ago on September 15, 1989, I was the flight director on the first hurricane hunter mission into the hurricane. We intercepted Hurricane Hugo as it approached the Caribbean islands, just before Hugo's destructive rampage through the Caribbean and into South Carolina. The crew of the airplane were the first people to encounter the mighty hurricane--and very nearly became its first victims. The mission remains the most harrowing flight ever conducted by the NOAA hurricane hunters. I served as flight meteorologist on that flight, and feel fortunate indeed to be able to tell the story.
Quiet in the Atlantic and Eastern Pacific
Jumping back to September 21, 2014, it's quiet in the Atlantic, where tropical wave 95L off the coast of Africa remains disorganized. In their 8 am EDT Sunday Tropical Weather Outlook, NHC gave the wave 2-day and 5-day odds of development near 0%. This wave will bring heavy rain showers to the Cape Verdes Islands on Sunday and Monday.
In the Eastern Pacific, minimal-strength Tropical Storm Polo continues to weaken due to high wind shear as it heads west-northwest out to sea. All watches and warnings have been dropped in Mexico for Polo. A weak area of low pressure (99E) a few hundred miles south of the Guatemala/Mexico border was given 5-day odds of development of 40% by NHC in their 8 am EDT Sunday Tropical Weather Outlook. Our reliable computer models do not show 99E being a threat to make landfall during the next five days.
In the Western Pacific, Tropical Storm Fung-Wong made landfall in southern Taiwan Sunday morning with sustained winds near 55 mph, knocking out power to 40,000 customers. Fung-Wong brushed the northern end of the Philippines' Luzon Island on Friday morning with sustained winds of 45 mph, bringing torrential rains that flooded Manila and killed ten people. The storm is headed north towards a third landfall in Mainland China, which is expected to occur Monday evening.
Hurricane expert Steve Gregory has a more detailed look at the tropics in his Sunday afternoon post.
Jeff Masters
No comments:
Post a Comment