When it comes to water, wind speed matters less than the size of the wind field. Ten years ago today, Hurricane Ike made landfall as "only" a Category 2 hurricane along Galveston Island near Houston. Though Ike had 110mph winds at landfall, it had grown very large over the Gulf of Mexico, and this large size allowed it to develop an enormous amount of "integrated energy" that manifested itself as a devastating storm surge. With about $30 billion in damages, Hurricane Ike was, at the time, the second-costliest US hurricane on record. As of Thursday morning, Hurricane Florence has weakened to 110 mph as it contends with slightly increased wind shear and drier air. Technically this means Florence is no longer a "major" hurricane, and it may not be when it reaches the North Carolina coast early on Friday morning. Practically, however, that won't matter when it comes to storm surge and inland rainfall. The simplest, most common metric for the measurement of a storm's intensity is maximum wind speed, and certainly this matters in terms of pure destructive potential when it comes to, say, losing a roof or propelling debris through the air. But when it comes to water, the maximum wind speed matters less than the size of the wind field for both storm surge and the destructive power of waves moving onshore. And Florence is a large storm, with hurricane-force winds extending outward up to 80 miles from the center and tropical-storm-force winds outward up to 195 miles. The primary example of this is 2012's Hurricane Sandy, which had modest 80mph winds by the time it reached the New York and New Jersey areas. But because the storm was so large it produced a destructive storm surge in New York City and caused an estimated $65 billion in damage in the United States. (At the time, it became the second costliest US hurricane but has since been supplanted by Harvey and Maria, both in 2017). Thursday, September 13th is the 10 year anniversary of Hurricane Ike. The storm's 15'+ surge devastated the Bolivar peninsula. The outer banks of North Carolina may face a similar threat from Florence. Our thoughts are with you Carolina. Prep for the worst, and hope for the best The area to the north of Florence's landfall along the North Carolina coast—storm surge is always worst to the "right" of a storm's center, where its rotation pushes water onshore—is less populated and developed than the New Jersey and New York shores. But the storm surge will be no less devastating for homes and businesses located there. Areas from Cape Fear to Cape Lookout face a potential 9 to 13 feet of storm surge, the National Hurricane Center warns, on top of the normal tides. Florence's slow movement over the next two or three days will add another element of uncertainty. Meteorologist Greg Diamond has noted that areas along the coast of North Carolina on the right side of the storm could experience a significant storm surge through multiple high tide cycles, which would have a cumulative battering effect. The National Hurricane Center has, accordingly, warned that "Life-threatening, catastrophic flash flooding and prolonged significant river flooding are likely over portions of the Carolinas and the southern and central Appalachians late this week into early next week, as Florence is expected to slow down as it approaches the coast and moves inland. " It is important to recognize that, while attention will be focused on coastal impacts from Florence, inland flooding will remain a problem for some areas well into next week.
As Hurricane Florence bears down on the East Coast, its intensity is coming into sharp relief. The Category 2 hurricane had sustained winds of 105 miles per hour at the time of writing, with tropical storm-force winds stretching more than 335 square miles in all directions. Rainfall was predicted to reach 40 inches in regions of coastal Carolina, and Wilmington — which just had its rainiest year to date — might get eight months worth of rain in three days. One firm closely tracking Florences progress is The Weather Company, the weather forecasting division of IBM whose consumer-facing brands include the weather.com, intellicast.com, and Weather Underground. Its systems analyze more than 100 terabytes of third-party data and generate 25 billion customized regional models daily. Our models provide a forecast evolution of what the atmosphere is going to look like in the coming days, Dr. James Belanger, a senior meteorological scientist for The Weather Company, told VentureBeat in an interview. The system keeps in memory what the forecasts are all across the globe. One of the predictive technologies its data scientists tap is Deep Thunder, an IBM research project spun out of the companys Deep Computing initiative. Leveraging public satellite imagery, proprietary datasets, and sensors — including more than 250,000 personal weather stations and smartphone barometer readings — its able to produce short-term, hyperlocal weather forecasts for local governments and corporate clients alike. In a pilot in Rio de Janeiro, Deep Thunder predicted floods and anticipated where storms might trigger mudslides. And in the U.S., it enabled a utility company to pinpoint where storms were likely to bring down power lines. Its capable of even greater precision, Belanger explained. Using historical weather data, it can create probability distributions by modeling synthetic storms (think a computer-generated tropical cyclone.) And later this year, itll be used to issue probabilistic snowfall reports seven days in advance. Another tool in The Weather Companys arsenal are forecast runs from government agencies like the National Weather Service, which are typically released 10-15 days in advance of shifting weather patterns. Theyre ingested and run through adaptive regression models — statistical models that automatically plot interactions between variables — that apply weight and bias corrections for any given target location. Its a really scalable system, Belanger said. The calibration information is continually updated … Were able to distribute temperature and precipitation forecasts for anywhere in the globe. So hows The Weather Data use that backend to track high-profile storms like Florence? While it defers to the National Weather Service on forecasted storm impacts — going so far as to impose what Belanger calls guardrails and adjustments that ensure its messaging remains in alignment — its consumer team employs analytics to identify the best times to issue alerts. They look at the times of day when consumers are most actively engaging our content, Belanger said, and make sure to keep people informed of rainfall and flood threats. Its an important way we deliver messages and communications to people who are the most vulnerable.