Tag Archives: 2018 North Atlantic Hurricane Season

2018 Atlantic Hurricane Season: Your Questions Answered

I had the privilege of joining Property Casualty 360 for a Facebook Live video discussion last week, together with my colleague Wallace Hogsett, client manager at RMS. Danielle Ling, associate editor at PC360 was the host of the discussion, entitled “2018 Hurricane Season: Where Are We Now?”.

We began by providing a perspective on the impacts of this season’s hurricanes. The two big hurricane events to impact the U.S. in 2018 (so far) have obviously been Hurricanes Florence and Michael, but each possessed very different characteristics. Florence maintained Category 4 status on the Saffir-Simpson Hurricane Wind Scale (SSHWS) for around a week, before wind shear tempered it to a Category 1 as it made landfall near Wrightsville Beach, North Carolina on September 14. While many areas were subject to significant wind gusts and storm surge, Florence was primarily a flood event, causing historic rainfall and inland flooding throughout the Carolinas.

On the other end of the scale, Wallace stated how Michael was a classic intense hurricane — the most intense to make landfall in the U.S. since Andrew in 1992 — almost reaching Category 5 status upon its landfall in Mexico Beach on October 10. The scenes of structures reduced to their “slabs” with just their foundations left showed that this was primarily a wind and storm surge event. In total, damages stretched from the Florida Panhandle region through the Southeast and the Carolinas.

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2018 North Atlantic Hurricane Season: Where Are We Now?

In the last month or so, two significant North Atlantic hurricane events have brought the latter half of the current hurricane season into sharp focus — and what marks these two events out was how different they were. With Hurricane Florence making landfall on September 14 in North Carolina, this event was one of the most intense storms to go above 30 degrees north in recent history.

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Hurricane Florence: Rainfall up to a 1,000-year Return Period

Florence’s much anticipated landfall occurred at 11:15 UTC (7.15 a.m. local time) today, Friday, September 14, near Wrightsville Beach, North Carolina, as a Category 1 hurricane. Florence remains just within the Category 1 hurricane classification on Saffir-Simpson Hurricane Wind Scale (SSHWS); as of the 18:00 UTC National Hurricane Center (NHC) advisory today, maximum sustained winds were 75 miles per hour (120 kilometers per hour). Previous observations showed that at Cape Lookout there were sustained winds of 83 miles per hour (133 kilometers per hour) and gusts of 106 miles per hour (170 kilometers per hour). Florence is now moving slowly toward the west at near five miles per hour (7 kilometers per hour).

Over the coming 36 hours, Florence is expected to meander into northern South Carolina and then progress further inland across the western Carolinas and into the Appalachian Mountains through the early part of next week.

The expectation that surge and inland flooding, rather than wind, would be the primary hazards associated with Florence was quickly realised as the storm approached the Carolinas coastline yesterday.

Excessive rainfall and dangerous storm surge present the greatest threat over the next few days. The potential for heavy rainfall has extended to the south and west given the change in projected track over the last 48 hours. Projections of over 15 inches (380 millimeters) of rain now cover much of southern North Carolina and northeast South Carolina — much of North Carolina is expected to receive in excess of six inches (152 millimeters) of rain.

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Florence Update: September 13

Over the last 24 hours, the structure and forecast track of Hurricane Florence has evolved significantly as the storm begins to impact the Carolinas, but the material wind, storm surge and flood threat it poses to the Southeastern and Mid-Atlantic U.S. remains.

As of 1200 UTC yesterday (September 12), Florence’s wind field was large and powerful as the storm inched closer to the U.S. coast through favorable environmental conditions. According to RMS HWind analyses, which utilize more than 30 public and private observational data sources to generate objective, ground-truth-based tropical cyclone wind field analytics, maximum 1-minute sustained winds were estimated to be 124 miles per hour (199 kilometers per hour) (Figure 1 below), placing the storm squarely in the Category 3 range on the Saffir Simpson Wind Scale.

In addition, the Integrated Kinetic Energy (IKE), an indicator of tropical cyclone strength and damage potential, was estimated to be 104 Terajoules (TJ), putting it on par with historical events like Frances (2004), Gustav (2008), and Isabel (2003).

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Florence: A New Twist in the Tale

No hurricane landfall forecast is simple. But looking back at the forecast tracks for Hurricane Florence from the National Hurricane Center (NHC) and the ensemble members of the leading global forecast models a couple of days ago, what stood out was how relatively straightforward they were. Florence was anticipated to make a steady, assured progress directly towards the Carolinas, make landfall, and move directly inland.

In a somewhat remarkable turn of events that few, if any, models predicted 48 hours ago, Florence is now expected to stall over, or very near to, the Carolina coastline.

The huge shift in the forecast guidance is the anticipated result of a reduction in Florence’s steering flow due to two competing areas of high pressure. The hurricane is currently being steered across the southwestern Atlantic Ocean towards the southeastern U.S. around the southeastern periphery of a mid-level ridge centered northeast of Bermuda. As the system approaches land, it will come under increasing influence from a competing mid-level ridge that is forecast to begin building over the east-central United States later today. The net result of these competing steering flows will see Florence slow, meander, or even become stationary for possibly 48 hours before the system moves ashore.

This possibility could bring prolonged hurricane-force winds and storm surge throughout Saturday and Sunday, to coastal areas along North and South Carolina, and significant inland flooding to whole region.

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Hurricane Florence: A Rare Event

The forecasts for Hurricane Florence have been unusually consistent this far in advance of an anticipated landfall, projecting its path to cross the coast of the Carolinas at major hurricane intensity. For some perspective, if we look at the historical hurricane record since 1850, we find major hurricane landfalls are quite rare along this part of the U.S. Atlantic coastline:

RMS Reconstructed Loss values are based on wind and storm surge damage to present-day exposure, and not on trending forward historical losses

Over the past 167 years, there have been just nine major hurricanes that made landfall along the coast of North and South Carolina. So, on average we can expect one major landfall along this 490-mile stretch of coastline every eighteen and a half years. Certainly, a rare event. Only three of these storms — Hazel, Gracie, and Hugo — were Category 4 (on the Saffir-Simpson Hurricane Wind Scale) at landfall. There has never been a Category 5 landfall north of Florida.

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Fixated on Florence

It seems somehow fitting that a storm underwent rapid intensification today, the peak of the North Atlantic hurricane season. Indeed, as forecast, Florence grew impressively from a tropical storm to a  powerful Category 4 major hurricane — as of 1600 UTC on Monday, September 10, — with maximum sustained winds near 130 miles per hour (195 kilometers per hour), according to data from a recent National Oceanographic and Atmospheric Administration (NOAA) reconnaissance aircraft mission into the storm.

A ridge of high pressure is guiding Florence on a west-northwest to northwest path across the southeastern Atlantic Ocean between Bermuda and the Bahamas towards the southeastern U.S. Swells generated by Florence are already affecting Bermuda, with warnings of life-threatening surf and rip current conditions.

With each advisory, the chances of the storm missing the U.S. is rapidly narrowing. Most global models call for a landfall over the Carolinas as a major hurricane. Although the latest National Hurricane Center (NHC) “cone of uncertainty” includes the possibility of landfall between South Carolina and southern Virginia, there has been a strong, consistent guidance that a landfall over North Carolina is the most likely scenario. RMS HWind now shows that the two cities with the highest probability of greatest impact are both in North Carolina: Jacksonville and Wilmington.

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Central Gulf Coast Waits for Gordon’s Arrival

With alerts ranging from hurricane warnings to storm surge and flood watches, the central Gulf Coast states from Louisiana to the western counties of the Florida Panhandle await the arrival of Tropical Storm Gordon.

Located only 130 miles offshore of Mobile, Alabama, the outer rain bands of Gordon are beginning to bring deteriorating weather conditions to the Florida Panhandle and central Gulf coastline. A band of deep convection near its well-defined surface center and increased lightning activity near the inner core is indicative of an organized system with the potential to intensify. This is reflected in the latest National Hurricane Center (NHC) advisory, which calls for Gordon to be a Category 1 hurricane when it makes landfall in the north-central Gulf of Mexico coastline later tonight. Gordon looks set to be first hurricane to hit the contiguous U.S. this year, though it is not the first named system to threaten the central Gulf coastline; Alberto affected Louisiana and Alabama earlier in the season as a subtropical storm.

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Hurricane Season Outlook: Are We Heading for a Repeat of 2017?

With the 2018 Atlantic hurricane season underway, the (re)insurance industry is still reflecting on the events of last year. The 2017 season will be remembered as one of the most active, damaging, and costliest seasons on record, and specifically for the impacts of three storms: Harvey, Irma, and Maria.

RMS followed its longstanding strategy of delivering thoughtful and thorough analysis of all available data sources when responding to the events of 2017, including the use of instrumentation and in-person RMS staff research and reconnaissance.

For Harvey, we provided insight into our event response with regular updates from across the organization and outlined how we deployed the new RMS® U.S. Inland Flood HD Model in real-time to support a pipeline of flood deliverables for our clients. And for Maria, the use of the latest modeling innovations, up-to-date exposure and vulnerability data supported by on the ground presence and local knowledge helped us to provide clients with a clearer picture of post-event losses across the islands impacted.

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Recapping a Memorable 2017 Atlantic Hurricane Season

RMS has released its 2017 North Atlantic Hurricane Season Review documenting one of the most active, damaging, and costliest seasons on record. The 2017 season saw a total of 17 named storms, with ten of these storms reaching hurricane strength and occurring consecutively within a hyperactive period between August and October. The season will be remembered for its six major hurricanes and specifically for the impacts of three of these storms: Harvey, Irma, and Maria.

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