WunderBlog Archive » Category 6™

Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.

Matthew, Atlantic’s Deadliest Hurricane in 11 Years, Heads for Georgia, S. Carolina

By: Bob Henson and Jeff Masters 10:15 PM GMT on October 07, 2016

Friday brought very good news and very bad news on Hurricane Matthew. The powerful storm stayed just far enough offshore to spare Florida its worst, but reports from Haiti showed that Matthew was far more of a disaster than initially thought. Now that relief workers and other offiicals have made it to Haiti’s hard-hit southwest corner, they report catastophic conditions and a mounting death toll. More than 800 people have died in Haiti, and that number is expected to grow, perhaps dramatically, as rescue and relief efforts continue.

As of 5 pm EDT Friday, the center of Matthew was located about 40 miles east of Jacksonville Beach, FL, moving north at 12 mph. Matthew’s top sustained winds had dropped to 110 mph, making it a high-end Category 2 storm. According to Phil Klotzbach (Colorado State University) Matthew’s impressive duration of just over seven days as a major hurricane (Category 3 or stronger) put it in a tie for the fifth-longest such stretch since satellite observations began in the Atlantic in 1966.

Figure 1. MODIS satellite image of Matthew taken at 12 pm EDT October 7, 2016. At the time, Matthew was a Category 3 storm with 120 mph winds. Image credit: NASA.

Matthew’s track: a parallel reality
Matthew jogged just far enough to the east over the Bahamas so that its generally well-predicted track parallel to the central and north Florida coast kept the center just offshore--far enough so that the hurricane’s western eyewall only nicked the coastline. The top wind gust reported thus far was 107 mph at Cape Canaveral, which juts out a few miles into the Atlantic and was thus closer to Matthew’s higher winds. The impact was much less than feared at Kennedy Space Center, mainly limited to scattered debris and some roof damage. Elsewhere along the Florida coast, top sustained winds were surprisingly low, generally in the tropical storm range, resulting in fairly minor damage overall. Daytona Beach received sustained winds of at least 46 mph, with gusts as high as 67 mph. Saint Augustine notched peak sustained winds of 51 mph, with gusts to 67 mph.

Matthew is carrying out a classic round-the-bend path on the west side of a zone of high pressure over the subtropical Atlantic. The latest NHC forecast keeps Matthew hugging the Southeast coast all the way to central South Carolina by Saturday afternoon. Matthew’s gradual weakening should continue, but it may still be a hurricane as it nears Charleston, SC, and a brief landfall is possible if the path arcs slightly more leftward than expected.

Figure 2. Heavy waves caused by Hurricane Matthew pounds the boat docks at the Sunset Bar and Grill, October 7, 2016 on Cocoa Beach, Florida. Image credit: Mark Wilson/Getty Images.

Figure 3. A truck negotiates around trees downed by Hurricane Matthew, Friday, Oct. 7, 2016, in Daytona Beach, Florida. Image credit: AP Photo/Eric Gay.

Storm surge and inland flooding are now the main threat from Matthew
Matthew’s track nudged ever closer to the coast on Friday afternoon, causing progressively more serious problems with storm surge. Much of historic Saint Augustine, FL, was under water for several hours close to the midday high tide on Friday (see embedded tweet below). Althena Masson (@Wx_Goddess), a meteorologist and doctoral student at the University of Toronto from the Saint Augustine area, filed numerous tweets from the scene. “Matthew, you will not take my thesis research!” she exclaimed at one point, later evacuating to the second story of her home. Water also poured across the barrier-island community of Jacksonville Beach, as captured by a news helicopter. One videographer captured a huge tree being uprooted in Jacksonville, where Matthew may deliver the most severe hurricane-related impacts since Dora in 1964.

NHC projects that inundation levels of up to 11 feet are possible along the Georgia and southern South Carolina coasts as Matthew approaches. Already on Friday afternoon, Matthew was producing once-in-a-century high water levels ahead of its track. At Fernandina Beach, FL, the early-afternoon high tide combined with the storm surge for a crest of 4.11 feet above mean high high water (MHHW) on Friday afternoon. This is the highest water observed at Fernandina Beach in more than 100 years, beating the peak MHHW of 3.9 feet observed during Hurricane Dora (1964) and topped only by the reading of 6.94 feet recorded on October 2 during the Hurricane of 1898. On Georgia’s Brunswick River, at Village Pier on St. Simons Island, Georgia, a river crest of 6.15 feet observed around 5 pm EDT Friday beat the reading of 5.93 feet observed there on February 7, 1993. Based on the surge values during low tide Friday, Fort Pulaski, Georgia, is likely to see water at least 4 to 5 feet above MLLW during the high-tide cycle centered around midnight Friday night. In records going back to the 1930s, the highest reading observed at Fort Pulaski is 3.4 feet above MLLW, recorded on October 15, 1947. Comparable levels of surge may extend to the Low Country of South Carolina, a highly vulnerable area. The National Weather Service office in Charleston is warning of the potential for life-threatening surge in some coastal locations between Charleston and the Georgia border. In its afternoon weather discussion, the office stated:

”Many beach communities will see extensive damage to beach front properties due to a combination of large breaking waves, high surge and dangerous winds. Homes at Edisto Beach [were] already being undermined at high tide earlier this afternoon and Tybee Island saw significant flooding along the beach front. Expect considerably worse conditions tonight and it can not be stressed enough that how dangerous this scenario is.”

You can monitor surge as it moves up the Southeast coast using our wundermap with the “Storm Surge” layer turned on (note that these values are relative to mean low low water rather than mean high high water). Two other good sources are the NOAA Tides and Currents storm page for Matthew, and storm surge expert Dr. Hal Needham’s U-SURGE page for Matthew. Dr. Needham has some excellent information on the storm surge history of the north Florida to southern South Carolina coast in a Friday morning blog post, The "Protected Coast" is Now the Most Dangerous Place of All.

Very heavy rains are the other looming threat from Matthew. Totals of 10” to 15” may occur along the immediate coast ahead of Matthew, and 3” - 10” can be expected over large parts of the eastern Carolinas. These rains may produce dangerous flooding well inland. Wind gusts could reach the 40-60 mph range over the eastern Carolinas from Saturday night into Sunday. Given the wet soils that preceded Matthew, compounded by any rains from the hurricane itself, many trees could be felled and widespread power outages are possible.

Figure 4. Three-day forecasts issued for Hurricane Katrina (left) on Friday, August 26, 2005, and for Hurricane Matthew (right) on Tuesday, October 4, 2016. The red circles denote the actual locations of each storm three days after the forecasts were issued. The "cone of uncertainty" is based on forecast errors over the prior five years, so it was narrower for Matthew than for Katrina. Image credit: NOAA/NWS/NHC.

Matthew’s forecast: Accuracy goes head-to-head with geometry
People along the central Florida coast can be forgiven for thinking that the NHC forecast for Matthew was a bust. Millions of folks on the coast who were warned about the potential of fierce Category 3 winds ended up with sustained winds barely above tropical-storm strength. Yet the actual forecast for Matthew--the storm itself--was remarkably accurate. The right-hand side of Figure 4 shows the 3-day forecast issued by NHC for Matthew on Tuesday morning, October 4. Matthew’s location on Friday morning was within 75 miles of the 3-day forecast position, well within the “cone of uncertainty”. The cone width is based on error statistics for the five preceding hurricane seasons; at any point in the forecast, there’s a one-third chance that the hurricane will fall outside the cone. On the left-hand side of Figure 4, we see that the forecast for Katrina issued three days before landfall (on Friday, August 26, 2005) was far less accurate, with the actual position of Katrina more than 150 miles from the 3-day forecast location. Even with the wider cone of uncertainty circa 2005 (reflecting the greater track errors of 10-15 years ago), Katrina’s 3-day position was barely within the cone.

Figure 4 also shows us the geographic challenge of forecasting Matthew. Had Florida’s coast been oriented from west to east, like the central Gulf Coast, then Matthew would have slammed directly into some point on the coast, as Katrina did, with significant wind damage a near-certainty. Instead, Matthew tracked virtually parallel to the coast, which meant that the relatively minor (but impact-significant) forecast error relative to the coast was extended over a much longer time period.

Figure 5. Small towns along the western coast of Haiti suffered extreme damage from storm surge during Hurricane Matthew. This photo was tweeted by a United Nations aerial survey. Image credit: United Nations Stabilization Mission in Haiti (MINUSTAH), via univision.com.

Yet another disastrous hurricane for Haiti
Matthew’s death toll makes it the deadliest year for hurricanes in Haiti since 2008, when four storms--Fay, Gustav, Hanna, and Ike--dumped heavy rains on the impoverished nation. The rugged hillsides, stripped bare of 98% of their forest cover thanks to deforestation, let flood waters rampage into large areas of the country. According to reliefweb.org, Haiti suffered 793 killed, with 310 missing and another 593 injured due to hurricanes in 2008. Matthew is the deadliest Atlantic hurricane since Hurricane Katrina of 2005, which killed 1833 people (though Hurricane Stan of 2005 was indirectly responsible for 1000 - 2000 flooding deaths that year, as well.) So far, Matthew does not make it on the list of the 30 deadliest Atlantic hurricanes in history, which consists of storms that killed at least 1,500 people.

We’ll be back with our next update on Matthew by Saturday morning.

Bob Henson and Jeff Masters



The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.