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Atlantic and East Coast Hurricanes 1900-98: a Frequency and Intensity Study for the Twenty-First Century

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Atlantic and East Coast Hurricanes 1900-98: a Frequency and Intensity Study for the Twenty-First Century Atlantic and East Coast Hurricanes 1900-98: A Frequency and Intensity Study for the Twenty-First Century Eddie Smith Wilmington, North Carolina ABSTRACT The Atlantic Ocean has spawned three hurricanes in three years that have made direct hits on the U.S. east coast. The unusual activity has sparked a question of whether East Coast landfalling hurricanes are increasing in frequency and intensity. Results of data studied from 1900-98 indicate that there is a slight increase in hurricane frequency and a fairly constant intensity level for East Coast landfalling hurricanes. The recent landfall of Hurricane Bonnie in North Carolina, Hurricane George in Alabama/Mississippi, and simulta- neous formation of four hurricanes in the mid-Atlantic during the 1998 season have stimulated the question of whether hurricanes are becoming more frequent and intense along the East Coast heading into the twenty-first century. 1 • Introduction FEMA98) advises that 10 tropical cyclones will de- velop in the North Atlantic each year, 6 may strengthen A recent study of hurricanes in the Gulf of Mexico to hurricanes, and 2 are likely to make landfall in the (Bove et al. 1998) has concluded that landfalling hur- United States. This sudden increase in averages was ricanes along the Gulf Coast states have not increased also noted by Caviedes (1991), who used time series in frequency or intensity this century. However, the analysis to show an increase in the number of hurri- East Coast has experienced three landfalling hurri- canes since the 1770s. canes, two of which were category 3, in the past three years. According to Degg (1992), exposure to natural hazards, especially hurricanes, is increasing along with 2. Hurricane information rising costs to East Coast states. The purpose of this paper is to examine the frequency and intensity of East A hurricane is a tropical storm with winds that have Coast landfalling hurricanes during the past 99 years. reached sustained speeds of 74 mph or more. The eye For the purpose of this research, landfalling hurricanes of a hurricane is usually 20 miles wide and can extend are categorized as storms with winds at least 74 mph 400 miles or more (Herbert and Taylor 1979). (64.3 kt) where the eye of the hurricane has moved Hurricanes can last for more than two weeks over open inland. Atlantic water and can travel on a path across the en- Herbert and Taylor (1979) noted the average num- tire East Coast. ber of hurricanes to make landfall in the United States The Atlantic hurricane season begins 1 June and was only one every four years. Today, the Federal ends 30 November every year. The peak of hurricane Emergency Management Agency (1998, hereafter season is mid-August through early October (Herbert and Taylor 1979; Landsea 1993). It is during this peak season when historically most hurricanes form (Landsea 1993). However, many hurricanes remain Corresponding author address: Eddie Smith, 4141 Hearthside over the ocean and never threaten land. Dr., #102, Wilmington, NC 28412. E-mail: [email protected] Hurricanes are rated by wind speed on the Saffir- In final form 9 July 1999. Simpson scale of 1-5. A category 1 hurricane produces ©1999 American Meteorology Society minimal sustained winds of 74-95 mph and the least Bulletin of the American Meteorological Society 2629 Unauthenticated | Downloaded 10/01/21 05:10 AM UTC Hurricane Center 1998). The high- TABLE 1. Saffir-Simpson scale and East Coast examples. est frequency of hurricanes might be occurring this last decade of the Scale category Sustained winds Damage Examples: century. The total of 20 hurricanes (mph) East Coast landfalls combined in 1995 and 1996 is the highest ever recorded for a two-year 1 74-95 Minimal Charley (1988), NC 2 96-110 Moderate Bob (1991), RI period (Avila and Pasch 1997). 3 111-130 Extensive Fran (1996), NC During the 1996 season, six out of 4 131-155 Extreme Andrew (1992), FL the nine were major hurricanes Hugo (1989), SC (Avila and Pasch 1997); and not 5 155 Catastrophic None since the Atlantic Ocean produced seven major hurricanes in 1961 (Source: National Hurricane Center 1998; Herbert and Taylor 1979; Henson 1998) have there been so many. According to National Hurri- amount of damage. On the other end of the scale, a cane Center data and FEMA98 numbers, during the category 5 hurricane produces winds in excess of past 99 years five hurricanes made landfall on the 155 mph with catastrophic damage. Table 1 illustrates United States coastline every three years—an average the Saffir-Simpson scale with examples of East Coast of 1.6 landfalling hurricanes per year. Two out of these landfailing hurricanes. five were considered category 3 or higher (FEMA98). Herbert and Taylor (1979) found on average that a category 4 or greater hurricane will strike the United 3. Data and methodology States once every five years, which has remained true through the 1990s. The most hurricanes to make land- To study if hurricane frequency and intensity have fall in the United States in one year was six in 1916 increased during the past 99 years, data were collected (Herbert and Taylor 1979). There have been 17 years from the National Oceanic and Atmospheric Admin- since 1900 with no U.S. landfalling hurricanes, the lat- istration (NOAA) and the National Hurricane Center est being 1981 and 1982. (NHC). Atlantic hurricane totals and category The results of East Coast hurricane frequency in strengths were gathered for each year between 1990 Fig. 2 reveal the total number of landfalling hurricanes and 1998. The author's East Coast study area includes the Florida peninsula (excluding the entire Florida Keys) north to Maine (see Fig. 1). Similar to the Bove et al. (1998) study, wind speeds at the time of landfall are used to gauge intensity; a major hurricane is de- fined as being category 3 or higher, and the frequency is measured as the total number of landf ailing hurricanes. 4. Frequency Herbert and Taylor (1979) identified the average number of hurricanes a year to be six at best using fig- FIG. 1. Area of research: U.S. east coast. ures from 1960 to 1979. Avila and Pasch (1997) noted the average was also six during the past 10 years. The frequency of hurri- canes in the Atlantic Ocean was low between 1900 and 1920, increasing to a modest level of activity between the 1940s and the 1960s (Caviedes 1991) before considerably slowing down during the 1970s and 1980s (National FIG. 2. U.S. A East Coast hurricane direct hits by decade, 1900-98. 2632 Vol. 80, No. 12,, December 1999 Unauthenticated | Downloaded 10/01/21 05:10 AM UTC calculated from northeast and southeast landfalls on TABLE 2. East Coast states and number of hurricane direct hits, the Atlantic Ocean side (the Labor Day Storm of 1935 1900-98. is not included)]. Table 2 also illustrates the lack of hurricane activity in the northeast United States. State No. of hurricane direct hits Florida 35 Georgia 5 5. Intensity South Carolina 14 North Carolina 26 All hurricanes are dangerous, but some are more Virginia 4 dangerous than others. Major hurricanes vary in inten- Maryland 1 sity from year to year and occur 95% of the time be- Delaware 0 New Jersey 1 tween August and October (Landsea 1993). The New York 9 strongest hurricane ever recorded was the category 5 Connecticut 8 Florida Keys storm of 1938 (Herbert and Taylor 1979). Rhode Island 5 A category 5 hurricane must have maximum sustained Massachusetts 6 winds of at least 155 mph. Through 1997, only 21 New Hampshire 2 Atlantic storms have reached this intensity and eight Maine 5 of these were category 5 at landfall (FEMA98). No (Source: National Hurricane Center 1998; available online at category 5 hurricanes have struck the East Coast. w w w. nhc. noaa. go v/paststate .html) Table 3 lists all Atlantic-born hurricanes that were category 5 during landfall. Despite the absence of category 5 landfalling hur- ricanes on the East Coast, scientists are finding that on the East Coast has followed a constant up and down correctly forecasting the intensity of hurricanes is a trend with no notable pattern. The largest number of problem too important to ignore (Henson 1998). landfalling East Coast hurricanes occurred between Notable East Coast hurricanes not listed in Table 3, 1950 and 1959. On average, 7.1 hurricanes made land- which had reached category 5 intensity but weakened fall each decade over the past 99 years (1900-98); an by the time of landfall, include Hurricane Donna average of .71 landfalling hurricanes a year. The East (1960, North Carolina), Hurricane David (1979, Florida), Coast average has increased to 1.0 landfalls per year and Hurricane Hugo (1989, South Carolina) (Vega and in the 1990s. Therefore, the evidence presented indi- Binkley 1993). Hurricane Andrew was a strong cat- cates a slight increase in the East Coast hurricane fre- egory 4 storm but never reached category 5 status. quency in the 1990s. Figure 3 reveals the total number of hurricanes to Along the East Coast, the northeastern states from make an East Coast landfall by decade with the num- Maryland to Maine have managed to escape a high ber of major (category 3-5) hurricanes also listed. frequency of hurricanes. Wagner (1988) also observed Unlike the, frequency of hurricanes to strike the East the irregular frequency of hurricanes and noted that decades fill in gaps be- ______ tween years in which "clusters" of TABLE 3: Atlantic category 5 hurricanes and landfalls. storms form. Since 1960, only two major hurricanes have made direct hits Storm name Max.
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