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Weatherwise -- May-June 2015

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The 2014 Atlantic Hurricane Season: U.S. East Coast Escapes Damage in a Below Average Year

Tropical cyclone activity in the Atlantic basin during the 2014 season was somewhat below average. Of the eight tropical storms that formed, six became hurricanes, and two reached major hurricane strength (Category 3 or higher on the Saffir-Simpson Hurricane Wind Scale). In comparison, the 1981–2010 averages are 12 tropical storms, six hurricanes, and three major hurricanes. The Accumulated Cyclone Energy (ACE) index, a measure that takes into account both the strength and duration of the season's tropical storms and hurricanes, was about 72% of the long-term median value. Most of the season's hurricanes occurred well east of the East Coast of the United States, although Arthur made landfall on the North Carolina Outer Banks. Bermuda was affected by two hurricanes (Fay and Gonzalo) in less than a week's time in October, and there was extensive damage on the island. Gonzalo was the strongest Atlantic hurricane since Igor of 2010. There was also a tropical depression during July that failed to strengthen into a tropical storm. Figure 1 depicts the tracks of the tropical storms and hurricanes of the 2014 Atlantic hurricane season. Dates are based on Coordinated Universal Time (UTC).

Hurricane Arthur

Arthur, the earliest hurricane in a season to make landfall in North Carolina since records began in 1851, developed from a non-tropical disturbance that formed over the southeastern United States and spawned a low pressure system just off the coast of South Carolina on June 28. The low then moved south during the next couple of days, becoming more organized over the warm waters of the Gulf Stream east of Florida. Deep convection became sufficiently well organized and persistent for the low to be designated as a tropical depression early on July 1 about 80 miles north of Freeport in the Bahamas. The depression drifted westward and strengthened, becoming a tropical storm later that day. On July 2, a mid-level anticyclone began building over the western Atlantic, causing Arthur to accelerate toward the north. Light upper-level winds and warm ocean temperatures near 28°C allowed Arthur to gradually strengthen while east of Florida, although mid-level dry air in the vicinity of the cyclone limited the rate of intensification. Arthur continued moving northward and became a hurricane early on July 3 while centered 145 miles east-southeast of Savannah, Georgia.

On July 3, Arthur turned north-northeastward and accelerated while it moved between the ridge over the western Atlantic and an approaching mid- to upper-level trough over the eastern United States. The hurricane reached its peak intensity of 100 mph early on July 4 just before it turned northeastward and made landfall on Shackleford Banks, just west of Cape Lookout, North Carolina, at 0315 UTC July 4. After crossing the Outer Banks, Arthur accelerated northeastward over the western Atlantic late on July 4 and early on July 5, then weakened to a tropical storm early on July 5 while located 130 miles east of Cape Cod. Shortly after that, Arthur became a strong extratropical storm over the Bay of Fundy just west of Nova Scotia. The cyclone moved across Atlantic Canada and Labrador, and dissipated on July 9 to the west of southern Greenland.

Morehead City, North Carolina, WSR-88D radar image of Hurricane Arthur making landfall on July 4, 2014.

The highest sustained winds measured in North Carolina were 83 mph in Salvo, and the highest measured wind gust was 101 mph at Cape Lookout. There were no reports of casualties associated with Arthur, and the United States was spared from significant damage. Insured losses from the hurricane did not meet the Property Claim Services' $25 million threshold. Despite the relatively modest damage, one of the hardest hit areas was Dare County, North Carolina, which includes part of the Outer Banks. The worst damage occurred south of Oregon Inlet on Hatteras Island, especially in the Rodanthe, Salvo, and Waves areas, where wind and water damaged numerous residences, businesses, and campgrounds. In North Carolina and New England, more than 110,000 customers lost power. During its post-tropical stage, Arthur knocked down numerous large trees and caused extensive power outages across Atlantic Canada.

Hurricane Bertha

Bertha originated from a tropical wave that moved off the west coast of Africa on July 24 with limited thunderstorm activity. A significant burst of convection occurred on July 28 due to a convectively coupled Kelvin wave passing through the region, resulting in a low pressure area forming the following day. Thunderstorm activity was not well organized, however, due to northeasterly shear and some drier air. The low finally acquired enough persistent deep convection to be declared a tropical storm early on August 1, when it was located about 345 miles east-southeast of Barbados.

A large mid-level ridge over the central tropical Atlantic caused Bertha to move quickly westward to west-northwestward, while southwesterly shear from a trough over the western Atlantic and dry air aloft prevented much strengthening. The cyclone reached a first peak intensity of about 50 mph as it passed just north of Martinique late on August 1, but increased shear and continued dry-air entrainment caused the system to become less organized when it moved over the northeastern Caribbean Sea on August 2. Bertha's circulation became better defined the next day while the storm moved near the northeast coast of the Dominican Republic and the southeastern Bahamas, where there was less shear and more moisture. The small storm then rapidly intensified, becoming a hurricane with a peak intensity of 80 mph on August 4 about 200 miles north-northeast of San Salvador in the central Bahamas.

Figure 1.  Tracks of the Atlantic tropical storms and hurricanes of 2014.

The intensification was short-lived, however, due to increasing shear ahead of a mid-latitude trough and gradually decreasing sea-surface temperatures. Bertha weakened late on August 4 and turned northward to the east of the trough, moving about midway between Bermuda and the northeast Florida coast. Increasing southwesterly flow aloft caused Bertha to accelerate northeastward on August 5, with the cloud pattern of the cyclone becoming distorted due to stronger shear and interaction with a surface trough. Bertha became embedded within a developing cold front the following day, and by midday August 6, the cyclone had become extratropical about 275 miles south-southeast of Halifax, Nova Scotia.

Rip currents generated by Bertha caused two direct deaths: a man died near Frisco, North Carolina, and a woman died near Atlantic City, New Jersey. The most significant impacts reported by the media were on Martinique, where power outages affected 150,000 buildings. Flooding, which caused mud slides and collapsed roads, was also noted in the Dominican Republic and Puerto Rico. Tropical-storm-force wind gusts were reported on many islands of the Caribbean, including Puerto Rico, Dominica, Guadeloupe, and Martinique.

Hurricane Cristobal

Cristobal can be traced back to a tropical wave that moved off the west coast of Africa late on August 14. This system, in combination with another wave to the west, produced a broad area of disturbed weather that moved westward across the tropical Atlantic and approached the Leeward Islands by August 21. The disturbance's cloud pattern began to show signs of organization, but observations from an Air Force Reserve Hurricane Hunter aircraft on the following day indicated that the system did not have a well-defined circulation. Over the next couple of days, the disturbance moved west-northwestward across the northern Leeward Islands, Puerto Rico, and Hispaniola, and then approached the Turks and Caicos Islands. It was not until the afternoon of August 23 that aircraft data indicated a definite circulation center, signifying the formation of a tropical depression just to the south of the Caicos Islands.

During the early stages of Cristobal's existence, the cyclone moved slowly north-northwestward to northward toward a break in the mid-level subtropical ridge. Moderate northwesterly to northerly shear was affecting the system, and it strengthened quite slowly, becoming a tropical storm early on August 24 while centered just north of Mayaguana in the southeastern Bahamas. The next day, the storm turned to the north-northeast and northeast at a slower forward speed under the influence of a mid-level trough to the north of the tropical cyclone. Despite persistent north-northwesterly shear, Cristobal strengthened into a hurricane early on August 26, and over the following day or so the system moved generally northward, along the western periphery of the subtropical ridge while maintaining an intensity of 75–80 mph. By August 28, the cyclone accelerated toward the northeast and east-northeast in the flow ahead of a mid-latitude shortwave trough. On that day, Cristobal's cloud pattern became significantly more symmetrical, and the hurricane strengthened to its peak intensity of 90 mph at an unusually high latitude of 37.5°N over the open Atlantic. Soon after reaching its maximum intensity, the cyclone's cloud pattern began to lose symmetry, and the central convection decreased in coverage and intensity. By the morning of August 29, a frontal boundary wrapped around the southern portion of the circulation, and the system became extratropical, although it maintained hurricane-force winds until the next day. The cyclone passed over Iceland on September 1 and merged with another low over the far north Atlantic shortly thereafter.

The slow-moving tropical cyclone dumped torrential rains over the Turks and Caicos Islands and the southeastern Bahamas. A rainfall total of 10.9 inches was observed at Providenciales International Airport in the Caicos Islands on August 22–23, where there was severe flooding. Portions of the Caicos Islands were reportedly inundated by floodwaters up to five feet deep. Heavy rains also occurred over portions of Hispaniola.

Cristobal caused seven direct deaths, all due to drowning. Rip currents claimed the lives of two young men at Sandy Hook, New Jersey, and Ocean City, Maryland. One person drowned in rain-induced floodwaters at Providenciales in the Caicos Islands, two people drowned in Haiti, and two people drowned in the Dominican Republic. In Haiti, there was flood damage, and at least 3,600 people were displaced. Over 600 homes were damaged or destroyed by flooding in the Dominican Republic.

Tropical Storm Dolly

Dolly originated from a tropical wave that moved westward from the coast of Africa on August 19. The wave produced little shower activity until it reached the eastern Caribbean Sea on August 27, when the associated convection increased. A low pressure area formed on August 31 over the Yucatan Peninsula of Mexico, and became better defined on September 1 when it reached the Bay of Campeche. It is estimated that a tropical depression developed near midday about 325 miles east-southeast of Tampico, Mexico. The depression moved north-northwestward and became a tropical storm early on September 2. A turn toward the northwest then occurred while Dolly reached a peak intensity of 50 mph. Later that day, Dolly weakened slightly due to northwesterly shear and turned west-southwestward, reaching the coast of Mexico just south of Tampico near 0400 UTC September 3. After landfall, Dolly weakened and moved generally westward into the mountains of eastern Mexico, where it dissipated on September 4.

Widespread rainfall totals of four to eight inches occurred over portions of eastern Mexico over the period of September 1–4. Some totals exceeded 10 inches, with a maximum reported total of 15.23 inches at La Encantada in the state of Tamaulipas. There were media reports of wind damage to homes near Cabo Rojo, Mexico, as well as damage due to freshwater flooding in portions of the state of Veracruz. There are no reliable monetary figures for the damage.

Hurricane Edouard

Edouard developed from a westward-moving tropical wave accompanied by a broad area of low pressure that exited the coast of western Africa late on September 6. Four days later, convection increased near the center of the low, and by the morning of September 11, deep convection had become sufficiently organized to designate the system as a tropical depression about 760 miles west of the Cape Verde Islands. The depression turned toward the northwest and maintained that general motion for the next five days, while the cyclone moved around the southwestern periphery of a deep-layer subtropical ridge. Slow but steady strengthening occurred, with the system becoming a tropical storm early on September 12 and a hurricane two days later. Edouard became a major hurricane early on September 16, reaching its peak intensity of 120 mph when it was located about 400 miles east of Bermuda, making it the first major hurricane to develop in the Atlantic basin since Sandy of 2012. However, an eyewall replacement and possible cold upwelling/mixing of the ocean beneath the hurricane soon caused Edouard to weaken. The cyclone moved northward then turned northeastward and accelerated on September 17 ahead of an approaching mid-latitude trough. The next day, Edouard turned eastward and began to rapidly weaken as the hurricane encountered strong westerly vertical wind shear. Edouard decayed to a tropical storm late on September 18, and transformed into a strong post-tropical cyclone early on September 19 about 440 miles west of the western Azores Islands.

Hurricane Fay

Fay, the first hurricane to make landfall on Bermuda since Emily of 1987, formed from a mid- to upper-level disturbance over the central Atlantic Ocean that moved westward on October 7. This system induced the development of a sharp surface trough, and when a cold low became situated over the disturbance on October 9, a comma-shaped cloud band developed. The convective organization of the low continued to increase, and the system became a subtropical storm about 575 miles south of Bermuda early on October 10.

Fay strengthened and moved north-northwestward around the western periphery of a mid-level ridge over the central Atlantic. The first reconnaissance mission into the storm late on October 10 found that the radius of maximum winds had shrunk to about 45 miles, while deep convection became more concentrated near the center. These changes led to the transition of Fay into a tropical cyclone early the next day. Fay turned northward and then north-northeastward while accelerating. Additional strengthening occurred despite strong south-southwesterly shear, and Fay reached hurricane intensity when it was about 40 miles south of Bermuda early on October 12. Fay made landfall on Bermuda around 0810 UTC that day, and strong winds and heavy rains buffeted the island for a few hours. Fay then turned sharply toward the east-northeast and accelerated. Stronger southwesterly wind shear began to affect Fay, and the tropical cyclone degenerated into an open trough a few hundred miles east-northeast of Bermuda early on October 13.

The estimated peak intensity of 80 mph is based primarily on radar data and surface data from Bermuda. Fay's winds toppled utility poles and downed trees and street signs throughout Bermuda, with the damage likely exacerbated by saturated soils from heavy summer rains. Nearly 27,000 customers were left without power. Strong winds damaged the roof of the terminal building at the L. F. Wade International Airport, with several reports of severe flooding in that building. Several major roads were inundated, including Front Street in Hamilton. Large boats broke from their moorings and were pushed onshore, heavily damaged or destroyed.

Hurricane Gonzalo

The development of Gonzalo can be traced to a tropical wave that departed the west coast of Africa on October 4. The wave was accompanied by a large area of cloudiness and thunderstorms while it moved westward across the tropical Atlantic during the following several days, with the shower activity becoming more concentrated after the passage of an eastward-moving atmospheric Kelvin wave around October 10. The tropical wave then moved into an area of low wind shear, and it is estimated that a tropical depression formed early on October 12 about 390 miles east of the Leeward Islands. The cyclone became a tropical storm later that day while centered 250 miles east of Antigua, and soon developed a well-defined inner core, resulting in rapid strengthening. An eye became apparent in radar imagery early on October 13, and Gonzalo became a hurricane in the morning hours when it was located just east-southeast of Antigua. Gonzalo turned from a westward to a west-northwestward heading and passed directly over the island a couple of hours later, and continued to strengthen while it passed through the northern Leeward Islands that afternoon. Gonzalo then turned northwestward before the southwestern portion of the eye moved over Saint Barthélemy around 2000 UTC, with the center of the eye passing just north of the island about an hour later. Gonzalo made landfall on the island of Saint Martin at about 2245 UTC with an estimated intensity of 85 mph, and passed over Anguilla about 45 minutes later. The hurricane then moved northwestward around the southwestern periphery of a deep-layer ridge over the central Atlantic, and rapidly intensified into a major hurricane around midday on October 14 when it was located about 175 miles north of San Juan, Puerto Rico. Over the next 12 to 18 hours, an eyewall replacement occurred, and Gonzalo weakened slightly. During this time, the hurricane began moving north-northwestward around the western portion of the ridge, which was beginning to shift eastward. After the eyewall replacement, Gonzalo's eye contracted late on October 15, and the hurricane intensified again while it turned northward. Gonzalo reached its estimated peak intensity of 145 mph early on October 16 when it was centered about 500 miles south-southwest of Bermuda. After that time, Gonzalo turned north-northeastward between the retreating ridge to its east and a mid- to upper-level trough that was located along the east coast of the United States.

Late on October 16, the hurricane exhibited a double eyewall structure and began to weaken. Increasing southwesterly shear and slightly cooler sea surface temperatures caused Gonzalo to gradually weaken on October 17 while it approached Bermuda. The hurricane made landfall on the southwestern coast of Bermuda with an estimated intensity of 110 mph shortly after 0000 UTC October 18. The hurricane continued to accelerate north-northeastward, and increasing southwesterly vertical wind shear and cool waters caused additional weakening. Gonzalo passed about 50 miles southeast of the southeastern tip of the Avalon Peninsula of Newfoundland early on October 19, then became a strong extratropical cyclone later that day while centered about 440 miles northeast of Cape Race, Newfoundland. The extratropical cyclone turned east-northeastward and weakened before it was absorbed by a cold front several hundred miles south-southwest of Iceland by early on October 20.

Gonzalo brought hurricane-force winds to several of the northern Leeward Islands on October 13 and 14. Sustained hurricane-force winds were also reported on Saint Barthélemy, and likely occurred over portions of Saint Martin and Anguilla. Media reports indicate that strong winds from Gonzalo caused numerous downed trees and utility lines in Anguilla, Saint Barthélemy, both the French and Dutch sides of Saint Martin, and Anguilla. The downed trees and power lines caused extensive power outages and made many roads impassable after the storm. No monetary damage estimates have been received for any of the Leeward Islands.

Gonzalo is estimated to have been a 110-mph hurricane when it made landfall on Bermuda. The strongest sustained winds experienced on Bermuda were likely of category 2 intensity and occurred on the back side of the hurricane from a northwesterly direction in the southwestern eyewall. Several observing sites on the island reported light winds and minimum pressures of around 952 mb between about 0020 and 0040 UTC as the center of the eye passed over the island. According to media reports, Gonzalo produced $200–$400 million in insured losses on Bermuda. Strong winds downed numerous trees and utility poles, and also caused some structural damage, including the loss of roofs and collapsed walls. Most of Bermuda was without electricity after the hurricane, and it took more than two weeks to fully restore power on the island.

Gonzalo is believed to be responsible for three direct deaths, all in the Leeward Islands. No deaths or serious injuries were reported in Bermuda.

Gonzalo's 145-mph peak intensity makes it the strongest October or November hurricane over the Atlantic waters north of 20°N and east of 80°W. Gonzalo was the strongest hurricane to affect Bermuda since Hurricane Fabian in September 2003, and is the strongest October hurricane to make landfall on Bermuda since 1926. Gonzalo and Fay passed directly over Bermuda within a six-day period; this is the first time that two hurricanes made landfall on Bermuda in one hurricane season, let alone less than one week apart.

Tropical Storm Hanna

The genesis of Hanna was associated with the remnants of eastern Pacific Tropical Storm Trudy. Although the low-level circulation of Trudy had dissipated, the associated moisture and mid-level vorticity moved northward into the southwestern Bay of Campeche on October 19. An area of surface low pressure developed in association with the mid-level feature early on October 21, and the low moved slowly eastward while producing disorganized showers and thunderstorms. Deep convection increased later that day, resulting in the formation of a tropical depression early on October 22, about 170 miles west of Campeche, Mexico, on the Yucatan peninsula.

The depression did not remain a tropical cyclone for very long, as southwesterly shear and dry air caused the cyclone to quickly lose deep convection. The system degenerated into a remnant low late on October 22 when it was located just west of the southwestern coast of the Yucatan peninsula, and it made landfall a few hours later. The weak low crossed the Yucatan peninsula and moved into the northwestern Caribbean Sea on October 24, but the environment remained unfavorable due to strong shear and dry air associated with a nearby frontal boundary. The low decayed into a trough and moved southeastward just east of the front during the next day or so.

The front began weakening on October 26, and the remnants of the depression became a little better organized as they slowed down and moved southeastward and then southward. Satellite images and surface observations indicate that the remnant trough developed into a small, closed area of low pressure on the morning of October 26 about 115 miles east-northeast of the Nicaragua/Honduras border. The low then turned westward back toward the coast of Central America, while deep convection gradually increased. It is estimated that the system became a tropical depression again by early on October 27, when it was located about 80 miles east of the Nicaragua/Honduras border. The cyclone strengthened to a tropical storm six hours later and maintained minimal tropical storm strength until it moved inland over extreme northeastern Nicaragua around 1600 UTC October 27. Hanna degenerated into a remnant low over eastern Honduras early on October 28, then moved over the Gulf of Honduras later that day, and dissipated over northwestern Guatemala on October 29.

The cyclone summaries are based on Tropical Cyclone Reports prepared by the authors and Lixion Avila, Robbie Berg, Jack Beven, Daniel Brown, John Cangialosi, Todd Kimberlain, and Stacy Stewart. These reports are available on the Internet athttp://www.nhc.noaa.gov/data/tcr/index.php?season=2014&basin=atl.

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