Original: english review of the past hurricane season summary of the past season



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WORLD METEOROLOGICAL ORGANIZATION

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RA IV HURRICANE COMMITTEE


THIRTY-NINTH SESSION
SAN JOSE, COSTA RICA
23 TO 26 MARCH 2017




RA IV/HC-39/Doc.3.1

(7.III.2017)

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ITEM: 3.1

ORIGINAL: ENGLISH



REVIEW OF THE PAST HURRICANE SEASON
SUMMARY OF THE PAST SEASON
2016 Atlantic and eastern North Pacific Hurricane Season Summary
(Submitted by RSMC Miami)


  1. Atlantic

Tropical cyclone activity in the Atlantic basin during the 2016 season was above the 1981-2010 long–term average and well above the average of the 2013-2015 hurricane seasons. Fifteen tropical storms formed, of which 7 became hurricanes, and 3 reached major hurricane strength (category 3 or higher on the Saffir-Simpson Hurricane Wind Scale). There was also one tropical depression that did not reach tropical storm strength. By comparison, the 1981-2010 averages are 12 tropical storms, 6 hurricanes and 3 major hurricanes. The Accumulated Cyclone Energy (ACE) index, a measure that takes into account the strength, duration, and frequency of the season’s tropical storms and hurricanes, was 140% of the long-term median value. Figure 1 depicts the tracks of the 2016 Atlantic tropical storms and hurricanes.


Many of the 2016 cyclones had impacts on land areas. The season’s most devastating hurricane was Matthew, which left a long trail of destruction from the Lesser Antilles across Haiti, eastern Cuba, and the Bahamas to the southeastern United States. Earl caused significant damage as it made landfall in Belize and additional damage in southeastern Mexico. Hermine made landfall as a hurricane along the Florida Gulf coast, while Nicole struck Bermuda at major hurricane strength. The season’s last cyclone, Otto, made landfall as a hurricane in southern Nicaragua and then crossed northern Costa Rica into the eastern Pacific.
Hurricane Alex
Alex was the first hurricane to form in January in the Atlantic basin since 1938, and the first hurricane to be ongoing in January since Alice in 1955. A frontal low over northwestern Cuba on January 6 intensified as it moved northeastward toward Bermuda and the Atlantic during the next 2 or 3 days. Turning east-southeastward, the low developed hurricane-force winds on January 10. While the winds subsequently decreased a little, during the next couple of days convection increased near the center of the low and the associated fronts dissipated. This led to the formation of a subtropical storm on January 12 about 1150 miles west-southwest of the Canary Islands.
Subtropical Storm Alex moved east-northeastward and northeastward on January 13-14, and during that time the associated convection increased further and an eye developed. This signaled Alex’s transformation from a subtropical storm to a hurricane, which reached an estimated peak intensity of 75 kt near 1200 UTC January 14. Alex then weakened while moving northward, and it made landfall as a tropical storm on the island of Terceira in the Azores at 1315 UTC January 15. A few hours later, Alex became extratropical, and it became absorbed within a larger extratropical low over the far north Atlantic early on January 17.
Alex caused tropical-storm conditions over portions of the Azores, but there were no reports of damages of casualties from Alex.


Tropical Storm Bonnie
Bonnie originated from a mid- to upper-level low that cut off from the mid-latitude westerlies over the Bahamas on May 25 and helped spawn a well-defined surface low on May 27. The convection associated with the low gradually increased that day, and a tropical depression formed around 1800 UTC about 200 miles northeast of Great Abaco in the Bahamas. After genesis, the depression moved quickly west-northwestward between a mid-level ridge to the northeast and the mid- to upper-level low to the southwest of the tropical cyclone. As this occurred, the cyclone strengthened to a tropical storm and reached a peak intensity of 40 kt near 1800 UTC May 28. Vertical wind shear then caused Bonnie to weaken back to a depression before it made landfall around 1230 UTC May 29 on the Isle of Palms, South Carolina.
Bonnie moved slowly over the coastal area of South Carolina and degenerated into to a remnant low on May 30. The low emerged over the Atlantic the next day, and by June 2 it had re-developed into a tropical depression about 45 miles southeast of Cape Lookout, North Carolina. After moving east-northeastward just off of the coast of North Carolina, Bonnie regained tropical storm strength while east of Cape Hatteras on June 3. The cyclone continued eastward and again decayed, becoming a remnant low on June 5, and an extratropical low on June 7. The system dissipated south-southwest of the Azores on June 9.
One person drowned in surf produced by Bonnie at Carolina Beach, North Carolina. The storm caused minor property damage in the United States.
Tropical Storm Colin
Colin originated from a tropical wave that moved off the west coast of Africa on May 27. The wave moved westward for the next several days across the tropical Atlantic and the Caribbean Sea where the associated deep convection gradually increased. A low pressure area formed near the east coast of the Yucatan Peninsula and moved slowly northward. On June 5, the system developed a closed circulation and organized deep convection to be considered a tropical depression, and it strengthened to a tropical storm later that day.
Colin was always poorly organized with the strongest winds and deepest convection located well to the east of the center. The storm moved generally northward for a day or so and the maximum winds increased to a peak intensity of 45 kt. Then, a broad mid-level trough moved into the eastern United States, causing Colin to turn toward the northeast and accelerate. The center made landfall in the Big Bend area of Florida near Keaton Beach around 0200 UTC June 7, followed by a motion across northern Florida and extreme southeastern Georgia into the Atlantic. Moving roughly parallel to the coasts of the Carolinas, the storm became a frontal low around 1200 UTC June 7. The storm-force extratropical cyclone moved rapidly northeastward to east-northeastward over the Atlantic well offshore of the northeastern United States and merged with another extratropical low near Atlantic Canada by June 9.
Colin caused minor damage from tropical-storm-force winds, rains, and one tornado. There were no deaths directly associated with the storm. However, three people drowned along the Florida coast due to rip currents during Colin’s extratropical phase.
Tropical Storm Danielle
The formation of Danielle was associated with a tropical wave that emerged from the coast of Africa on June 8, and first showed signs of development over the southwestern Caribbean Sea on June 15. The disturbance moved northwestward and it was located over the Yucatan peninsula of Mexico on June 17. A low pressure area formed the next day when the system reached the Bay of Campeche, and a tropical depression developed near 1200 UTC June 19 about 145 miles east-northeast of Veracruz, Mexico. A mid-level ridge over the southern United States provided an east-southeast to west-northwest steering flow, and the cyclone moved in that general direction, albeit somewhat erratically, during its short lifetime. The depression became a tropical storm early on June 20, and reached a peak intensity of 40 kt about 1200 UTC that day.
Later on June 20, Danielle turned west-southwestward and weakened slightly, making landfall near Tamiahua, Mexico (in the state of Veracruz about 80 miles south-southeast of Tampico) around 2200 UTC. Continuing west-southwestward after landfall, the system quickly dissipated on June 21 over the mountains of eastern Mexico.
Danielle caused one death by freshwater flooding in the municipality of Ciudad Madero, Tamaulipas. Minor property damage also occurred in portions of eastern Mexico.
Hurricane Earl
The tropical wave that spawned Earl moved off of the west coast of Africa on July 26. The disturbance moved rapidly westward across the tropical Atlantic and reached the Lesser Antilles on July 30. As the wave moved across the eastern and central Caribbean Sea on July 31-August 1, the system’s forward speed slowed and vertical wind shear decreased. These conditions favored an increase in organization of the thunderstorm activity. The system was already producing tropical-storm-force winds on August 1, but lacked a well-defined circulation. The next day, the system became a tropical storm about 115 miles south of Jamaica.
Earl moved in a general west-northwestward direction for the next three days along the southern periphery of a strong deep-layer ridge that extended from the central Atlantic westward across Florida, and the Gulf of Mexico to mainland Mexico. The cyclone steadily intensified and became a hurricane around 1800 UTC August 3. Maximum sustained winds increased to 75 kt before the center made landfall on the Belize island of Turnleffe Caye near 0400 UTC August 4. It then made a second landfall 2 h later along the mainland coast of Belize just south of Belize City. Earl weakened to a tropical storm over extreme northeastern Guatemala, and it maintained tropical storm status while it trekked west-northwestward across southeastern Mexico and into the extreme southern Bay of Campeche. After moving back over water, Earl re-strengthened to a 50 kt tropical storm before the cyclone made its third and final landfall around 0230 UTC August 6, along the eastern coast of mainland Mexico to the southeast of Veracruz near Salinas.
After the final landfall, Earl continued west-northwestward and weakened, eventually dissipating near Mexico City. Earl’s remnants moved westward across central Mexico and emerged over the eastern North Pacific Ocean a few days later, triggering the formation of Tropical Storm Javier in that basin.
Media reports and information from emergency management agencies indicate that torrential rains and strong winds associated with pre-Earl caused considerable damage across portions of the northern Caribbean Islands, Central America, and Mexico, along with at least 81 direct fatalities in Mexico. This makes Earl the deadliest Atlantic hurricane to affect Mexico since Stan in 2005. An additional 13 deaths were reported in the Dominican Republic when Earl passed over that country as a tropical disturbance.
Tropical Storm Fiona
A tropical wave moved westward from the coast of Africa late on August 13. After passing south of Cabo Verde, the system showed increasing organization, and a tropical depression formed around 1800 UTC August 16 about 555 miles west-southwest of the southernmost Cabo Verde Islands. The system subsequently moved west-northwestward and became a tropical storm. However, vertical shear prevented the system from intensifying beyond an estimated peak intensity of 45 kt on August 19-20, and this shear eventually caused Fiona to decay to a remnant low on August 23 about 375 miles south-southwest of Bermuda. Fiona’s remnants were later absorbed into the frontal system from which Tropical Depression Eight developed on August 28.
Hurricane Gaston
The first major hurricane of 2016 began as a strong tropical wave that departed the west coast of Africa late on August 20, accompanied by a broad low pressure area and disorganized showers and thunderstorms. Additional organization led to the formation of a tropical depression by 1200 UTC August 22 about 300 miles southwest of the southernmost Cabo Verde Islands. The depression quickly strengthened to a tropical storm as it moved west-northwestward to the south of the Atlantic subtropical ridge. Intensification continued, and Gaston became a hurricane on August 24. Later on August 24-25, Gaston encountered strong southwesterly shear while it turned northwestward, and as a result it weakened to a tropical storm. Little change in strength would occur through August 26.
Gaston re-intensified to a hurricane as the shear decreased on August 27, and this was followed by rapid intensification to an estimated peak intensity of 105 kt early on August 29. Shortly after this, Gaston weakened a little and became nearly stationary about 565 miles east-southeast of Bermuda. An east-northeastward motion on August 30 was accompanied by another round of intensification, and maximum winds reached 105 kt for a second time early the next day. After that time, strong shear and decreasing sea surface temperatures caused rapid weakening, and Gaston decayed to a gale-force post-tropical cyclone before it moved through the Azores on September 2. The post-tropical low continued to quickly weaken and it degenerated into a trough of low pressure a couple of hundred miles northeast of the central Azores the next day.
As a post-tropical cyclone, Gaston brought gale-force wind gusts to portions of the Azores. However, no damages or casualties were reported.
Hurricane Hermine
Hermine was the first hurricane to make landfall in Florida since Wilma in 2005. The cyclone was spawned by a tropical wave that moved off the west coast of Africa on August 16-17. Heavy rains associated with this disturbance spread over the Leeward Islands and Greater Antilles on August 23-25, and the open wave had gale-force winds at this time. However, shear prevented any additional organization as the system crossed the Greater Antilles and the Bahamas. Finally, on August 28 a tropical depression formed over the Straits of Florida about 60 miles south-southeast of Key West, Florida. The cyclone moved slowly westward through August 30 south of a mid-level high pressure system centered over Appalachian Mountains. Moderate northwesterly shear prevented intensification into a tropical storm until 31 August. Hermine moved northeastward that day and became a hurricane late on September 1. Maximum sustained winds increased to 70 kt before the center made landfall just east of St. Marks, Florida at 0530 UTC September 2. Hermine weakened quickly once it moved inland and became a tropical storm shortly thereafter near the Florida-Georgia border.
As a tropical storm, Hermine moved northeastward just inland over coastal portions of Georgia, South Carolina, and North Carolina during September 2 and early on September 3. The storm became a storm-force extratropical cyclone on September 3 while centered near Oregon Inlet, North Carolina. The extratropical cyclone moved generally eastward over the Atlantic Ocean away from the coast with little change in strength until early on September 5. The low then steadily weakened, and it turned northwestward and westward on 5 and 6 September, moving closer to the mid-Atlantic coast. The cyclone meandered offshore of New Jersey and Long Island on September 7 with its winds dropping below gale force. The weakened low then moved northeastward on September 8 and dissipated late that day near Chatham, Massachusetts.
Hermine brought hurricane conditions to portions of the Florida Big Bend area, as well as tropical storm conditions over other portions of Florida, Georgia, and South Carolina. As an extratropical cyclone, Hermine produced storm- and gale-force winds over portions of eastern North Carolina and southeastern Virginia. The cyclone caused two deaths, one in Florida as a tropical cyclone and one in North Carolina as an extratropical cyclone. The combination of winds, storm surge, freshwater flooding, and tornadoes produced an estimated $500 million in damage in the United States.
Tropical Storm Ian
Ian originated from a tropical wave that crossed the west coast of Africa on September 6. After several days of unsteady development that included winds of gale force, the system became a tropical storm on September 12 about 1140 miles southeast of Bermuda. Moving generally northward, Ian moved under an upper-level low on September 14 and became a subtropical storm for a short time. The storm then moved northeastward away from the low and regained tropical storm status, with an estimated peak intensity of 50 kt on September 16. The cyclone became extratropical over the North Atlantic later that day.

Tropical Storm Julia
Julia is traceable to a tropical wave that left western Africa on September 1. On September 6, convection increased near the wave and small low pressure area formed over the Atlantic. The low weakened to a trough, but it re-formed between south Florida and Grand Bahama late on September 12. By 0600 UTC 13 September, the low had acquired enough convective organization to be considered a tropical depression when it made landfall near Jensen Beach, Florida.
Strong convection developed after landfall in the northeastern quadrant of the asymmetric cyclone, and the depression strengthened to a tropical storm 6 h after formation. Julia moved erratically north-northwestward, parallel to, but just inland of the east coast of Florida. A peak intensity of 50 mph occurred around 1800 UTC September 13, with the strong winds occurring near and offshore of the Florida coast. Early on September 14, Julia moved over southeastern Georgia and then back over the Atlantic. The system meandered of off the southeastern U.S. coast for a couple of days before strong shear caused it to weaken to a depression on September 17. The cyclone decayed to a remnant low on September 19, and the remnants merged with a frontal system the next day. The frontal low dissipated over eastern North Carolina on September 21.
Julia caused minor damage in northeastern Florida due to winds and one associated tornado.
Tropical Storm Karl
Karl formed from a tropical wave that crossed the western coast of Africa on September 12. A low pressure area associated developed later that day and moved slowly northwestward for a day or so, and on September 14, the system acquired enough organized deep convection to be classified as a tropical depression while centered near the eastern Cabo Verde Islands. The depression strengthened to a tropical storm on September 15, but strong shear prevented additional strengthening as Karl moved on a mainly westward track over the tropical Atlantic for several days. Early on September 21, Karl moved very near an upper-level low, and the tropical cyclone weakened to a depression.
The cyclone turned toward the northwest and remained below storm strength for a day or so, but on September 22, Karl encountered more favorable upper-level winds and regained tropical storm strength late that day. Karl intensified further while turning toward the north and northeast around the western periphery of a mid-level anticyclone, and the storm passed about 45 miles southeast of Bermuda on September 24 with maximum winds near 55 kt. While accelerating toward the east-northeast, Karl reached its estimated peak intensity of 60 kt on September 25 just before the cyclone merged with a frontal system. The resulting extratropical cyclone moved rapidly northeastward and merged with another extratropical low pressure system over the north Atlantic, well to the east-southeast of Newfoundland, the next day.
Tropical-storm-force winds and heavy rains associated with Karl caused minor damage on Bermuda.


Tropical Storm Lisa
A tropical wave and associated low pressure area moved westward from the coast of Africa on September 16. Steady development began on September 19, and a tropical depression formed near 1200 UTC that day about 225 miles west-southwest of the southern Cabo Verde Islands. For the first several days of its life, the cyclone was steered generally northwestward by a low- to mid-level ridge to the north. The depression became a tropical storm early on September 20, and Lisa reached an estimated peak intensity of 45 kt the next day. Thereafter, increasing wind shear and dry air entrainment halted development. The associated convection dissipated late on September 24, and Lisa quickly decayed to a remnant low pressure area early the next day. The remnants of Lisa turned northward and northeastward on September 25-26 and dissipated late on September 26 about 800 miles west-southwest of the western Azores.
Hurricane Matthew
The strongest and deadliest hurricane of the season was spawned by a tropical wave that emerged from the coast of Africa on September 23 and moved generally westward across the tropical Atlantic for the next several days. The system showed signs of organization and was already producing gale-force winds on September 26-27. It became a tropical storm on September 28 when a closed circulation formed just west-northwest of Barbados, and a few hours later, the center passed between St. Lucia and St. Vincent in the Windward Islands. Matthew continued westward across the southeastern Caribbean Sea and it intensified into a hurricane late on September 29. This was followed by very rapid intensification during the next 30 hours, and the hurricane reached a peak intensity of 140 kt early on October 1. During this strengthening, Matthew moved west-southwestward to a position about 90 miles northwest of the Guajira peninsula of Colombia.
Matthew moved slowly on October 2 and then started a north-northeastward motion the next day. This brought the eye to a landfall along the southwestern coast of Haiti near Les Anglais around 1100 UTC October 4 as a Category 4 hurricane. A northward motion across the Gulf of Gonâve led to a second landfall near Juaco, Cuba, around 0000 UTC October 5, also as a category 4 hurricane. A ridge of high pressure to the north and east caused a turn toward the northwest toward the area between Cuba and the southeastern Bahamas on October 5, and a track through the central and northwestern Bahamas on October 6-7. At Category 4 strength, the center passed just west of Nassau and later over the western end of Grand Bahama Island.
The hurricane moved north-northwestward and northward after leaving the Bahamas, with the center moving close but just offshore of the coast of the northern Florida peninsula and Georgia. Weakening took place during this part of Matthew’s journey, and the hurricane was down to category 1 strength when it made landfall just south of McClellanville, South Carolina, in the Cape Romain Wildlife Sanctuary, around 1500 UTC October 8. After this final landfall, Matthew moved east-northeastward just offshore of the coast of North Carolina, and it was about 230 miles east of Cape Hatteras when it merged with a frontal system early on October 10. The extratropical low was absorbed by a larger extratropical low pressure system near Atlantic Canada the next day.
Matthew brought hurricane conditions to portions of Haiti, eastern Cuba, the Bahamas, and the southeastern coast of the United States, with tropical storm conditions affecting portions of the Lesser Antilles as well. Widespread damage from wind, storm surge, and freshwater flooding occurred along the path of the storm. Casualty figures are incomplete as of this writing, but it is believed that Matthew caused 500-1000 deaths in Haiti alone which would make it the deadliest Atlantic hurricane since Stan of 2005.
Hurricane Nicole
The longest-lived cyclone of 2016 began as a tropical wave that emerged from the west coast of Africa on September 25. The system first showed signs of organization on September 30, but additional development was slow due to hostile upper-level winds. More favorable conditions on October 3 led to the formation of a low pressure area with increasing deep convection. The system produce gale-force winds early the next day, and the low became a tropical storm about 530 miles northeast of San Juan, Puerto Rico. Nicole initially moved northwestward in strong northwesterly shear caused by the outflow from Hurricane Matthew. The forward motion came to a halt on October 6 while the cyclone encountered decreasing shear, which allowed Nicole to strengthen to a hurricane. However, this was followed by another round of shear the next day which weakened Nicole back to a tropical storm. High pressure to the north pushed Nicole southward for the next couple of days, and a combination of shear, dry air, and cooler sea surface temperatures prevented intensification. Nicole turned northward on October 10 into a more favorable environment, and as a result, Nicole regained hurricane strength on October 11. It then rapidly intensified to a peak intensity of 115 kt on October 13.
Nicole turned northeastward just after it reached its peak intensity, and the center passed over Bermuda around 1400-1500 UTC October 13 as a category 3 hurricane. After that time, Nicole weakened rapidly as it moved northeastward over the North Atlantic. Although the cyclone ingested some cooler air, an interaction with the jet stream on October 15-16 caused Nicole to re-intensify with the cyclone’s wind field nearly doubling in size. Another jet stream pulse moving through Atlantic Canada that day caused Nicole to accelerate northeastward. This path brought the cyclone over progressively colder waters and into a cooler air mass. Nicole weakened to a tropical storm on October 18 and became extratropical shortly thereafter while turning north-northeastward with increasing forward speed. The cyclone was absorbed by a larger extratropical storm the next day several hundred miles southeast of Greenland.
Hurricane conditions on Bermuda resulted in widespread, but minor, damage to property. Swells generated by Nicole affected much of the North Atlantic Ocean during the cyclone’s life.
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