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Hurricane Alex (2016)

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Hurricane Alex
Category 1 hurricane (SSHWS/NWS)
File:Alex 2016-01-14 1435Z.jpg
Hurricane Alex at peak intensity on January 14
Formed January 13, 2016 (January 13, 2016)
Dissipated January 17, 2016 (January 17, 2016)
(Extratropical after January 15)
Highest winds 1-minute sustained: 85 mph (140 km/h)
Lowest pressure 981 mbar (hPa); 28.97 inHg
Fatalities 1 indirect
Damage Minimal
Areas affected Bermuda, Azores
Part of the 2016 Atlantic hurricane season

Hurricane Alex was the first Atlantic hurricane in January since Alice in 1955, and the first to form in the month since 1938. Alex originated as an extratropical cyclone near the Bahamas on January 7, 2016. The system initially traveled northeast, passing Bermuda on January 8, before turning southeast. It subsequently deepened and acquired hurricane-force winds by January 10. Slight weakening took place thereafter, and the system eventually turned east and northeast as it acquired tropical characteristics. On January 13, it developed into a subtropical cyclone well south of the Azores, becoming the first tropical or subtropical system during January in the North Atlantic since an unnamed storm in 1978. As it turned north-northeast, Alex transitioned into a full-fledged tropical cyclone on January 14 and became a hurricane. The storm peaked as a Category 1 on the Saffir–Simpson hurricane wind scale with maximum sustained winds of 85 mph (140 km/h) and a barometric pressure of 981 mbar (hPa; 28.97 inHg). After weakening slightly, Alex made landfall on Terceira Island as a tropical storm the next day. Concurrently, Alex began transitioning back into an extratropical cyclone; it completed this cycle hours after moving away from the Azores. The system ultimately merged with another extratropical cyclone over the Labrador Sea on January 17.

The hurricane prompted the issuance of hurricane and tropical storm warnings for the Azores and the closure of schools and businesses. Alex ultimately brought gusty winds and heavy rain to the archipelago, causing generally minor damage. One person died from a heart attack when the inclement weather prevented a helicopter from transporting them to a hospital.

Background

As currently defined, the Atlantic hurricane season lasts from June 1 to November 30, the period in which tropical cyclones are most likely to develop across the basin. Occasionally, systems develop outside the season,[1] most frequently in May or December.[2] Activity in January is considered extremely rare, with only five other known instances since 1851: an unnamed hurricane in 1938, an unnamed tropical storm in 1951, Hurricane Alice in 1954–55, an unnamed storm in 1978, and Tropical Storm Zeta in 2005–06.[3] Since Alice originated in December 1954, Alex is only the second hurricane to develop solely within January, after the 1938 storm.[3][4] When Alex made landfall on Terceira as a strong tropical storm this marked only the second time that an Atlantic tropical cyclone has made landfall in January, with the other being Hurricane Alice of 1955 which made landfall on Saint Martin and Saba.[5] In addition to forming well outside of hurricane season, Alex developed unusually far north and east, becoming only the second hurricane to form north of 30°N and east of 30°W.[6]

Unrelated to Alex, Hurricane Pali developed over the Central Pacific in early January, and persisted through the formation of Alex. This marked the first known occurrence of simultaneous January tropical cyclones between the two basins.[3]

Meteorological history

File:Alex 2016 track.png
Map plotting the track and intensity of the storm according to the Saffir–Simpson hurricane wind scale

Hurricane Alex originated in a non-tropical weather disturbance that developed over Cuba and the Bahamas on January 6, 2016.[7] Moving northeast ahead of the subtropical jet stream, the system acquired a surface vortex the following day.[8] Initial conditions, including strong wind shear, low sea surface temperatures, and dry air,[9] inhibited formation of a tropical cyclone as the storm moved northeast toward Bermuda.[8] The large system featured gale-force winds, with maximum sustained winds of 60–65 mph (95–100 km/h).[9] On January 8, the system passed about 75 mi (120 km) north of Bermuda, bringing strong winds and heavy rain to the islands.[10] On January 9, the system turned east and later southeast, entering a region slightly more favorable for subtropical development.[11] Hurricane-force winds developed around the core of the cyclone the following day, though convective activity near the center remained sparse.[12] The storm's separation from the jet stream, similar to a cut-off low, allowed it to move southeast and gradually acquire tropical characteristics.[3] Slight weakening took place on January 11.[13] Convection began increasing around the storm's center on January 12, by which time it was situated 1,100 mi (1,770 km) southwest of the Azores.[14]

Frontal features associated with the storm dissipated on January 13 and banding features around the defined low increased in coverage and depth. Though relatively shallow, owing to the seasonally low level of the tropopause, convection was deemed deep enough for the system to be classified a subtropical storm at 21:00 UTC. Accordingly, the National Hurricane Center (NHC) assigned the name Alex to the storm.[15] Upon its classification, Alex was situated 785 mi (1,260 km) south-southwest of the Azores.[16] Situated to the east of a shortwave trough, Alex traveled northeast and gradually turned more to the north, steered by broad cyclonic flow over the central Atlantic.[15] An eye feature soon appeared, marking intensification, within a complex of several banding features.[17] The 20 mi (25 km) wide feature cleared out early on January 14 and was surrounded by a ring of −75 °F (−60 °C) cloud tops. The storm remained situated under a cold-core low, though the development of upper-level outflow indicated the system was becoming increasingly tropical.[18] Despite moving over 68 °F (20 °C) waters, Alex continued to deepen and transitioned into a full-fledged tropical cyclone by 09:00 UTC. The transition was enabled by colder-than-average upper-tropospheric temperatures which created greater instability than would otherwise be expected.[4]

Upon transitioning into a tropical cyclone, satellite intensity estimates—using the Dvorak technique—indicated Alex achieved hurricane strength. Forecasters at the NHC estimated maximum winds of 85 mph (140 km/h) and a barometric pressure of 981 mbar (hPa; 28.97 inHg); this made it a Category 1 on the Saffir–Simpson hurricane wind scale and constituted the storm's peak intensity.[4] As Alex moved north toward the Azores, decreasing sea surface temperatures and increasing wind shear caused it to weaken late on January 14 and into January 15.[19][20] The hurricane's eyewall opened up and its convective structure decayed, indicating the start of its transition back into an extratropical cyclone.[20] Becoming increasingly tilted with height due to shear,[21] Alex weakened to a tropical storm before making landfall over Terceira Island at 13:15 UTC with winds of 70 mph (110 km/h).[22] Hours later the system completed its transition into an extratropical cyclone, with its circulation becoming more elongated and the radius of maximum winds expanding significantly. Furthermore, the overall structure became more "comma shaped", a feature of frontal systems. Consequently, the NHC issued its last advisory on Alex.[23] Turning northwest, the system deepened slightly as it approached Greenland and re-acquired hurricane-force winds on January 17.[24] Alex soon merged with another extratropical cyclone over the Labrador Sea, marking its dissipation.[25]

Structural evolution of Hurricane Alex from a non-tropical low into a hurricane
A non-tropical cyclone with clouds wrapping cyclonically around an open center
The precursor occluded cyclone on January 10 
The cyclone becomes increasingly separated from frontal boundaries on January 11
The cyclone becomes increasingly separated from frontal boundaries on January 11 
Convection develops atop the circulation center on January 12
Convection develops atop the circulation center on January 12 
The system hours before being classified as a subtropical cyclone, on January 13
The system hours before being classified as a subtropical cyclone, on January 13 
Alex develops a well-defined eye and core structure, as it becomes a hurricane on January 14
Alex develops a well-defined eye and core structure, as it becomes a hurricane on January 14 

Preparations and impact

Bermuda

The precursor to Alex brought gale-force winds and heavy rain to Bermuda on January 8. Gusts to 60 mph (97 km/h) disrupted air travel, downed trees, and left sporadic power outages, while waves as high as Lua error in Module:Convert at line 1851: attempt to index local 'en_value' (a nil value). necessitated small craft advisories for the islands.[10] Ferry services to and from Cavello Bay, Dockyard, Belmont, Hodsdon’s Ferry, and Lower Ferry were suspended.[26] During the three days in which the system impacted the territory, 1.33 in (34 mm) of rain fell at Bermuda International Airport.[27]

Azores

File:Alex's final waves over Azores.jpg
Rough surf from Hurricane Alex on São Miguel Island, in the Azores

Upon Alex's classification as a hurricane on January 14, the Azores Meteorological Service issued a hurricane warning for the islands of Faial, Pico, São Jorge, Graciosa, and Terceira. They also issued a tropical storm warning for São Miguel and Santa Maria.[28] A red alert—the highest stage for meteorological warnings—was declared for central and eastern islands.[29] Homeowners protected doors and windows with plywood and sandbags in anticipation of damaging winds and flooding. Officials closed schools and administrative buildings for the duration of the hurricane on January 15.[30] SATA Air Açores cancelled 33 domestic and international flights for the morning of January 15, stranding more than 700 passengers.[31][32] The hurricane and tropical storm warnings were discontinued after Alex's passage on January 15.[22]

The first hurricane to impact the Azores since Hurricane Gordon in 2012, Alex brought heavy rain and gusty winds to the archipelago.[30] It is the only known hurricane to track within 230 mi (370 km) of the Azores outside of August and September.[33] Rainfall totals reached 4.04 in (103 mm) in Lagoa, São Miguel,[34] and 3.71 in (94 mm) in Angra do Heroísmo, Terceira.[35] Wind gusts exceeded 50 mph (80 km/h) on Santa Maria Island and peaked at 57 mph (92 km/h) in Ponta Delgada, São Miguel.[7][33] The strong winds brought down trees, inflicted damage on some roofs, and triggered scattered power outages. Additionally, minor flooding was observed.[30][36] Six homes in Ponta Delgada sustained flood damage and another had its roof destroyed.[37] Landslides occurred across parts of the central islands, though they caused only limited damage.[29] The overall effects of the storm were less than initially feared.[30] The hurricane indirectly led to one death—the person suffered a heart attack unrelated to the storm—when an Island Health Unit helicopter was unable to take off due to turbulent conditions.[38]

See also

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 3.2 3.3 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ 7.0 7.1 Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ 8.0 8.1 Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ 9.0 9.1 Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ 15.0 15.1 Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  18. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  19. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  20. ↑ 20.0 20.1 Lua error in package.lua at line 80: module 'strict' not found.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  22. ↑ 22.0 22.1 Lua error in package.lua at line 80: module 'strict' not found.
  23. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  24. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  25. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  26. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  27. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  28. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  29. ↑ 29.0 29.1 Lua error in package.lua at line 80: module 'strict' not found.
  30. ↑ 30.0 30.1 30.2 30.3 Lua error in package.lua at line 80: module 'strict' not found.
  31. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  32. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  33. ↑ 33.0 33.1 Lua error in package.lua at line 80: module 'strict' not found.
  34. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  35. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  36. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  37. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  38. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

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