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2017 Atlantic hurricane season

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2017 Atlantic hurricane season
Season summary map
Seasonal boundaries
First system formedApril 19, 2017
Last system dissipatedSeason ongoing
Strongest storm
NameArlene
 • Maximum winds50 mph (85 km/h)
(1-minute sustained)
 • Lowest pressure993 mbar (hPa; 29.32 inHg)
Seasonal statistics
Total depressions1
Total storms1
Hurricanes0
Major hurricanes
(Cat. 3+)		0
Total fatalitiesNone
Total damageNone
Related articles
Atlantic hurricane seasons
2015, 2016, 2017, 2018, 2019

The 2017 Atlantic hurricane season is an ongoing event in the annual formation of tropical cyclones in the Atlantic basin. The season officially began on June 1, and will end on November 30, 2017. These dates historically describe the period each year when most tropical cyclones form in the Atlantic basin and are adopted by convention. However, as shown by the exceptionally rare Tropical Storm Arlene, which was only the second named storm on record to form in April, the formation of tropical cyclones is possible at any time of the year.

For the third consecutive year activity began early, with the formation of Tropical Storm Arlene on April 19, nearly a month and a half before the official start of the season. It is only the second named storm on record to exist in the month in April, with the first being Ana in 2003, as well as the strongest overall for the month of April.

Beginning this year, the National Hurricane Center has the option issue advisories, and thus allow watches and warnings to be issued, on disturbances that are not yet tropical cyclones but have a high chance to become one, and are expected to bring tropical storm or hurricane conditions to landmasses within 48 hours. Such systems are termed "potential tropical cyclones", and advisories on these storms have the same content in an advisory includes the chances of formation to the regular advisory package.[1] This was first demonstrated on June 18 with the designation of Potential Tropical Cyclone Two east-southeast of the Windward Islands.

Seasonal forecasts

Predictions of tropical activity in the 2017 season
Source Date Named
storms 		Hurricanes Major
hurricanes
Average (1981–2010[2]) 12.1 6.4 2.7
Record high activity 28 15 7
Record low activity 4 2† 0†
–––––––––––––––––––––––––––––––––––––––––––––––––––––––
TSR[3] December 13, 2016 14 6 3
TSR[4] April 5, 2017 11 4 2
CSU[5] April 6, 2017 11 4 2
TWC[6] April 17, 2017 12 6 2
NCSU[7] April 18, 2017 11–15 4–6 1–3
TWC[8] May 20, 2017 14 7 3
NOAA[9] May 25, 2017 11–17 5–9 2–4
TSR[10] May 26, 2017 14 6 3
CSU[11] June 1, 2017 14 6 2
–––––––––––––––––––––––––––––––––––––––––––––––––––––––
Actual activity
 1 0 0
* June–November only.
† Most recent of several such occurrences. (See all)

Ahead of and during the season, several national meteorological services and scientific agencies forecast how many named storms, hurricanes and major (Category 3 or higher on the Saffir–Simpson scale) hurricanes will form during a season and/or how many tropical cyclones will affect a particular country. These agencies include the Tropical Storm Risk (TSR) Consortium of the University College London, the National Oceanic and Atmospheric Administration (NOAA) and Colorado State University (CSU). The forecasts include weekly and monthly changes in significant factors that help determine the number of tropical storms, hurricanes, and major hurricanes within a particular year.[3] Some of these forecasts also take into consideration what happened in previous seasons and the dissipation of the 2014–16 El Niño event. On average, an Atlantic hurricane season between 1981 and 2010 contained twelve tropical storms, six hurricanes, and two major hurricanes, with an Accumulated Cyclone Energy (ACE) index of between 66 and 103 units.[2]

Pre-season outlooks

The first forecast for the year was issued by TSR on December 13, 2016.[3] They anticipated that the 2017 season would be a near-average season, with a prediction of 14 named storms, 6 hurricanes, and 3 major hurricanes. They also predicted an ACE index of around 101 units.[3] On December 14, CSU released a qualitative discussion detailing five possible scenarios for the 2017 season, taking into account the state of the Atlantic Multidecadal Oscillation and the possibility of El Niño developing during the season.[12] TSR lowered their forecast numbers on April 5, 2017 to 11 named storms, 4 hurricanes, and 2 major hurricanes, based on recent trends favoring the development of El Niño.[4] The next day, CSU released their prediction, also predicting a total of 11 named storms, 4 hurricanes, and 2 major hurricanes.[5] On April 17, The Weather Company released their forecasts, calling for 2017 to be a near-average season, with a total of 12 named storms, 6 hurricanes, and 2 major hurricanes.[6] The next day, on April 18, North Carolina State University released their prediction, also predicting a near-average season, with a total of 11–15 named storms, 4–6 hurricanes, and 1–3 major hurricanes.[7] On May 20, The Weather Company issued an updated forecast, raising their numbers to 14 named storms, 7 hurricanes, and 3 major hurricanes to account for Tropical Storm Arlene as well as the decreasing chance of El Niño forming during the season.[8] On May 25, NOAA released their prediction, citing a 70% chance of an above average season due to "a weak or nonexistent El Niño", calling for 11–17 named storms, 5–9 hurricanes, and 2–4 major hurricanes.[9] On May 26, TSR updated its prediction to around the same numbers as its December 2016 prediction, with only a minor change in the expected ACE index amount to 98 units.[10]

Mid-season outlooks

CSU updated their forecast on June 1 to include 14 named storms, 6 hurricanes and 2 major hurricanes to include Tropical Storm Arlene.[11] It was based on the current status of the North Atlantic Oscillation, which was showing signs of leaning towards a negative phase, favoring a warmer tropical Atlantic; and the chances of El Niño forming were significantly lower. However, they stressed on the uncertainty that the El Niño Southern Oscillation could be in a warm-neutral phase or weak El Niño conditions by the peak of the season.

Seasonal summary

Saffir–Simpson hurricane wind scale

The Accumulated cyclone energy (ACE) index for the 2017 Atlantic hurricane season, as of Arlene's final advisory, is 0.565 units.[nb 1]

Systems

Tropical Storm Arlene

Tropical storm (SSHWS)
 
DurationApril 19 – April 21
Peak intensity50 mph (85 km/h) (1-min);
993 mbar (hPa)
See also: List of off-season Atlantic hurricanes

An extratropical cyclone formed along a cold front well to the southeast of Newfoundland on April 15, producing waves as high as 40 feet (12 m) over subsequent days.[13] The system initially failed to organize appreciably; by April 17, however, sporadic convection began to coalesce around an increasingly well defined circulation. This process continued with the formation of a curved banding feature near the center on April 19, prompting the National Hurricane Center (NHC) to upgrade the low to Subtropical Depression One at 15:00 UTC that day.[14] At this time, the system was situated 890 mi (1,435 km) southwest of the Azores.[15] Little change in strength occurred throughout the day.[16]

Convection became more concentrated and the system's wind field contracted during the early morning hours of April 20, and the system transitioned to a fully tropical cyclone at 15:00 UTC that day.[17] Six hours later, despite forecasts predicting it would dissipate, the storm unexpectedly strengthened into Tropical Storm Arlene.[18] Revolving around the aforementioned low to its west, Arlene defied forecasts again and attained a peak intensity of 50 mph (85 km/h) at 03:00 UTC on April 21, despite a deteriorating satellite presentation.[19] Twelve hours later, however, Arlene became embedded within the aforementioned larger extratropical cyclone, and lost its identity as a tropical cyclone.[20] Arlene's remnants continued to persist through the next day, executing a counterclockwise loop around the larger extratropical cyclone, while in the process of merging with it.[21] Early on April 23, the remnants of Arlene fully merged into the larger extratropical system.[22]

Upon its formation as a subtropical depression on April 19, Arlene was the sixth known subtropical or tropical cyclone to form in the month of April in the Atlantic basin; the other instances were Ana in 2003, a subtropical storm in April 1992, and three tropical depressions in 1912, 1915, and 1973, respectively. When Arlene became a tropical storm on April 20, this marked only the second such occurrence on record, after Ana in 2003.[23][nb 2] Furthermore, it had the lowest central pressure of any Atlantic storm recorded in the month of April, with a central pressure of 993 mbar (hPa; 29.32 inHg), again surpassing Ana.[24] Additionally, unrelated to Arlene, Tropical Storm Adrian in the Eastern Pacific basin also formed before the corresponding hurricane season was set to officially begin, being the earliest named storm in the Eastern Pacific proper. The last time where the first storms in both basins were pre-season storms was in 2012.[25]

Potential Tropical Cyclone Two

Potential Tropical Cyclone Two
Current storm status
Potential tropical cyclone (1-min mean)
Satellite image
Forecast map
As of:11:00 a.m. AST (12:00 UTC) June 19
Location:8°48′N 56°48′W / 8.8°N 56.8°W / 8.8; -56.8 (Potential Tropical Cyclone Two) ± 30 nm
About 325 mi (525 km) ESE of Trinidad
About 405mi (650 km) ESE of Grenada
Sustained winds:35 kt (40 mph; 65 km/h) (1-min mean)
gusting to 45 kt (50 mph; 85 km/h)
Pressure:1005 mbar (hPa; 29.68 inHg)
Movement:W at 25 mph (41 km/h)
See more detailed information.

A tropical wave moved off the coast of Africa on June 13 and was first monitored by the National Hurricane Center shortly afterwards.[26] Development, if any, was expected to be slow to occur due to its low latitude and relatively fast motion. As it moved swiftly across the Main Development Region of the Atlantic, the disturbance began to organize, albeit slowly, and the NHC raised development chances slightly on June 16.[27] Little change in organization occurred until June 18, when a burst of convection near the center of the disturbance prompted the NHC to designate the system as Potential Tropical Cyclone Two at 21:00 UTC that day, the first such designation of a disturbance by the agency that had not yet developed into a tropical cyclone.[28]

Current storm information

As of 8:00 a.m. AST (12:00 UTC) June 19, Potential Tropical Cyclone Two is located within 30 nautical miles of 8°42′N 55°42′W / 8.7°N 55.7°W / 8.7; -55.7 (PTC Two), about 400 miles (645 km) east-southeast of Trinidad, or about 470 miles (755 km) east-southeast of Grenada. Maximum sustained winds are 35 knots (40 mph; 65 km/h), with gusts up to 45 knots (50 mph; 85 km/h). The minimum barometric pressure is 1005 mbar (hPa; 29.68 inHg), and the system is moving west at 20 knots (23 mph; 37 km/h). Tropical storm-force winds extend outward up to 60 miles (95 km) from the center of Potential Tropical Cyclone Two, mainly to the north.

For latest official information, see:

Watches and warnings

Template:HurricaneWarningsTable Template:HurricaneWatchTable


Storm names

Main articles: Tropical cyclone naming, History of tropical cyclone naming, and List of historical tropical cyclone names

The following list of names will be used for named storms that form in the North Atlantic in 2017. Retired names, if any, will be announced by the World Meteorological Organization in the spring of 2018. The names not retired from this list will be used again in the 2023 season.[29] This is the same list used in the 2011 season, with the exception of the name Irma, which replaced Irene.

  • Arlene
  • Bret (unused)
  • Cindy (unused)
  • Don (unused)
  • Emily (unused)
  • Franklin (unused)
  • Gert (unused)
  • Harvey (unused)
  • Irma (unused)
  • Jose (unused)
  • Katia (unused)
  • Lee (unused)
  • Maria (unused)
  • Nate (unused)
  • Ophelia (unused)
  • Philippe (unused)
  • Rina (unused)
  • Sean (unused)
  • Tammy (unused)
  • Vince (unused)
  • Whitney (unused)

Season effects

This is a table of all the storms that have formed in the 2017 Atlantic hurricane season. It includes their duration, names, landfall(s), denoted in parentheses, damages, and death totals. Deaths in parentheses are additional and indirect (an example of an indirect death would be a traffic accident), but were still related to that storm. Damage and deaths include totals while the storm was extratropical, a wave, or a low, and all the damage figures are in 2017 USD.

Saffir–Simpson scale
TD TS C1 C2 C3 C4 C5
2017 North Atlantic tropical cyclones season statistics
Storm
name 		Dates active Storm category
at peak intensity 		Max 1-min
wind
mph (km/h) 		Min.
press.
(mbar) 		Areas affected Damage
(USD) 		Deaths Ref(s)
Arlene April 19 – 21 Tropical storm 50 (85) 993 None None None
Season aggregates
1 systems April 19 –
Season ongoing 		  50 (85) 993 None None  

See also

Footnotes

  1. ^ The totals represent the sum of the squares for every (sub)tropical storm's intensity of over 33 knots (38 mph, 61 km/h), divided by 10,000. Calculations are provided at Talk:2017 Atlantic hurricane season/ACE calcs.
  2. ^ It should be noted that Arlene would likely not have been detected without the help of satellites, and there may well have been other similar storms this early in the year in the pre-satellite era (1966 and before).[18]

References

  1. ^ "Update on National Hurricane Center Products and Services for 2017" (PDF). National Hurricane Center. Retrieved March 12, 2017.
  2. ^ a b "Background Information: The North Atlantic Hurricane Season". Climate Prediction Center. National Oceanic and Atmospheric Administration. August 9, 2012. Retrieved December 13, 2013.
  3. ^ a b c d Mark Saunders; Adam Lea (December 13, 2016). Extended Range Forecast for Atlantic Hurricane Activity in 2017 (PDF) (Report). London, United Kingdom: Tropical Storm Risk.
  4. ^ a b Mark Saunders; Adam Lea (April 5, 2017). April Forecast Update for Atlantic Hurricane Activity in 2017 (PDF) (Report). London, United Kingdom: Tropical Storm Risk.
  5. ^ a b Phillip J. Klotzbach; William M. Gray (April 6, 2017). "Extended Range Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2017" (PDF). Colorado State University. Retrieved April 6, 2017.
  6. ^ a b "2017 Atlantic Hurricane Season Forecast Calls For a Near-Average Number of Storms, Less Active Than 2016". weather.com. Retrieved 20 April 2017.
  7. ^ a b WRAL (18 April 2017). "NCSU researchers predict 'normal' hurricane season :: WRAL.com". wral.com. Retrieved 20 April 2017.
  8. ^ a b "2017 Atlantic Hurricane Season Forecast Update Calls For An Above-Average Number Of Storms". weather.com. Retrieved 20 May 2017.
  9. ^ a b "Above-normal Atlantic hurricane season is most likely this year". National Oceanic and Atmospheric Administration. May 25, 2017.
  10. ^ a b Mark Saunders; Adam Lea (May 26, 2017). Pre-Season Forecast for North Atlantic Hurricane Activity in 2017 (PDF) (Report). London, United Kingdom: Tropical Storm Risk.
  11. ^ a b Phillip J. Klotzbach; William M. Gray (June 1, 2017). "Extended Range Forecast of Atlantic Seasonal Hurricane Activity and Landfall Strike Probability for 2017" (PDF). Colorado State University. Retrieved June 1, 2017.
  12. ^ Phillip J. Klotzbach (December 14, 2016). "Qualitative Discussion of Atlantic Basin Seasonal Hurricane Activity for 2017" (PDF). Colorado State University. Retrieved December 24, 2016.
  13. ^ "@NWSOPC on Twitter: "W Atlantic rapid cyclogenesis produced #hurricane force winds, seas to 40 ft -- 2day satellite loop via GOES16 non-op and preliminary data"". Ocean Prediction Center. April 17, 2017. Retrieved April 20, 2017 – via Twitter.
  14. ^ Lixion Avila (April 19, 2017). "Subtropical Depression One Discussion Number 1". National Hurricane Center. Retrieved April 19, 2017.
  15. ^ Lixion Avila (April 19, 2017). Subtropical Depression One Advisory Number 1 (Report). Miami, Florida: National Hurricane Center. Retrieved April 22, 2017.
  16. ^ "Subtropical Depression One Discussion Number 3". National Hurricane Center. April 19, 2017. Retrieved April 19, 2017.
  17. ^ Lixion Avila (April 20, 2017). "Tropical Depression One Discussion Number 5". National Hurricane Center. Retrieved April 20, 2017.
  18. ^ a b Lixion Avila (April 20, 2017). "Tropical Storm Arlene Discussion Number 6". National Hurricane Center. Retrieved April 20, 2017.
  19. ^ Lixion Avila (April 20, 2017). "Tropical Storm Arlene Discussion Number 7". National Hurricane Center. Retrieved April 20, 2017.
  20. ^ Lixion Avila (April 21, 2017). "Post-Tropical Cyclone Arlene Discussion Number 9". National Hurricane Center. Retrieved April 21, 2017.
  21. ^ Mike Tichacek (April 22, 2017). "Atlantic Tropical Weather Discussion: 2:04 PM EDT Sat Apr 22 2017". National Hurricane Center. Retrieved April 23, 2017.
  22. ^ Formosa (April 23, 2017). "Atlantic Tropical Weather Discussion: 6:28 AM EDT Sun Apr 23 2017". National Hurricane Center. Archived from the original on April 23, 2017. Retrieved April 23, 2017. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  23. ^ "Tropical Storm Arlene Forms in the Atlantic; No Threat to Land". The Weather Channel. April 20, 2017. Retrieved April 20, 2017.
  24. ^ Phillip Klotzbach (April 20, 2017). "The current central pressure of TS #Arlene of 993 mb is the lowest pressure for any April Atlantic TC or subtropical TC on record". Twitter. Retrieved April 21, 2017.
  25. ^ Henson, Bob (May 11, 2017). "Adios, Adrian: Earliest Tropical Storm in East Pacific Annals Dissipates". Wunderground. Retrieved May 11, 2017.
  26. ^ http://www.nhc.noaa.gov/archive/xgtwo/gtwo_archive.php?current_issuance=201706140528&basin=atl&fdays=2
  27. ^ "NHC Graphical Outlook Archive". www.nhc.noaa.gov. Retrieved 18 June 2017.
  28. ^ "Potential Tropical Cyclone Two Forecast Discussion". www.nhc.noaa.gov. Retrieved 18 June 2017.
  29. ^ "Tropical Cyclone Names#Atlantic". National Hurricane Center. Retrieved December 24, 2016.
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