Cyclone Wilma

Severe Tropical Cyclone Wilma was a powerful tropical cyclone that affected the Samoan Islands, Tonga and New Zealand. Forming out of a trough of low pressure on 19 January 2011 to the northwest of Fiji, Cyclone Wilma initially tracked eastward towards the Samoan Islands. On 22 January, the system took a sharp southward turn, bringing its centre directly over American Samoa the following day. After turning towards the southwest and accelerating, Wilma steadily intensified into a severe tropical cyclone before striking Tonga. The storm reached its peak intensity on 26 January as a Category 4 cyclone with winds of 185 km/h (115 mph) and a barometric pressure of 930 mbar (hPa; 27.46 inHg). Gradually re-curving towards the southeast, Wilma weakened quickly as it moved over cooler sea surface temperatures; by 28 January, it was downgraded to a tropical cyclone. Later that day, the storm brushed the North Island of New Zealand before transitioning into an extratropical cyclone.

Severe Tropical Cyclone Wilma
Category 4 severe tropical cyclone (Aus scale)
Category 4 tropical cyclone (SSHWS)
Severe Tropical Cyclone Wilma on January 26
Formed19 January 2011
Dissipated30 January 2011
(Extratropical after 29 January 2011)
Highest winds10-minute sustained: 185 km/h (115 mph)
1-minute sustained: 215 km/h (130 mph)
Lowest pressure930 hPa (mbar); 27.46 inHg
Fatalities3 direct
Damage$22 million (2011 USD)
Areas affectedAmerican Samoa, Samoa, Tonga, New Zealand
Part of the 2010–11 South Pacific cyclone season

Throughout Wilma's path, three countries were affected, with New Zealand experiencing the most severe damage. At least three fatalities in American Samoa have been blamed on the storm, two from flooding and one from high seas. In Tonga, "major damage" was reported across the Ha'apai Islands. In New Zealand, several homes were destroyed by the storm and hundreds of people were evacuated. However, there were no reports of fatalities. Torrential rain in the country, exceeding 280 mm (11 in) in some places, triggered 50-year flood events and isolated towns.

Meteorological history
Map plotting the track and the intensity of the storm, according to the Saffir–Simpson scale

Early on 19 January, RSMC Nadi reported that Tropical Disturbance 06F had developed along a trough of low pressure about 665 km (413 mi) to the northeast of Nadi, Fiji.[1] During that day convection surrounding the disturbance gradually became more organised, and early the next day, RSMC Nadi reported that it had intensified into a tropical depression.[2] On 22 January, The Joint Typhoon Warning Center (JTWC) started monitoring the system as Tropical Cyclone '08P'.[3] Later the same day, RSMC Nadi upgraded Tropical Depression 06F to a tropical cyclone and named it 'Wilma'.[4] Early on 24 January, RSMC Nadi further upgraded Wilma to a Category 2 Tropical Cyclone, and then Category 3 later that day.[5][6] Wilma continued to strengthen and on 26 January, the RSMC Nadi upgraded it into a Category 4 Severe Tropical Cyclone.[7] Early on 27 January, Wilma entered TCWC Wellington's area of responsibility.[8] A few hours later, TCWC Wellington took full responsibility of Wilma, and downgraded it into a Category 3 Severe Tropical Cyclone.[9] The next day, Wilma continued to weaken and TCWC Wellington further downgraded it into a tropical cyclone.[10] Later that day, the JTWC, issuing their final warning, reported that the system took a southeast curve along the coast of North Island, New Zealand and started becoming extratropical.[11] A few hours later, the TCWC Wellington discontinued advisories, no longer considering it a tropical cyclone.[12]

Preparations, Impact and aftermath

American Samoa

Following harsh criticism for the lack of a warning siren after the 2009 Samoa earthquake and tsunami, in which more than 100 perished, the American Samoan Government ensured that residents were aware of Cyclone Wilma several days prior to its arrival. Many people boarded up their homes and Homeland Security was on standby in case of evacuations. As a precautionary measure, ten shelters were also opened on the island.[13]

On 23 January, Wilma passed directly over American Samoa, bringing winds in excess of 95 km/h (60 mph).[13] The local National Weather Service office recorded sustained winds of 66 km/h (41 mph) with gusts to 95 km/h (59 mph) while the National Oceanic and Atmospheric Administration's Earth System Research Laboratory on Cape Matatula, Tutuila, observed sustained winds of 93 km/h (58 mph) and gusts of 130 km/h (81 mph).[14] These winds downed numerous trees and power lines, leaving several towns and cities without electricity.[13] Several structures also had their roofs blown off.[15] Heavy rains amounting to 243 mm (9.56 in) triggered a few landslides but overall damage was light.[14] With that, the Pago Pago International Airport was closed and the American Samoa Governor, Togiola Tulafono ordered local government agencies to help those in need.[16] Wilma caused severe damage to the StarKist Samoa tuna cannery which was then shut down for a week.[17] Across the region, three fatalities due to drowning were blamed on the storm. One of these was a child who was swept away by a swollen river while he was playing near it.[18]

In the days after Wilma's passage, health officials warned residents to stay away from standing water as it may have been contaminated to prevent the spread of water-borne diseases.[19] Following preliminary assessments of damage, Governor Tulafono stated that there was sufficient losses to warrant an emergency declaration from President Barack Obama. However, he also requested that a second, in-depth report of the situation be made to better determine how to move forward; the second assessment was set to start on 27 January.[20] According to the Federal Emergency Management Agency, power and water supplies were restored to all areas by 25 January and the airport was set to reopen that day. Harbours were to remain closed for several more days as debris was being cleared from coastal waters.[21]

Tonga and Lau Islands

After Wilma moved over American Samoa, a tropical cyclone alert was issued in Tonga and Lau Islands.[22] On the morning of 25 January, Wilma blew over Tonga as a severe tropical cyclone.[23] Major damage was reported in the Ha'apai Islands of Tonga.[24] Wilma also disrupted New Zealand Foreign Minister, Murray McCully's trip to Tonga.[25] Throughout Tonga, damage amounted to $3 million.[26]

New Zealand
Flooding in Kaukapakapa after Cyclone Wilma

According to the media, Wilma was expected to approach the coasts of Cape Reinga on 29 January, as a Category 2 Tropical Cyclone.[27] In combination with previous flooding expected to be worsened by Wilma, officials in New Zealand evacuated numerous towns in the Thames-Coromandel District.[28] At least 70 people sought refuge in public shelters during the storm.[29]

As Cyclone Wilma brushed the North Island, it brought torrential rains to much of the region, with several areas recording 200 mm (7.9 in) during a 24‑hour span.[28] One station recorded 280 mm (11 in) in 12–14 hours.[30] With this, several areas neared record-breaking rainfall totals for the month of January. These rains, in combination with heavy rains a week prior, caused several rivers to swell. One river, the Whakatane, was expected to reach levels seen in 50-year flood events. Large amounts of debris was reported to be flowing down rivers into the ocean. High winds accompanying these rains caused significant damage as well; several homes were destroyed and electricity was cut off to many towns and cities as power lines were felled. Numerous roads across the island were shut down due to treacherous conditions. Two rural towns, Waimana and Ruatoki Valley, were isolated by flooding as high water covered all roads leading to and from the areas.[28] In parts of the Coromandel Peninsula, sewage treatment plants were overwhelmed by the amount of rain and began spilling raw sewage into nearby communities as well as Whangamata harbour.[30] Along the slopes of Mount Maunganui, campers were forced to evacuate in the middle of the night as flood waters began to threaten their rest areas.[31] Several landslides were also reported during the passage of Wilma, cutting off roads and damaging homes.[31] On Waiheke Island, two residents managed to escape their cottage, after the family dog began barking outside, before the hill it was situated on gave way, destroying their house.[32]

Throughout New Zealand, damage from Wilma was at least NZ$25 million (US$19 million).[33][34] While other cyclones have weakened and turned into extratropical storms that then hit New Zealand, Cyclone Wilma is the first known to hit New Zealand as a tropical cyclone.[35]

Retirement

The name Wilma was retired in 2012 and was replaced with Wano.[36]

See also

References
  1. RSMC Nadi – Tropical Cyclone Centre (19 January 2010). "Tropical Disturbance Summary January 19, 2010 09z". Fiji Meteorological Service. Archived from the original on 19 January 2011. Retrieved 16 November 2014.
  2. "Tropical Disturbance Summary 20 January 2010 09z". Fiji Meteorological Service. Archived from the original on 20 January 2011. Retrieved 21 January 2011.
  3. "JTWC Tropical Cyclone 08P Warning 01". Joint Typhoon Warning Center. Archived from the original on 22 January 2011. Retrieved 22 January 2011.
  4. "Storm Warning for Cyclone Wilma 22 January 2010 12z". Fiji Meteorological Service. Archived from the original on 22 January 2011. Retrieved 22 January 2011.
  5. "RSMC Nadi Hurricane Warning 062 for Tropical Cyclone Wilma". Fiji Meteorological Service. Archived from the original on 24 January 2011. Retrieved 24 January 2011.
  6. "TROPICAL DISTURBANCE ADVISORY NUMBER A12 for TROPICAL CYCLONE WILMA". Fiji Meteorological Service. Archived from the original on 24 January 2011. Retrieved 25 January 2011.
  7. "HURRICANE WARNING 073 for TROPICAL CYCLONE WILMA". Fiji Meteorological Service. Archived from the original on 26 January 2011. Retrieved 26 January 2011.
  8. "JTWC Tropical Cyclone 08P Warning 11". Joint Typhoon Warning Center. Archived from the original on 27 January 2011. Retrieved 27 January 2011.
  9. "TCWC Wellington – HURRICANE WARNING 490". TCWC Wellington. Archived from the original on 27 January 2011. Retrieved 27 January 2011.
  10. "TCWC Wellington – HURRICANE WARNING 490". TCWC Wellington. Archived from the original on 27 January 2011. Retrieved 28 January 2011.
  11. "JTWC Tropical Cyclone 08P Warning 14". Joint Typhoon Warning Center. Archived from the original on 28 January 2011. Retrieved 28 January 2011.
  12. "Marine Weather Bulletin for Former Tropical Cyclone Wilma". Tropical Cyclone Warning Center, Wellington. Archived from the original on 28 January 2011. Retrieved 29 January 2011.
  13. Vanessa Stewart (27 January 2011). "Tropical Cyclone Wilma passes, no major damage to American Samoa". KHON2. Archived from the original on 29 January 2011. Retrieved 27 January 2011.
  14. American Samoa Event Report: Hurricane (Typhoon). National Weather Service Office in American Samoa (Report). National Climatic Data Center. 2011. Retrieved 28 April 2015.
  15. "Cyclone Wilma blows over Samoa, strengthening en route to Fiji". Honolulu Star Advertiser. 24 January 2011. Retrieved 24 January 2011.
  16. "Pacific nations on cyclone alert". People's Daily. Retrieved 24 January 2011.
  17. "Cyclone causes cannery shutdown in American Samoa". Radio New Zealand International. Retrieved 26 January 2011.
  18. "Samoan flood deaths could have been avoided – disaster official". Radio New Zealand. 27 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  19. "Health warnings in American Samoa following Cyclone Wilma". Radio New Zealand. 27 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  20. "Gov. Togiola receives preliminary assessment for Tropical Cyclone Wilma; requests second report". Government of American Samoa. 25 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  21. "National Situation Update: Tuesday, January 25, 2011". Federal Emergency Management Agency. 25 January 2011. Archived from the original on 21 July 2011. Retrieved 29 January 2011.
  22. "Cyclone alert for Tonga, Fiji". Australia News Network. Archived from the original on 14 March 2012. Retrieved 24 January 2011.
  23. "Cyclone passes Tonga tourist spot". Fairfax New Zealand Limited. Retrieved 25 January 2011.
  24. "Major destruction on Tonga's Ha'apai from Cyclone Wilma". Radio New Zealand International. Retrieved 25 January 2011.
  25. "McCully delays trip to Tonga". Radio New Zealand. Retrieved 25 January 2011.
  26. United Nations Office for the Coordination of Humanitarian Affairs (3 February 2011). "Tonga: Tropical Cyclone Wilma, Situation Report #1, 3 February 2011" (PDF). ReliefWeb. Retrieved 6 February 2011.
  27. "Cyclone on track to strike New Zealand". Fairfax New Zealand Limited. Retrieved 26 January 2011.
  28. "Cyclone Wilma leaves trail of destruction". Radio New Zealand. 29 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  29. "Cyclone Wilma batters New Zealand". Herald Sun. Australian Associated Press. 29 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  30. "Raw sewage overflows in Coromandel". The New Zealand Herald. 29 January 2011. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  31. Tim Lambourne (29 January 2011). "Cyclone Wilma leaves trail across the North Island". 3News.NZ. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  32. ONE News (29 January 2011). "Lucky escape after house collapses". TV New Zealand. Archived from the original on 29 January 2011. Retrieved 29 January 2011.
  33. Abby Gillies (20 February 2011). "Cyclone leaves $25m bill". The New Zealand Herald. Retrieved 20 February 2011.
  34. "Northland counts cost of cyclone damage". Radio New Zealand. 2 February 2011. Retrieved 6 February 2011.
  35. "Tropics move into the upper North Island". The New Zealand Herald. 6 February 2011. Retrieved 7 February 2011.
  36. Tropical Cyclone Programme (2012). Tropical Cyclone Operational Plan for the South Pacific and South-East Indian Ocean (PDF) (Report). World Meteorological Organization. Retrieved 13 December 2012.
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