Cyclone Orson

{{storm path|Orson 1989 track.png|alt=A map of a path across the eastern Indian Ocean near Australia. Most of the country can be seen in the right side of the image. Some of the Indonesian islands are visible at the top.}}

Cyclone Orson originated out of a tropical low, monitored by the Australian Bureau of Meteorology, that formed northwest of Darwin, Northern Territory on 17 April 1989. The system tracked southwest throughout the day before turning due west and strengthening into a tropical cyclone, at which time it received the name Orson.{{cite report|publisher=Australian Bureau of Meteorology |access-date=12 April 2012 |year=1992 |url=http://www.bom.gov.au/cyclone/history/pdf/orson_full.pdf |archive-url=https://web.archive.org/web/20120320213830/http://www.bom.gov.au/cyclone/history/pdf/orson_full.pdf |archive-date=20 March 2012 |url-status=live |author1=Hanstrum, B. |author2=Foley, G |title=Report on Tropical Cyclone Orson }} At this time, the Joint Typhoon Warning Center (JTWC) also began monitoring the storm as Tropical Storm 28S.{{cite report|author=Joint Typhoon Warning Center, Naval Western Oceanography Center |publisher=United States Navy, United States Air force |year=1990 |access-date=6 August 2009 |title=1989 Annual Tropical Cyclone Report |url=http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/atcr/1989atcr/pdf/1989_complete.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110606231751/http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/atcr/1989atcr/pdf/1989_complete.pdf |archive-date=6 June 2011 }} The forward motion of the storm gradually slowed as it intensified and on 19 April, Orson attained Category 3 status on the Australian tropical cyclone intensity scale, classifying Orson as a severe tropical cyclone. Later that day, as the storm attained Category 4 status, an eye developed. By this time, Orson began to turn towards the southwest and on 20 April, the storm intensified into a Category 5 cyclone with winds of {{convert|210|km/h|mph|abbr=on}} (10-minute sustained).{{cite web|publisher=Bureau of Meteorology|year=2008|access-date=6 August 2009|title=Australian Region Tropical Cyclone Best Tracks|url=http://www.bom.gov.au/cgi-bin/silo/cyclones.cgi}}

The JTWC also reported significant strengthening during the same period. They assessed Orson to have attained an intensity equivalent to a Category 5 hurricane on the Saffir–Simpson hurricane scale on 22 April with winds of {{convert|260|km/h|mph|abbr=on}} 1-minute sustained). Around this time, the storm tracked directly over the North Rankin gas platform. The platform was in the {{convert|40|km|mi|abbr=on}} wide eye of Orson for roughly 40 minutes. A weather station there recorded a barometric pressure of 904 hPa (mbar; 26.69 inHg) and wind gusts of {{convert|250|km/h|mph|abbr=on}} before the station was damaged. This was, at the time, the lowest pressure ever recorded in the Australian region since records began.{{cite web|publisher=Australian Bureau of Meteorology|date=March 1991|access-date=6 August 2009|title=The South Pacific and southeast Indian Ocean tropical cyclone season 1988–89|url=http://www.bom.gov.au/amm/docs/1991/drosdowsky.pdf|author=Drosdowsky L.|author2=Woodcock F.}} It was later surpassed by Severe Tropical Cyclone Gwenda in 1999 when that storm attained a pressure of 900 hPa (mbar).{{cite report|access-date=12 April 2012|url=http://www.bom.gov.au/cyclone/history/pdf/gwenda.pdf|title=Severe Tropical Cyclone Gwenda|last=Perth Tropical Cyclone Warning Centre|date=29 April 2009|publisher=Australian Bureau of Meteorology}} By this time, Cyclone Orson was roughly {{convert|555|km|mi|abbr=on}} in diameter.{{cite book|author2=Lai, L.L.|publisher=Springer Berlin/Heidelberg|author1=Zhang, Q.P.|author3=Sun, W.C.|title=Advances in Machine Learning and Cybernetics |chapter=Location of Tropical Cyclone Center with Intelligent Image Processing Technique |year=2006|access-date=7 August 2009|chapter-url=https://link.springer.com/chapter/10.1007/11739685_94|series=Lecture Notes in Computer Science|volume=3930|pages=898–907|doi=10.1007/11739685_94|isbn=978-3-540-33584-9}}

File:Orson 21 apr 1989 0605Z.jpg

Continuing on a southerly track, accelerating ahead of an approaching cold front, Cyclone Orson made landfall, near Dampier, around 4:45 am AWST on 23 April (2045 UTC 22 April). with winds of {{convert|220|km/h|mph|abbr=on}} (10-minute sustained). The JTWC also reported that Orson had weakened, with winds at landfall estimated at {{convert|230|km/h|mph|abbr=on}} 1-minute sustained).{{cite web|work=Joint Typhoon Warning Center, Naval Western Oceanography Center|publisher=United States Navy, United States Airforce|year=2002|access-date=6 August 2009|title=Tropical Cyclone 28S (Orson) Best Track|url=http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/best_tracks/1989/1989s-bsh/bsh261989.txt|archive-date=4 October 2013|archive-url=https://web.archive.org/web/20131004153344/http://www.usno.navy.mil/NOOC/nmfc-ph/RSS/jtwc/best_tracks/1989/1989s-bsh/bsh261989.txt|url-status=dead}} Tracking at {{convert|28|km/h|mph|abbr=on}}, the weakening storm passed over Pannawonica. Less than 12 hours after landfall, the storm weakened below Category 3 status. By this time, the JTWC was no longer monitoring the system. Around 5:00 am AWST on 24 April (2100 UTC 23 April), Orson weakened to a tropical low while situated over southern Western Australia. Continuing to accelerate to nearly {{convert|50|km/h|mph|abbr=on}}, the remnants of the storm moved over the Great Australian Bight late on 24 April. Several hours after moving back over water, the storm dissipated.

The Australian Bureau of Meteorology uses 10-minute sustained winds, while the Joint Typhoon Warning Center uses one-minute sustained winds.{{cite web|title=Frequently Asked Questions|author=Joint Typhoon Warning Center|date=2011-06-17|access-date=12 April 2012|url=http://www.usno.navy.mil/JTWC/frequently-asked-questions-1|publisher=United States Navy, United States Air force|archive-date=1 September 2013|archive-url=https://web.archive.org/web/20130901174657/http://www.usno.navy.mil/JTWC/frequently-asked-questions-1|url-status=dead}} The conversion factor between the two is 1.14.{{cite web|publisher=United States Navy|year=2009|url=http://www.nrlmry.navy.mil/~chu/chap6/se200.htm|title=Section 2 Intensity Observation and Forecast Errors|access-date=6 August 2009|archive-date=30 August 2012|archive-url=https://web.archive.org/web/20120830042306/http://www.nrlmry.navy.mil/~chu/chap6/se200.htm|url-status=dead}} The Bureau of Meteorology's peak intensity for Orson was {{convert|250|km/h|mph|abbr=on}} 10-minute sustained, or {{convert|290|km/h|mph|abbr=on}} one-minute sustained. The JTWC's peak intensity for Orson was {{convert|260|km/h|mph|abbr=on}} one-minute sustained, or {{convert|220|km/h|mph|abbr=on}} 10-minute sustained.

{{Most intense Australian cyclones|align=right}}As Cyclone Orson approached the coast of Western Australia, residents were urged to prepare for the storm; people proceeded to clean up litter, secure outdoor items and make sure their disaster kits were stocked. All 200 personnel from a A$1.5 billion gas platform off the coast were evacuated ahead of the storm.{{cite news|title=West Stays On Alert As Cyclone Tracks Inland|work=Courier-Mail|date=24 April 1989}} (Accessed via Lexis-Nexis) Since Cyclone Orson made landfall in a sparsely populated region, its effects were relatively light compared to its intensity. More than 20 fishermen were reported missing during the storm.

On 23 April, a rescue mission with three aircraft recovered roughly 20 fisherman, while one was still missing.{{cite news|work=Sunday Tasmanian|date=23 April 1989|title=Search and Rescue Finds 20 Fishermen}} Offshore, the storm killed four Indonesian fishermen after their ships sank in swells up to {{convert|20|m|ft|abbr=on}} produced by the storm. The North Rankin gas platform sustained minor damage despite wind gusts reaching {{convert|270|km/h|mph|abbr=on}}{{cite web|author=Fahey, Martin |publisher=The University of Western Australia |year=2005 |access-date=6 August 2009 |title=North Rankin 'A' Platform, North West Shelf |url=http://www.isfog.civil.uwa.edu.au/perspectives.pps |url-status=dead |archive-url=https://web.archive.org/web/20090913034614/http://www.isfog.civil.uwa.edu.au/perspectives.pps |archive-date=13 September 2009 }} and waves estimated at {{convert|21|m|ft|abbr=on}}.Christopher C. Burt and Mark Stroud Extreme Weather p. 219 The large swells also delayed the find of a major oil field that contained more than {{convert|200|Moilbbl|m3}} of oil. The waves knocked a drill rig used to find oil out of position; it would take several days for the drill rig to be repositioned.{{cite news|date=25 April 1989|title=Cyclone Delays News of 'Major Oil Find'|work=Sydney Morning Herald|page=23}} After an assessment of damage, it was found that the drill rig snapped off and broke the chains of two anchors before drifting nearly {{convert|2|km|mi|abbr=on}} from the platform. The repositioning and cleanup of the drill rig delayed the project by nearly two weeks.{{cite web|author=Luker, Paul|work=The Age |date=9 May 1989|access-date=7 August 2009|title=Woodside faces further delay in WA oil tests|url=https://news.google.com/newspapers?id=pWERAAAAIBAJ&sjid=FJcDAAAAIBAJ&pg=1418,6526806&dq=cyclone+orson}} The damages from Cyclone Orson increased the total cost of the platform to roughly {{ntsp|20000000||A$}} ({{ntsp|16800000||US$}}).{{cite web|author=Hextall, Bruce|work=The Sydney Morning Herald|date=16 May 1989|access-date=7 August 2009|title=First Shelf gas shipment to Japan likely in July|url=https://news.google.com/newspapers?id=ORURAAAAIBAJ&sjid=nOcDAAAAIBAJ&pg=2315,5736470&dq=cyclone+orson}}

Upon making landfall, Orson produced a storm surge of {{convert|3.1|m|ft|abbr=on}}. This came during low tide, having a height of {{convert|1.6|m|ft|abbr=on}}. Severe erosion was recorded along coastal areas, some losing nearly {{convert|20|m|ft|abbr=on}} of rocks.{{cite news|title=Cyclone Orson Was Nation's Strongest Ever|work=Holbart Mercury|date=25 April 1989}} (Accessed via Lexis-Nexis) Wind gusts in Dampier reached {{convert|183|km/h|abbr=on}} and a station near where Orson made landfall recorded a wind gust of {{convert|211|km/h|abbr=on}}. Harbour officials stated that several ships were knocked off their moorings and washed up onshore. In Karratha, the local weather radar sustained roughly A$900,000 (US$760,000) in damages. A nearby airport was also damaged. The jetty at Point Samson was severely damaged and eventually removed.{{cite web|publisher=Karratha and Districts Tourist Information Centre |year=2009 |access-date=13 December 2011 |title=Point Samson |url=http://www.pilbaracoast.com/towns/point-samson |url-status=dead |archive-url=https://web.archive.org/web/20120131203527/http://www.pilbaracoast.com/towns/point-samson |archive-date=31 January 2012 }} (Accessed via Lexis-Nexis)

The most severe damage took place in the mining town of Pannawonica, where 70 homes were damaged by the storm. Numerous trees and power lines were downed along the storm's path. Before dissipating, the storm left one additional person missing after contact was lost with his yacht. Later reports confirmed that the missing person drowned during the storm.{{cite news|work=Sydney Morning Herald|title=Cyclone Death|date=23 April 1989}} (Accessed via Lexis-Nexis) Twenty people were also injured during the storm, 60 were left homeless and about 1,000 were affected.{{cite web|publisher=Australian Emergency Management Agency |title=North-western coast, WA: Cyclone |date=13 September 2006 |access-date=13 December 2011 |url=http://www.disasters.ema.gov.au/Browse%20Details/DisasterEventDetails.aspx?DisasterEventID=895 |archive-url=https://web.archive.org/web/20120426001932/http://www.disasters.ema.gov.au/Browse%20Details/DisasterEventDetails.aspx?DisasterEventID=895 |url-status=dead |archive-date=26 April 2012 }} Total damages from the storm were estimated at A$20 million (US$16.8 million) and repair costs reached A$5 million (US$4.1 million).{{cite news|work=Courier-Mail|title=Cyclone Orson's bill may top $20M|date=25 April 1989}} (Accessed via Lexis-Nexis) Due to the severity of the storm, the name Orson was retired after the season.{{cite web|access-date=6 August 2009|author=RA V Tropical Cyclone Committee|title=Tropical Cyclone Operational Plan for the South Pacific and South-East Indian Ocean|year=2008|url=http://www.wmo.int/pages/prog/www/tcp/documents/TCP24-English2008.pdf|publisher=World Meteorological Organization}}

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• Cyclone Ilsa (2023) – another powerful tropical cyclone which took a similar path to Orson.

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• [http://australiasevereweather.com/tropical_cyclones/1988_1989/bom/tropical_cyclone_orson.htm Track of Cyclone Orson] (provided by Australia Severe Weather)

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Orson, cyclone

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Category:1989 disasters in Australia