Tropical Cyclone Alan was considered to be one of the worst
natural disasters
A natural disaster is "the negative impact following an actual occurrence of natural hazard in the event that it significantly harms a community". A natural disaster can cause loss of life or damage property, and typically leaves some econo ...
experienced in
French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
. The system, first noted as a
tropical disturbance
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few scales of classifications are used officially by the mete ...
on April 17, 1998 east of the
Northern Cook Islands
The Northern Cook Islands is one of the two chains of atolls which make up the Cook Islands. Lying in a horizontal band between 9° and 13°30' south of the Equator, the chain consists of the atolls of Manihiki, Nassau, Penrhyn, Pukapuka, Rakaha ...
, initially moved erratically prior to its designation as Alan upon developing into a
tropical cyclone
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
on April 21. The following day, Alan reached its estimated peak intensity with 10-minute maximum sustained wind speeds of , posing several forecasting challenges due to difficulties in establishing its location and intensity. On April 23, Alan appeared to become
shear
Shear may refer to:
Textile production
*Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
*Shear strength (soil), the shear strength ...
ed with the
low-level circulation center
The eye is a region of mostly calm weather at the center of tropical cyclones. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the ''eyewall'', a ring of towering thunderstorms where the most severe weat ...
displaced about from the nearest
atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference layer in the atmosphere. Different lapse rates within dry and moist air masses lead to instability. Mixing of air during the day which expands the ...
. However, over the next day, after the mid-level
trough
Trough may refer to:
In science
* Trough (geology), a long depression less steep than a trench
* Trough (meteorology), an elongated region of low atmospheric pressure
* Trough (physics), the lowest point on a wave
* Trough level (medicine), the l ...
of
low pressure
In meteorology, a low-pressure area, low area or low is a region where the atmospheric pressure is lower than that of surrounding locations. Low-pressure areas are commonly associated with inclement weather (such as cloudy, windy, with possible ...
shearing the system moved faster than expected, Alan became better organized. While situated about west-northwest of the
French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
n island of Tahiti, the system drifted south-southeastward. Early on April 25, Alan passed near to or over the French Polynesian Society Islands of Maupiti, Bora-Bora, and Raiatea. However, strong wind shear pulled the system apart, with visible imagery confirming the system's degeneration into a depression with a fully exposed low-level circulation. The system affected French Polynesia with high winds and torrential rain, causing several
landslides
Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, ...
on the
Society Islands
The Society Islands (french: Îles de la Société, officially ''Archipel de la Société;'' ty, Tōtaiete mā) are an archipelago located in the South Pacific Ocean. Politically, they are part of French Polynesia, an overseas country of the F ...
. The landslides resulted in the collapse of two bridges, and also overturned trees, in turn obstructing roads. Overall, ten people died as a result of the system, while thirty others were injured, with a majority of the casualties a result of landslides. On the islands of
Raiatea
Raiatea or Ra'iatea ( Tahitian: ''Ra‘iātea'') is the second largest of the Society Islands, after Tahiti, in French Polynesia. The island is widely regarded as the "centre" of the eastern islands in ancient Polynesia and it is likely that the ...
,
Taha'a
Taha’a (sometimes spelled as "Tahaa") is an island located among the western group, the Leeward Islands, of the Society Islands in French Polynesia, an overseas territory of France in the Pacific Ocean. The islands of Taha’a and neighboring R ...
and
Huahine
Huahine is an island located among the Society Islands, in French Polynesia, an overseas territory of France in the Pacific Ocean. It is part of the Leeward Islands group ''(Îles sous le Vent).'' At the 2017 census it had a population of 6,075. ...
, several churches, schools and clinics were damaged, while water and electricity supplies were cut off. On the islands, around 750 houses were destroyed, with 430 and 150 wrecked on Huahine and Ra'iātea, respectively.
Meteorological history
On April 17, 1998, the
Fiji Meteorological Service
The Fiji Meteorological Service (FMS) is a Department of the government of Fiji responsible for providing weather forecasts and is based on the grounds of Nadi Airport in Nadi. The current director of Fiji Meteorological Service is Misaeli Funaki. ...
(FMS) started to monitor the development of a tropical disturbance east of the Northern
Cook Islands
)
, image_map = Cook Islands on the globe (small islands magnified) (Polynesia centered).svg
, capital = Avarua
, coordinates =
, largest_city = Avarua
, official_languages =
, lan ...
.
Before the FMS initiated advisories on the system on April 19, the system moved erratically; it later developed into a weak depression while it located about north of
Manihiki Atoll in the Northern Cook Islands.
Over the next couple of days, the system slowly moved northwards, gradually organizing, with gale-force winds developing in its southern quadrant on April 20.
Over the next day, the system developed into a category 1 tropical cyclone on the
Australian tropical cyclone intensity scale
Tropical cyclones are ranked on one of five tropical cyclone intensity scales, according to their maximum sustained winds and which tropical cyclone basins they are located in. Only a few scales of classifications are used officially by the mete ...
, before the FMS named the system Alan at 1800 UTC.
By this time, the cyclone, located about east-southeast of Manihiki, started to move westwards.
On April 22, the FMS estimated that Alan reached its peak intensity with 10-minute
maximum sustained wind
The maximum sustained wind associated with a tropical cyclone is a common
indicator of the intensity of the storm. Within a mature tropical cyclone, it is found within the eyewall at a distance defined as the radius of maximum wind, or RMW. Unl ...
speeds of 75 km/h (45 mph), just as the system started to pose several forecasting challenges due to difficulties in establishing its location and intensity.
Later that day the
Naval Pacific Meteorology and Oceanography Center (NPMOC) started to issue warnings on Alan and accidentally assigned it the designation 32P as opposed to 36P, estimating peak 1-minute sustained wind speeds of 85 km/h (50 mph).
On April 23, the system appeared to become sheared, with the low-level circulation center displaced about from the nearest atmospheric convection.
As a result, the FMS reported Alan's weakening into a depression, while the NPMOC subsequently issued their final advisory on the system.
Over the next day, as a mid-level trough of low pressure shearing Alan moved faster than expected, the depression became better organized and developed favorable upper-level outflow.
As a result, the NPMOC initiated advisories on the system again on April 24, and later that day, the FMS reported that Alan re-intensified into a Category 1 tropical cyclone.
While located about west-northwest of the
French Polynesia
)Territorial motto: ( en, "Great Tahiti of the Golden Haze")
, anthem =
, song_type = Regional anthem
, song = " Ia Ora 'O Tahiti Nui"
, image_map = French Polynesia on the globe (French Polynesia centered).svg
, map_alt = Location of Frenc ...
n island of
Tahiti
Tahiti (; Tahitian ; ; previously also known as Otaheite) is the largest island of the Windward group of the Society Islands in French Polynesia. It is located in the central part of the Pacific Ocean and the nearest major landmass is Austr ...
, the system moved south-southeastward under the influence of an upper-level anticyclone located to its east.
Early on April 25, Alan passed near to or over the French Polynesian
Society Islands
The Society Islands (french: Îles de la Société, officially ''Archipel de la Société;'' ty, Tōtaiete mā) are an archipelago located in the South Pacific Ocean. Politically, they are part of French Polynesia, an overseas country of the F ...
of
Maupiti
Maupiti is an island in the western Leeward Islands in French Polynesia. It is the westernmost volcanic high island in the archipelago, northwest of Tahiti and west of Bora Bora. It has a population of 1,286 people. The largest town is Vaiea.
...
,
Bora-Bora
Bora Bora (French: ''Bora-Bora''; Tahitian: ''Pora Pora'') is an island group in the Leeward Islands. The Leeward Islands comprise the western part of the Society Islands of French Polynesia, which is an overseas collectivity of the French Re ...
, and
Ra'iātea
Raiatea or Ra'iatea ( Tahitian: ''Ra‘iātea'') is the second largest of the Society Islands, after Tahiti, in French Polynesia. The island is widely regarded as the "centre" of the eastern islands in ancient Polynesia and it is likely that the ...
.
As the system moved near Bora Bora, a maximum wind gust of and a pressure observation of were recorded,
indicating the minimal strength of Alan; however, the wind gust was stronger than that expected of similarly intense tropical cyclones.
It was later speculated that squalls within Alan's convective feeder band may have been responsible for the stronger wind gusts.
On April 25, strong wind shear pulled the system apart, with visible imagery revealing a fully exposed low-level circulation.
As a result, the FMS reported that the system weakened into a depression at 1800 UTC that day, while located about west-northwest of Tahiti.
The NPMOC subsequently reissued their final advisory early the next day as the system drifted south-southeastward while located west of Tahiti.
Preparations and impact
Cyclone Alan produced high winds and torrential rain over French Polynesia between April 24 and 25, causing several landslides on the Society Islands,
resulting in the collapse of two bridges and obstruction of roads by fallen trees.
Damage associated with the system was mainly confined to the
Leeward Islands
french: Îles-Sous-le-Vent
, image_name =
, image_caption = ''Political'' Leeward Islands. Clockwise: Antigua and Barbuda, Guadeloupe, Saint kitts and Nevis.
, image_alt =
, locator_map =
, location = Caribbean SeaNorth Atlantic Ocean
, coor ...
of
Bora Bora
Bora Bora ( French: ''Bora-Bora''; Tahitian: ''Pora Pora'') is an island group in the Leeward Islands. The Leeward Islands comprise the western part of the Society Islands of French Polynesia, which is an overseas collectivity of the Frenc ...
,
Tahaa
Taha’a (sometimes spelled as "Tahaa") is an island located among the western group, the Leeward Islands, of the Society Islands in French Polynesia, an overseas territory of France in the Pacific Ocean. The islands of Taha’a and neighboring R ...
,
Ra'iātea
Raiatea or Ra'iatea ( Tahitian: ''Ra‘iātea'') is the second largest of the Society Islands, after Tahiti, in French Polynesia. The island is widely regarded as the "centre" of the eastern islands in ancient Polynesia and it is likely that the ...
and
Huahine
Huahine is an island located among the Society Islands, in French Polynesia, an overseas territory of France in the Pacific Ocean. It is part of the Leeward Islands group ''(Îles sous le Vent).'' At the 2017 census it had a population of 6,075. ...
, which had all been damaged by
Cyclone Osea
Severe Tropical Cyclone Osea was the second of seven cyclones to affect French Polynesia during the 1997–98 South Pacific cyclone season. The fourth tropical cyclone and second severe tropical cyclone of the very active season, Osea began as a ...
earlier in the season.
Overall, ten people died as a result of the system, while thirty others were injured, with the majority of the casualties occurring due to landslides.
On Bora Bora, wind gusts of up to were reported, while on Tahaa, wind gusts of up to were reported.
On the islands of Ra'iātea, Tahaa and Huahine, several churches, schools and clinics were damaged, while water and electricity supplies were cut off.
On the islands, around 750 houses were destroyed, with 430 and 150 wrecked on Huahine and Ra'iātea, respectively.
On Huahine, the extent of the damage, along with a sharp dip on the
Uturoa
Uturoa is a Communes of France, commune located in Raiatea, the largest island of the Leeward Islands (Society Islands), Îles Sous le Vent (Leeward Islands) in French Polynesia. It is situated in between the Administrative divisions of French P ...
barograph trace, suggested that a
tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...
may have been spawned in one of Alan's
convective bands.
In the system's aftermath a, 60-person relief team was deployed from Tahiti to the affected islands to assist with emergency operations.
The
French President
The president of France, officially the president of the French Republic (french: Président de la République française), is the executive head of state of France, and the commander-in-chief of the French Armed Forces. As the presidency is ...
Jacques Chirac
Jacques René Chirac (, , ; 29 November 193226 September 2019) was a French politician who served as President of France from 1995 to 2007. Chirac was previously Prime Minister of France from 1974 to 1976 and from 1986 to 1988, as well as Ma ...
and
Prime Minister
A prime minister, premier or chief of cabinet is the head of the cabinet and the leader of the ministers in the executive branch of government, often in a parliamentary or semi-presidential system. Under those systems, a prime minister is not ...
Lionel Jospin
Lionel Robert Jospin (; born 12 July 1937) is a French politician who served as Prime Minister of France from 1997 to 2002.
Jospin was First Secretary of the Socialist Party from 1995 to 1997 and the party's candidate for President of France in ...
both sent messages of support to the Leeward Islands, and in French Polynesia, the system was considered to be one of the worst natural disasters in the islands' history.
A few days after Cyclone Alan impacted the islands, Cyclone Bart caused an additional ten deaths and some minor damage to the French territory.
During December 1998, the
European Community Humanitarian Office responded to a government appeal, providing for tents, medical aid, food and clothing.
See also
*
Cyclone Wasa
*
Cyclone Oli
Severe Tropical Cyclone Oli (RSMC Nadi designation 07F, JTWC designation 12P) was the first severe tropical cyclone within the South Pacific basin since Cyclone Gene in 2008.
At least one person was killed by large swells produced by the storm i ...
References
External links
{{DEFAULTSORT:Alan
1997–98 South Pacific cyclone season
Tropical cyclones in French Polynesia
1998 in French Polynesia
Category 1 South Pacific cyclones