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Cyclone Urmil (2006)
Encyclopedia
Tropical Cyclone Urmil was a short lived storm that explosively intensified to reach its peak intensity as a high-end Category 2 cyclone on the Australian Scale, just 12 hours after being named. Forming out of a tropical disturbance early on January 14, Urmil quickly intensified before weakening just as quickly. The intensification was a result of the main convective
banding feature
wrapping around the center of circulation
. However, the combination of high wind shear
and the rapid movement of the cyclone caused convection to become separated from the center. By January 15, the storm transitioned into an extratropical cyclone
shortly before dissipating. Urmil had only minor effects on land; scattered vegetation damage was reported in Tonga
.
over the open waters of the south Pacific Ocean
on January 13. Around 1800 UTC
, the Regional Specialized Meteorological Centre
(RSMC) in Nadi, Fiji classified the system as Tropical Disturbance 06F, while it was located about 370 km (230 mi) west of Pago Pago, American Samoa
. Forming in the wake of Tropical Cyclone Tam
, the disturbance rapidly organized within an environment of favorable diffulence aloft, warm waters (29°C
; 84.2°F
), and moderate wind shear
. Six hours later, RSMC Nadi upgraded 06F to a tropical cyclone and gave it the name Urmil while it was situated near Niuatoputapu
, Tonga
. Shortly after, the Joint Typhoon Warning Center
(JTWC) issued a Tropical Cyclone Formation Alert
as the storm quickly traveled towards the south-southeast. Around 0600 UTC on January 14, the JTWC classified Urmil as Tropical Cyclone 07P.
During the following six hours, Urmil underwent explosive deepening
as the main feeder band
wrapped around the center of circulation
. After the brief period of intensification, the storm reached its peak intensity with winds of 110 km/h (70 mph) according to both the RSMC Nadi and the JTWC, making it a high-end Category 2 cyclone on the Australian Scale. The highly favorable environment, in combination with the fast forward motion of the storm, allowed Urmil to rapidly reach its peak intensity, despite wind shear reaching 35 km/h (25 mph). However, as quickly as the storm strengthened, it began to weaken as convection weakened. With both wind shear and forward motion increasing, the cyclone quickly became disorganized. Around 0000 UTC on January 15, the center of circulation was devoid of shower and thunderstorm activity. About six hours later, Urmil transitioned into an extratropical cyclone
and was subsequently absorbed into the mid-latitude westerlies
.
, Tonga
, the Cook Islands
, and French Polynesia
. A flood advisory and small craft advisory
were issued for Samoa
. Later that day, the strong wind warnings for the Cook Islands and French Polynesia were canceled, as Urmil no longer posed a threat to the islands. By January 15, all of the warnings associated with Urmil were lifted.
Early on January 14, 06F passed close to Tafahi
and Niuatoputapu
, produced heavy rains and near gale-force winds over the islands. The highest winds in Tonga were recorded on Niuatoputapu; sustained winds reached 35 km/h (25 mph) with gusts to 65 km/h (40 mph). The winds caused minor damages, mainly limited to vegetation. Some fruit trees were damaged, mainly banana trees. The rains from Urmil exaggerated flooding produced by Cyclone Tam just a few days earlier.
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 lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
banding feature
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
wrapping around the center of circulation
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
. However, the combination of high wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
and the rapid movement of the cyclone caused convection to become separated from the center. By January 15, the storm transitioned into an extratropical cyclone
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
shortly before dissipating. Urmil had only minor effects on land; scattered vegetation damage was reported in Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
.
Meteorological history
Tropical Cyclone Urmil originated from a weak tropical disturbanceTropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
over the open waters of the south Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
on January 13. Around 1800 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
, the Regional Specialized Meteorological Centre
Regional Specialized Meteorological Centre
A Regional Specialized Meteorological Centre is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as part of the World Weather Watch.-Tropical...
(RSMC) in Nadi, Fiji classified the system as Tropical Disturbance 06F, while it was located about 370 km (230 mi) west of Pago Pago, American Samoa
Pago Pago, American Samoa
Pago Pago , also spelled ', is the capital of American Samoa. In 2000, its population was 11,500. The city is served by Pago Pago International Airport. Tourism, entertainment, food, and tuna canning are the primary industries here. From 1878 to 1951, this was a coaling and repair station for the...
. Forming in the wake of Tropical Cyclone Tam
Cyclone Tam (2006)
Tropical Cyclone Tam was the first named storm of the 2005–06 South Pacific cyclone season. Forming out of a tropical depression on January 6, the storm gradually intensified, becoming a tropical cyclone on January 12 and receiving the name Tam...
, the disturbance rapidly organized within an environment of favorable diffulence aloft, warm waters (29°C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
; 84.2°F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
), and moderate wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
. Six hours later, RSMC Nadi upgraded 06F to a tropical cyclone and gave it the name Urmil while it was situated near Niuatoputapu
Niuatoputapu
For the 2009 tsunami, see the main article: 2009 Samoa tsunami.Niuatoputapu is an island in the island nation of Tonga, Pacific Ocean. Its name means sacred island. Older European names for the island are Traitors island or Keppel island.Niuatoputapu is located in the north of the country,...
, Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
. Shortly after, the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
(JTWC) issued a Tropical Cyclone Formation Alert
Tropical Cyclone Formation Alert
A Tropical Cyclone Formation Alert is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Naval Maritime Forecast Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been...
as the storm quickly traveled towards the south-southeast. Around 0600 UTC on January 14, the JTWC classified Urmil as Tropical Cyclone 07P.
During the following six hours, Urmil underwent explosive deepening
Rapid deepening
Rapid deepening, also known as rapid intensification, is a meteorological condition that occurs when the minimum sea-level atmospheric pressure of a tropical cyclone decreases drastically in a short period of time. The National Weather Service describes rapid deepening as a decrease of...
as the main feeder band
Rainband
A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as...
wrapped around the center of circulation
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
. After the brief period of intensification, the storm reached its peak intensity with winds of 110 km/h (70 mph) according to both the RSMC Nadi and the JTWC, making it a high-end Category 2 cyclone on the Australian Scale. The highly favorable environment, in combination with the fast forward motion of the storm, allowed Urmil to rapidly reach its peak intensity, despite wind shear reaching 35 km/h (25 mph). However, as quickly as the storm strengthened, it began to weaken as convection weakened. With both wind shear and forward motion increasing, the cyclone quickly became disorganized. Around 0000 UTC on January 15, the center of circulation was devoid of shower and thunderstorm activity. About six hours later, Urmil transitioned into an extratropical cyclone
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
and was subsequently absorbed into the mid-latitude westerlies
Westerlies
The Westerlies, anti-trades, or Prevailing Westerlies, are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east, and steer extratropical...
.
Preparations and impact
Upon being designated Tropical Disturbance 06F, tropical cyclone alerts and strong wind warnings were issued for NiueNiue
Niue , is an island country in the South Pacific Ocean. It is commonly known as the "Rock of Polynesia", and inhabitants of the island call it "the Rock" for short. Niue is northeast of New Zealand in a triangle between Tonga to the southwest, the Samoas to the northwest, and the Cook Islands to...
, Tonga
Tonga
Tonga, officially the Kingdom of Tonga , is a state and an archipelago in the South Pacific Ocean, comprising 176 islands scattered over of ocean in the South Pacific...
, the Cook Islands
Cook Islands
The Cook Islands is a self-governing parliamentary democracy in the South Pacific Ocean in free association with New Zealand...
, and French Polynesia
French Polynesia
French Polynesia is an overseas country of the French Republic . It is made up of several groups of Polynesian islands, the most famous island being Tahiti in the Society Islands group, which is also the most populous island and the seat of the capital of the territory...
. A flood advisory and small craft advisory
Small craft advisory
A small craft advisory is a type of warning issued by the National Weather Service in the United States, most frequently in coastal areas. It is issued when winds have reached, or are expected to reach within 12 hours, a speed marginally less than gale force....
were issued for Samoa
Samoa
Samoa , officially the Independent State of Samoa, formerly known as Western Samoa is a country encompassing the western part of the Samoan Islands in the South Pacific Ocean. It became independent from New Zealand in 1962. The two main islands of Samoa are Upolu and one of the biggest islands in...
. Later that day, the strong wind warnings for the Cook Islands and French Polynesia were canceled, as Urmil no longer posed a threat to the islands. By January 15, all of the warnings associated with Urmil were lifted.
Early on January 14, 06F passed close to Tafahi
Tafahi
Tafahi is a small island in the north of the Tonga archipelago, in fact closer to Savaii than the main islands of Tonga. It is only north-northeast away from Niuatoputapu, and fishermen communicate in small outboard motorboats almost daily between the two.Other names for Tafahi are Cocos Eylant ...
and Niuatoputapu
Niuatoputapu
For the 2009 tsunami, see the main article: 2009 Samoa tsunami.Niuatoputapu is an island in the island nation of Tonga, Pacific Ocean. Its name means sacred island. Older European names for the island are Traitors island or Keppel island.Niuatoputapu is located in the north of the country,...
, produced heavy rains and near gale-force winds over the islands. The highest winds in Tonga were recorded on Niuatoputapu; sustained winds reached 35 km/h (25 mph) with gusts to 65 km/h (40 mph). The winds caused minor damages, mainly limited to vegetation. Some fruit trees were damaged, mainly banana trees. The rains from Urmil exaggerated flooding produced by Cyclone Tam just a few days earlier.