2006 Central Pacific cyclone
Encyclopedia
The 2006 Central Pacific cyclone, also called 91C.INVEST or Storm 91C, was an unusual weather event of 2006
. Forming on October 30 from a mid-latitude cyclone
in the north Pacific mid-latitudes, it moved over waters warmer-than-normal. It acquired some features more typical of subtropical
or even tropical cyclone
s. However, as it neared western North America it fell apart. Moisture from its remains then caused substantial rainfall in British Columbia
. The exact status and nature of this weather event is unknown, with meteorologists and weather agencies having differing opinions.
over the central north Pacific moved over an area of ocean with sea surface temperature
s as high as 2 °C above normal for two days. By October 31 the system had acquired convection
, a warmer-than-normal core, and an eye-like
feature. During this time it had moved east, then northeast, and then northwest. On November 1, the system had estimated winds of 100 km/h (60 mph) and its most developed convection. After that, it slowly weakened, looped counter-clockwise, and headed east towards the west coast of North America. On November 2, wind shear
started taking its toll, and all convection was gone by the next day, when it was located roughly 520 mi (840 km) off the coast of Oregon
. This system's center of circulation passed south of observation buoy
46637 on November 1. The buoy's lowest pressure reading was 989 mb/hPa. Other buoys indicated that a rather large area of low pressure was associated with the system. Buoy 46637 was not at the system's center of circulation, so it is possible that this system had a lower minimum pressure than was actually measured.
issued wind watches
for the Oregon Coast. The system brought heavy rain
to portions of Vancouver Island
.
If Storm 91C is considered a tropical or subtropical cyclone, it holds several records. Since it currently is not officially either, its holding these records is also unofficial. Since it formed at 36°N, this system is the northernmost formation in the eastern north Pacific basin
. The previous record-holder was Tropical Storm Wene, which formed at 32°N before crossing the dateline. In addition, this system's track data indicates that it crossed from the central to the east Pacific because it formed at longitude 149°W and dissipated at 135°W. Only two recorded other tropical cyclones had done that previously.
This system has been considered a tropical
, subtropical
, or extratropical cyclone
.
Mark Guishard, a meteorologist with Bermuda Weather Service
, was of the opinion that the system had completed tropical cyclogenesis
and was a tropical cyclone. Meteorologist Mark Lander thought that cloud tops were similar to several Atlantic hurricanes, Hurricane Vince
in particular. James Franklin
, a meteorologist at the National Hurricane Center
, thought that:
Clark Evans of Florida State University
reported that forecasting tools showed that the system's structure was consistent with that of a sub tropical or marginally tropical cyclone. NASA
, which is not a meteorological agency, thought that the system was a subtropical cyclone.
In its review of the 2006 Atlantic hurricane season
, the Canadian Hurricane Centre
considered this to be an extratropical cyclone.
Since this system had one-minute sustained winds of 100 km/h (60 mi/h), which are above the 60 km/h (39 mi/h) boundary between a depression and a storm, it would qualify as a named storm if it was a tropical or subtropical cyclone. However, neither of the official Regional Specialized Meteorological Center
s for the eastern north Pacific, the National Hurricane Center
and the Central Pacific Hurricane Center
, include this system in their annual archives, nor is it included in the official "best track" file. Hence, this system is not an official tropical or subtropical cyclone of the 2006 Pacific hurricane season
.
Weather in 2006
The weather in 2006 meant another year of extremes. The summer was very hot and dry in the Northern Hemisphere. Several regions experienced disastrous floods, but droughts were not avoided either...
. Forming on October 30 from a mid-latitude cyclone
Mid-latitude cyclone
Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere . Cyclogenesis is an umbrella term for several different processes, all of which result in the development of some sort of cyclone. It can occur at various scales, from the microscale to the synoptic scale...
in the north Pacific mid-latitudes, it moved over waters warmer-than-normal. It acquired some features more typical of subtropical
Subtropical cyclone
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
or even tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
s. However, as it neared western North America it fell apart. Moisture from its remains then caused substantial rainfall in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. The exact status and nature of this weather event is unknown, with meteorologists and weather agencies having differing opinions.
Meteorological history
A cut-off extratropical cycloneExtratropical 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...
over the central north Pacific moved over an area of ocean with sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s as high as 2 °C above normal for two days. By October 31 the system had acquired convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
, a warmer-than-normal core, and an eye-like
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...
feature. During this time it had moved east, then northeast, and then northwest. On November 1, the system had estimated winds of 100 km/h (60 mph) and its most developed convection. After that, it slowly weakened, looped counter-clockwise, and headed east towards the west coast of North America. On November 2, 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...
started taking its toll, and all convection was gone by the next day, when it was located roughly 520 mi (840 km) off the coast of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
. This system's center of circulation passed south of observation buoy
Weather buoy
Weather buoys are instruments which collect weather and ocean data within the world's oceans, as well as aiding during emergency response to chemical spills, legal proceedings, and engineering design. Moored buoys have been in used since 1951, while drifting buoys have been used since 1979...
46637 on November 1. The buoy's lowest pressure reading was 989 mb/hPa. Other buoys indicated that a rather large area of low pressure was associated with the system. Buoy 46637 was not at the system's center of circulation, so it is possible that this system had a lower minimum pressure than was actually measured.
Impact, preparation, and records
In response to the weather system, the American National Weather ServiceNational Weather Service
The National Weather Service , once known as the Weather Bureau, is one of the six scientific agencies that make up the National Oceanic and Atmospheric Administration of the United States government...
issued wind watches
Severe weather terminology (United States)
This article describes the United States National Weather Service severe weather terminology. The NWS defines precise meanings for nearly all its weather terms. This article describes NWS terminology and related NWS weather scales...
for the Oregon Coast. The system brought heavy rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
to portions of Vancouver Island
Vancouver Island
Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...
.
If Storm 91C is considered a tropical or subtropical cyclone, it holds several records. Since it currently is not officially either, its holding these records is also unofficial. Since it formed at 36°N, this system is the northernmost formation in the eastern north Pacific basin
Tropical cyclone basins
Traditionally, areas of tropical cyclone formation are divided into seven basins. These include the north Atlantic Ocean, the eastern and western parts of the northern Pacific Ocean, the southwestern Pacific, the southwestern and southeastern Indian Oceans, and the northern Indian Ocean. The...
. The previous record-holder was Tropical Storm Wene, which formed at 32°N before crossing the dateline. In addition, this system's track data indicates that it crossed from the central to the east Pacific because it formed at longitude 149°W and dissipated at 135°W. Only two recorded other tropical cyclones had done that previously.
Nature of the system
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
, subtropical
Subtropical cyclone
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
, or 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...
.
Mark Guishard, a meteorologist with Bermuda Weather Service
Bermuda Weather Service
The Bermuda Weather Service is Bermuda's national meteorological service. It provides public, marine, tropical and aviation weather forecasts as well as warnings and climatolological services. The service began operations under contract from the Department of Airport Operations, Ministry of...
, was of the opinion that the system had completed tropical cyclogenesis
Tropical cyclogenesis
Tropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
and was a tropical cyclone. Meteorologist Mark Lander thought that cloud tops were similar to several Atlantic hurricanes, Hurricane Vince
Hurricane Vince (2005)
Hurricane Vince was an unusual hurricane that developed in the northeastern Atlantic basin. Forming in October during the 2005 Atlantic hurricane season, the waters over which it developed were considered too cold for tropical development...
in particular. James Franklin
James Franklin (meteorologist)
James L. Franklin is a weather forecaster with the National Hurricane Center and its current branch chief. He is a graduate of the Massachusetts Institute of Technology and of Ransom Everglades School in 1976 in Miami, where he was a co-valedictorian....
, a meteorologist at the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
, thought that:
The system was of frontal origin... the frontal structure was eventually lost.... The convective structure resembled a tropical, rather than subtropical cyclone, and the radius of maximum winds (based on QuikSCATQuikSCATThe QuikSCAT is an earth-observing satellite that provided estimates of wind speed and direction over the oceans to National Oceanic and Atmospheric Administration and others. This "quick recovery" mission intended to replace the NASA Scatterometer , which failed in June 1997...
) was very close to the center, also more typical of tropical cyclones... on balance, it was more tropical than subtropical.
Clark Evans of Florida State University
Florida State University
The Florida State University is a space-grant and sea-grant public university located in Tallahassee, Florida, United States. It is a comprehensive doctoral research university with medical programs and significant research activity as determined by the Carnegie Foundation...
reported that forecasting tools showed that the system's structure was consistent with that of a sub tropical or marginally tropical cyclone. NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, which is not a meteorological agency, thought that the system was a subtropical cyclone.
In its review of the 2006 Atlantic hurricane season
2006 Atlantic hurricane season
The 2006 Atlantic hurricane season was significantly less active than the record previous season. It marked the first since 2001 in which no hurricanes made landfall in the United States, and was the first since 1994 that no tropical cyclones formed during October. Following the intense activity of...
, the Canadian Hurricane Centre
Canadian Hurricane Centre
The Canadian Hurricane Centre is a division of the Meteorological Service of Canada, an agency of Canada's Department of the Environment, which exists to advise Canadians on the threat of tropical cyclones such as hurricanes and tropical storms...
considered this to be an extratropical cyclone.
Since this system had one-minute sustained winds of 100 km/h (60 mi/h), which are above the 60 km/h (39 mi/h) boundary between a depression and a storm, it would qualify as a named storm if it was a tropical or subtropical cyclone. However, neither of the official Regional Specialized Meteorological Center
Regional Specialized Meteorological Center
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...
s for the eastern north Pacific, the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
and the Central Pacific Hurricane Center
Central Pacific Hurricane Center
The Central Pacific Hurricane Center of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central North Pacific Basin...
, include this system in their annual archives, nor is it included in the official "best track" file. Hence, this system is not an official tropical or subtropical cyclone of the 2006 Pacific hurricane season
2006 Pacific hurricane season
The 2006 Pacific hurricane season was the most active Pacific hurricane season since 2000 producing 19 tropical storms or hurricanes. Eighteen developed within the National Hurricane Center area of warning responsibility, which is east of 140ºW, and one storm formed between 140ºW and the...
.
See also
- 1975 Pacific Northwest hurricane
- 1996 Lake Huron cyclone1996 Lake Huron cycloneThe 1996 Lake Huron cyclone was a strong cyclonic storm system that developed over Lake Huron in September 1996. It had some characteristics of a tropical cyclone.-Storm history:...
- Tropical Storm Omeka (2010)