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Tropical Storm Zeta (2005)
Encyclopedia
Tropical Storm Zeta was a late-developing tropical storm over the central Atlantic which formed after the 2005 Atlantic hurricane season
had officially ended (on November 30), and continued into January 2006. Becoming a tropical depression at approximately midnight on December 30 (UTC),, it became the record-breaking thirtieth tropical cyclone of the 2005 Atlantic hurricane season and after intensifing into Tropical Storm Zeta six hours later, it become the season's twenty-seventh named storm. Zeta was one of only two Atlantic tropical cyclones to span two calendar years (the other being Hurricane Alice in 1954-55).
Zeta originated from an area of low pressure on December 29, which previously developed within an upper-level trough. After becoming a tropical storm, the National Hurricane Center
continually predicted it would weaken rapidly. Like the previous tropical cyclone, Hurricane Epsilon, Zeta defied these predictions. The storm reached its peak strength on January 2, 2006 before finally dissipating on January 6. As Zeta never approached land there was no impact from the storm other than minor shipping problems. Several ships encountered the storm, and several crews in the 2005 Atlantic Rowing Race
were affected by rough seas and high winds.
that interacted with a weakening frontal system in late-December 2005. By December 28, the trough had developed into a low pressure area
roughly 750 mi (1,210 km) west-northwest of the Cape Verde Islands. The following day, a low-level circulation developed and convective activity
began to increase around the low. By December 30, sufficient shower and thunderstorm
activity had developed for the National Hurricane Center
(NHC) to classify it as a tropical cyclone. Over the following several hours, convective banding
developed around the storm's center and by 0600 UTC
, the depression intensified into Tropical Storm Zeta, the record 28th tropical
or subtropical cyclone
to form during the 2005 Atlantic hurricane season
. Operationally, however, the NHC did not begin issuing advisories on Zeta until 1700 UTC. Traveling slowly northwestward in response to a mid-level low to the southwest, the storm gradually intensified in a region of favorable anticyclonic
outflow
.
By the afternoon of December 30, dry air caused the system to become slightly disorganized and led forecasters to anticipate further weakening of the storm and dissipating within three days. The following day, a mid-level ridge
to the north caused Zeta turn westward before nearly stalling due to upper-level westerlies
. By this time, the storm attained winds of 60 mph (95 km/h) but increasing wind shear
caused convection to become disorganized, resulting in a brief weakening period. Despite the shear, the shallow structure of Zeta allowed convection to regenerate and the storm gradually re-intensified. Around 1800 UTC on January 1, 2006, Zeta attained its peak intensity with winds of 65 mph (100 km/h) and a barometric pressure of 994 mbar
(hPa
; 29.35 inHg) roughly 1,035 mi (1,665 km) northwest of the Cape Verde Islands. By January 2, the storm began tracking towards the southwest in response to a mid-level trough located east of the storm.
Tropical Storm Zeta continued to defy forecasts of weakening.
The effects of wind shear finally took their toll late on January 4, and Zeta's convection began to die down. This led to Tropical Storm Zeta weakening to a minimal tropical storm. The NHC continued to overestimate how quickly Zeta would dissipate and early on January 5 they operationally downgraded Zeta to a depression, which was later confirmed to have been an error. Zeta continued to move west-northwestward, barely holding on to tropical storm status before becoming disorganized again. Zeta weakened into a tropical depression on January 6 and dissipated into a remnant later that day, finally ending the 2005 season. The remnant low retained its identity for a further day before it dissipated 660 miles (1060 km) southeast of Bermuda
.
were affected with heavy seas and strong adverse winds from Tropical Storm Zeta. Several teams encountered winds up to 50 mph (85 km/h) and large swells
up to 12 ft (3.7 m). Although battered by torrential rain and high winds, the direction of the winds assisted some of the ships in the race by speeding them closer to Antigua
. One Welsh
vessel was blown 25 mi (40.2 km) off-course, ending with an encounter with a 12 ft (3.7 m) shark that battered their ship. The ship Liberty Star made several reports of strong winds from Tropical Storm Zeta, including one of 40 mph (65 km/h) winds early on December 31, when the ship was about 45 miles (75 km) north of the storm.
When Zeta formed at 0600 UTC
on December 30, it became the second latest-forming tropical cyclone ever recorded in the Atlantic. Only Hurricane Alice of December 1954 formed later than Zeta, becoming a tropical storm around 1200 UTC. Additionally, Zeta became the second known Atlantic tropical cyclone, along with Alice, to exist in two calendar years. Tropical Storm Zeta also extended the record number of storms to form in the 2005 season to twenty-eight, seven more than the previous record held by the 1933 season
.
Although the storm affected several vessels during its existence, no land areas were threatened by Zeta. As a result, the NHC did not issue any tropical storm watches or warnings
.
NHC Zeta Report
The NHC's archive on Tropical Storm Zeta
2005 Atlantic hurricane season
The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history, repeatedly shattering numerous records. The impact of the season was widespread and ruinous with an estimated 3,913 deaths and record damage of about $159.2 billion...
had officially ended (on November 30), and continued into January 2006. Becoming a tropical depression at approximately midnight on December 30 (UTC),, it became the record-breaking thirtieth tropical cyclone of the 2005 Atlantic hurricane season and after intensifing into Tropical Storm Zeta six hours later, it become the season's twenty-seventh named storm. Zeta was one of only two Atlantic tropical cyclones to span two calendar years (the other being Hurricane Alice in 1954-55).
Zeta originated from an area of low pressure on December 29, which previously developed within an upper-level trough. After becoming a tropical storm, 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...
continually predicted it would weaken rapidly. Like the previous tropical cyclone, Hurricane Epsilon, Zeta defied these predictions. The storm reached its peak strength on January 2, 2006 before finally dissipating on January 6. As Zeta never approached land there was no impact from the storm other than minor shipping problems. Several ships encountered the storm, and several crews in the 2005 Atlantic Rowing Race
Atlantic Rowing Race
The Atlantic Rowing Race is a challenging ocean rowing race from the Canary Islands to the West Indies, a distance of approximately 2,550 nm . The race was founded by Sir Chay Blyth and first held in 1997 with subsequent races roughly every two years since. The early races were run by Challenge...
were affected by rough seas and high winds.
Meteorological history
Tropical Storm Zeta originated from an upper-level troughTrough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
that interacted with a weakening frontal system in late-December 2005. By December 28, the trough had developed into a low pressure area
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
roughly 750 mi (1,210 km) west-northwest of the Cape Verde Islands. The following day, a low-level circulation developed and convective activity
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...
began to increase around the low. By December 30, sufficient shower and thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
activity had developed for 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...
(NHC) to classify it as a tropical cyclone. Over the following several hours, convective banding
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...
developed around the storm's center and by 0600 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 depression intensified into Tropical Storm Zeta, the record 28th tropical
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...
or subtropical cyclone
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...
to form during the 2005 Atlantic hurricane season
2005 Atlantic hurricane season
The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history, repeatedly shattering numerous records. The impact of the season was widespread and ruinous with an estimated 3,913 deaths and record damage of about $159.2 billion...
. Operationally, however, the NHC did not begin issuing advisories on Zeta until 1700 UTC. Traveling slowly northwestward in response to a mid-level low to the southwest, the storm gradually intensified in a region of favorable anticyclonic
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
outflow
Outflow (meteorology)
Outflow, in meteorology, is air that flows outwards from a storm system. It is associated with ridging, or anticyclonic flow. In the low levels of the troposphere, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on weather...
.
By the afternoon of December 30, dry air caused the system to become slightly disorganized and led forecasters to anticipate further weakening of the storm and dissipating within three days. The following day, a mid-level ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to the north caused Zeta turn westward before nearly stalling due to upper-level 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...
. By this time, the storm attained winds of 60 mph (95 km/h) but increasing 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...
caused convection to become disorganized, resulting in a brief weakening period. Despite the shear, the shallow structure of Zeta allowed convection to regenerate and the storm gradually re-intensified. Around 1800 UTC on January 1, 2006, Zeta attained its peak intensity with winds of 65 mph (100 km/h) and a barometric pressure of 994 mbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
(hPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
; 29.35 inHg) roughly 1,035 mi (1,665 km) northwest of the Cape Verde Islands. By January 2, the storm began tracking towards the southwest in response to a mid-level trough located east of the storm.
Tropical Storm Zeta continued to defy forecasts of weakening.
The effects of wind shear finally took their toll late on January 4, and Zeta's convection began to die down. This led to Tropical Storm Zeta weakening to a minimal tropical storm. The NHC continued to overestimate how quickly Zeta would dissipate and early on January 5 they operationally downgraded Zeta to a depression, which was later confirmed to have been an error. Zeta continued to move west-northwestward, barely holding on to tropical storm status before becoming disorganized again. Zeta weakened into a tropical depression on January 6 and dissipated into a remnant later that day, finally ending the 2005 season. The remnant low retained its identity for a further day before it dissipated 660 miles (1060 km) southeast of Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
.
Impact and records
Several of the crews that were taking part in the 2005 Atlantic Rowing RaceAtlantic Rowing Race
The Atlantic Rowing Race is a challenging ocean rowing race from the Canary Islands to the West Indies, a distance of approximately 2,550 nm . The race was founded by Sir Chay Blyth and first held in 1997 with subsequent races roughly every two years since. The early races were run by Challenge...
were affected with heavy seas and strong adverse winds from Tropical Storm Zeta. Several teams encountered winds up to 50 mph (85 km/h) and large swells
Swell (ocean)
A swell, in the context of an ocean, sea or lake, is a series surface gravity waves that is not generated by the local wind. Swell waves often have a long wavelength but this varies with the size of the water body, e.g. rarely more than 150 m in the Mediterranean, and from event to event, with...
up to 12 ft (3.7 m). Although battered by torrential rain and high winds, the direction of the winds assisted some of the ships in the race by speeding them closer to Antigua
Antigua
Antigua , also known as Waladli, is an island in the West Indies, in the Leeward Islands in the Caribbean region, the main island of the country of Antigua and Barbuda. Antigua means "ancient" in Spanish and was named by Christopher Columbus after an icon in Seville Cathedral, Santa Maria de la...
. One Welsh
Wales
Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...
vessel was blown 25 mi (40.2 km) off-course, ending with an encounter with a 12 ft (3.7 m) shark that battered their ship. The ship Liberty Star made several reports of strong winds from Tropical Storm Zeta, including one of 40 mph (65 km/h) winds early on December 31, when the ship was about 45 miles (75 km) north of the storm.
When Zeta formed at 0600 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...
on December 30, it became the second latest-forming tropical cyclone ever recorded in the Atlantic. Only Hurricane Alice of December 1954 formed later than Zeta, becoming a tropical storm around 1200 UTC. Additionally, Zeta became the second known Atlantic tropical cyclone, along with Alice, to exist in two calendar years. Tropical Storm Zeta also extended the record number of storms to form in the 2005 season to twenty-eight, seven more than the previous record held by the 1933 season
1933 Atlantic hurricane season
The 1933 Atlantic hurricane season was the second most active Atlantic hurricane season on record, with 21 storms forming during that year in the northwest Atlantic Ocean. The season ran through the summer and the first half of fall in 1933, and was surpassed in total number of tropical cyclones by...
.
Although the storm affected several vessels during its existence, no land areas were threatened by Zeta. As a result, the NHC did not issue any tropical storm watches or warnings
Tropical cyclone warnings and watches
Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate...
.
See also
- 2005 Atlantic hurricane season2005 Atlantic hurricane seasonThe 2005 Atlantic hurricane season was the most active Atlantic hurricane season in recorded history, repeatedly shattering numerous records. The impact of the season was widespread and ruinous with an estimated 3,913 deaths and record damage of about $159.2 billion...
- List of tropical cyclones
- List of Atlantic hurricanes
- List of storms in the 2005 Atlantic hurricane season
- Timeline of the 2005 Atlantic hurricane seasonTimeline of the 2005 Atlantic hurricane seasonThe timeline of the 2005 Atlantic hurricane season documents the formations, strengthenings, weakenings, landfalls, extratropical transitions, and dissipations of the season's tropical and subtropical storms. The 2005 Atlantic hurricane season was the most active Atlantic hurricane season in...