Tropical Storm Zeta was a very late-developing tropical storm over the central Atlantic that formed after the 2005 Atlantic hurricane season and continued into January 2006. Becoming a tropical depression at approximately midnight on December 30, it became the record-breaking thirtieth tropical cyclone of the 2005 Atlantic hurricane season and after intensifying into Tropical Storm Zeta six hours later, it became the season's twenty-seventh named storm. Zeta was one of only two Atlantic tropical cyclones to span two calendar years. 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 degenerating into a remnant low on January 6 and dissipating on the next day. Since 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.
Meteorological history
Tropical Storm Zeta originated from an upper-level trough 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 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 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 anticyclonicoutflow. 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 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 and a barometric pressure of about to the 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 degenerated into a remnant later that day. With this transition, the very active 2005 hurricane season finally came to a close. The remnant low retained its identity for another day, before it dissipated to the southeast of Bermuda during January 7.
Impact and records
Several of the crews that were taking part in the 2005 Atlantic Rowing Race were affected with heavy seas and strong adverse winds from Tropical Storm Zeta. Several teams encountered winds up to 50 mph and large swells up to. 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 off-course, ending with an encounter with a shark that battered their boat. The ship Liberty Star made several reports of strong winds from Tropical Storm Zeta, including one of 40 mph winds early on December 31, when the ship was about 45 miles 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; NHC forecaster James Franklin noted that the atmosphere "seem to want to develop tropical storms ad nauseam". 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.
