After becoming a tropical storm, Zeta remained organized, defying predictions of a quick demise, and even grew slightly more intense.

Several ships encountered the storm, and several crews in the 2005 Woodvale Atlantic Rowing Race were affected by rough seas and high winds.

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.

[2] Traveling slowly northwestward in response to a mid-level low to the southwest, the storm gradually intensified in a region of favorable anticyclonic outflow.

[4] A few hours later, a deep burst of convection over the low-level circulation center allowed the storm to intensify a bit, with a central dense overcast forming.

"[11] Around 0000 UTC on January 3, Zeta attained its peak intensity with winds of 65 mph (100 km/h) and a barometric pressure of 994 hPa (29.35 inHg) about 1,035 mi (1,665 km) to the northwest of the Cape Verde Islands.

[1] NHC forecaster James Franklin noted that the atmosphere "seem[ed] to want to develop tropical storms ad nauseam".

[17] 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.

[20] One Welsh vessel was blown 25 mi (40 km) off-course, ending with an encounter with a 12 ft (3.7 m) shark that battered their boat.