Hurricane Epsilon - Tropical Storm Intensity

Tropical Storm Intensity

Operationally, the NHC did not initiate advisories until 1500 UTC on November 28, about nine hours after it actually developed. By that time, the convection had wrapped into a ring 45 mi (72 km) in diameter. In the first advisory on Epsilon, the NHC forecast steady strengthening to near hurricane status due to marginally favorable conditions, followed by extratropical transition within five days; an alternate possibility was Epsilon being absorbed by a larger extratropical storm. The storm moved westward after its development with a persistent ridge to its north. Initially, Epsilon was embedded beneath an upper-level low that provided an area of low wind shear and instability. An eye-like feature briefly developed in the center of the convection, although the thunderstorms waned late on November 28 due to restricted inflow. However, banding features and outflow improved at the same time.

By November 30, the NHC anticipated extratropical transition to occur within two days, although some strengthening was still expected. That day, there was an increase in convection over the center and the development of a ragged eye-feature. The winds briefly increased to 65 mph (105 km/h), although the intensity of the thunderstorms diminished. Initially Epsilon was predicted to continue westward and eventually turn to the north and northeast. Instead, it turned toward the southwest and executed a cyclonic loop; the unexpected motion caused larger than normal errors in the extended track forecast. As it moved to the south, the storm crossed over an area of warmer water temperatures, and the NHC remarked that "just a modest increase in convection needed to make Epsilon a hurricane." At the time, forecasters assessed the winds in Epsilon to be around 70 mph (110 km/h), although in a post-season re-analysis it was found to have been 10 mph (15 km/h) weaker. Late on November 30, Epsilon made its closest approach to Bermuda, passing about 645 miles (1045 km) east-southeast of the island.

Tropical Storm Epsilon began its motion to the east and northeast on December 1, due to an approaching trough. Its structure became that of a "shallow hybrid-type tropical cyclone", and an eye-feature again developed within the convection. At the time, the NHC and several computer models anticipated extratropical transition within 36 hours as it accelerated northeastward near the Azores. However, four computer models predicted an alternate scenario, and forecaster Stacy Stewart stated such transition would only occur "barring any southward motion over warmer water that would prolong both the lifetime of Epsilon and the 2005 Atlantic hurricane season." As it continued northeastward, the storm separated from upper-level low it was previously beneath. After a decrease in convection, the thunderstorm activity again increased over the center, and there were more banding features. Despite moving over slightly cooler water temperatures, Epsilon attained hurricane status late on December 2, following the development of a well-defined eye 29 miles (46 km) in diameter.