Hurricane Epsilon - Peak Strength and Hurricane Status

Peak Strength and Hurricane Status

A few hours after reaching hurricane status, the NHC thought Epsilon reached peak winds, as the storm was about to move over cooler water temperatures. Additionally, the hurricane was expected to stall near the Azores, in contrast to the original forecast of continued acceleration to the northeast. On December 3 it turned due eastward, still maintaining an eye, modest amounts of convection, and outflow. Despite moving into an area of cooler waters and generally unfavorable atmospheric conditions, Epsilon retained its hurricane status; the only entity supporting its intensity was its warm upper-level temperature. By late on December 3, its presentation was described as "remarkably well-organized for a hurricane at high latitude in December... embedded in a strong upper-level westerly wind environment and moving over water."

As it continued eastward, Epsilon developed characteristics of an annular hurricane; such cyclones, more often found in the deep tropics with greater intensity, have circular eyes, surrounded by a nearly uniform ring of convection and a general lack of thunderstorms outside the ring. For several days, the intensity fluctuated in a narrow range, and although Epsilon was briefly downgraded to tropical storm status on December 4, the NHC assessed it as remaining a hurricane. After it was thought to have weakened, the eye became more symmetric as the ring of convection became stronger. The hurricane remained difficult to forecast, as NHC forecaster Lixion Avila remarked, "There are no clear reasons... and I am not going to make one up... to explain the recent strengthening of Epsilon."

By late on December 4, the NHC was no longer anticipating extratropical transition, after a front passed north of the storm and there was no interaction. At 0600 UTC on December 5, the hurricane's appearance generated 4.7 on the Dvorak technique, a system used to estimate intensity from satellite imagery. This was the highest rating during Epsilon's duration, and suggested winds of 85 mph (140 km/h), which was its peak intensity. Around that time, the hurricane began a turn to the east-southeast, as the ridge to its north built behind the passage of a cold front. Despite the cold water temperatures and unfavorable strong upper-level winds, Epsilon maintained its intensity, and the Geophysical Fluid Dynamics Laboratory (GFDL) model predicted it would remain a hurricane for nearly three days.