After putting on an unexpected performance of rapid intensification, unprecedented in the central Atlantic this late in the season, Hurricane Epsilon peaked as a category 3 storm with 115 mph winds Wednesday afternoon and evening, becoming the fourth major Atlantic hurricane of this hyperactive season.

The 2020 Atlantic hurricane season is now above average in every measure of activity (see Tweet by Phil Klotzbach), and has an excellent chance of breaking the all-time record for most named storms in a season (28, set in 2005).

A remarkable feat of rapid intensification so late in year

In the 24 hours ending at 2 p.m. EDT October 21, Epsilon’s winds increased from 60 mph to 110 mph and the pressure dropped 35 mb. Epsilon’s intensification feat substantially exceeded the National Hurricane Center’s definition of rapid intensification, for which the threshold is at least a 35-mph increase in winds in 24 hours. Epsilon is the sixth 2020 Atlantic hurricane to rapidly intensify:

Also see: Climate change is causing more rapid intensification of Atlantic hurricanes

Hurricane Hanna, July 24–25, 35 mph in 24 hours;
Hurricane Laura, August 26–27, 65 mph in 24 hours;
Hurricane Sally, September 14–15, 40 mph in 24 hours;
Hurricane Teddy, September 17–18, 45 mph in 24 hours;
Hurricane Delta, October 5–6, 80 mph in 24 hours; and
Hurricane Epsilon, October 20–21, 50 mph in 24 hours.

In addition, Tropical Storm Gamma rapidly intensified October 2-3, with a 35 mph increase in winds in 24 hours, giving the Atlantic seven rapidly intensifying storms this year. Hurricanes Isaias, Marco, Nana, and Paulette did not rapidly intensify. According to statistics compiled by Tomer Berg, the highest number of rapidly intensifying Atlantic storms since 1979 occurred in 1995, with 10.

As shown in the Tweet from Sam Lillo, Epsilon is the only hurricane to have such a large drop in pressure so late in the year outside of the Caribbean Sea; Epsilon is also the only hurricane to rapidly intensify by at least 45 knots (50 mph) so far north in the Atlantic so late in the year.

A tropical storm warning for Bermuda

At 11 a.m. EDT Thursday, Epsilon had weakened to a category 1 hurricane with top sustained winds of 90 mph and a central pressure of 965 mb. The hurricane was headed northwest at 7 mph toward Bermuda, which was under a tropical storm warning. The western fringes of Epsilon were bringing heavy rain showers to Bermuda, as seen on Bermuda radar, and winds were gusting near tropical storm-force at the Bermuda airport. Epsilon is expected to turn to the north-northwest well before reaching Bermuda, likely passing about 150 miles to the east of the island on Thursday night.

A large storm, Epsilon has tropical storm-force winds that extend up to 310 miles to the north of the center. The large wind field is also generating large swells, which will be affecting the U.S. East Coast, Atlantic Canada, and the north-facing shores of the Caribbean islands this week.

Forecast for Epsilon

Moderate wind shear of 10-20 knots, combined with sea surface temperatures (SSTs) that will fall from 26 Celsius (79°F) on Thursday to 24 Celsius (75°F) on Saturday, will likely keep Epsilon at a steady intensity, or cause a slow weakening. On Saturday, Epsilon is expected to recurve to the northeast, and on Sunday, it may pass close and bring heavy rains to the southeastern portion of Newfoundland, Canada.

Epsilon will merge with a trough of low pressure to its north on Sunday and transition to a very powerful extratropical storm. Its central pressure on Tuesday, when it will be a few hundred miles south of Iceland, could be between 931-941 mb, according to the 0Z Thursday runs of the GFS, European, and UKMET models.

An eye on the western Caribbean this weekend

A trough of low pressure over the western Caribbean was bringing disorganized heavy rain showers to Cuba, Jamaica, the Cayman Islands and Haiti on Thursday afternoon. This system had some modest support for development from the Thursday morning runs of the GFS and European models and their ensembles, which showed it could become a tropical depression or weak tropical storm on Sunday or Monday in the western Caribbean or in the waters surrounding the Bahama Islands.

None of these model runs showed anything stronger than a weak tropical storm forming, but predicted a northeasterly track with a potential threat to Bermuda by Tuesday. Regardless of whether a tropical cyclone forms, heavy rains of 2-5 inches from this system will affect Cuba, the Bahamas, the Cayman Islands, South Florida and Jamaica through Monday. In an 8 a.m. EDT Thursday tropical weather outlook, NHC gave two-day and five-day odds of development of 10% and 30%, respectively, to this system. The next name on the Atlantic list of storms is Zeta.

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Posted on October 22, 2020(1:22pm EDT).