Hurricane Epsilon rapidly intensified into a category 1 storm with 90 mph winds overnight, becoming the tenth Atlantic hurricane of this hyperactive season. According to Colorado State’s Phil Klotzbach, only four other years in the satellite era (since 1966) have had 10 or more Atlantic hurricanes by October 20: 1969, 1995, 2005 and 2017. Update: at 1:30 p.m. EDT Wednesday, an Air Force Hurricane Hunter aircraft found Epsilon had further rapidly intensified to 110 mph winds, making it a high-end category 2 hurricane.

In the 24 hours ending at 11 a.m. EDT (15Z) October 21, Epsilon’s winds increased from 50 mph to 90 mph, meeting the National Hurricane Center definition of rapid intensification, which is at least a 35-mph increase in winds in 24 hours. According to Sam Lillo, only one other Atlantic tropical cyclone has had a larger rate of rapid intensification so far north so late in the year.

Epsilon is also the sixth 2020 Atlantic hurricane to rapidly intensify:
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
Hurricane Epsilon, October 20–21, 40 mph in 24 hours

Hurricanes Isaias, Marco, Nana, and Paulette did not rapidly intensify.

A tropical storm warning for Bermuda

At 1:30 p.m. EDT Wednesday, Epsilon had top sustained winds of 110 mph and a central pressure of 959 mb. The hurricane was headed west-northwest at 9 mph toward Bermuda, which was under a tropical storm warning. The western fringes of Epsilon are predicted to affect Bermuda on Thursday afternoon and evening, when Epsilon is expected to be a category 2 hurricane.

As of the 11 a.m. EDT Wednesday NHC advisory, the island was outside the western edge of the cone of uncertainty; NHC gave Bermuda a 30-40% chance of experiencing tropical storm-force winds of 39 mph or higher. An Air Force Reserve Hurricane Hunter mission into Epsilon is scheduled for Wednesday afternoon.

Forecast for Epsilon

Light to moderate wind shear of 5-15 knots will favor development of Epsilon through Friday. However, sea surface temperatures (SSTs) on Wednesday were marginal for development, near 26.5 Celsius (80°F). SSTs will cool to about 26 degrees Celsius (79°F) by Friday, and the total ocean heat content to fuel rapid intensification will be near zero through Friday. A large storm, Epsilon will have tropical storm-force winds that extend up to 435 miles to the north of the center. The large wind field will stir up cool waters well in front of the hurricane, further limiting how much intensification can occur. 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.

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

Epsilon will turn to the north well before reaching Bermuda, likely passing 150-200 miles to the east of the island on Thursday night. 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 Monday, October 26, and transition to an extraordinarily powerful extratropical storm. Its central pressure on Tuesday could be between 920-935 mb. The 12Z Tuesday run of the European model had ex-Epsilon bottoming out to the south of Iceland next week with an eye-popping central pressure of 912 mb; the model with its 0Z Wednesday run backed off a little on that forecast, predicting a 921 mb storm.

Editor’s note: this post was updated at 1:30 p.m. EDT Wednesday with data from a special NHC advisory upgrading Epsilon to a category 2 storm.

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Posted on October 21, 2020(1:10 p.m. EDT).