Sam intensifies into Category 4 hurricane but may avoid land in the long run

The storm’s peak winds could reach 150 mph Sunday

Satellite loop of Hurricane Sam late Saturday afternoon. (NOAA)

Amid an exceptionally busy Atlantic hurricane season, Sam has become the latest ferocious storm. Now a Category 4 hurricane with 140 mph winds, it is predicted to intensify even further. By Sunday, the National Hurricane Center predicts its peak winds will increase to 150 mph, not far from Category 5-strength.

The intense though compact storm is expected to be a very long-lived hurricane, churning over the Atlantic for at least another week. While subject to change, forecast models generally keep Sam over the ocean, rather than threatening land areas during this time.

At 5 p.m. Saturday, Sam was about 1,000 miles east of the Leeward Islands over the open Atlantic, headed to the west-northwest at 10 mph. The latest forecast track from the Hurricane Center keeps it far enough north of the Lesser Antilles such that they’ll avoid direct effects from Sam. This also holds true for the northern Caribbean, including the Virgin Islands and Puerto Rico. By Thursday, Sam’s forecast position is several hundred miles north of the Leeward Islands.

In the longer run, forecast models continue to predict that Sam will remain over the open ocean, although Bermuda may need to watch the storm by around next weekend. The chance that Sam gets pulled to the northwest toward the U.S. East Coast seems to be lessening but can’t be totally taken off the table. Newfoundland has a better chance of getting clipped by the storm in nine or 10 days, although the storm could even pass to its east over the North Atlantic. Predicting the storm’s course beyond five to seven days, however, is very difficult, as the configuration of steering currents could change.

Sam is an intense hurricane and is expected to remain one into early next week. The Hurricane Center predicts that it will peak as a high-end Category 4 storm with 150 mph winds Sunday before slowly weakening back to a Category 3 storm by the middle of next week.

Sam is the fourth major (Category 3 or stronger) hurricane of the 2021 Atlantic season. According to Phil Klotzbach, a hurricane expert at Colorado State University, only seven other seasons since 1966 have had at least four major hurricanes through Sept. 25. It is the second hurricane to attain Category 4 strength, joining Ida.

Joining Sam in the Atlantic is subtropical depression Theresa, which is 150 miles north of Bermuda. It is forecast to dissipate over the next few days.

In 2021, 19 named storms have formed in the Atlantic, with just two left in the list of storm names before it is exhausted. Victor and Wanda are the only remaining names. Assuming they form, forecasters will resort to a supplementary list of names for any additional storms.