Hurricane Season Update

 

Hurricane Grace (Source: NASA)

With the National Hurricane Center having written the final advisory on “Henri” as of 5 a.m. today, there are no active tropical storms or hurricanes anywhere in the Atlantic Ocean Basin.  Consequently, there will be a much-needed break after an active stretch of weather in the tropics.  Eight named storms have already developed this season, including three just this month.  That’s commensurate with NOAA’s updated hurricane forecast of a busier than average season.

NOAA’s August update to its 2021 hurricane forecast calls for a total of 15 – 21 tropical storms, of which 7 – 10 become hurricanes, with 3 – 5 major hurricanes.  A “major” hurricane has sustained winds of at least 111 mph, making it a Category 3 on the Saffir-Simpson Hurricane Wind Scale.  Hurricane Grace became the first major Atlantic hurricane of 2021 on August 21, when it reached Category 3 intensity in the Gulf of Mexico shortly before its landfall in Mexico.  Two tropical storms, Fred and Henri, made landfall in the United States this month.  They combined to bring much of the eastern United States a significant amount of rainfall with widespread flooding, particularly in the Northeast.

When Henri intensified into a minimal Category 1 hurricane on Saturday, it stirred memories of past hurricanes that made landfall in New York or New England such as Gloria in 1985 or Bob in 1991.  However, Henri weakened to a 60 mph tropical storm before it made landfall in Rhode Island on August 22.  It’s important to remember that there is little tangible difference in the effects of a strong tropical storm and a minimal hurricane when they make landfall.  Both are capable of producing a significant coastal surge, gusty and potentially damaging winds, along with flooding rainfall.

The 2021 hurricane season got off to an unusually fast start with Hurricane Elsa that became the earliest fifth named tropical storm on record July 1.  Despite the absence of any tropical storms or hurricanes in the tropical Atlantic, 2021 is well-positioned to become the sixth consecutive busier than average Atlantic hurricane season.

While the six-week period of late August through early October is climatologically the busiest time of the hurricane season, the tropics can remain active well into November.  Such was the case last year when November saw two major hurricanes (Eta, Iota) and a strong tropical storm (Theta).  Eta and Iota were both strong Category 4 hurricanes.  Iota was originally ranked as a Category 5 hurricane with peak sustained winds of 160 mph.   That would have made it the Atlantic’s first November hurricane of that intensity since 1932.  However, further analysis led scientists to reclassify it as an upper echelon Category 4 with peak sustained winds of 155 mph.

Hurricane season runs through November 30, so there are a few more months that careful attention should be given to the tropical Atlantic.  Fortunately, the National Hurricane Center doesn’t expect any new systems to develop during the next three to five days.