Additional hurricanes are likely over the Atlantic and may threaten the United States for the rest of the 2017 season. Hurricane season runs through the end of November, and it is possible the Atlantic may continue to produce tropical storms right up to the wire and perhaps into December.
As of Sept. 18, there have been four named systems that made landfall, including Harvey and Irma that made landfall in the U.S. as Category 4 hurricanes. The other two tropical storms were Cindy, near the Texas/Louisiana border in June, and Emily, just south of Tampa, Florida, at the end of July. Maria will, at the very least, have an indirect impact on the mainland U.S. from the rough surf and could approach the middle or upper part of the U.S. coast later next week.
Why do meteorologists believe that our hurricane season will be extended? Normally, strong west to northwest winds with cooler and drier air tend to scour tropical systems out of the western Atlantic during October and November. This may not be the case for this particular season. The concerns for this season are that these winds may not occur until later in the autumn or may be too weak to steer tropical threats away from the U.S.
This type of system is explained here by meteorologists: The warm weather pattern that has developed over the Central states and expanded into the eastern U.S. is a product of that development. Driving this warm weather pattern is a large area of high pressure, centered near Bermuda. The clockwise flow around this system will pump warm, humid air northward from the Gulf of Mexico and the western Atlantic. This means that the storms that develop will get caught up in the flow around this high-pressure area.
While is it unusual for this to occur so late in the season, there have been some damaging hurricanes during the middle of the autumn in the eastern and southern U.S. These include Hazel in 1954, Wilma in 2005, Sandy in 2012 and Matthew in 2016.
Image credits: Accuweather