By Alex Sosnowski, AccuWeather.com Senior Meteorologist
September 4,2015; 10:40PM,EDT
While lulls in tropical activity in the Atlantic will continue through the Labor Day weekend, a rapid end to the hurricane season in September does not always occur during an El Niño.
It is true that an El Niño can sometimes make the environment more hostile for tropical systems to form and survive faster than average. However, this is not always the case.
According to AccuWeather Hurricane Expert Dan Kottlowski, "There are some years where the cause and effect nature of El Niño practically bring an early shut down to the Atlantic hurricane season and other years where we see tropical storms or hurricanes well into October."
The average peak of the Atlantic hurricane season is around Sept. 10, according to NOAA.
Hostile conditions would be an uptick in strong cool fronts pushing off the Atlantic Coast and deep into the Gulf of Mexico, as well as large pockets of dry air and wind shear.
During strong wind shear, there is a rapid change in the direction and speed of the flow of air at different levels of the atmosphere which tend to prevent tropical storm formation or limit early development.
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"September is the prime time of the year for Cape Verde systems [westward-moving disturbances in the Equatorial Atlantic]," Kottlowski said. "Areas of wind shear and dry air are still present, but these inhibiting factors are not as ferocious as they were earlier in the season over much of the region."
Current loop of the tropical Atlantic basin. (Satellite/NOAA)"As for whether or not there will be tropical storms and hurricanes cruising the Atlantic during October and early November this year, we cannot say for sure," Kottlowski said.
This question will be answered as we see how quickly south wind shear and cool air progress later this month.
As Erika and the feature in the northwestern Gulf of Mexico fade away, the parade of disturbances moving westward from Africa will need to be monitored through September.
"The main areas to watch for development moving forward through the height of hurricane season and into late September will be from the Africa coast to the Caribbean Sea and the southern Gulf of Mexico," Kottlowski said.
Even though the Caribbean, for example, has been a hostile environment for development for much of the season due to dry air and wind shear, these conditions are less extreme at this time.
One or more disturbances moving off of Africa and into the western Atlantic could slowly organize and strengthen over the next week.
"One such system could become the next tropical cyclone in the Atlantic during the Labor Day weekend," Kottlowski said.
Fred, which struck the Cape Verde Islands as a hurricane during late August, could survive a trip to the Azores but not as a fully tropical system by later next week.
The system near Bermuda is less likely to take on tropical characteristics due to a push of dry air forecast to move in this weekend.
While El Niño does not reduce the number of tropical disturbances moving westward from Africa, it does limit the number of tropical storms and hurricanes in the Atlantic basin in general.
However, El Niño does not tend to reduce the number of strong systems, such as Category 3 hurricanes or greater, so much. If a system can move into a pocket of favorable conditions with low wind shear and moisture, then it can still progress to a major hurricane. An example of this during the present season was Danny.
As of Sept. 4, 2015, there have been four tropical storms, two hurricanes and one major hurricane for the Atlantic season.
While the forecast for the number of systems and landfalls are meant to be used as a rough guide, based on the AccuWeather 2015 Atlantic Hurricane Forecast, there is still room for more hurricanes, tropical storms and another landfall in the U.S. before the official season draws to a close in November.
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