AccuWeather.com: Atlantic may yield more systems as peak of hurricane season nears
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 September 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.
“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.”
Despite the influence of El Niño on the Atlantic basin this year, AccuWeather meteorologists do not expect a complete shutdown of tropical activity and an early end to hurricane season during most of September.
“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 fades 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.
Another zone to watch into early next week will be the waters around Bermuda.
“It is possible a non-tropical low pressure area gradually takes on tropical characteristics this weekend into next week,” Kottlowski said. “Conditions around Bermuda could range from just very spotty showers and breaks of sunshine to stormy weather with rounds of rain, rough seas and gusty winds, depending upon the strength and exact development location of the system.”
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 so much, such as Category 3 hurricanes or greater. 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 September 3, 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.
By Alex Sosnowski, Senior Meteorologist for AccuWeather.com
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