'There is still more of hurricane season to go': Expert warns another tropical threat may make US landfall

Even though the tropical Atlantic is void of organized storms at this time, conditions may again get busy over the next couple of weeks with a few areas of potential development.

Sept. 10 marked the peak of the Atlantic hurricane season from a climatology standpoint. However, hurricane season does not officially end until Nov. 30. The coming weeks into mid-October often bring several additional tropical storms and hurricanes. This year may not be any exception.

AccuWeather long-range tropical meteorologists, led by Hurricane Expert Dan Kottlowski, are projecting two to four more tropical storms, of which one or two may become hurricanes, following Tropical Storm Joyce.

Static Rest of Atlantic Hurricane Season Sep 20
Static Rest of Atlantic Hurricane Season Sep 20

There have been 10 tropical storms, of which five became hurricanes. Three named systems, Alberto, Florence and Gordon, made landfall in the United States.

Thus far, Florence has been the only major hurricane (Category 3 or higher) in the basin.

AccuWeather originally predicted 12 to 15 tropical storms, six to eight hurricanes and three to four named-storm landfalls back on April 2. Due to a potential El Niño, the numbers were lowered slightly during mid-summer to 10 to 12 tropical storms and five to six hurricanes.

"There are several things we look at that include the current conditions, the status of El Niño and another cycle that tracks rising air over the tropics," Kottlowski said.

El Niño is the warm phase of tropical Pacific sea surface temperatures. When El Niño is going strong, air is rising and promoting a great deal of tropical activity over the Pacific. At the same time, westerly winds tend to blast from North America through much of the Atlantic basin. These strong winds tend to suppress tropical activity over the Gulf of Mexico, Caribbean and the western part of the Atlantic Ocean.

"The anticipated El Niño for this upcoming fall and winter has been lagging, and we are still technically in a neutral phase," Kottlowski said.

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"That's one reason why we saw the flurry of tropical storms and hurricanes in the past couple of weeks in both the Atlantic and the Pacific. The delay in El Niño was a caveat we mentioned during the initial hurricane forecast and a midsummer update."

Another parameter tracks a slow-moving wave of rising air, which can lead to storms that can develop tropically when over warm water and under the right conditions. It moves west to east around the equator. That parameter is known as the Madden-Jullian Oscillation, or MJO for short.

"The MJO is forecast to be in a phase that favors rising air over the Atlantic basin starting next week," Kottlowski said.

The rising air in the absence of disruptive winds may allow another flurry of tropical activity during the latter part of September to early October.

AccuWeather long-range meteorologists still believe that El Niño will ramp up this autumn.

"If El Niño does what our long-range team thinks, increasing westerly winds from North America will tend to break across the Atlantic and really shut down the hurricane season later in October and November," Kottlowski said.

"Even so, there is the chance for one more direct impact by a tropical storm or hurricane on the United States for the rest of the season," he said.

Are there immediate tropical concerns?

What was Isaac has been ripped apart by disruptive winds over the western Caribbean. While this feature is not expected to develop, its moisture, along with a former tropical depression from the eastern Pacific, may enhance downpours in parts of Texas and the southern Plains this weekend.

"In the near term, there are three features AccuWeather meteorologists are monitoring for potential tropical storm formation through the end of September," Kottlowski said.

Static Atlantic Snapshot Sep 20
Static Atlantic Snapshot Sep 20

One system is located over the middle of the North Atlantic and contains some of the old moisture from Florence.

While the circulation from Florence has expired in this area, some of its original moisture may spawn a tropical storm and perhaps a hurricane during the last week of September. The rest of Florence's old moisture is forecast to pester the British Isles this weekend with rain and wind.

Farther south, a tropical disturbance, or tropical wave, has a slight chance of organizing east of the Leeward and Windward islands in the Caribbean over the next few days. However, if that system approaching the Caribbean waits too long to take shape, disruptive winds near the Caribbean may tear the disturbance apart.

Meanwhile, a new tropical wave has just emerged from Africa and is forecast to move westward.

This latest tropical wave may move on a general westward path over the next week.

"If this latest tropical wave stays south of a zone of disruptive winds, it may develop and could approach the Windward and Leeward islands later next week," Kottlowski said.

"So, even though we are over the hump, in terms of the average peak of hurricane season, there is still more of hurricane season to go," Kottlowski said.