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Atlantic Hurricane Season Lull to Persist as El Nino Limits Tropical Development

By By Alex Sosnowski, AccuWeather senior meteorologist.
August 18, 2015, 6:07:26 AM EDT

El Niño will continue to greatly limit tropical development in the Atlantic Basin and greatly scale back rainfall in the Caribbean.

El Niño is associated with warmer-than-average sea surface temperatures in the tropical Pacific Ocean. While this warm water and correspondingly rising air in part of the Pacific leads to stronger and more frequent tropical storms in the same basin, it generally translates to less storms and few opportunities for rainfall in the tropical Atlantic.

According to AccuWeather Hurricane Expert Dan Kottlowski, "During El Niño years, we often see strong upper-level winds [wind shear] and extensive rounds of dry air over the Atlantic Basin."


These characteristics are certainly going on now and are likely to continue through much of the summer and fall, provided El Niño does not weaken or break down.

AccuWeather Chief Long Range Expert Paul Pastelok expects El Niño to continue through the fall and perhaps through part of the winter.

"Through the middle of August, we have seen weak tropical waves moving westward in the tropical Atlantic and Caribbean," Kottlowski said.

Tropical waves are disturbances that are born over the Middle East or Africa and travel westward near the equator.

The El Niño setup generally does not effect the number of tropical waves, some of which give birth to the majority of tropical systems. However, El Niño inhibits development of the waves and greatly reduces the overall amount of drenching shower and thunderstorm activity associated with the waves.

"In the pattern, there is so much dry air and wind shear over the tropical Atlantic, that most tropical waves are moisture-starved and tend to look like a skeleton with only spotty thunderstorm activity and very limited rainfall," Kottlowski said.

Throughout the season, there can be some fluctuation in the pattern to allow a few systems to develop into a tropical storm or hurricane, but the number of named systems tends to be lower than average.

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"In terms of powerful hurricanes, people should not let their guard down as there can still be a small number of well-developed systems that could bring torrential rain, powerful winds and life-threatening conditions," Kottlowski said.

While one tropical wave gathered enough moisture to bring some showers and thunderstorms to part of the northern Caribbean islands during the middle of June, there is little sign of tropical waves with high moisture available moving forward into July.

Other than Cuba, Hispaniola, Jamaica and Puerto Rico, most of the remaining islands in the Caribbean are too small to produce pop up thunderstorms without the aid of a tropical system. There simply is not enough heat generated over the small islands compared to the larger island.

The frequent rounds of dry air invading the region will also inhibit the pop-up thunderstorms over the larger islands.

Until a tropical wave develops into a tropical storm or hurricane, the lack of rainfall will continue over the Caribbean during much of the summer and autumn. However, those opportunities for drenching rain will be few and far between.

In the Caribbean, rainfall thus far during May and June has be spotty and well below average with a few exceptions.

Rainfall Departure From Average Spanning May to Late June

Actual (Through June 24)
Average (Normal)
San Jan, Puerto Rico
Kingston, Jamaica
St. John's, Antigua
Bridgetown, Barbados
St. Croix, U.S. Virgin Islands
Key West, Fla.
Santiago, Cuba

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